STUK SÄTEILYTURVAKESKUS STRÅLSÄKERHETSCENTRALEN RADIATION AND NUCLEAR SAFETY AUTHORITY Kalvo 1 Beijing, October 2004 Licensing Aspects of new power plant

STUK • SÄTEILYTURVAKESKUSSTRÅLSÄKERHETSCENTRALENRADIATION AND NUCLEAR SAFETY AUTHORITY

Beijing, October 2004

Kalvo 1

Licensing Aspects of new power plant EPR in Finland

NERS meeting in ViennaSeptember 23-24, 2004

Jukka Laaksonen

Director General

STUK-Radiation and Nuclear Safety Authority



Kalvo 2

Government decision on nuclear option

• The Finnish Government made in January 2002 a Decision in Principle (DiP) which concludes that constructing of a new nuclear power plant (NPP) in Finland is in line with the overall good of the society. The Finnish Parliament ratified the decision in May 2002 with votes 107-92.

• DiP authorised the electricity generating company TVO

to continue preparations for the construction of a new NPP unit.



Kalvo 3

Olkiluoto 3 licensing phases

Decision in Principle

Construction License

Environmental Impact Assessment

Operating License

Feasibility study

Preparatory phase

Construction

1998-2000

2000-2002

first quarter 2005 ?

2008 ?

Technical part

Political part



Kalvo 4

Environmental Impact Assessment (EIA)

• EIA is based on environmental legislation, it is not included in the Nuclear Energy Act

• EIA provides useful input for the Decision in Principle which is the first step of NPP licensing according to the Nuclear Energy Act

• EIA does not require specific information on plant type and technology

• EIA was done separately for two alternative sites: Loviisa and Olkiluoto



Kalvo 5

Decision in Principle (1)

General criteria of approval

• a new NPP is in line with the overall good of society• this is to be decided by the Government and confirmed by the

Parliament

• no safety issues can be foreseen that would prevent the proposed plant(s) from meeting Finnish nuclear safety regulations

• this is assessed by STUK, full veto right

• proposed host municipality agrees to provide the site• also municipality has full veto right



Kalvo 6


General conclusions in STUK’s statement:

• all alternative NPP’s mentioned in the application could probably be made to fulfil Finnish safety requirements, if certain modifications would be made

• none of the plants seemed acceptable as presented, but some modifications would be needed in all designs (specific safety issues were identified for each alternative plant type)

• TVO needs to develop the competence of its own organisation (taking into account the planned 60 years lifetime)

• addition made at request of Ministry after September 11, 2001: it is possible to provide necessary protection even against worst plane crashes



Kalvo 7


Government made its positive decision in January 2002 and sent it to Parliament for ratification. The following supporting arguments were given:• Importance for electrical power supply

• Together with energy savings and increased use of renewable power sources a new NPP can keep the greenhouse gas releases within the agreed target.

• STUK’s positive statement on nuclear safety• Site suitability and acceptable environmental impact• Adequate arrangements for supply of nuclear fuel and

management of nuclear waste• Full private funding• Ability of the applicant to implement the construction project



Kalvo 8

Decision in Principle (4)• Parliament made a thorough assessment in 8 Committees

before voting in the plenary session:

• Out of the 200 Parliament members, 115 attended the work during spring 2002 in one or more committees. Each committee heard a very large number of experts (up to 85 in one committee) in order to get different views.



Kalvo 9

Arguments listed by the Parliament’s Commerce Committee in favour of a new NPP

• A new plant helps to maintain multiple sources for power production, thus increasing self-sufficiency and improving preparedness for crisis

• Production costs of nuclear power are smaller than costs of other alternatives

• Accident risks are small• There are no releases to the atmosphere and also otherwise the

environmental impact is small• From the national economics point of view, nuclear power is the best

way to reduce carbon dioxide releases• Nuclear fuel supply and nuclear waste management can be arranged

using the existing infrastructure• The only realistic alternative to a new NPP would be increased use of

gas for power production, but this would strongly increase the dependence on import from Russia and increase the power price and the need for state support to the energy section



Kalvo 10

Public opinion after DiP ratification

• A poll was conducted among the general public immediately after the Parliament ratification. A clear majority of those questioned approved the decision: 55 % were for, 31 against, and 13 undecided;

• Main editorials in all larger newspapers welcomed the decision in a positive spirit. According to a study done for the Ministry for Trade and Industry, not a single main editorial took a negative position on the decision.

