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Seismic Analysis and Testing of Nuclear Power PlantsA Safety Guide

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From Safety Series No. 46 onwards the various publications in the series aredivided into four categories, as follows:

(1) IAEA Safety Standards. Publications in this category comprise the Agency’s safety standards as defined in “The Agency’s Safety Standards and Measures” , approved by the Agency’s Board of Governors on 25 February 1976 and set forth in IAEA document INFCIRC/18/Rev. 1. They are issued under the authority of the Board of Governors, and are mandatory for the Agency’s own operations and for Agency-assisted operations. Such standards comprise the Agency’s basic safety standards, the Agency’s specialized regulations and the Agency’s codes of practice. The covers are distinguished by the wide red band on the lower half

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SEISMIC ANALYSIS AND TESTING OF NUCLEAR POWER PLANTS

A Safety Guide


T he fo llow ing S ta tes are M em bers o f the In te rn a tio n a l A tom ic E nergy A gency:

AFGHANISTANALBANIAALGERIAARGENTINAAUSTRALIAAUSTRIABANGLADESHBELGIUMBOLIVIABRAZILBULGARIABURMABYELORUSSIAN SOVIET

SOCIALIST REPUBLIC CANADA CHILE COLOMBIA COSTA RICA CUBA CYPRUSCZECHOSLOVAKIA DEMOCRATIC KAMPUCHEA DEMOCRATIC PEOPLE’S

REPUBLIC OF KOREA DENMARKDOMINICAN REPUBLICECUADOREGYPTEL SALVADORETHIOPIAFINLANDFRANCEGABONGERMAN DEMOCRATIC REPUBLICGERMANY, FEDERAL REPUBLIC OFGHANAGREECEGUATEMALAHAITI

HOLY SEEHUNGARYICELANDINDIAINDONESIAIRANIRAQIRELANDISRAELITALYIVORY COASTJAMAICAJAPANJORDANKENYAKOREA, REPUBLIC OF KUWAIT LEBANON LIBERIALIBYAN ARAB JAMAHIRIYALIECHTENSTEINLUXEMBOURGMADAGASCARMALAYSIAMALIMAURITIUSMEXICOMONACOMONGOLIAMOROCCONETHERLANDSNEW ZEALANDNICARAGUANIGERNIGERIANORWAYPAKISTANPANAMAPARAGUAYPERU

PHILIPPINESPOLANDPORTUGALQATARROMANIASAUDI ARABIASENEGALSIERRA LEONESINGAPORESOUTH AFRICASPAINSRI LANKASUDANSWEDENSWITZERLANDSYRIAN ARAB REPUBLICTHAILANDTUNISIATURKEYUGANDAUKRAINIAN SOVIET SOCIALIST

REPUBLIC UNION OF SOVIET SOCIALIST

REPUBLICS UNITED ARAB EMIRATES UNITED KINGDOM OF GREAT

BRITAIN AND NORTHERN IRELAND

UNITED REPUBLIC OF CAMEROON

UNITED REPUBLIC OF TANZANIA

UNITED STATES OF AMERICA URUGUAY VENEZUELA VIET NAM YUGOSLAVIA ZAIRE ZAMBIA

The Agency’s Statute was approved on 23 October 1956 by the Conference on the Statute o f the IAEA held at United Nations Headquarters, New York; it entered into force on 29 July 1957. The Headquarters o f the Agency are situated in Vienna. Its principal objective is “ to accelerate and enlarge the contribution o f atomic energy to peace, health and prosperity throughout the world” .

© IAEA, 1979

Permission to reproduce or translate the information contained in this publication may be obtained by writing to the International Atomic Energy Agency, Wagramerstrasse 5, P.O. Box 100, A-1400 Vienna, Austria.

Printed by the IAEA in Austria November 1979


SAFETY SERIES No. 50-SG-S2

SEISMIC ANALYSIS AND TESTING

OF NUCLEAR POWER PLANTS/

A Safety Guide

INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 1979


THIS SAFETY GUIDE IS ALSO PUBLISHED IN FRENCH, RUSSIAN AND SPANISH

SEISMIC ANALYSIS AND TESTING OF NUCLEAR POWER PLANTS:A SAFETY GUIDE

IAEA, VIENNA, 1979 STI/PUB/545

ISBN 9 2 - 0 - 6 2 3 0 7 9 - 4


FOREWORD

by the Director General

The demand for energy is continually growing, both in the developed and the developing countries. Traditional sources of energy such as oil and gas will probably be exhausted within a few decades, and present world-wide energy demands are already overstraining present capacity. Of the new sources nuclear energy, with its proven technology, is the most significant single reliable source available for closing the energy gap that is likely, according to the experts, to be upon us by the turn of the century.

During the past 25 years, 19 countries have constructed nuclear power plants. More than 200 power reactors are now in operation, a further 150 are planned, and, in the longer term, nuclear energy is expected to play an increasingly important role in the development of energy programmes throughout the world.

Since its inception the nuclear energy industry has maintained a safety record second to none. Recognizing the importance of this aspect of nuclear power and wishing to ensure the continuation of this record, the International Atomic Energy Agency established a wide-ranging programme to provide the Member States with guidance on the many aspects of safety associated with thermal neutron nuclear power reactors. The programme, at present involving the preparation and publication of about 50 books in the form of Codes of Practice and Safety Guides, has become known as the NUSS programme (the letters being an acronym for Nuclear Safety Standards). The publications are being produced in the Agency’s Safety Series and each one will be made available in separate English, French, Russian and Spanish versions. They will be revised as necessary in the light of experience to keep their contents up to date.

The task envisaged in this programme is a considerable and taxing one, entailing numerous meetings for drafting, reviewing, amending, consolidating and approving the documents. The Agency wishes to thank all those Member States that have so generously provided experts and material, and those many individuals, named in the published Lists of Participants, who have given their time and efforts to help in implementing the programme. Sincere gratitude is also expressed to the international organizations that have participated in the work.

The Codes of Practice and Safety Guides are recommendations issued by the Agency for use by Member States in the context of their own nuclear safety requirements. A Member State wishing to enter into an agreement with the Agency for the Agency’s assistance in connection with the siting, construction,


commissioning, operation or decommissioning of a nuclear power plant will be required to follow those parts of the Codes of Practice and Safety Guides that pertain to the activities covered by the agreement. However, it is recognized that the final decisions and legal responsibilities in any licensing procedures always rest with the Member State.

The NUSS publications presuppose a single national framework within which the various parties, such as the regulatory body, the applicant/licensee and the supplier or manufacturer, perform their tasks. Where more than one Member State is involved, however, it is understood that certain modifications to the procedures described may be necessary in accordance with national practice and with the relevant agreements concluded between the States and between the various organizations concerned.

The Codes and Guides are written in such a form as would enable a Member State, should it so decide, to make the contents of such documents directly applicable to activities under its jurisdiction. Therefore, consistent with accepted practice for codes and guides, and in accordance with a proposal of the Senior Advisory Group, “shall” and “should” are used to distinguish for the potential user between a firm requirement and a desirable option.

The task of ensuring an adequate and safe supply of energy for coming generations, and thereby contributing to their well-being and standard of life, is a matter of concern to us all. It is hoped that the publication presented here, together with the others being produced under the aegis of the NUSS programme, will be of use in this task.

STATEMENT

by the Senior Advisory Groupf

The Agency’s plans for establishing Codes of Practice and Safety Guides for nuclear power plants have been set out in IAEA document GC(XVIII)/526/Mod.l. The programme, referred to as the NUSS programme, deals with radiological safety and is at present limited to land-based stationary plants with thermal neutron reactors designed for the production of power. The present publication is brought out within this framework.

A Senior Advisory Group (SAG), set up by the Director General in September 1974 to implement the programme, selected five topics to be covered by Codes of Practice and drew up a provisional list of subjects for Safety Guides supporting the five Codes. The SAG was entrusted with the task of supervising, reviewing and advising on the project at all stages and approving draft documents for onward transmission to the Director General. One Technical Review Committee (TRC), composed of experts from Member States, was created for each of the topics covered by the Codes of Practice.


In accordance with the procedure outlined in the above-mentioned IAEA document, the Codes of Practice and Safety Guides, which are based on documentation and experience from various national systems and practices, are first drafted by expert worjdng groups consisting of two or three experts from Member States together with Agency staff members. They are then reviewed and revised by the appropriate TRC. In this undertaking use is made of both published and unpublished material, such as answers to questionnaires, submitted by Member States.

The draft documents, as revised by the TRCs, are placed before the SAG. After acceptance by the SAG, English, French, Russian and Spanish versions are sent to Member States for comments. When changes and additions have been made by the TRCs in the light of these comments, and after further review by the SAG, the drafts are transmitted to the Director General, who submits them, as and when appropriate, to the Board of Governors for approval before final publication.

The five Codes of Practice cover the following topics:

Governmental organization for the regulation of nuclear power plantsSafety in nuclear power plant sitingDesign for safety of nuclear power plantsSafety in nuclear power plant operationQuality assurance for safety in nuclear power plants.

These five Codes establish the objectives and minimum requirements that should be fulfilled to provide adequate safety in the operation of nuclear power plants.

The Safety Guides are issued to describe and make available to Member States acceptable methods of implementing specific parts of the relevant Codes of Practice. Methods and solutions varying from those set out in these Guides may be acceptable, if they provide at least comparable assurance that nuclear power plants can be operated without undue risk to the health and safety of the general public and site personnel. Although these Codes of Practice and Safety Guides establish an essential basis for safety, they may not be sufficient or entirely applicable. Other safety documents published by the Agency should be consulted as necessary.

In some cases, in response to particular circumstances, additional requirements may need to be met. Moreover, there will be special aspects which have to be assessed by experts on a case-by-case basis.

Physical security of fissile and radioactive materials and of a nuclear power plant as a whole is mentioned where appropriate but is not treated in detail. Non-radiological aspects of industrial safety and environmental protection are not explicitly considered.


When an appendix is included it is considered to be an integral part of the document and to have the same status as that assigned to the main text of the document.

On the other hand annexes, footnotes, lists o f participants and bibliographies are only included to provide information or practical examples that might be helpful to the user. Lists of additional bibliographical material may in some cases be available at the Agency.

A list of relevant definitions appears in each book.These publications are intended for use, as appropriate, by regulatory bodies

and others concerned in Member States. To fully comprehend their contents, it is essential that the other relevant Codes of Practice and Safety Guides be taken into account.


CONTENTS

1. INTRODUCTION

2. GENERAL RECOMMENDATIONS FOR SEISMIC CLASSIFICATION, LOADING COMBINATIONS AND ALLOWABLE LIMITS ...................................................... 2

2.1. Seismically safe nuclear power plant 222.2. Seismic classification of systems, structures and components

2.2.1. General considerations2.2.2. Seismic category 12.2.3. Seismic category 22.2.4. Uncategorized items2.2.5. Functions to be assured by the seismic design2.2.6. Interaction between items belonging to

different categories2.3. Loading conditions and combinations for category 1

and 2 items ........................................................................................... 42.3.1. Earthquake input2.3.2. Criteria for combination of earthquake loads with

other plant process loading conditions2.4. Allowable limits for stress and deformation for

category 1 items .................................................................................. 52.4.1. General considerations2.4.2. Allowable limits for loading combinations including

the SI ground motion loads2.4.3. Allowable limits for loading combinations including

the S2 ground motion loads2.4.4. No-loss-of-function limits2.4.5. Low-cycle fatigue effects

3. SEISMIC ANALYSIS METHODS 6

3.1. Introduction 673.2. Civil engineering structures

3.2.1. Buildings important to safety3.2.2. Buried long structures3.2.3. Foundation and earth structures


3.3. Mechanical and electrical components 11

3.3.1. Seismic input3.3.2. Piping3.3.3. Mechanical equipment3.3.4. Instrumentation, electrical equipment and

similar items3.4. Hydraulic e ffec ts................................................................................. 15

3.4.1. Sloshing effects3.4.2. Other hydraulic effects

4. IMPLICATIONS FOR SEISMIC DESIGN ............................................ 164.1. General approach to seismic design ................................................. 16

4.1.1. Measures for mitigating forces generated by earthquakes4.1.2. Measures for reducing relative differential movements

between structures4.1.3. Layout of process equipment

4.2. Civil engineering structures ............................................................... 174.2.1. Experience from past earthquakes4.2.2. Recommendations for design

4.3. Earth structures ................................................................................. 184.4. Piping and associated equipm ent...................................................... 19

4.4.1. Supports4.4.2. Improvement of vibration resistance of components4.4.3. Possible modes of failure of new equipment4.4.4. Considerations related to functional aspects for

seismic design4.5. Effects of vertical ground motion ................................................. 20

5. SEISMIC TESTING AND QUALIFICATION .................. ..................... 215.1. Introduction ...................................................................................... 215.2. General concepts........................................................................:....... 215.3. Full-scale testing ................................................................................. 22

5.3.1. Laboratory testing5.3.2. Plant testing

5.4. Reduced-scale model testing ........................................................... 23


6.1. Introduction ....................................................................................... 246.2. Instrumentation for evaluating the need for post

earthquake inspection and analysis .................................................. 246.3. Instrumentation for collecting design check data .......................... 256.4. Inspection after earthquake................................................................ 25

APPENDIX A. Methods of seismic analysis................................................... 26APPENDIX B. Modelling techniques ............................................................ 26APPENDIX C. Material property characterization ..................................... 30APPENDIX D. Seismic response of soil deposits and earth structures ...... 31APPENDIX E. Liquefaction and ground failure .......................................... 34APPENDIX F. Slope stability .......................................................................... 36

ANNEX I. Sloshing effects in water pools....................................................... 38ANNEX II. Qualification testing by means of the transport vehicle ......... 40

REFERENCES ..................................................................................................... 41

DEFINITIONS ..................................................................................................... 47

LIST OF PARTICIPANTS .................................................................................. 51

6. SEISMIC INSTRUMENTATION.................................................................... 24

PROVISIONAL LIST OF NUSS PROGRAMME TITLES 55



1. INTRODUCTIONThis Safety Guide, which supplements the IAEA Code of Practice on

Safety in Nuclear Power Plant Siting (IAEA Safety Series No. 50-C-S), forms part of the Agency’s programme, referred to as the NUSS programme, for establishing Codes of Practice and Safety Guides relating to land-based stationary thermal neutron power plants. The Provisional List of NUSS Programme Titles is printed at the end of this publication.

