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Regulatory Impact to the Design of Nuclear Power Plants in Finland

byAmi RastasConsultant

Nuclear-electricity in Chile: How far, How close.International Seminar on Possibilities, Gaps and Challenges

January 28th, 2010Hyatt Hotel, Santiago, Chile.

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QUESTIONS TO BE ADDRESSED

The Finnish case:

How a strong regulatory body can trigger technical innovations on the reactors' design?

Importance of having the required human resource in the regulatory body?

The questions will be addressed based on my former experience built up as an employee (retired) of TVO that is the owner/operator of the Olkiluoto nuclear power plant.

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CONTENTS

• Status of nuclear power in Finland• Finnish nuclear safety regulations• Examples of regulatory impacts to the design of the

existing nuclear power plants in Finland• Finnish influence in the development of new plant designs• Examples of regulatory impacts to the Olkiluoto 3 plant

unit• Organization and staff of the regulatory body STUK• Technical and scientific support • Conclusions

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STATUS OF NUCLEAR POWER IN FINLAND

Four nuclear power plant units in operation, one unit under construction and the next unit(s) in the early phase of licensing

Extensive modernization projects (including power uprating) completed for each existing unit in the late 90’s

Operational results of the existing units very favourableLife time load factors until the end of 2009

– Loviisa plant (LO1 and LO2) 87.7 %– Olkiluoto plant (OL1 and OL2) 93.0 %

Advanced nuclear waste management program and funding system

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Loviisa

LO1 PWR 488 MW 1977

LO2 PWR 488 MW 1979

OL1 BWR 860 MW 1978OL2 BWR 860 MW 1980

OL3 PWR 1600 MW 2012

Olkiluoto Loviisa

Helsinki

NUCLEAR POWER PLANTS IN FINLANDNUCLEAR POWER PLANTS IN FINLAND

Olkiluoto

Teollisuuden Voima Oyj(TVO)

Fortum Power and Heat Oy(FPH, previous IVO)

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STUK’S ROLE IN PREPARATION OF NUCLEAR SAFETY LEGISLATION AND REQUIREMENTS

• Nuclear Energy Act and Nuclear Energy Decree (1957, latest revision 2008)

– preparation coordinated by Ministry (MEE), STUK provides input to safety related parts

• Government Decisions (1991, revised to be Decrees 2008)

– four separate Decrees: safety of NPPs, physical protection of NPPs, emergency preparedness, safety of the disposal of nuclear waste

– drafts written by STUK, final format given by Ministry (MEE)

• YVL Guides issued by STUK– detailed requirements for plant design and licensing process– prepared by STUK in close co-operation with relevant stakeholders– overall reform of YVL Guides initiated in 2006 and continues until 2011 – YVL Guides are to be applied as such to new nuclear power plants, application to

plants in operation or under construction is considered case by case

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FINNISH NUCLEAR LICENSING PROCESS

ENVIRONMENTALENVIRONMENTALIMPACTIMPACT

ASSESSMENTASSESSMENT

Ministry of Ministry of Employment Employment

and Economyand Economy

DECISIONDECISIONIN PRINCIPLEIN PRINCIPLE

GovernmentGovernmentParliamentParliament

CONSTRUCTIONCONSTRUCTIONPERMITPERMIT

GovernmentGovernment

OPERATINGOPERATINGLICENSELICENSE

GovernmentGovernment

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DEVELOPMENT OF SAFETY REQUIREMENTS IN FINLAND

• The need for Finnish nuclear safety requirements arose in 1970 when a decision to buy a Soviet designed NPP had been made (Loviisa, VVER-440)

• STUK has since then developed and updated national safety requirements • Safety requirements are based on well established 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

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GENERAL PRINCIPLES APPLIED IN FINNISH SAFETY REQUIREMENTS FOR DESIGN (1/2)

• 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 consists of the defence-in-depth principle and deterministic postulation of certain design basis accidents

• As a necessary complement to the deterministic safety design, a probabilistic risk analysis (PRA) is required to be presented for getting Construction Permit and has to be kept up-to-date since then. Risk informed approach to safety strengthens the traditional design practice.