• Discussion stopped very quickly, also opposition concluded that the final decision has been made.• nuclear power was not an issue in Parliament election in 2003



Kalvo 11

Milestones of the contracting stage

• TVO started preparation of tender documents after DiP in May 2002• call for tenders out end of September 2002• tenders in end of March 2003

• Vendor and site were decided in October 2003• two different plant types by vendor were still considered• site Olkiluoto

• Contract was signed on the 19th of December 2003• plant vendor is Consortium Framatome ANP - Siemens, lead by

FANP - Turnkey delivery• plant type is EPR - 1600 MWe PWR



Kalvo 12

OL3 Comparison Table

Type of plants N4 EPR (OL3) KONVOI

Core thermal power (MWth) 4250 4300 3850Net power output (MWe) 1475 1600 1400Number of loops 4 4 4

N° of fuel assemblies 205 241 193Type of fuel assemblies (17x17), 25 (17x17), 25 (18x18), 24Active length (cm) 427 420 390Total F.A. length (cm) 480 480 483Rod linear heat rate (W/cm) 179 155 163

N° of control rods 73 89 61



Kalvo 13

OL3 Comparison Table

Type of plants N4 EPR (OL3) KONVOI

Total flow-rate (kg/s) 19714 22135 18800Primary pressure 155 155 158Vessel outlet temp. (°C) 329.1 327.2 324.5Vessel inlet temp. (°C) 292.1 295.9 292.5

S.G. heat exch. surface (m²) 7308 7960 5400Steam Pressure (bar) 72.5 78 64.5

Containment volume (m³) 73000 80000 70000



Kalvo 14

OL3 main schedule

2003

Construction permit

2004 2005 2006 2007 2008 2009 2010

Construction

Operating license

Trial Run

Operation



Kalvo 15

Construction Permit (CP) process (1)

• Processing of the CP application, in consultation with the stakeholders, is the task of the Ministry of Trade and Industry

• Construction Permit is to be granted by the Government• Government has publicly committed to take fast action

after Ministry has received STUK’s statement on adequate safety



Kalvo 16

Construction Permit (CP) process (2)

• Construction Permit application was submitted to the Ministry of Trade and Industry on January 8, 2004

• All stakeholders except STUK have made their statements by April 30, as requested by ministry• no significant objections have been expressed against

the CP

• Ministry asked STUK to give its statement on safety of the plant by the end of 2004, if possible• gradually improving revisions of CP documents have

been submitted to STUK between Jan-Sep 2004



Kalvo 17

Preparatory work before receiving the CP• Site works started immediately after signing the contract

• Excavations - 500 000 m3 of soil and rock to be removed by end of 2004

• Construction of site infrastructure: roads, power&water supply• Anchors for pre-stressing cables at the bottom of reactor building,

installation of the reinforcing steels for bottom plate by April 2005

• Reactor Pressure Vessel and SG’s were purchased already in early summer 2003 and manufacturing started in the fall 2003

• Bids for subcontracts and subcontracting• Systems design, specification and purchase of equipment • First concrete to bottom plate is planned 1st May 2005



Kalvo 18

STUK activities during CP stage (1)

• Review of submitted CP documentation

• Auditing of activities of plant vendor• design process, project management

• Independent calculations to validate accident analysis• both in-house and in co-operation with expert

organisations, also contracted work



Kalvo 19

STUK activities during CP stage (2)