The Guide describes the procedure for performing seismic analyses and qualification tests for the structures, systems and components of nuclear power plants. It also includes consideration of a possible seismic classification of plant items, possible load combinations and allowable limits which represent a working basis for a seismic analysis. Experience gained from past earthquakes, insofar as it pertains to seismic analysis and design, is reflected in various sections and summarized in section 4. Consideration is also given to the fact that after-shocks may follow a major earthquake. Finally, there is a short section (section 6) on the seismic instrumentation that should be used to obtain the necessary information for assessing the safety of a plant after an earthquake or other ground-shaking phenomenon. The Guide has been developed in conjunction with another one, “Earthquakes and Associated Topics for Nuclear Power Plant Siting: A Safety Guide” (IAEA Safety Series No. 50-SG-S1), sincethe two subjects are closely related.

In the present Guide it is recognized that there is more than one possible engineering solution to problems and the approach adopted for one nuclear power plant may result in significant differences in that plant’s design when compared to another for which a different approach has been adopted. The recognition that different approaches are possible is consistent with the Code of Practice, which states, in the Introduction (section 1):

The acceptability o f a site is closely related to the design o f the proposed nuclear power plant. From the safety point o f view a site is acceptable if there are technical solutions to site-related problems, which give assurance that the proposed plant can be built and operated with an acceptably low risk to the population o f the region.

It is important to add that the approach adopted to solving earthquake- related problems should be complete and self-consistent.

This Guide is not necessarily applicable to sites of low seismicity as outlined in the scope of Safety Series No. 50-SG-S 1. It is also understood that all nuclear power plants would comply with applicable national codes and requirements.

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2. GENERAL RECOMMENDATIONS FOR SEISMIC CLASSIFICATION, LOADING COMBINATIONS

AND ALLOWABLE LIMITS

2.1. Seismically safe nuclear power plantThe methods and procedures described in this Guide should be taken as the

basis for the design of a seismically safe nuclear power plant; in some cases, however, they may need to be supplemented by other methods.

2.2. Seismic classification of systems, structures and components2.2.1. General considerations

A seismic classification of the items of a nuclear power plant is required to provide a rational basis for design. In this Guide the classification is based on:

(1) the need to ensure safety in the event of earthquakes, and(2) the need to inspect certain items after an earthquake that exceeds a

specified severity.Items are either classified into seismic category 1 or seismic category 2, or are uncategorized.

2.2.2. Seismic category 1

Seismic category 1 should be established for each plant.1 Items in category 1 should be designed for both the SI and the S2 earthquake ground motions (see sub-section 2.3.1 of the present Guide and Safety Series No. 50-SG-S1) in accordance with the provisions of this Guide and the other relevant IAEA Codes of Practice and Safety Guides. If the methods and margins adopted in designing for the S2 ground motion meet or exceed the SI ground motion design requirements there is no need to perform explicit calculations for the S I .

Category 1 should include:(1) Items of the nuclear power plant whose failure could directly or

indirectly cause accident conditions(2) Items of the nuclear power plant that are required for shutting down

the reactor safely, for maintaining it in a shut-down condition and for removing residual heat

(3) Items of the nuclear power plant that would be needed during or after the earthquake to mitigate the consequences of failures that may be

1 In some Member States category 1 is divided into additional sub-categories.

2


assumed to occur in spite of precautions taken in the design of items in (1).

2.2.3. Seismic category 2

Seismic category 2 may be established for each plant. Items in category 2 should be designed for a specific level of earthquake ground motion up to the SI level. The criteria used in defining allowable limits and load combinations for category 2 items may be established in accordance with the concepts, methods and techniques outlined in sub-sections 2.3 and 2.4 for category 1 items. Seismic category 2 would include all items of the nuclear power plant needed for safety that are not included in category 1.

In some Member States another concept is used: after an accident that has been allowed for in the design, but is not related to the occurrence of an earthquake, certain structures, systems and equipment in the nuclear power plant should remain functional for a long enough period to keep the plant in a safe shut-down state and to cope with the consequences of the accident. It is considered that there is a fairly high probability of an SI level earthquake occurring during this period; therefore certain items important to safety (structures, systems and equipment), not designed for the S2 ground motion, should be included in category 2.

2.2.4. Uncategorized items

Items of the nuclear power plant not included in categories 1 and 2 may be designed for earthquake resistance according to the national practice for non-nuclear applications.

2.2.5. Functions to be assured by the seismic design

The inclusion of an item in seismic category 1 or 2 should be based on a clear understanding of the functions which should be assured during or after an earthquake or after an accident not caused by an earthquake. Structural integrity, degree of leak tightness, mechanical or electrical function capability, and preservation of geometrical dimensions are examples of aspects which should be considered.

2.2.6. Interaction between items belonging to different categories

When the collapse or loss of function of a nuclear power plant item, which would otherwise be in category 2 or uncategorized, could jeopardize the functioning of items in a higher category, i.e. category 1 or category 2 respectively,

3


either (1) such items should be classified in the same category as the endangered items,

or (2) the absence of collapse or no loss of function under the referenceground motion for the lower category items should be demonstrated.

2.3. Loading conditions and combinations for category 1 and 2 items

2.3.1. Earthquake input

Two design basis vibratory ground motion levels should be considered for loading combinations (see section 3 of Safety Series No. 50-SG-S1):

(1) Ground motion level 1 (SI), which is the maximum that reasonably can be expected to be experienced at the site area once during the operating life of the nuclear power plant

(2) Ground motion level 2 (S2), which is considered to be the maximum earthquake potential at the site area.

2.3.2. Criteria for combination o f earthquake loads with other plant process loading conditions

The plant process load conditions of nuclear power plant items can be grouped as follows:

LI for loads during normal operationL2 for loads during anticipated operational occurrencesL3 for loads during accident conditions.

The following combinations should be considered:

(1) LI load conditions should be combined with the SI and S2 ground motions for category 1 items, and with SI alone for category 2 items.

(2) L2 load conditions initiated by failure or by loss of function of items not designed to withstand the SI ground motion should be combined with S I ; and L2 load conditions initiated by failure or by loss of function of items not designed to withstand the S2 ground motion should be combined with S2.

(3) Consideration should also be given to the need of taking into account appropriate combinations of the S1 and S2 ground motions with L2 and L3 conditions initiated by the failure or loss of function of items made to withstand these ground motions (see in particular item (3) of sub-section 2.2.2). In this connection the following factors should be taken into account:

4


(a) The probability of failure or loss of function of the items, which may depend on:

The relative magnitude of SI or S2 ground motion load in comparison with other loadsThe degree of conservatism and quality assurance applied to design, construction, testing and operation.

(b) The consequences resulting from the failure or loss of function of the items.

Considerations of this type have been incorporated in various national codes and practices [1—3].

(4) Environmental conditions and other natural phenomena assumed tq exist for the purpose of carrying out each evaluation in this section should be chosen on the basis of a risk evaluation.

2.4. Allowable limits for stress and deformation for category 1 items

2.4.1. General considerations

Allowable limits for those load combinations which include vibratory ground motion loads should be defined according to the normal practice used for the design of different types of plant items, taking into account:

(1) The probability of occurrence of the set of events which is based on the probability of each event in the set

(2) The nature of structural response which includes the type of response, e.g. whether ductile or non-ductile

(3) The seismic portion of the total load on the item(4) The potential consequences of the failure of the item.

2.4.2. Allowable limits for loading combinations including the SI ground motion loads

For load combinations involving the SI ground motion with LI or L2 the usual margins of safety should be considered: typically for general primary membrane stresses these margins of safety are about 1.5 on the limiting behaviour conditions such as yielding in ferritic steel; in some Member States, however, where the SI ground motion is very conservatively defined, these margins are reduced with the approval of the regulatory body.

5


2.4.3. Allowable limits for loading combinations including the S2 ground motion loads

Allowable limits of load combinations for sets of events including the S2 ground motion loads, and therefore having an extremely low probability of occurrence, should be the same as those adopted in related practices. Allowable limits between near-yield and near-ultimate capacity are specified according to the usual national design practice [1—3].

2.4.4. No-loss-of-function limits

For the set of events including the SI and/or the S2 ground motions the seismic design should be consistent with the maintenance of the safety functions specified in sub-section 2.2.5. As far as the maintenance of function depends on limiting stress and limiting deformation, limits for stress and deformation derived in sub-sections 2.4.2 and 2.4.3 may need to be suitably reduced [1 ].

2.4.5. Low-cycle fatigue effects

Earthquake loads are cyclical in nature and therefore fatigue analyses should be required as far as they are technically justified by being a sufficient fraction of the usage factor.

Fatigue effects have, in particular, to be considered for sets of events including the SI ground motion. For design purposes a number of equivalent cycles and amplitudes corresponding to several SI events may be assumed, consistent with the duration of the strong phase of the vibratory ground motion for each event and with the dynamic behaviour of the item in question. This assumption is intended to take into account the possibility of after-shocks and of a number of events of up to the SI ground motion level.

3. SEISMIC ANALYSIS METHODS

3.1. IntroductionMethods of analysis used for the seismic evaluation and design of nuclear

power plant items are outlined in this section. More details of some of these methods together with other pertinent comments and data are presented in the Appendices.

6


3.2. Civil engineering structures

3.2.1. Buildings important to safety

3.2.1.1. Seismic input

The two horizontal and the vertical components of the ground motion should be considered individually or in combination as inputs for the dynamic analysis. When the components are used individually, then the corresponding structural response should be suitably combined (see Appendix A). In some countries an equivalent static input is used in the vertical direction.

3.2.1.2. Modelling of structures

In the model of the structure, soil structure interaction should be suitably taken into account (see Appendix B).

Consideration should be given to translational, rocking and torsional modes, individually or coupled, as appropriate.

If a lumped mass and stiffness model is used, consideration should be given to the adequacy of the number and distribution of masses chosen to represent the main structures (see Appendix B). A sensitivity analysis can provide the basis for this decision; it can also permit the choice of the size and number of finite elements if this modelling technique is used.

Sub-systems (which may include inertia effect of a contained liquid) located in the building should be taken into account in the model of the building structures. Depending on the nature of the sub-systems, the following procedures may be used:

(a) For stiff items rigidly connected to the structure, or sub-systems that meet the decoupling criteria presented in Appendix B, the mass of the sub-system should be included in the mass of the supporting part of the structure.

(b) For parts connected to the structure by very flexible connection the sub-system may be neglected.

(c) For other sub-systems, the sub-system should be included in the analysis of the main structural model.

Two-dimensional models may be used where it can be reasonably demonstrated that they are appropriate, e.g. where uncoupled degrees of freedom exist; otherwise three-dimensional models are appropriate.

Adjacent buildings on the same foundation structure should be included in the same model. However, adjacent structures on separate foundations may also

7


mutually interact, in which case this effect should then be investigated and if necessary at least approximately evaluated.

Typically, normal nuclear power plant buildings can be modelled in one of the following ways, according to their structural characteristics:

(a) Shell-type buildings with internal structures (e.g. typical containment buildings): lumped mass or finite element models.

(b) Box-like buildings (e.g. typical auxiliary buildings): these can usually be modelled as rigid structures on elastic foundation; if this is not the case, finite element or lumped mass models may be considered but some difficulties may be encountered if the complexity and size of the structure are great.

(c) Frame-like buildings: lumped mass model.(d) Slender chimney-like structures: any reasonable model.

3.2.1.3. Analysis methods

A dynamic analysis should be performed to determine seismic motions or loads. Both the time history method and the response spectra method are in principle acceptable. An equivalent static load method without a parallel dynamic analysis can be used only if its conservatism is satisfactorily demonstrated.

Linear dynamic analyses are generally adequate for structures (see Appendix C). Alternatively, non-linear dynamic analysis may be used but special care should be given to:

(a) the suitability of the methods applied(b) appropriate stress/strain relationships selected for use.

3.2.1.4. Damping

Damping for various types of structures and soils is discussed in Appendix C. For a dynamic analysis, modal damping factors for composite structures can be obtained by the energy weighting technique [4]. The most important contribution to foundation-structure damping is energy dissipation within the ground. The actual radiation damping for nuclear power plants may be as great as 20% to 40% of critical damping. It is recognized that the value of damping that is used in seismic analysis of structures will require conservatively applied engineering judgment; conservative practices should be followed in all cases. If the structure is rigid, the radiation damping value depends on the mode of motion of the structure and the coupling of the operative modes of motion. If the structure is not rigid, a discrete representation of the structural contact with the half-space may be necessary [5, 6]. Variation of damping factors with frequency could be taken into account if warranted by experimental data.


3.2 .1 .5 . Lateral earth pressures

Lateral earth pressure induced on underground portions of structures by ground motion should be evaluated. This evaluation may be made by using procedures such as those outlined in Appendices D and E. Usually these procedures provide values of the dynamic pressure increment induced by the earthquake; this increment is then added to the applicable static lateral earth pressure. Simplified procedures [7, 8] may also be used to calculate this dynamic pressure increment. These simplified procedures, however, do not take into account the effect of adjacent structures on this pressure increment; the effect may, in some cases, be significant, depending on the plant layout.

3.2.1.6. Other considerations

Adequacy of shake space in structural joints between adjacent structural parts (see item (4) of sub-section 4.4.2) or between adjacent buildings should be checked, taking into account the need for an adequate safety margin.

3.2.2. Buried long structures

The following earthquake effects on buried long structures (e.g. buried pipes and ducts, well casings) should be taken into account:

Deformations imposed by surrounding soil during the earthquake Differential displacements or loads at end connections to buildings or other structures.

Both effects can be evaluated by a complete simulation of the soil structure complex. However, simplified conservative methods can also be applied [5,9].

3.2.3. Foundation and earth structures

3.2.3.1. General recommendation

The seismic performance and stability of all soil and rock supporting the nuclear power plant foundations and all earth structures (such as slopes, both natural and man-made, embankments, dams) as they affect safety should be evaluated.

3.2.3.2. Liquefaction

The liquefaction potential of saturated granular soil layers during the design basis vibratory ground motion should be evaluated for the limiting earthquakeSI or S2 ground motion and the availability of appropriate safety margins should

9


be demonstrated (see Appendix E). Appropriate measures to prevent liquefaction in these layers should be undertaken if the results of the evaluation indicate a lack of the required safety margins. These measures may include in-place treatment (e.g. compaction, grouting), excavation and replacement with properly compacted fill or permanent surcharging, or a combination of these measures.Field verification to assure attainment of the desired improvement in soil characteristics should be made.