• Meetings with license applicant and vendor• several meetings weekly on technical issues and

quality management

• STUK inspections on design and manufacturing of Reactor Vessel and Steam Generators started in October 2003• also other component specific inspections will start in

parallel with CP application review



Kalvo 20

Support to STUK from experts organisations (1)

Finnish organisations• VTT: advice and independent analysis of several

topics including PSA, water chemistry, postulated accidents, severe accidents and I&C validation, inspections of mechanical components to supplement STUK’s inspection resources

• Lappeenranta Technical University: tests and assessment of approach to severe accident management



Kalvo 21

Support to STUK from experts organisations (2)

Foreign organisations• DGSRN and IRSN France: exchange of information on

assessment of several design topics, in specific I&C systems

• GRS Germany: assessment of Break Preclusion concept for primary and secondary systems; independent analysis and assessment of aircraft crash protection approach

• ISaR Germany: independent analysis of specific accidents, assessment of the ECCS

• Belgian consultant (retired from AVN ): digital I&C issues



Kalvo 22

Development of regulations in Finland (1)

• The nuclear safety authority STUK has since early 1970’s developed Finnish safety regulations and kept them up to date • Safety requirements are based on national and international

practices - IAEA Safety Standards are becoming increasingly important

• The leading principle has been to incorporate the state-of-the-art in the nuclear safety technology into the safety requirements

• operating experience

• research

• development of science and technology



Kalvo 23


• Mandatory safety requirements are presented in Government Decisions• the Government Decisions are drafted and proposed

for the Government by STUK • views of stakeholders are requested and taken into

account in preparation of final drafts • these mandatory requirements are of the type of

general safety principles



Kalvo 24


• STUK issues detailed regulations called YVL Guides

• YVL guides are rules that shall be complied with unless some other acceptable procedure or solution is presented to STUK by which the safety level laid down in an YVL guide is achieved

• Currently there are 73 YVL Guides in force. The Guides are up to date - as needed for licensing of the new plant

• Finnish nuclear and radiation legislation as well as Goverment Decisions and YVL Guides are available in internet, www.stuk.fi



Kalvo 25

General principles used in Finnish safety requirements for design (1)

• The nuclear safety philosophy applied worldwide since late 1960’s has been 100% successful at commercial nuclear power plants • there has never been a large radioactive offsite release

at plants which apply this philosophy

• It is well-founded to keep safety requirements based on this successful philosophy• the core of the safety philosophy is the defence-in-

depth principle



Kalvo 26


• Systematic application of the defence-in-depth principle requires that well specified accidents are postulated as design basis of • the reactor core, • the release barriers, and• the safety systems

• Traditional deterministic approach to safety is thus followed

• Safety margins and protection against a wide spectrum of other less specific accidents are provided by overlapping design basis accidents• this has proven to ensure the safety also in unforeseen situation



Kalvo 27


• As a necessary complement to the deterministic safety design, a probabilistic risk analysis (PRA) is required to verify the reliability of all vital safety functions in a systematic manner• PRA results indicate the balance of the design features from the

safety point of view, and help to identify the weakest points that possibly need to be strengthened

• experience has shown that insights from the PRA have increased the understanding of the safety factors, and helped to remove risks that have gone unnoticed in the previous engineering assessment

• Risk informed approach to safety strengthens the traditional design practice



Kalvo 28


• All calculations in the safety analysis have to be made with models that simulate the physical reality with the best possible manner• safety margins must be used in the model parameters

to account for estimated inaccuracies in simulation of the real situation

• failures in the safety systems have to be postulated as specified in detail in the YVL Guides

• conservative unphysical assumptions should be avoided in order not to give a distorted picture of the course of accidents



Kalvo 29


• Acceptance criteria for the safety analysis are connected with the actual estimated probability of each accident category• acceptance criteria take into account what might

actually be tolerable consequences (releases, doses, physical “cliff-edge” limits implying a potential change of an accident process)

• no physically meaningless limits are used, such as the traditional acceptance criteria for LOCA analysis: maximum fuel temperature of 1204°C and maximum cladding oxidation 17%



Kalvo 30

Technical requirements specified by the utility (in call for tender, contract, and PSAR)

• The technical requirements were specified by using the European Utility Requirements (EUR) document as a reference• The application of EUR document represented a new approach that had

not yet been used earlier

• The EUR document represents a European set of requirements compiled by the utilities• EUR needs to be complemented with the safety requirements set by the

national regulatory bodies • TVO’s specifications deviated from EUR mainly in those points

where Finnish requirements are more stringent than EUR



Kalvo 31

Example of defense-in-depth based deterministic approach: loss of coolant accidents (1)

• Postulated loss-of-coolant accidents are important for defining the design targets for the fuel, reactor core, mechanical structures, and safety systems, as well as for setting respective operational limits for them.

• Unambiguous assumptions on design basis accidents help

• to estimate available safety margins and • to avoid gradual reduction of the margins as a consequence of

small successive design modifications



Kalvo 32

Example of defense-in-depth based deterministic approach: loss of coolant accidents (2)

• Design basis requirements based on postulated LOCA’s take into account

• experience from the safety systems at the existing plants: do not remove the protective features that are proven to be feasible (e.g., fuel and core design limits, ECCS, containment)

• development of technology: make safety improvements that are reasonably achievable

• need to provide protection against unforeseen events or events left outside the design basis



Kalvo 33

Example of defense-in-depth based deterministic approach: loss of coolant accidents (3)1) Eliminate the possibility of sudden large breaks of the reactor coolant

circuit by applying Break Preclusion (BP) principle2) Postulate a sudden guillotine break of the largest pipeline, but limit the

physically possible maximum break flow areas (and consequent fluid transients in the reactor coolant circuit) by means of pipe whip restraints

• use the maximum estimated break flow as the design basis for specific mechanical structures

3) Postulate a loss of coolant accident that is equal to a free flow from both ends of the broken pipe

• use the large break LOCA as the design basis for safety systems, thus providing protection also for unforeseen events

• study the actual strength of mechanical structures under influence of dynamic forces, by using best estimate assumptions for physical phenomena



Kalvo 34

Break Preclusion principle to eliminate possibility of sudden large breaks

Break Preclusion (BP) principle used to eliminate the possibility of sudden large breaks of the reactor coolant circuit must involve:

• qualified construction (materials, fabrication, QA), operation (loadings, chemistry), and surveillance to prevent major cracking throughout plant life

• strength analysis to demonstrate adequate safety margins in all design-basis load conditions

• effective in-service inspections of welds and other stressed areas

• effective leak detection and verification of the leak-before-break principle



Kalvo 35

Limitation of maximum break flow in connection with primary circuit breaks

Limitation of the break flow area after a potential guillotine break by restricting the pipe motion is required in order to limit dynamic forces on mechanical structures. Vital structures that need to preserve their integrity after a sudden (1 msec) limited break with adequate margin are among others

• support and anchoring structures of the main components• reactor pressure vessel internals, including fuel (mechanical

strength) and control rod drive systems• steam generator tubes and other internals• main coolant pump flywheels• reactor containment internals



Kalvo 36

Loss of coolant accidents, beyond design studies

Beyond design studies are made to demonstrate the actual mechanical strength under the influence of dynamic forces that would result from the maximum free leak from both ends of the broken main coolant pipe

• best estimate assumptions can be used for physical phenomena such as break opening time

• items to be looked at are the fuel, reactor vessel internals, steam generator tube bundle and its supports, steam generator primary side manhole and main coolant pump flywheel



Kalvo 37

Example of defense-in-depth based deterministic approach: design basis for Containment1) Large break LOCA

• adequate capacity to carry pressure loads and to limit radioactive releases must be shown in conditions expected after a LB LOCA