3.2.3.3. Settlements

Potential settlements (especially differential settlements) caused by shaking may be of significance particularly in non-uniform soil conditions, where they should be evaluated. An available procedure for making such evaluations includes the use of results of a response analysis (Appendix D) together with data relating volume change to induced shear strains [ 10,11 ]. This procedure calculates settlement in the free field only; judgement should be exercised in estimating settlements in the vicinity and beneath the structures based on the results of the free field calculations.

3.2.3.4. Soil-bearing capacity

The potential for a failure of the bearing capacity during or after an earthquake should be investigated. Normally, the bearing capacity factor of safety under static loading conditions is reasonably high. Therefore, unless there is a significant reduction in the strength of the soil due to seismic loading (e.g. liquefaction in granular soils, or reduction in strength due to development of high shear strains in softer clays), the bearing capacity factor of safety under the combined static and seismic loads is expected to remain adequately high.

The safety factor can be calculated by using conventional procedures [12,13]. In such calculations, the seismic loads imposed by the structures should also be taken into account. These loads are normally calculated from the dynamic analysis of the structure (sub-section 3.2.1) and are then assumed to act as static loads.

Such calculations are usually needed in cases where structures important to safety are situated near slopes.

3.2.3.5. Slope stability

The seismic stability of slopes can be evaluated by using procedures such as those outlined in Appendix F.

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3.3. Mechanical and electrical components

3.3.1. Seismic input

For components not modelled together with the supporting structure the input for analysis is the floor response, expressed either as design floor time histories or as design floor response spectra. In some countries, an equivalent static input is used in the vertical direction.

3.3.1.1. Design floor response spectrum

The design floor response spectrum can be obtained on the basis of structure response to design basis ground motion.

Simplified methods have been proposed to calculate design floor response spectra [14], such as the decayed sinusoidal ground motion methods [15], the continuous beating sine wave method [16,17] and stochastic methods [18, 19].In the case of slightly damped systems, the assumption of a stationary process incorporated in the stochastic methods can be accepted; the results are then conservative.

It is recommended that before using a simplified method it should be ascertained that for representative cases the conservatism of the results is comparable to that provided by the direct time-history solution.

3.3.1.2. Recommendations concerning use of floor response spectra methods

Once the floor response curve is obtained for a particular floor of a building, a critical review of the calculated floor response spectrum should be made to assess the reasonableness of it, on the basis of sound engineering judgement, the relationship between the vibration characteristics of the building and the supporting ground, and the shape of the floor response curve.

The calculated floor response spectrum should be adjusted, to account for possible uncertainties in the evaluation of vibration characteristics of the building components. Examples of current procedures are given in Ref. [5] and section3.7.2 of Ref. [20]. For systems having closely spaced resonances the use of such adjusted response spectra may be modified in order to avoid overconservatism [21].

Consideration should be given to the modification of floor response spectrum input to piping and equipment attached on very flexible structural members and, when significant torsional motion of the building is present, to those items located away from the centre of shear of the building.

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3.3 .1 .3 . Design floor time histories

The design floor time histories can be obtained from the structural response to design basis ground motion.

In the analysis of mechanical and electrical components using design floor response spectra the uncertainties of such input due to material and structural characteristics should be taken into account by broadening the peak of the response spectra. A similar uncertainty effect should be considered in analysis in which floor motion time history rather than response spectrum are used by altering the time scale to define the time history motion (see section 3.7.1 of Ref. [20], and Ref. [22]).

3.3.1.4. Damping

Material damping is briefly discussed in Appendix C. Constant load hangers, spring hangers and snubbers tend to increase the damping of piping systems.

3.3.2. Piping

3.3.2.1. Modelling

Methods commonly used for modelling piping systems include:(1) Lumped mass method(2) Finite element method(3) Transfer matrix method, with matrix coefficient calculated according

to the beam theory [18, 23].

The flexibility or stiffness of bands, tees, spring hangers, and hydraulic and mechanical snubbers shall be evaluated. Constant spring hangers have usually no stiffness effect but they behave as a constant external load on the system through their travel range. If there is a pump or a valve on piping its contribution to the response should be evaluated. All additional masses such as valves, pumps, snubbers, liquid inside the pipe, thermal insulation, effective mass of mechanical snubbers, should be taken into account. The stiffness of any other support elements should be taken into consideration unless it can be demonstrated that their stiffness characteristics do not significantly alter the dynamic response characteristics of the piping system.3.3.2.2. Analysis methods

Dynamic methods (Appendix A) should be used, except as specified in subsection 3.3.2.3. However, when pipes are connected to two or more points

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having different movements, use of response spectra modal analyses requires some modification. A usually accepted method is to use, for all the support points, an envelope of the input at each support. The results of this method are usually rather conservative. Other methods can be used where design conservatism can be demonstrated [24]. Consideration should be given to the possible effects of differential motions between supporting joints.

3.3.2.3. Simplified analysis methods

Two simplified analysis methods are typically used to simplify evaluation of the seismic design adequacy of piping systems. One design adopted consists of over-restraining pipe-runs to increase natural frequencies and therefore minimize amplification effects. This solution is feasible only for those pipelines which are not subjected to large-amplitude thermal cycles. It may also greatly increase the number of seismic restraints that would be required to restrain the system.

In this case, a simplified assessment of earthquake loading may be obtained by the following steps:

(1) Calculating conservatively a lower limit for the fundamental natural frequency of each pipe length between two adjacent supports. This can be accomplished by modelling each pipe length as a separate beam of pertinent shape and specifying conservatively chosen end conditions; natural frequencies can be obtained for various beam shapes by using methods presented in handbooks or nomographs [18].

(2) Evaluating a first estimate of the inertia load for each pipe length on the basis of the previously determined natural frequency and of floor response spectra.

(3) Multiplying the load evaluated at step 2 by a factor of safety to be chosen on the basis of the fundamental frequency [2].

This procedure can be accepted if the fundamental natural frequency of each pipe length is fairly high (15 to 30 Hz).

A second simplified analytical method frequently used is to apply the peak of the applicable design floor response spectrum acceleration, multiplied by a suitable safety factor, to the mass distribution of the piping system in order to determine an inertial force to be applied to the system. A safety factor of 1.5 has typically been used in the past (see section 3.7.2 of Ref. [20]). However, lower values may be used for the particular piping geometry under consideration, provided that such lower values can be shown to give conservative answers when compared to dynamic analysis results. For a system of piping modelled separately the justification of the dynamic model with respect to size and boundary conditions should be presented.

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A variation of the second method has been used in combination with the first method. Here the maximum acceleration of the design response spectrum in the frequency range between 0.5 and 2.0 ff (where ff is the fundamental frequency of the piping system) is taken as the design acceleration. Again a suitable safety factor typically 1.5 times such a maximum has been applied.

3.3.2.4. Stress analysis

The calculated stresses can be a direct output of the dynamic analysis. Alternatively, when the piping movements are simple, a static stress analysis can be used, taking into account the inertia forces obtained from the dynamic analysis.

3.3.3. Mechanical equipment

3.3.3.1. Modelling

Models of structures and items are typically divided into the following five categories. These five categories are defined as follows:

(a) Rigid body model. For this model the item itself is assumed rigid (i.e. the fundamental frequency is larger than the typically accepted limit of30 Hz).2 The model is typically represented as a rigid body with attachment at support points represented by springs or stiffness or flexibility matrices. Response of the item then would be by rocking or translational modes of vibration at support points. Typical valves, pumps, motors, fans and some heat exchangers fall into this category.

(b) Single mass model. For this model the total mass is assumed to be lumped at a single point with the composite stiffness restraining the mass represented as a single element. More than one degree of freedom may be permitted. In general this modelling is considered as an alternative to method (a) and is applicable to the same types of items.

(c) Beam model or one-dimensional finite element. This type of modelling is typically applied to beams, columns, frames, piping, ducts, cable trays, conduits, symmetric tanks,cabinets, storage racks, pressure vessels and heat exchangers and can be expressed as a continuous or one-dimensional finite element in a two- or three-dimensional space. Masses may be represented by lumped parameters which develop a diagonalized elemental mass matrix or by the mean of consistent mass matrices which have the same off-diagonal form as the elemental stiffness or flexibility matrices.

2 This limit may differ from 30 Hz depending on site conditions.

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(d) Plate or shell or two-dimensional finite element. This type of modelling is typically performed on items whose primary mode of failure is by biaxial bending stress, plane stress or plane strain. Typically included in this category are: foundation media, cabinets, slabs and tanks, pressure vessels and heat exchangers whose shells support significant eccentric loads which would tend to excite shell or lobar modes of vibration.

(e) Three-dimensional finite element. This type of modelling has not been used extensively to date but it has been applied mainly to thick-wall vessels.

3.3.3.2. Methods of analysis

Dynamic methods such as those outlined in Appendix A and in sub-section3.3.2 as applicable, can be used.

Possible internal liquid sloshing effects should be taken into consideration (see sub-section 3.4).

3.3.4. Instrumentation, electrical equipment and similar items

The behaviour of those components included in category 1 should be evaluated for the SI and S2 ground motions. The seismic qualification of such items should be accomplished by testing, analysis or a combination of both.The functional capability of these items should be checked by shaking tests (see section 5).

It should be verified by the response analysis of the supporting structures, or panel structure, that the acceleration or velocity at the point where the item is installed is lower than the input used for testing by an appropriate margin. Consideration should be given to adopting similar procedures for category 2 items. More details about testing methods and procedure are contained in section 5. In general the simplified analysis methods of sub-section 3.3.2.3 are used to evaluate cable tray and conduit runs.

3.4. Hydraulic effects

3.4.1. Sloshing effects

Liquid oscillations due to an earthquake can occur in tanks, pools and basins. Their effects should be evaluated (see Annex I) and taken into account. Effects on the structure of the containing vessels and on the submerged structures should be considered [25, 26]. These effects may involve the reduction of functional capability (e.g. loss of shielding efficiency of fuel pools, disturbance of instrument signals).

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Input ground motion for these effects may not be supplied by the SI andS2 ground motions because of the long vibration periods possibly involved. For evaluation of adequate input ground motion see Annex I.

3.4.2. Other hydraulic effects

Although sloshing is a primary effect of earthquakes on an hydraulic tanklike system, there are other potentially relevant effects to be evaluated in connection with structural stability and hydraulic loading problems. Attached mass, hydraulic coupling, pumping and damping effects should be taken into account; all of them can greatly alter the dynamic behaviour of submerged structures. In particular, the pumping effect of water oscillations inside the gaps between fuel channels in a reactor core can be as relevant as the well known attached mass effect; indeed it may cause dynamic coupling of the various fuel elements [27].

4. IMPLICATIONS FOR SEISMIC DESIGN

4.1. General approach to seismic design

In the early stages of the design of the plant a preliminary arrangement of the main facilities should be laid down; this should subsequently be periodically reviewed to achieve the most suitable solution for the seismic design. All procedures for seismic design must be firmly based on a clear appreciation of the results of past destructive earthquakes and must adopt and realistically apply this knowledge. In this preliminary work, the following principles should be taken into account.

4.1.1. Measures for mitigating forces generated by earthquakes

Fundamentally, seismic forces can be minimized by:(1) Locating the centre of gravity of buildings as low as practicable(2) Selecting a plan and elevation that is as simple as practicable(3) Avoiding protruding sections as far as practicable(4) Making the centre of rigidity at the various elevations as close to the

centre of gravity as practical(5) Using antiseismic systems and devices.

4.1.2. Measures for reducing relative differential movements between structures

To reduce undesirable differential movements of structures consideration should be given to connecting these structures to the extent practicable with

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monolithic foundations. In locating the plant, significant differences in soil properties below the foundation should be avoided. If spread footings are used, adjacent foundation elements should be connected by horizontal stiff and strong girders. Design loads for such connecting elements should be chosen according to established practice [9, 28, 29],

4.1.3. Layout o f process equipment

The adoption of very simple layouts and connections to structures will improve the reliability of seismic analysis of piping and equipment appended to buildings.

4.2. Civil engineering structures

4.2.1. Experience from past earthquakes

Experience indicates that particular attention should be paid to the following points in the design and design review of structures:

(1) The adequacy of the supporting soil(2) The suitability of types of foundation supports or of different types

of foundations under interconnected structures (e.g. part of the foundation of one building being supported on piles and part being set directly on soil should be avoided)

(3) The correct arrangement of structural frames and shear walls and the achievement of a balanced weight distribution

(4) The possibility of collision between adjacent buildings as a consequence of their dynamic deformations (this phenomenon may also occur in weakly coupled structures)

(5) The adequacy of the connections of annexes and appendages to the main structure

(6) The need to ensure sufficient resistance of some structural elements — especially to shear forces

(7) The need to ensure sufficient ductility and avoid rapid failure by shear or compression, e.g. by ensuring that there is an adequate amount of reinforcement steel, in particular enough hoop ties for columns

(8) A proper arrangement and distribution of reinforcing bars. Too high a concentration of bars may cause the cracking of concrete along the lines of the bars

(9) The correct design of joints between structural elements. (For example, anchor lengths that are too short or an inadequate amount of transverse tie reinforcement must be avoided)

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(10) An evaluation of the bending moments arising from the vertical forces and the lateral deformation due to the effect of the earthquake on the structures (P - 5 effect) should be considered when large deformations are permitted

(11) Full consideration should be given to the effect of “non-structural” elements, like partition walls, on structural elements. Cracks have sometimes occurred at column beam connections as a result of inplane forces in a partition wall. This may particularly occur at the highest floor where the beneficial effect of the vertical loads is reduced

(12) In the evaluation of large integrated monolithic structures designed to resist differential earthquake motions, consideration should be given to the correct and detailed design of construction joints and to thermally induced stresses in such structures.

4.2.2. Recommendations for design

In implementing the seismic design of structures the following recommendations should be taken into account:

(1) Welds in steel structures important to safety that are particularly stressed by seismic loads should be made to a high standard, and strict quality control must be enforced

(2) The stiffness of a containment vessel is sometimes greater than that of the surrounding concrete structures; in which case, if they are interconnected or may interact, the earthquake loads of the concrete structures may be transferred to the containment vessel. The effects of this transfer of forces should be evaluated. Where, owing to the complexity of the interacting structures, it is too difficult to evaluate such forces, it is recommended to decouple, to the extent possible, such structures above the foundation level.

4.3. Earth structures

Experience gathered from past earthquakes indicates that for earth structures such as dams the seismic behaviour is controlled more by the type and densification of the soil than by the geometry. However, greater attention to the geometry of the soil structure is required when the static performance of the structure is being evaluated. Improvement of seismic behaviour in many cases can be achieved by a change of soil or by an increase in densification requirements or both. Sometimes, however, minor adjustments in the geometry of the soil structure may also be warranted.

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4.4. Piping and associated equipment

Experience of past earthquakes indicates that most failures of piping and associated equipment in non-nuclear installations were caused by design, manufacture or installation deficiencies. Attention should therefore be paid to the following recommendations.

4.4.1. Supports

With regard to equipment and piping supports:(1) Care should be taken in the design of these supports to assure that all

joints are designed to behave as assumed in the analysis of the supportand to transmit the full range of loads determined in the connected members. In particular, if integral supports are used, they should be designed and manufactured to minimize the danger that any unexpected failure or crack initiated in the supporting element propagates to the functional parts such as the pressurized shell and the primary piping.

(2) Care should be taken in the design of devices for anchoring equipment,e.g. the possible use of hook-shaped or end-plate anchor bolts, to ensure that all potential forces and moments are fully evaluated and that anchoring materials are suitable for their purpose.

4.4.2. Impro vement o f vibration resistance o f components

The following points should be taken into account to improve the resistance of components to vibration:

(1) The commonly accepted way to avoid unexpected failures from earthquake loads of equipment such as piping, instrumentation and core internals, is to design them to be as rigid as possible. In particular, equipment support legs should be cross-braced unless their dimensions warrant departure from this recommended practice. In most cases stiffness can be increased to avoid resonance; however, in some cases (e.g. for core internals), the vibration characteristics of the reactor building itself might be modified to prevent resonance effects. If systems are made stiffer for this purpose, particular attention should be paid to thermal stresses, other dynamic loads and differential motions of the supporting points because of the increase of stress caused by high rigidity.

(2) It is important to avoid, as far as is reasonably practicable, resonance of equipment such as piping, instrumentation and core internals with the frequency of the dominant modes of supporting structures. In

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some cases where the response of equipment, although significant, cannot practicably be reduced by other means, the damping of the system may be increased by suitable design modifications such as the use of dampers.

(3) To provide restraints for piping and components during earthquakes and at the same time allow freedom for thermal deformations, hydraulic or mechanical snubbers are extensively used in nuclear power plants. Experience has demonstrated that such devices should be analysed with particular care (e.g. for endurance of materials to radiation, temperature, humidity of the environment, for ageing of components such as seal gaskets).

(4) Particular attention should be paid to the possibility of collision between adjacent components, or between components and adjacent parts of a building, as a consequence of their dynamic displacement.

4.4.3. Possible modes o f failure o f new equipment

It is very important to recognize which part (or parts) of a piece of equipment is essential for its stability and functional capability. This means that a systematic analysis of the possible modes of failure related to earthquakes is important and has to be performed on new types of equipment for which there is no relevant experience concerning its earthquake resistance. Seismic qualification tests can identify the modes of failure and for this reason these tests are also recommended.

4.4.4. Considerations related to functional aspects for seismic design

The designer should have a thorough and practical understanding of the functional requirements and potential modes of failure of a mechanism when considering its seismic design.

4.5. Effects of vertical ground motion

Vertical motions produced by an earthquake have the effect of cyclically increasing and decreasing the vertical loads on structures. Critical conditions may also be reached during the phase in which load is decreased for those structures or pieces of equipment whose stability depends on frictional or confinement effects (e.g. non-anchored pieces of equipment, vertical reinforced concrete structural elements). Positive anchoring devices are to be preferred.

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5. SEISMIC TESTING AND QUALIFICATION5.1. Introduction

When, by analysis, the integrity or functional capability of an item cannot be demonstrated with a reasonable degree of confidence, an experimental test may be needed to prove or to assist in proving the corresponding item.

Among the items for which such a procedure should be used are control rod mechanisms, pumps, valves, relays, electrical equipment and instrumentation.

Seismic tests may be performed on the item itself or on full-scale models or, where appropriate, on reduced-scale models. However, for qualification purposes, the equipment itself or a full-scale model should be tested; if there is no other practical alternative the careful use of a reduced-scale model may be permitted. The tests include functional tests intended to ensure the continued adequate functioning of the equipment during and after an earthquake and integrity tests aimed at proving the mechanical strength of the equipment.

5.2. General concepts

A meaningful test performed with the purpose of assessing the integrity or functional capability of a system requires that the conditions existing for this system on the plant during an earthquake are correctly simulated or that any departure from these will not significantly influence the result. Among these conditions the most important are:

Mechanical boundary conditionsEnvironmental conditions (e.g. pressure, temperature)Operational conditions (if functional capability has to be assessed)Input motion.

The philosophy of the testing procedure is based on the submission of the device to conservatively derived test conditions in order to give effects at least as severe as those of the design conditions.

The functional and integrity testing of complex structures, such as control panels, may require initially the functional testing of individual components and then the testing of the full assembly, or of a suitable model of it, to establish that the forces exerted on components during an earthquake do not exceed limits derived from the initial tests on the components.

In establishing a qualification test, account should be taken of such effects as ageing, or other conditions which may cause deterioration or otherwise alter the characteristics of the item during its in-service life. In addition consideration should be given to the need for and possibility of in-service inspection.

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Tests can also be used to check a calculation or to validate an analytical model.

5.3. Full-scale testing

Full-scale testing of equipment or piping, and of their associated components, and to a limited extent also of structures, may be used to check calculations, to validate analytical models used or more directly to verify the integrity and, where necessary, the functional capability of the equipment and structures during an earthquake.

This full-scale testing can be done directly on the plant during the construction or before start-up, or in a laboratory with a shaking-table or other suitable devices.

5.3.1. Laboratory testing

5.3.1.1. Preliminary testing

Natural frequencies and other vibration characteristics of the components may generally be assessed by a preliminary test (for which a sinusoidal-shaped input can be used) during which any response parameter of interest is monitored (e.g. displacements, electrical signals).

5.3.1.2. Qualification testing

A sinusoidal motion can be used for qualification testing of stiff systems at a frequency significantly lower than the first natural frequency of the system and having the required maximum acceleration and number of cycles. Stiff systems are those systems having a lowest natural frequency which is higher than the frequency for which the response spectrum acceleration is sufficiently close to the maximum corresponding ground or floor accelerations.

When, on the contrary, the system has one or more mechanical resonances in the frequency range of interest, the test input motion used should have a response spectrum not less than the required design response spectrum. This can be achieved by using a natural or artificial time history (see sub-section 3.3.1.3) and, in particular, by a suitable combination of sinusoidal waves.

When the natural frequencies are well separated, independent tests can be made, e.g. with suitably scaled sinusoidal movements at the given natural frequency enveloped by a half sine [30] or other time envelope of interest.‘Suitably scaled’ means that the corresponding amplitude of the spectrum at the natural frequency is adequately higher than the amplitude of the required spectrum.

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However, it is recommended that tests be made with one or more natural or artificial time histories whose spectrum is not less than the required design response spectrum. Several different time histories may be used to overcome simulation deficiencies which could arise from the peculiarities of a single time history.

If random vibration input motion is used, detailed recommendations like those listed in section 3.10 of Ref. [20] should be followed. Input motion duration should be decided on the basis of anticipated earthquake duration (see IAEA Safety Series No. 50-SG-S 1) and number of possible after-shocks.In practice, however, usually no problem arises from this aspect of testing performance, because it is feasible to run conservatively prolonged tests.

The input motion should be applied to three perpendicular axes, unless symmetrical conditions exist. It may be necessary to give careful consideration to the application of simultaneous movements in the vertical and in one or even two horizontal directions.

For components whose functional capability has to be demonstrated by test under earthquake conditions, excitation in one direction at a time can be considered adequate when one of the following conditions applies:

The component design review and visual inspection or exploratory tests clearly demonstrate that the effects of excitation in the three directions on the component are sufficiently independent of each otherThe severity of shaking-table tests can be increased in such a way as to take into account the interaction effects from simultaneous excitation in the three directions. (For example, one can increase the amplitude excitation and vary the excitation directions).

5.3.2. Plant testing

The validity of some of the calculations can be checked experimentally during construction or during the start-up tests of nuclear power plants.

Because of the low level of excitation that can be used during these tests (natural excitation by wind and ground, functional excitation by pump operation or fluid flow, or mechanical excitation by shakers, blasts or other means), only the natural frequencies and possibly mode shapes of structures with a linear behaviour,can generally be checked.

5.4. Reduced-scale model testing

For structures or equipment that are too big to be full-scale tested, model tests can be made for checking the analytical models or, in those cases where there is no practical alternative, for directly qualifying the system.

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Great care must be taken in designing and performing model tests and in interpreting their results. The scale of models should not be less than a value dependent on the adequacy of the modelling technique to simulate correctly at that reduced scale the material structural and geometrical properties of the original. For example, ratios of 1/5 for concrete structures and 1/10 for steel are often used as reasonable limiting values at the present stage of development of the technique. The similarity law used should be clearly expressed with special attention given to the method used to correct the necessary discrepancy between the gravity and stiffness effects. The amplitude and frequency content of the input motion should be adequately scaled. Where possible the representativeness of the model should be verified by vibration testing of the component or structure, preferably after installation.

6. SEISMIC INSTRUMENTATION6.1. Introduction

Currently there are three main reasons for installing seismic instrumentation at a nuclear power plant. One reason is for recording the response to an earthquake and evaluating the need for post-earthquake inspection of certain items. Another is for collecting data on the behaviour of structures, systems and components of the nuclear power plant during earthquakes in order to verify the adequacy of the design analysis. A third reason, particularly in regions of high seismicity, is, by provision of strong motion sensors, for triggering alarms and in some countries for shutting down the reactor.

6.2. Instrumentation for evaluating the need for post-earthquake inspectionand analysisThe amount of instrumentation to be installed should be a function of the

degree of seismic activity and severity in the area. As a guideline for areas of moderate to high seismicity the following instrumentation can be used [31,32]:

(1) At least one triaxial strong motion recorder installed to register the free field motion time history.

(2) Triaxial strong motion recorders installed so as to record (a) the motion of the base mat of the reactor building, (b) the motion of one other category 1 structure and, if necessary, (c) the motion of the base mat of other important structures of the same category. The aim is to achieve an understanding of the response to an earthquake of all the different types of structures important to safety with different foundations.

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(3) Triaxial strong motion recorders installed on the most representative floors of some category 1 buildings in order to gain an understanding of the response of the different types of buildings important to safety.Consideration should be given to the installation of:

(4) Strong motion devices on some typical category 1 equipment and piping to obtain an understanding of the response of the main items important to safety of this type. While it is recognized that difficulties have been encountered in the past in finding reliable measuring devices that could continuously withstand the severe environmental conditions and permit frequent maintenance in certain parts of the plant, the coverage of these devices should be extended as far as practicable.

These instruments should be set to be triggered at levels of motion consistent with the seismicity of the area. Consideration should be given to having a common trigger system and a common time scanning device.

6.3. Instrumentation for collecting design check data

For nuclear power plants in areas of high seismicity it is very useful to verify the adequacy of the seismic design analysis. For this purpose instrumentation of the type described in sub-section 6.2 but possibly with a larger dynamic range and lower trigger setting may be installed.

6.4. Inspection after earthquake

After an earthquake all relevant data from seismic instrumentation shall be evaluated to determine the level of severity of that earthquake. If this exceeds the SI ground motion level, the plant should be adequately inspected.

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Appendix A METHODS OF SEISMIC ANALYSIS

To calculate the maximum relative displacements, relative velocities, absolute accelerations and maximum stresses during an earthquake, the following methods are in current use: the quasistatic method, the response spectrum method, and the time history method.

The quasistatic method can be used to obtain conservative results for simple systems, especially when they are rigid enough.

The standard dynamic methods for major structures, systems and components are the response spectrum and the time history methods.

In the response spectrum method, the maximum response of each mode is calculated by direct use of the design spectrum. Usually the maximum response is taken as the square root of the sum of the squares of each modal response.For closely spaced modal frequencies, a conservative procedure is to take the sum of the absolute value of each closely spaced modal response [33]. When the modal directions are different, this procedure may be too conservative, and suitable modification of the procedure may be considered.

In the time history method, the response of the system is calculated as a function of time directly or after a transformation to modal co-ordinates. The input motion may be natural or artificial time histories of acceleration at ground level or specific floor level, suitably chosen to represent the design response spectrum. Alternatively, the input time history can be represented by its Fourier transform and the solution worked out in the frequency domain.

When required, responses due to input acceleration in the different directions can be combined by taking the square root of the sum of the square of individual responses. When the time history method is used, an alternative procedure is to sum algebraically the response components as a function of time and then take the maximum of the combined response.

Appendix B MODELLING TECHNIQUES

B.l. Introduction

A nuclear power plant is a very complex system and a single complete model of the entire plant would be too cumbersome. Thus the first step in the analysis of a plant is to identify the sub-structures, by defining main systems and subsystems.

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Major structures that are considered in conjunction with foundation media in forming a soil-structure interaction model constitute the main systems. Other structures, systems and components constitute the sub-systems.

B.2. Decoupling criteria

Certain criteria have to be used to decide if a particular sub-system has to be taken into account in the analysis of the main system. Such decoupling criteria are obtained by putting some limits on the relative mass ratio between the sub-system and the supporting main system, limits which have to be more severe when there is a possibility of resonance between the sub-system and the main system (see section 3.7.2 of Ref. [20]).

If the decoupling criteria are not satisfied, a suitable model of the subsystem should be included in the main system model. For a sub-system having all its resonant frequencies (the flexibility of the support being taken into account) higher than the amplified frequencies (15 to 30 Hz for usual design earthquakes), only its mass needs to be included in the main system model.

For detailed analysis of sub-systems, if necessary, the seismic input can be obtained by the analysis of the main system. When there is no decoupling, it is essential for the model of the sub-system included in the analysis of the main system to have at least the same natural frequencies and modal masses as the detailed model of the sub-system in the frequency range of interest.

IB.3. Modelling of systems or sub-systems

The stiffness, mass and damping characteristics of the structural systems should be adequately incorporated in the analytical models.