• this gives a sound basis to manage also severe accidents

2) Severe accidents• all foreseeable loads threatening the containment integrity in

connection with a severe core damage must be identified, and necessary protection (prevention or mitigation) must be provided against each load

3) External events• potential external events must be identified and protected against



Kalvo 38

Severe accidents

• Severe accident management strategy is mandated in containment design • high pressure failure of reactor vessel prevented by dedicated

depressurization system• hydrogen management with autocatalytic recombiners to prevent

detonation• low pressure melt arrested in a core catcher, with passive long-term

cooling • containment integrity against dynamic loads• containment pressure management in long term• containment leak tightness criteria from release limits

• AC power supply systems and I&C systems dedicated to support severe accident management are required

• For systems dedicated for protection against severe accidents, single failure criterion applies



Kalvo 39

Protection against external threats

After September 11, 2001: political and public will was expressed to improve protection against terrorist actions• Reconsideration of aircraft crash design basis

- consider large passenger and military aircrafts - no immediate release of significant amount of radioactive

substances- initiation and maintenance of key safety functions in spite of

the direct consequences of the event (penetration of structures by impacting parts, vibration, explosion, fire)

• Microwave and biologic weapon consideration



Kalvo 40

System design requirements

• Safety classification• N+2 failure criterion for systems that deal with

design basis events (redundancy, diversity, segregation)

• Proven technology• properly evaluated operational experience• experimental demonstration & analysis (novelties,

such as “passive” systems)• Performance / safety margins required



Kalvo 41

Event classification for setting fuel damage and radioactive release criteria

• Event categories• anticipated transients• postulated (design basis) accidents - “minor and major”• severe accidents

• Single SG tube rupture is considered as an anticipated transient

• Some low-probability high consequence events are postulated accidents

• large primary-to-secondary leak: no major discharge to atmosphere is wanted

• ATWS: good confidence in adequate reactivity control • LB LOCA remains within Design Basis



Kalvo 42

Acceptance criteria for preventing / limiting fuel damage

• Anticipated events, f > 10-2/a• 95/95 confidence with respect DNB or dry-out, no (internal) fuel

melting, nor damage due to pellet-cladding mechanical interaction.

• “Minor” postulated accidents, 10-2/a > f > 10-3/a • number of rods in heat transfer crisis < 1%, PCT < 650 °C, and

extremely low probability of fuel damage by the mechanical interaction between fuel and cladding

• ”Major" postulated accidents, f < 10-3/a• the higher the frequency of a postulated accident, the smaller the

number of damaged fuel rods. Number of damaged fuel rods < 10%. Enthalpy limit 140 cal/g for failure (230 cal/g not be exceeded). No danger to long-term coolability



Kalvo 43

Acceptance criteria for radioactive releases / max doses to general public

Normal operation• radiation dose limit 0,1 mSv / year for the entire site

Anticipated events• radiation dose limit 0,1 mSv

Design basis accidents• radiation dose limit 5 mSv

Severe accidents• release < 100 TBq Cs-137 equivalent• no acute health effects

• can be fulfilled only if containment integrity is guaranteed



Kalvo 44

Fire protection

• High importance to lay-out• systematic and complete division of the whole

plant into fire areas housing separate redundancies

• Separation with structures, and reliable fire suppression within fire zones is emphasized • cable channels• cables spreading areas• reactor building



Kalvo 45

Fuel burn-upYVL Guide • Limit of 40 MWd/kgU is given for fuel assembly

average burn-up• this is used unless higher burn-up is not supported

with adequate experimental evidence

Operating plants in Finland• 45 MWd/kgU has been approved with experimental

evidence

EPR burn-up target• The licence applicant has indicated target value of 50

MWd/kgU for burn-up; no regulatory position at this stage

Documents

STUK SÄTEILYTURVAKESKUS STRÅLSÄKERHETSCENTRALEN RADIATION AND NUCLEAR SAFETY AUTHORITY Kalvo 1 Beijing, October 2004 Licensing Aspects of new power plant