More than one model might be needed when some doubt exists on the real behaviour of some part of the structure. Models might also be validated by testing in order to resolve possible uncertainties.

For the stiffness and mass characteristics, well known and well proven methods starting directly from use of the equation of continuum mechanics and material properties can be used. The three commonly used methods are described in sub-sections B.3.1 toB.3.3.

B.3.1. Lumped mass method

The lumped mass method is the most commonly used for the main systems.It consists in lumping the masses (and inertia moments, if necessary) at some adequately chosen points (e.g. floor levels in a building) and determining the stiffness (or flexibility) coefficients by a static study of all the single movements corresponding to the selected degrees of freedom. This method is described in various publications [9 ,34-36].

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Selection of an adequate number of degrees of freedom is often straightforward for technical reasons, as for example in the calculation of a conventional building with floors. In other cases, for shell or beam type structures, this selection is not evident and depends in fact on the number of modes needed for the seismic analysis. The requirement that the number of degrees of freedom be at least twice the number of modes is sometimes given; such a rule has to be used with care. (See item II 1 a (4) of section 3.7.2 of Ref. [20]).

B.3.2. Finite element method

The finite element method is described in detail in many publications (e.g. Refs [37,38]). Various types of elements can be used: beam elements (for frames, pipes or long slender cylindrical structures); axisymmetrical shell elements, which can account for non-axisymmetrical loadings or displacements by a Fourier representation on the azimuthal variable (for containment buildings, pressure vessels, or other axisymmetrical structures); shell and plate elements (for complex shell structures or box-type buildings); three-dimensional elements (for massive structures).

The mesh size to obtain correct results depends on the type of element used. A general requirement is that the shape of the deformed structure can be well represented by the set of elements chosen to model it.

B. 3.3. Transfer matrix method

The basis of the transfer matrix method is that for some structures (pipes, axisymmetrical shells and more generally monodimensionally modelled simple structures) it is possible to calculate analytically for each frequency the transfer matrix between a vector state (forces, moments, displacements and rotations) at a point and the vector state at the next point. Then, by successive matrix multiplication, it is possible to obtain the frequency-dependent matrix of the whole system, including boundary conditions. This allows the determination of the natural frequencies, mode shapes or response to sinusoidal inputs, or, by a Fourier transform, the response to more general inputs [18, 23]. While there is no mesh size problem, care must be exercised in the use of this method, because of possible accumulation of errors in the multiplication process.

B.4. Damping

For each of the models described in this Appendix, knowledge of the damping characteristics of the main systems and sub-systems is required. The way in which damping needs to be expressed depends on the method of solution used to evaluate the response of the model (see Appendix A). In the response

28


spectrum, or time history modal analysis methods, damping is most conveniently expressed in terms of modal damping coefficients. In the time history direct integration method, it is necessary to construct a damping matrix. The commonly used procedure is to express the damping matrix as a combination of the mass and stiffness matrices of the model as follows:

[C] = a[M ]+0[K ]

where [C], [M] and [K] are the damping, mass and stiffness matrices, respectively, of the model. The parameters a and |3 are determined by the requirement that the modal damping in the frequency range of interest is equal to, or less than, the prescribed modal damping. Other methods for obtaining the damping matrix are available [38].

B.5. Soil-structure interaction considerations

The basic procedures described in this Appendix regarding modelling are also used for soil-structure interaction considerations. These considerations are necessary to account for the interaction of the structure with the adjacent and underlying soils (and possibly with other nearby structures) during the postulated ground motions. The soil-structure system can be modelled by using for the soil a discrete parameter representation (springs and dashpots) or a finite element model.

For the discrete parameter representation, analytical methods (based on exact or approximate closed form solutions) for an elastic or viscoelastic halfspace (uniform or layered) are used to derive impedance functions. Equivalent springs and dashpots are thus deduced from these impedance functions and incorporated in the model of the structure. The response of the system can then be calculated by usual procedures. Embedment effects can be accounted for by modifying the impedance functions. Non-linearities in the soil can be accounted for by using equivalent linear properties and by iterating the solution until strain- compatible properties are obtained. Alternatively, the impedance functions can also be derived by using finite element representation for the soil. By using finite elements for the soil and finite elements (or lumped masses) for the structure the response of the soil-structure system can be calculated in one step. Non- linearities in the soil are accounted for by using strain-dependent properties.

These procedures are summarized in Ref. [39], which also includes guidelines on their usage. Additional details regarding the calculation of impedance functions can be found, for example, in Refs[40—54]. Additional details regarding the use of finite elements can be found, for example, in Refs [37,38, 41 ,42 ,55 -61],

2 9


B.6. Non-linear analysis o f structures

When the stresses in the structures are higher than the elastic limit of the material, or for other reasons (fretting, gaps), the stiffness matrix can be dependent on the amplitude of response.

For sufficiently weak non-linearities, the main effect is an increase of the energy losses which is taken into account by larger damping coefficients [9,62].

For higher non-linearities, it is necessary to take care of the change in stiffness which can significantly change the natural frequency of the system, and thus the amplitude of displacements.

Appendix C MATERIAL PROPERTY CHARACTERISTICS

C .l. Introduction

For a seismic analysis, data on the material properties of structures, components and systems and of soils under dynamic loading conditions are required.The most important parameters are those which define the damping and the stiffness characteristics.

C.l. Structures and components

Current practice in several countries includes the use of linear analysis procedures for structures and components (see Appendix A). For such analysis procedures, the basic stiffness properties required are Young’s modulus and Poisson’s ratio. Current codes and industrial guides in several Member States specify applicable values of Young’s modulus and Poisson’s ratio for various structural materials. For new material, appropriate tests are required to measure these properties.

The internal material damping of usual structural materials is generally very low. Effective damping in structures is due to a combination of energy losses (e.g. frictional, hysteretic and other possible non-linearities). This effective damping generally increases with the amplitude of motion. The usual practice is, therefore, to recommend the use of an overall modal structural damping coefficient, expressed in terms of a ratio to critical damping, for the various items of a nuclear power plant. Such coefficients can be specified for two or more ranges of stresses.

Values of damping coefficients applicable to various structures and components are contained in Refs [9] and [62]. Results of appropriate tests to evaluate damping coefficients for specific items can also be used for analysis.

30


For non-linear analyses of structures or components a more complete definition of the stress/strain relationships of the structural materials would be required. These relationships should be based on an appropriate testing of these materials.

C.3. Soils

Soils exhibit a strong non-linear behaviour under cyclic loading conditions. This basic material characteristic must, therefore, be taken into account when evaluating seismic response of soil deposits or earth structures (see Appendix D). Methods for measuring modulus (including field and laboratory procedures) and damping (laboratory procedures) of soils together with ranges of values of these characteristics for various types of soils, are presented in Ref. [63].

At each specific nuclear power plant site an adequate amount of field measurements (geophysical shear wave measurements in particular) and cyclic laboratory tests (particularly, resonant column tests and controlled-strain triaxial tests) should be conducted on representative samples of soils to develop the variations of moduli and damping as a function of strain level for these soils. The results of these field and laboratory tests (together with other field and laboratory data usually obtained for a nuclear power plant for purposes other than seismic analysis) would provide the necessary soil stress/strain relationships for use in seismic analysis.

The extent of field measurements and the number of laboratory tests should be sufficient to develop an adequate relationship between these properties and strain for all the major soil layers to a depth of approximately 50 to 100 m at the site. The actual details of field and laboratory programmes, however, should be decided on a case-by-case basis.

Appendix D SEISMIC RESPONSE OF SOIL

DEPOSITS AND EARTH STRUCTURESD .l. Introduction

Evaluation of the seismic response of the soil deposit at a nuclear plant site is required to ensure that instability in the foundation or surrounding soils does not occur during or after the postulated design earthquake. This evaluation must be made both in the free field and adjacent to and beneath the plant structures. In addition, the stability of earth structures (e.g. earth dams, ponds, man-made or natural slopes) must be evaluated. This Appendix summarizes available procedures that may be used to calculate the response of such deposits

31


and earth structures during the postulated seismic event. Procedures for evaluating stability are discussed in Appendices E and F.

The procedures outlined in this Appendix should be considered as part of a continuing development of the technique. Therefore, as in all engineering approaches, the use of these procedures should be coupled with a careful understanding of the basic assumptions and limitations inherent in any method of analysis.

Full treatment of the seismic waves arriving at a site is an extremely complex matter and is beyond the current state of knowledge. Usually, several simplifying assumptions are made to provide mathematically tractable solutions. Two basic solution techniques are at present available: (1) body-wave solutions (shear and compression), and (2) surface-wave solutions (Love and Raleigh).The body-wave solutions, which have been correlated with observed behaviour, have been commonly used in practice for assessing the seismic response of soil deposits and earth structures. The use of these solutions is justified on the basis that they constitute a reasonable engineering approximation to an extremely complex problem and also because the body waves account for a major part of the destructive nature of seismic motions.

D.2. Body-wave solutions

Body-wave solutions, which have been employed from the early 1900s, have been modified in the past fifteen or so years to incorporate more correctly the stress/strain behaviour of soils under cyclic loading conditions. Such solutions are available for one, two- and three-dimensional conditions.

Deposits located away from plant structures and consisting essentially of extensive horizontal soil layers may be considered as semi-infinite layers and can be treated as one-dimensional shear beams. Methods of solution for a shear beam representation are summarized in sub-section D.2.1.

Deposits that have significant geometric variations from those considered above (e.g. significantly sloping underlying rock boundaries) cannot be treated as semi-infinite layers, and the two- or three-dimensional effects must be taken into consideration. The two- or three-dimensional effects must also be taken into consideration for deposits adjacent to plant structures and for earth structures; the methods of solution for these cases are summarized in subsection D.2.2.

D.2.1. One-dimensional solutions

The seismic response of a shear beam representation of a soil deposit may be calculated by several procedures. Each procedure must be capable of taking into account the non-linear behaviour of soils under cyclic loading conditions.

3 2


Except for very soft soils, the equivalent linear approach [64] is considered acceptable to represent this non-linear behaviour.

(1) Lumped mass method. This method has been used with either a bilinear representation (see, for example, Refs [65,66]) of the soil stress/strain characteristics or an equivalent linear representation (see, for example, Ref. [66]). The solution is worked out in the time domain.

(2) Method o f characteristics. This method (see, for example, Ref. [67]) uses a non-linear representation of the soil stress/strain characteristics. The solution is worked out in the time domain.

(3) Complex modulus method. This method (see, for example, Ref. [68]) is also referred to as the wave-propagation method; its solution is worked out in the frequency domain but the final output may be transformed into the time domain. The non-linear soil behaviour is accounted for by the equivalent linear approach. This method has been widely used in practice at nuclear power plant sites.

(4) Finite element method. This method has also been used for the evaluation of the seismic response of a semi-infinite layer. The solution can be worked out either in the time domain (see, for example, Ref. [55]) or in the frequency domain (see, for example, Ref. [56]). The non-linear soil behaviour is accounted for by the equivalent linear approach.

When methods (3) and (4) are used, engineering judgement should be exercised in interpreting the results.

Particular techniques have to be used for specifying the input. (1) Normally the input motion to the shear beam representing the semi-infinite layer is specified at the base of the layer, where it is considered to be rock or rock-like material (for this purpose rock-like material is defined as rock or soil having an in-situ shear wave velocity greater than approximately 700 m/s. (2) Solutions worked out in the frequency domain allow for specifying the input motion at any point in the soil deposit. When the input motion is, for example, specified at the ground surface, the response of the deposit can then be computed utilizing this feature of these solutions. Motion at the base of the deposit can then be computed and used as input in other analyses.

D.2.2. Two-or three-dimensional solutions

The finite element method has been widely used for analysing the seismic response of soil deposits and earth structures requiring two- or three-dimensional solutions. In most situations, a two-dimensional solution is adequate. The solution can be worked out in the time domain [55] or in the frequency domain [56]. The non-linear soil behaviour is accounted for by the equivalent linear

3 3


approach. Other methods, such as the method of characteristics and the lumped mass method, have also been used for two-dimensional analyses [67,69].

The solution algorithm outlined in Ref. [55] has been commonly used for analysis of earth dams and slopes. The behaviour of the soils adjacent to and beneath structures has normally been evaluated by using the solution algorithm outlined in Ref. [56].

D.3. Surface-wave solutions

Surface-wave solutions have long been used in seismological evaluations and also for evaluating the nature of ground motions in soil deposits [70—73], but are not commonly used in practice. Studies and investigations on applications for these solutions are continuing.

Appendix E LIQUEFACTION AND GROUND FAILURE

E .l. Introduction

Liquefaction and consequent ground failure resulting from earthquakes have been the cause of significant or catastrophic damage. Examples of damage or ground failure caused by such liquefaction include:

(1) Settling and tilting of buildings [74—76](2) Floating of buried structures [77](3) Major landslides [78—81 ](4) Lateral movement of bridge supports [79](5) Failure or significant lateral movement of waterfront-retaining

structures [82](6) Failure or significant lateral deformations of dams and embankments

[80,81].

Therefore, potentially liquefiable soil layers at a nuclear power plant site shall be identified, their characteristics evaluated, and the potential and consequences of their liquefaction during the postulated seismic event assessed. Appropriate field and laboratory investigations are required to identify and evaluate the static and dynamic characteristics of these soil layers; similar investigations should be made on fill material that may be used for the support or embedment of seismic category 1 structures or components.

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E.2. Methods of evaluation

The liquefaction potential at a site can be evaluated by using either an empirical approach or an analytical approach coupled with appropriate laboratory tests [83]. Each approach requires appropriate field tests to be conducted.

A common empirical approach is based on the correlation of observations from past earthquakes for a wide range of conditions [83] and the use of a simplified procedure [84] for calculating the level of stresses induced by the postulated design earthquake. Other empirical approaches (see, for example,Refs [74,85]), also relying on observations from past earthquakes, are available but are valid for the more limited range of site conditions and seismic excitation upon which they are based.

The analytical evaluation of liquefaction potential comprises the following steps [40, 84]:

(1) Calculation of the stresses induced by the design earthquakes (the procedures summarized in Appendix D may be used). These stresses, which have non-uniform amplitudes as a function of time, must be converted to an equivalent number of uniform cycles of shear stress [86,87],

(2) Establishment of the cyclic strength characteristics of the soil at each layer. Field data, such as penetrometer results and standard penetration blow count, may be used as a basis for estimating cyclic strength. Where appropriate, a cyclic testing programme [88] on representative samples should also be conducted to establish the cyclic strength. Details regarding the appropriate utilization of these field and/or laboratory tests are discussed in Ref. [89].

(3) Comparison of the available cyclic strength data with the estimated stresses induced by the earthquake. From the calculations it should result that a sufficient margin of safety exists against the development of liquefaction in the critical soil layers and fill.

It is recommended that, for sites in high seismic regions, both the analytical and, as a check, the empirical approach be used to the extent possible. For sites of relatively low seismicity, the empirical approach is generally sufficient. Note that the use of detailed geological information and prior earthquake history of the region can be extremely useful in the final evaluation. The final determination of liquefaction potential often requires considerable judgment based on a synthesis of all information available.

35


E.3. Factors of safety

A factor of safety against the occurrence of liquefaction is computed as the ratio of the applicable available cyclic strength (based on the stress required to cause a specified level of strain) to the induced stress. This ratio should be greater than unity in all critical soil layers and fill. The minimum acceptable value of this safety factor should be decided on a case-by-case basis. Generally, a minimum safety factor of about 1.5 should be used. However, a substantially lower value can be accepted if warranted by the details of the geological, seismological and soil evaluations. In deciding a minimum acceptable value for a specific site, the following factors should be taken into account: the selected failure criterion used in evaluating the liquefaction, the degree of conservatism incorporated into the determination of the pertinent seismological and site characteristics, and the consequences of liquefaction on the safety of the plant structures and components.

Appendix F SLOPE STABILITY

F .l. Introduction

Slope failures have occurred in several historic earthquakes. Earth and rock slopes, both natural and man-made (e.g. cuts, fills, embankments, dams), shall therefore be adequately evaluated. Appropriate field and laboratory investigations are required to determine:

(1) The extent and distribution of soil layers (or rock formations for rock slopes) within, adjacent to, and beneath the slope

(2) The geometry of the slope(3) The static and dynamic characteristics of the soils (rock)(4) The water levels and fluctuations of the water table.

For rock slopes, information on layer formation and zones of fracture (e.g. orientation, localized weathering) should also be gathered.

F.2. Methods of evaluation

The seismic stability of slopes is normally evaluated by either the pseudostatic method or the dynamic method of analysis.

36


F.2.1. Pseudo-static method

In the pseudo-static method the stability of the slope is assessed by computing a factor of safety against sliding. A conventional method of slices [12] is used.The driving forces consist of gravity, surcharge and earthquake loads. The earthquake load is represented by a seismic coefficient and is assumed to act at the centroid of the potential sliding mass. Determination of the resisting forces is based on the static strength of the soils computed along the potential sliding surfaces.

F.2.2. Dynamic method

The dynamic method is based on the use of dynamic response analysis incorporating soil strength characteristics determined by laboratory cyclic tests [80, 81, 90]. The dynamic response analysis is done by using the two- dimensional method outlined in Appendix D. A model of the slope and its foundation soils is constructed using the finite element method. The input to this model is a time history of motion, compatible with the specified ground motion at the plant site, and having either its horizontal component or its horizontal plus vertical components simultaneously applied at the base of the model. The results of the response evaluation provide the time histories of induced stresses throughout the model.

These stresses are to be compared with the cyclic test results. Because cyclic strength depends on the initial stresses, the static stresses within the slope and its foundation soils (i.e. stresses existing before the earthquake) must be computed; this computation is done using static finite element procedures [90].

The local factor of safety is defined as the ratio of the cyclic strength stress limit to the induced stress and is computed at various locations throughout the model. The stability of the slope is then assessed by examining the range and variations of the values of this local factor of safety.

Procedures also exist for computing the amount of potential deformation of the slope using the results of these dynamic analyses.

F. 2.3. Other methods

Procedures based on the concept of yielding acceleration [91 ] can also be used to calculate the potential movement of slopes.

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Annex I SLOSHING EFFECTS IN WATER POOLS

1.1. Concept

The oscillation of a free liquid surface [25] has been called “sloshing”. This phenomenon is very similar to the seiches of a lake or basin and it can be treated by the theory of the potential. For the seismic design only the fundamental frequency is important. Its natural period is about one second for a cylindrical vessel whose diameter is approximately one metre, while that of a 100-m-dia. vessel is still less than 11s. So one can say that the natural period of sloshing motion lies in the range of 1 s to 10s for the cases relevant for seismic design.

1.2. Theory

To evaluate this motion the concept of “free water” and “fixed water” is generally used [26]. This sub-division derives from the fact that only the semi- spherical or cylindrical part of water having as diameter its free surface average dimension is moving in the case of an axisymmetrical or rectangular vessel. Therefore, if the depth is greater than one half of the diameter, the natural period is only a function of the diameter. The response of this fixed water is the same as that of a dead mass and the response of the free water is related to the ground motion displacement. The effect of the rigidity of the supporting shell is usually low, because of the separation of its natural period. Even if there is an inner cylinder the natural period is mainly a function of the outer diameter. However, the vibrational response of certain vessels may be affected in various ways by the contained water.

1.3. Design

For the response analysis, the assumption of three-wave input [25] could be made. This method assumes that the input consists of only three sinusoidal waves, the period of each being equal to the natural period of the sloshing movement.But it does not take into account the possibility of resonance of the upper ground layers with the natural frequency of the vessel. If this possibility has to be investigated because of some particular importance of sloshing phenomena for the safety of the plant, the predominant period of ground motion can be estimated on the basis of local site characteristics and geology. If this period coincides with the period of sloshing, the number of sinusoidal waves of the

3 8


input would need-to be increased to five or more according to the natural frequency and earthquake duration.

For smaller earthquakes, the technique of theoretical seismograms produced by numerical computation according to a wave propagation theory (under the assumption of a certain length of fault, depth of fault, amount of differential movement of fault and velocity of crack development) may be used [92].

1.4. Resonance effects

Sometimes resonance phenomena have been observed and damage to fuel storage and underground water reservoirs has been reported. The ground motion of high magnitude earthquakes sometimes reaches total displacement values up to one metre of single amplitude. If the sloshing resonates with the ground motion its wave height can easily reach several metres.

1.5. Damping ratio

The damping ratio is extremely low, approximately 0.1% if the surface of the free water is not disturbed. It can roughly be said that if the vertical component of the acceleration at the free water surface is over 1.0 g then waves at the free surface would be generated. Therefore non-linear damping effects should be considered in the response.

1.6. Additional comments

The sloshing phenomena may cause high hydrodynamic pressures on the vessel walls and structures either contained or submerged in water, so attention should be paid to them, especially in areas where earthquakes of magnitude higher than 8 can be expected, even if the related epicentre distance may be larger than 100 km.

The input displacement and response spectrum for estimating sloshing movement cannot as yet be clearly defined because of a lack of knowledge of the ground motions in the range of periods from 2 s to 20 s. Some data measured in 1923 in Tokyo showed that peak-to-peak ground displacements can reach values of up to one metre for earthquakes of magnitude close to 8. Analytical evaluations performed on the basis of fault movement and wave propagation models [92] are in reasonable agreement with the measured values.

Some other data obtained by integrating strong motion accelograms show that peak-to-peak displacements reaching one metre can also occur [93] for earthquakes of magnitude less than 8.

Refinements in the techniques for estimating displacement due to a certain earthquake are in progress and some correlations with observed data have been

3 9


made [73, 92]; more work is still required to arrive at general relationships for use in design, and no generally agreed technique has been established. The criterion that consists o f assuming the figure of one metre for single-amplitude and long-period ground motions caused by an earthquake, may have some justification. Such an earthquake may be different from earthquakes causing the SI and S2 ground motions, because the lower frequency components o f ground motion in the range of 2 s to 20 s are more relevant than those of the shorter period range. Therefore, the effects of sloshing due to an earthquake of magnitude greater than 8 at a distance larger than 100 km may become stronger than those of earthquakes causing the SI and S2 ground motions.

Annex II QUALIFICATION TESTING

BY MEANS OF THE TRANSPORT VEHICLE

In some instances it may be possible to perform a qualification test, to the satisfaction o f the regulatory body, by monitoring the dynamic loads induced in items during the shipment. In such instances the transport vehicle at the point o f attachment as well as the item should be instrumented to record both input and response motions. The item should be mounted in the transportation mode in a manner analogous to the manner in which it will be mounted in the plant.

40


REFERENCES

R eferences with an asterisk may be used as a general bibliography for the topic covered in this

Safety Guide. Those num bered 94 to 1 0 8 are not specifically referred to in the text.

[1] U.S. ATOMIC ENERGY COMMISSION, “Design limits and loading combinations for seismic category 1 fluid system components”, US Atomic Energy Commission (now US Nuclear Regulatory Commission), Regulatory Guide 1.48 (1973).

*[2] UDOGUCHI, T., OHSAKI, Y., SHIBATA, H., “The aseismic design of nuclear powerplants in Japan”, Peaceful Uses of Atomic Energy (Proc. Fourth Int. Conf. Geneva, 1971) Vol. 3, UN, New York and IAEA, Vienna (1972) p. 297.

[3] KERNTECHNISCHER AUSSCHUSS, Design of Nuclear Power Plants Against Seismic Events, Part 1: Basic principles, Report KTA 2201, Kerntechnischer Ausschuss, KTA- Geschaftsstelle beim Institut fur Reaktorsicherheit des technischen Uberwachungs- Verein eV,Koln, FRG(1975).

[4] ROESSET, J.M., WHITMAN, R.V., DOBRY, R., “Modal analysis for structures with foundations interaction”, J. Struct. Div., Am. Soc. Civ. Eng. 99 ST3 (1973) 389.

[5] BECHTEL POWER CORPORATION, Topical Report: Seismic Analyses of Structures and Equipment for Nuclear Power Plants; Revision 3, Report BC-TOP-4-A, Bechtel Power Corporation, San Francisco, California (1974).

[6] INSTITUT FUR BAUTECHNIK, Richtlinien fur die Bemessung von Stahlbetonbauteilen von Kernkraftwerken fur aussergewohnliche aussere Belastungen (Erdbeben, aussere Explosionen, Flugzeugabsturz),Institut fur Bautechnik, Berlin, Edition (Fassung) July1974.

[7] SCOTT, R.F., “Earthquake induced earth pressures on retaining walls”, in: Proc. Fifth World Conf. Earthquake Engineering, Rome, Italy, 1973.

[8] SEED, H.B., WHITMAN, R.V., “Design of earth retaining structures for dynamic loads”, in: Proc. Specialty Conf. Lateral Stresses in the Ground and Design of Earth Retaining Structures, Soil Mechanics and Foundations Division, American Society of Civil Engineers, June 1970.

*[9] NEWMARK, N.M., ROSENBLUETH, E., Fundamentals of Earthquake Engineering, Prentice-Hall, Englewood Cliffs, N.J., USA (1971).

[10] SILVER, M.L., SEED, H.B., Deformation characteristics of sands under cyclic loading,J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 97 SM8 (1971) 1081.

[11] BROWN, P.T., “Influence of soil inhomogeneity on raft behaviour”, Soils and Foundations (Japan) 14 1 (March 1974).

[12] CORPS OF ENGINEERS, Engineering and Design Stability of Earth and Rock-Fill Dams, Manual N. EM 1110-2-1902, Office of the Chief of Engineers, Dept, of the Army, USA (1970).

[13] REDDY, A.S., SRINIVASAN, R.J., “Bearing capacity of footings on clays”, Soils and Foundations (Japan) I I 3 (Sept. 1971).

[14] DUFF, C.G., “Simplified method for development of earthquake ground and floor response spectra for nuclear power plant design”, in: Second Canadian Conf. Earthquake Engineering, Hamilton, Ontario, Canada, 1975.

[15] BIGGS, J.M., “Seismic response spectra for equipment design in nuclear power plants”, First Int. Conf. Structural Mechanics in Reactor Technology, Berlin, Sept. 1971,Paper K4/7.

[16] STEIGELMANN, W.H., “Seismic qualification testing of class I electric equipment”,First Int. Conf. Structural Mechanics in Reactor Technology, Berlin, Sept. 1971,Paper K7/1.

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[17] MORRONE, A., Seismic vibration testing with sine beat, Nucl. Eng. Des. 24 3 (1973) 344.[18] SHIBATA, H., WATARI, A., SATO, H., SHIGETA, T., SHIMIZU, N., SUZUKI, K.,

FUGII, S., IGUCHI, M., KIYAMA, Y., OKUMURA, A., Development of aseismic design of piping, vessels and equipment in nuclear facilities, Nucl. Eng. Des. 22 2 (1972) 247.

[19] SINGH, M.P., SINGH, S., CHU, S.L., “Stochastic concepts in seismic design of nuclear power plants”, Second Int. Conf. Structural Mechanics in Reactor Technology, Berlin, Sept. 1973, Paper K l/4 .

[20] U.S. NUCLEAR REGULATORY COMMISSION, USNRC Standard Review Plan (1975).[21] U.S. NUCLEAR REGULATORY COMMISSION, Development of Floor Design

Response Spectra for Seismic Design of Floor-Supported Equipment or Components, USNRC, Regulatory Guide 1.122, Revision 1 (Feb. 1978).

[22] TSAI, N.C., Transformation of time axes of accelerograms, J. Eng. Mech. Div., Am.Soc. Civ. Eng. 95 EM3 (1969) 807.

*[23] PESTEL, E.C., LECKIE, F.A., Matrix Methods in Elastomechanics, McGraw-Hill, New York (1963).

[24] YAMAMURO, M., SHINKAI, H., KUROGOCHI, T., SHIBATA, H., SHIGETA, T., “Experimental study on the response of a model system to natural earthquakes in the field and on a shaking table”, in: Second Int. Conf. Structural Mechanics in Reactor Technology, Berlin, Sept. 1973, Paper K5/5.

[25] SOGABE, K., On sloshing effects of liquid in cylindrical and spherical vessels during a strong earthquake, Bull, of Earthquake Resistant Structure Research Center No. 8, University of Tokyo (1974) p. 18.

*[26] U.S. ATOMIC ENERGY COMMISSION, Nuclear Reactors and Earthquakes, USAEC (now U.S. Nuclear Regulatory Commission), Report TID 7024 (1969).

[27] SASAKI, Youichi, SASAKI, Ykio, HAYASHI, Takuro, “An analysis on the dynamic behaviour of boiling water reactor core”, in: Proc. Specialist Meeting Anti-Seismic Design of Nuclear Installations, Dec. 1975, OECD/NEA.

[28] AMERICAN CONCRETE INSTITUTE, Standard Building Code Requirements for Reinforced Concrete, Report ACI-3/8-71, American Concrete Institute (1970).

[29] AMERICAN INSTITUTE OF STEEL CONSTRUCTION, Specification for the Design, Fabrication and Erection of Structural Steel for Building, AISC (1969).

[30] INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS, Recommended Practices for Seismic Qualifications of Class IE Equipment for Nuclear Power Generating Stations, IEEE Std. 344-1975 (1975).

[31 ] U.S. ATOMIC ENERGY COMMISSION, Instrumentation for Earthquakes, USAEC (now U.S. Nuclear Regulatory Commission), Regulatory Guide 1.12, Revision 1 (April 1974).

[32] AMERICAN NUCLEAR SOCIETY, Earthquake Instrumentation Criteria for Nuclear Power Plants, ANS Standards Committee, ANS-2 Sub-Committee, Revision 1, Draft 1 (Sept. 1976).

[33] U.S. NUCLEAR REGULATORY COMMISSION, Combining Modal Responses and Spatial Components in Seismic Response Analysis, USNRC, Regulatory Guide 1.92, Revision 1 (Feb. 1976).

*[34] WIEGEL, R.L., Earthquake Engineering, Prentice-Hall, Englewood Cliffs, N.J., USA(1970).

*[35] HANSEN, R.J., Seismic Design for Nuclear Power Plants, The MIT Press, Cambridge, Mass. and London (1970).

*[36] HISADA, T., AKINO, K., IWATA, T., KAWAGUCHI, O., OHMATSUZAWA, K.,SATO, H., SHIBATA, M., SONOBE, Y., TAJIMI, H., Philosophy and practice of the aseismic design of nuclear power plants - Summary of the Guidelines in Japan,Nucl. Eng. Des. 20 2 (1972) 339.

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ZIENKIEWICZ, O.C., CHEUNG, Y.K., Finite Element Method in Structural and Continuum Mechanics, McGraw-Hill, New York (1967).CLOUGH, R.W., BATHE, K.J., Finite Element Analysis of Dynamic Response (ODEN, J.T., Ed.),University of Alabama (1970).AMERICAN SOCIETY OF CIVIL ENGINEERS, Analyses of Soil-Structure Interaction Effects for Nuclear Power Plants, Report by Ad Hoc Group on Soil-Structure Interaction, Nuclear Structures and Material Committee of the Structural Division of ASCE; presented at the Specialty Conference on Nuclear Plants, New Orleans, 1975.TSAI, N.C., NIEHOFF, D., SWATTA, M., HADJIAN, A.E., The use of frequency independent soil-structure interaction parameters, Nucl. Eng. Des. 31 2 (1974) 168. KAUSEL, E., ROESSET, J.M., Soil-structure interaction problems for nuclear containment structures, American Society of Civil Engineering, Power Division Specialty Conference, Boulder, Colorado, Aug. 1974.LYSMER, J., KUHLEMEYER, R.L., A finite dynamic model for infinite media, J. Eng. Mech. Div., Am. Soc. Civ. Eng. 95 EM4 (1969) 859.RAINER, J.H., “Simplified analysis and parameter study of dynamic structure-ground interaction” , in: Second Canadian Conf. Earthquake Engineering, McMaster University, June 1975.VELETSOS, A.S., WEI, Y.T., Lateral and rocking vibration of footing, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 97 SM9 (1971) 1227.ARNOLD, R.N., BYCROFT, G.N., WARBURTON, G.B., Forced vibrations of a body on a infinite elastic solid, J. Appl. Mech. 22 3 (1955) 391.BYCROFT, G.N., Forced vibrations of a rigid circular plate on a semi-infinite elastic space and on an elastic stratum, Philos. Trans. R. Soc. London, Ser. A 248 (1956) 493. THOMSON, W.T., KOBORI, T., Dynamical impliance of rectangular foundations on an elastic half space, J. Appl. Mech. (Dec. 1963) 579.KOBORI, T., MINAI, R., KUSAKABE, K., “Dynamical ground compliance of rectangular foundation”, Proc. Sixteenth Japan National Congress for Applied Mechanics, 1966, p. 301.KOBORI, T., SUZUKI, T., “Foundation vibration of a viscoelastic multi-layered medium”, Proc. Third Japan Earthquake Engineering Symposium, Tokyo, Nov. 1970, p. 493.KOBORI, T., MINAI, R., “Dynamical interaction of multiple structural systems on a soil medium, in: Proc. Fifth World Conf. Earthquake Engineering, Rome, Italy, 1973. KOBORI, T., SUZUKI, T., “Vibrations of structures embedded in a visco-elastic layered medium”, Proc. Fourth Japan Earthquake Engineering Symp., Tokyo, Nov.1975, p. 335.TAJIMI, H., “Dynamic analysis of a structure embedded in an elastic stratum ”, in: Proc. Fourth World Conf. Earthquake Engineering, Santiago, Chile, Vol. 3 A-6 (1969) p. 53. BIGGS, J.M., WHITMAN, R.V., “Soil structure interaction in nuclear power plants”,Proc. Third Japan Earthquake Engineering Symp. Tokyo, Nov. 1970, p. 89.MIZUNO, N., TSUSHIMA, T., “Experimental and analytical studies for a BWR nuclear reactor building, evaluation of soil-structure interaction behaviour”, Trans. Third International Conf. Structural Mechanics in Reactor Technology, London, Sept. 1975,Vol. 4, Part K.IDRISS, I.M., LYSMER, J., HWANG, R., SEED, H.B., Quad-4, A Computer Program for Evaluating the Seismic Response of Soil Structures by Variable Damping Finite Element Procedures, Report EERC 73-16, Earthquake Engineering Research Center, University of California, Berkeley, California (1973).

43


[56] LYSMER, J., UDAKA, T., SEED, H.B., HWANG, R., LUSH - A Computer Program for Complex Response Analysis of Soil-Structure Systems, Report EERC 74-4, Earthquake Engineering Research Center, University of California, Berkeley, California (1974).

[57] SEED, H.B., LYSMER, J., HWANG, R., “Soil-structure interaction analyses for seismic response”, J. Geotech. Eng. Div., Am. Soc. Civ. Eng. 101 SM4 (1975).

[58] BERGER, E., LYSMER, J., SEED, H.B., “Comparison of plane strain and axisymmetric soil-structure interaction analysis”, Second ASCE Specialty Conf. Structural Design of Nuclear Plant Facilities, New Orleans, Dec. 1975, Vol. 1 A, p. 809.

[59] HWANG, R.N., LYSMER, J., BERGER, E., “A simplified three-dimensional soil-structure interaction study”, Second ASCE Specialty Conf. Structural Design of Nuclear Power Plant Facilities, New Orleans, Dec. 1975, Vol. 1 A, p. 786.

[60] IDRISS, I.M., SADIGH, K., “SSI analyses for nuclear plant structures”, in: Proc. ASCE Annual Convention, Denver, 1975.

[61] LYSMER, J., DRAKE, L.A., “ A finite element method for seismology”, Methods in Computational Physics (ADLER, B., FERNBACK, S., BOLT, B.A., Eds), Academic Press, Vol. II, Chapter 4 (1972) p. 181.

[62] U.S. ATOMIC ENERGY COMMISSION, Damping Values for Seismic Design of Nuclear Power Plants, USAEC (now U.S. Nuclear Regulatory Commission), Regulatory Guide 1.61 (1973).

[63] SEED, H.B., IDRISS, I.M., Soil Moduli and Damping Factors for Dynamic Response Analysis, Report EERC 70-10, Earthquake Engineering Research Center, University of California, Berkeley, California (1970).

[64] IDRISS, I.M., DEZFULIAN, H., SEED, H.B., Computer Programme for Evaluating the Seismic Response of Soil Deposits with Non-Linear Characteristic with Equivalent Linear Procedures for Representation of Non-Linear Behaviour of Soils”, Research Report, University of California, Berkeley, California (1969).

[65] PENZIEN, J., SCHEFFEY, C.F., PARMELEE, R.A., Seismic analysis of bridges on long piles, J. Eng. Mech. Div., Am. Soc. Civ. Eng. 90 EM3 (1974).

[66] IDRISS, I.M., SEED, H.B., Seismic response of horizontal soil layers, J. Soil Found.Div., Am. Soc. Civ. Eng. 94 SM4 (1968) 1003.

[67] STREETER, V.L., WYLIE, E.B., RICHARD, F.E., Soil motion computations by characteristics method, J. Geotech. Eng. Div., Am. Soc. Civ. Eng. 100 GT3 (1974) 247.

[68] SCHNABEL, P.B., LYSMER, J., SEED, H.B., SHAKE - A Computer Program for Earthquake Response Analysis of Horizontally Layered Sites, Report EERC 72-12, Earthquake Engineering Research Center, Univ. of California, Berkeley, California (1972).

[69] KEIGHTLEY, W.O., A Dynamic Investigation of Bouquet Canyon Dam, Earthquake Engineering Research Lab., California Institute of Technology, Pasadena, California (1964).

[70] DRAKE, L.A., MAL, A.K., Love and Rayleigh waves in the San Fernando Valley,Bull. Seismol. Soc. Am. 62(1972) 1673.

[71] LYSMER, J., DRAKE, L.A., The propagation of love waves across non-horizontally layered structures, Bull. Seismol. Soc. Am. 61 (1971) 1233.

[72] MURPHY, J.R., DAVIS, A.H., Amplification of Rayleigh Waves in a Surface Layer of Variable Thickness, AEC Report NVA-1163-175 (1969).

[73] BOORE, D.M., Finite Difference Solutions to the Equations of Elastic Wave-Propa- gation, with Application to Love Waves over Dipping Interfaces, Ph. D. dissertation, Massachusetts Inst, of Tech., Cambridge (USA) (1970).

*[74] OHSAKI, Y., Niigata earthquake, 1964: building damage and soil conditions, Soils and Foundations (Japan) 6 2 (1966).

44


[75] SEED, H.B., IDRISS, I.M., Analysis of soil liquefaction, Niigata earthquake, J. Soil.Mech. Found. Div., Am. Soc. Civ. Eng. 93 SM3 (1967) 83.

*[76] FUKUOKA, M., Damage to civil engineering structures, Soils and Foundations (Japan)6 2 (1966).

*[77] YOUD, T.L., “Landslides in vicinity of Van Norman Lakes in the San Fernando Earthquake”, U.S. Geological Survey, Professional Paper No. 733, U.S. Dept of Interior(1971) p. 105.

*[78] SEED, H.B., Landslides during earthquakes due to liquefaction, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 94 SM5 (1968) 1053.

*[79] COULTER, H.W., MIGLIACCIO, R.R., “Effects of the Earthquake of March 27, 1964 at Valdez, Alaska” US Geological Survey, Professional Paper No. 542-C, U.S. Dept, of Interior (1966).

*[80] SEED, H.B., LEE, K.L., IDRISS, I.M., Analysis of Sheffield Dam failure, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 95 SM6 (1969).

*[81] SEED, H.B., LEE, K.L., IDRISS, I.M., MAKDISI, F., Analysis of the Slides in the San Fernando Dams during the Earthquake of February 9, 1971, Report EERC 73-2, Earthquake Engineering Research Center, University of California, Berkeley,California (1973).

*[82] HAYASHI, S., KUBO, K., NAKASE, A., Damage to harbour structures by the Niigata earthquake, Soils and Foundations (Japan) 6 1 (1966).

[83] SEED, H.B., “Evaluation of soil liquefaction effects on level ground during earthquakes” , State-of-the art paper presented at Symp. Soil Liquefaction, American Society of Civil Engineering National Convention, Philadelphia,Oct. 1976.

[84] SEED, H.B., IDRISS, I.M., A simplified procedure for evaluating soil liquefaction potential, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 97 SM9 (1971) 1249.

[85] KISHIDA, H., Characteristics of liquefied sands during Mino-Owari, Tohnankai and Fukui earthquakes, Soils and Foundations (Japan) 9 1 (1969).

[86] SEED, H.B., IDRISS, I.M., MAKDISI, F.I., BANERJEE, N., Representation of Irregular Stress Time Histories by Equivalent Uniform Stress Series in Liquefaction Analyses, Report EERC 75-20, Earthquake Engineering Research Center, University of California, Berkeley, California (1975).

[87] DONOVAN, N.C., “A stochastic approach to the seismic liquefaction problem” in: Proc. First Int. Conf. Applications of Statistics and Probability to Soil and Structural Engineering, Hong Kong, Sept. 1971.

[88] LEE, K.L., SEED, H.B., Cyclic stress conditions causing liquefaction of sand, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 93 SMI (1967) 47.

[89] SEED, H.B., ARANGO, I., CHAN, C.K., Evaluation of Soil Liquefaction Potential During Earthquakes, Report EERC 75-28, Earthquake Engineering Research Center, University of California, Berkeley, California (1975).

[90] SEED, H.B., DUNCAN, J.M., IDRISS, I.M., “Static and dynamic analysis of earth dams”, in: Proc. Int. Conf. Numerical Analysis of Earth Dams, Swansea, U.K. (1975).

[91 ] NEWMARK, N.M., Effects of earthquakes on dams and embankments, Geotechnique 15 2 (1965) 139.

[92] ANDO, M., A fault-origin model of the Great Kanto earthquake of ’23 as deduced from geotectonic data, Bull. Earthquake Res. Inst. (Japan) 49 (1971) 11.

[93] JENNINGS, P.C., Engineering Features of the San Fernando Earthquake (Annex 1), Report EERI 71-02 (Cal. Tech.) (June 1971) p. 13.

*[94] JAPAN ELECTRIC ASSOCIATION, TOKYO, Technical Guidelines for Aseismic Design of Nuclear Power Plants (1970) (in Japanese).

45


*[95] SISCHER, E.G., Sine beat vibration testing related to earthquake response spectra,Shock Vib. Bull. 42 Part 2 (1972).

*[96] WHITMAN, R.V., PROTONOTARIOS, J.N ., NELSON, M.F., Case Study of Soil-Structure Interaction, Am. Soc. Civ. Eng. Meeting, Houston, Texas, 16—22 Oct. 1972.

*[97] SHIBATA, H., AKINO, K., KATO, H., On estimated modes of failure of NPP by potential earthquakes, Nucl. Eng. Des. 28 2 (1974) 257.

*[98] THE M.W. KELLOG CO., Design of Piping Systems, J. Wiley & Sons, New York and London (1956).

*[99] HARDIN, B.C., DRNEVICH, V.P., Shear modulus and damping in soils, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 98 SM6 (1972) 603, and SM7 (1972) 667.

*[100] LYSMER, J., UDAKA, T., TSAI, C.F., SEED, H.B., “FLUSH” - A Computer Program for Approximate 3-D Analysis of Soil-Structure Interaction Problems, Report EERC 75-30, Earthquake Engineering Research Center, University of California, Berkeley (1975).

*[101] RICHARD, F.E., HALL, J.R ., WOODS, R.D., Vibration of Soils and Foundations, Prentice-Hall, New York (1970).

*[102] SEED, H., LEE, K.L., Liquefaction of saturated sands during cyclic loading, J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 92 SM6 (1966) 105.

*[103] KULHAWY, F.H., DUNCAN, J.M., SEED, H.B., Finite Element Analysis of Stresses and Movements in Embankments During Constructions, Report TE-69-4, U.S. Army Engineers Waterways Experiment Station, Vicksburg, USA (1969).

*[104] SEED, H.B., GOODMAN, R.E., “Earthquake Stability of Slopes of Cohesionless Soils”,J. Soil Mech. Found. Div., Am. Soc. Civ. Eng. 90 SM6 (1964) 43.

*[105] LYSMER, J., SEED, H.B., UDAKA, T., HWANG, R.N., TSAI, C.F., Efficient Finite Element Analysis of Seismic Structure-Soil-Structure Interaction, Second Am. Soc.Civ. Eng. Specialty Conference Structural Design of Nuclear Plant Facilities, New Orleans, Dec. 1975, Vol. II, p. 125.

*[106] SEED, H.B., WHITMAN, R.V., LYSMER, J., “Soil-structure interaction effects in the design of nuclear power plants”, presented at Special Conf. at University of Illinois, Urbana, Oct. 1975.

*[107] TAJIMI, H., “A statistical method of determining the maximum response of building structure during an earthquake”, Proc. Second World Conf. Earthquake Engineering, Tokyo and Kyoto, Vol. 2 (1960) p. 781.

*[108] TAJIMI, H., “Dynamic analysis of a structure embedded in an elastic stratum ”, Proc.Fourth World Conf. Earthquake Engineering, Santiago, Chile, 1969, Vol. 3, A-6, p. 53.

46


DEFINITIONS

The following definitions are intended for use in the NUSS programme and may not necessarily conform to definitions adopted elsewhere for international use.

Accident Conditions

Substantial deviations from Operational States which are expected to be infrequent, and which could lead to release of unacceptable quantities of radioactive materials if the relevant engineered safety features did not function as per design intent.1

Anticipated Operational Occurrences

All operational processes deviating from Normal Operation which are expected to occur once or several times during the operating life of the plant and which, in view of appropriate design provisions, do not cause any significant damage to Items Important to Safety nor lead to Accident Conditions2 (see Operational States).

Construction

The process of manufacturing and assembling the components of a Nuclear Power Plant, the erection of civil works and structures, the installation of components and equipment, and the performance of associated tests.

Design Floor Response Spectrum

Response spectrum defined at a particular building elevation which is obtained by modifying one or more floor response spectra in order to consider the variability and uncertainty of input ground motion and o f the characteristics o f both building and foundation.

1 A substantial deviation may be a major fuel failure, a Loss of Coolant Accident (LOCA), etc. Examples of engineered safety features are: an Emergency Core Cooling System (ECCS), and containment.

2 Examples of Anticipated Operational Occurrences are loss of normal electric power and faults such as a turbine trip, malfunction of individual items of a normally running plant, failure to function o f individual items o f control equipment, loss of power to main coolant pump.

47


Design Floor Time Histories

Time histories of floor motion of structure under consideration derived from the design basis ground motion, including the variability and uncertainty in input ground motion and in building and foundation characteristics.

Floor Response Spectrum

For a given ground motion, the floor response spectrum at a particular level of a structure is the response spectrum of the motion at that level.

Item3

A structure, system, sub-system, piece of equipment or component taken individually or collectively according to the context.

Items Important to Safety

The items which comprise:

(1) those structures, systems, and components whose malfunction or failure could lead to undue radiation exposure of the Site Personnel or members of the public;4

(2) those structures, systems and components which prevent Anticipated Operational Occurrences from leading to Accident Conditions;

(3) those features which are provided to mitigate the consequences of malfunction or failure of structures, systems or components.

Normal Operation

Operation of a Nuclear Power Plant within specified Operational Limits and Conditions including shut-down, power operation, shutting down, starting up, maintenance, testing and refuelling (see Operational States).

Nuclear Power Plant

A thermal neutron reactor or reactors together with all structures, systems and components necessary for Safety and for the production of power, i.e. heat or electricity.

3 This definition is limited to the topic of this Safety Guide.4 This includes successive barriers set up against the release of radioactivity from nuclear

facilities.

48


Operation

All activities performed to achieve, in a safe manner, the purpose for which the plant was constructed, including maintenance, refuelling, in-service inspection and other associated activities.

Operational States

The states defined under Normal Operation and Anticipated Operational Occurrences (see Normal Operation and Anticipated Operational Occurrences).

Potential

A possibility worthy of further consideration for Safety.%

Quality Control

Quality Assurance actions which provide a means to control and measure the characteristics o f an item, process or facility in accordance with established requirements.

Region

A geographical area, surrounding and including the Site, sufficiently large to contain all the features related to a phenomenon or to the effects of a particular event.

Regulatory Body

A national authority or a system of authorities designated by a Member State, assisted by technical and other advisory bodies, and having the legal authority for conducting the licensing process, for issuing Licences and thereby for regulating nuclear power plant Siting, Construction, Commissioning, Operation and Decommissioning or specific aspects thereof.5

5 This national authority could be either the government itself, or one or more departments of the government, or a body or bodies specially vested with appropriate legal authority.

49


Residual Heat

The sum of the heat originating from radioactive decay and shut-down fission and the heat stored in reactor-related structures and in heat transport media.

Safety

Protection o f all persons from undue radiological hazard.

Site

The area containing the plant, defined by a boundary and under effective control of the Plant Management.

Siting

The process o f selecting a suitable Site for a Nuclear Power Plant, including appropriate assessment and definition of the related design bases.

50


Dates of meetings: 29 September to 11 October 1975, 14 to 18 February 1977

Consultants

LIST OF PARTICIPANTS

WORKING GROUP

Livolant, M.

Petrangeli, G.

Shibata, H.

Idriss, I.M.Stevenson, J.D.

IAEA staff members

Karbassioun, A.

Iansiti, E.

France

Italy

Japan

United States of America

Scientific Secretary (Siting)

TECHNICAL REVIEW COMMITTEE (TRC) - SITING

Dates of meetings: 17 to 21 November 1975, 18 to 22 April 1977, 24 to 28 April 1978

Members and alternates participating in the meetings

Candes, P. (Chairman)

Carmona, J.

Beare, J.W.Schwarz, G.

Kriz, Z.Dlouhy, Z.

Witulski, H.

Soman, S.D.

Giuliani, P.

France

Argentina

Canada

Czechoslovakia

Germany, Federal Republic of

India

Italy

51


Akino, K.Omote, S. JapanMochizuki, K.Jeschki, W. „ , .„ . _ SwitzerlandHeimgartner, E.

Tildsley, F.C.J. United Kingdom

Mattson, R.J.Roberts, I. Craig United States of AmericaGammill, W.P.

Participants from international organization

Ilari, O. OECD Nuclear Energy Agency

Participants from the Working Group

Livolant, M. France

Petrangeli, G. Italy

Shibata, H. Japan

Idriss, I.M. United States of AmericaStevenson, J.D.

Experts for co-ordination between TRC-Design and TRC-Siting

Fischer, J. Chairman of TRC-Design

assisted by T. Tellkamp and H. Wolfel of the Federal Republic of Germany

IAEA staff members

Karbassioun, A.

Iansiti, E. Scientific Secretary (Siting)

SENIOR ADVISORY GROUP

Dates of meetings: 30 August to 3 September 1976, 20 to 24 June 1977, 19 to 23 June 1978

Members and alternates participating in the meetings

Hurst, D. (Chairmanj Canada

52


Klik, F.Sevcik,A.Kriz, Z.

Messiah, A.Clement, B.

Franzen, L.F.

Ganguly, A.K.

Uchida, H.

Velez, C.Sanchez Gutierrez, J.

Hedgran, A.

Zuber, J.F.

Kovalevich, O.M.

Gausden, R.A. Gronow, W.S.

Hendrie, J.Minogue, B.

Czechoslovakia

France

Germany, Federal Republic of

India

Japan

Mexico

Sweden

Switzerland

Union of Soviet Socialist Republics

United Kingdom

United States of America

Participants from international organizations

Commission of the European Communities

Burkhardt, W. Council for Mutual Economic Assistance

International Organization for Standardization

OECD Nuclear Energy Agency

Van Reijen, G. Pele, J.

Nilson, R. Becker, K.

Stadie, K.

Observer

Akino, A. Japan

Participants from TRC — Siting

Candes, P. Chairman of TRC — Siting


IAEA staff members

Karbassioun, A.

Konstantinov, L.

Iansiti, E. Scientific Secretary (SAG and Siting)

S c ie n tif ic C o -o rd in a to r

54


PROVISIONAL LIST OF NUSS PROGRAMME TITLES

Safety SeriesNo.

Provisional title Publication dateof English version

1. Governmental Organization

Code o f Practice

50-C-G Governmental organization for theregulation o f nuclear power plants

Safety Guides 50-SG-G1

50-SG-G2

50-SG-G3

50-SG-G4

50-SG-G6

50-SG-G8

Published 1978

Qualifications and training o f staff of Published 1979 the regulatory body for nuclear power plants

Information to be submitted in Published 1979support o f licensing applications for nuclear power plants

Conduct of regulatory review and assessment during the licensing process for nuclear power plants

Inspection and enforcement by the regulatory body for nuclear power plants

. Preparedness of public authorities for emergencies at nuclear power plants

Licences for nuclear power plants: content, format and legal considerations

2. Siting

Code o f Practice

50-C-S Safety in nuclear power plant siting Published 1978

55


Safety Series Provisional titleNo.

Publication dateof English version

Safety Guides 50-SG-S 1

50-SG-S2

50-SG-S3

50-SG-S4

50-SG-S5

50-SG-S6

50-SG-S 7

50-SG-S9

50-SG-S 10A

50-SG-S 1 OB

50-SG-S 11

Earthquakes and associated topics Published 1979in relation to nuclear power plantsiting

Seismic analysis and testing o f Published 1979nuclear power plants

Atmospheric dispersion in relation to nuclear power plant siting

Site selection and evaluation for nuclear power plants with respect to population distribution

Extreme man-induced events in relation to nuclear power plant siting

Hydrological dispersion of radioactive material in relation to nuclear power plant siting

Nuclear power plant siting — hydro- geological aspects

Site survey for nuclear power plants

Determination of design basis floods for nuclear power plants on river sites

Determination of design basis floods for nuclear power plants on coastal sites

Evaluation of extreme meteorological events for nuclear power plant siting

56




Code o f Practice 50-C-D

Safety Guides 50-SG-D 1

50-SG-D2

50-SG-D3

50-SG-D4

50-SG-D5

50-SG-D6

50-SG-D7A

50-SG-D8

50-SG-D9

3. Design

Design for safety of nuclear power Published 197 8 plants

Safety functions and component Published 1979classification for BWR, PWR and PTR

Fire protection in nuclear power Published 1979plants

Protection systems and related features in nuclear power plants

Protection against internally generated missiles and their secondary effects in nuclear power plants

Man-induced events in relation to nuclear power plant design

Ultimate heat sink and directly associated heat transport systems for nuclear power plants

Emergency electrical power systems at nuclear power plants

Instrumentation and control of nuclear power plants

Design aspects of radiological protection for operational states of nuclear power plants

57




Safety Guides (cont.)50-SG-D10 Fuel handling and storage systems in

nuclear power plants

4. Operation

Code o f Practice 50-C-0 Safety in nuclear power plant opera

tion, including commissioning and decommissioning

Published 1978

Safety Guides

50-SG-01 Staffing of nuclear power plants andrecruitment, training and authorization of operating personnel

50-SG-02 In-service inspection for nuclearpower plants

50-SG-03 Operational limits and conditionsfor nuclear power plants

50-SG-04 Commissioning procedures fornuclear power plants

50-SG-05 Radiological protection duringoperation of nuclear power plants

50-SG-06 Preparedness of the operatingorganization for emergencies at nuclear power plants

50-SG-07 Maintenance o f nuclear power plants

50-SG-08 Standard tests of important systemsand components in nuclear power plants

Published 1979

Published 1979

58




Code o f Practice 50-C-QA

Safety Guides 50-SG-QA 1

50-SG-QA2

50-SG-QA3

50-SG-QA4

50-SG-QA5

50-SG-QA6

50-SG-QA7

50-SG-QA8

50-SG-QA10

50-SG-QA11

5. Quality assurance

Quality assurance for safety in Published 1978nuclear power plants

Preparation o f the quality assurance programme for nuclear power plants

Quality assurance records system for Published 1979nuclear power plants

Quality assurance in the procurement Published 1979of items and services for nuclear power plants

Quality assurance during site construction o f nuclear power plants

Quality assurance during operation of nuclear power plants

Quality assurance in the design of nuclear power plants

Quality assurance organization for nuclear power plants

Quality assurance in the manufacture of items for nuclear power plants

Quality assurance auditing for nuclear power plants

Quality assurance in the design and manufacture of fuel and fuel cladding for nuclear power plants

59


HOW TO ORDER IAEA PUBLICATIONS

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■ In the following countries IA E A publications may be purchased from the sales agents or booksellers listed or through your major local booksellers. Payment can be made in local currency or with UNESCO coupons.

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IN T E R N A T IO N A L SU B J E C T G R O U P : 11A T O M IC E N E R G Y A G E N C Y Nuclear Safety and Environmental Protection/Nuclear SafetyV IE N N A , 1979 P R IC E : Austrian Schillings 100,—


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