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GENERAL PRINCIPLES USED IN FINNISH SAFETY REQUIREMENTS FOR DESIGN (2/2)

• Safety requirements are performance based, as opposite to being prescriptive

• Consequently, there are several expressions that in some other countries could be considered to cause “regulatory uncertainty”: “as necessary”, “take into account…”, “adequately”, “as

appropriate”, “suitable”, “as far as possible”, …

• Successful use of this type of requirements demands high technical knowledge of the regulatory staff mutual trust and common understanding on acceptable

safety level among the involved parties (vendor, licensee, regulator)

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EXAMPLE OF DESIGN BASIS ACCIDENTS: LOSS OF COOLANT ACCIDENTS

Postulated loss-of-coolant accidents (e.g. pipe breaks) are important for defining the design targets for fuel,reactor core, mechanical structures, and safety systems, as well as for setting respective operational limits

for them.

Systems designed for protection against loss-off-coolant accidents, shall be able to carry out their functions even though an individual component in any system would fail to operate and additionally any component affecting the safety function would be out of operation simultaneously due to repairs or maintenance. (N+2 redundancy is needed.)

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FEATURES REQUIRED TO PREVENT RADIOACTIVE RELEASES FROM A SEVERE ACCIDENT

• Containment integrity must be protected by dedicated systems designed to take into account core meltdown related phenomena

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

• For systems designed for protection against severe accidents, single failure criterion (N+1 redundancy) applies. Those systems have to be independent from the safety systems for design bases accidents.

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PROTECTION AGAINST EXTERNAL THREATS

After September 11, 2001: political and public will was expressed to improve protection against terrorist actions. Safety requirements were revised accordingly:

Crash of large passenger and military aircraft has to be taken into account in the design 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)

Plant has to be protected against microwave and biologic weapons.

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EXAMPLES OF LOVIISA 1 AND 2 DESIGN MODIFICATIONS

• The original Sovjet VVER 440 design was supplemented already in the beginning with the reactor containment, emergency cooling systems and I&C systems fulfilling the Western safety requirements.

• Arrangements to cope core meltdown accidents have been implemented (inside reactor vessel retention approach) a couple of years ago.

• Modernization of I&C systems is in progress (digital I&C).

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EXAMPLES OF OLKILUOTO 1 AND 2 DESIGN MODIFICATIONS

• Arrangements (thermal protection of the lower part of the containment, flooding of molten core, filtered containment venting, containment fill-up) to cope with core meltdown accidents were implemented in the late 80’s.

• An extensive modernization program including safety uppgrading and power uprating was carried in the late 90’s interlinked with the operation license renewal.

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OLKILUOTO 1 AND 2 – ARRANGEMENTS FOR SEVERE ACCIDENTS

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MAIN MODIFICATIONS INPLEMENTED DURING THE MODERNIZATION OF OLKILUOTO 1 AND 2 IN 1994-1998

New­type­of­fuel­(10x10)2­new­safety/reliefvalves

New­type­of­fuel­(10x10)2­new­safety/reliefvalves

New­safety­analyses,­upgrading­of­safety­systems

New­safety­analyses,­upgrading­of­safety­systems

Reactor­power­2160­->­2500­MWt

Reactor­power­2160­->­2500­MWt

Upgrading­of­boron­system

New­steam­separators/­­­­­­­­­­­­­­­­­­scroud­head

New­electrical­systems­of­reactor­

internal­pump

New­neutron­fluxmeasuring­system

New­loading­machine­automation

Improvements­of­waste­and­waste­water­treatment­systems

New­generator

New­main­transformer

New­generator­circuit­breaker

Strengthening­ofthe­outer­grid

New­LP-turbines­(n.­+35­MW)

Modification­of­HP-turbine

New­turbine­control/safety­system

New­HP-control/safety­valves

New­moisture­separators(SCRUPS)­to­cross­underpipes­and­process­modifications

Modifications­of­reheaters

Modifications­of­preheaters

Modificatons­of­condensateand­feed­water­pumps

710­->­ca­840­MWe710­->­ca­840­MWe

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DEVELOPMENT OF NEW PLANT DESIGNS

• Finnish utilities participated in the development of new plant designs in the 1980s-1990s

• Fortum: VVER 1000, AP1000• TVO: BWR 90/90+, ESBWR, SWR 1000 (Kerena)

• One reason for the participations was to influence to the plant concepts so that they would meet the Finnish safety requirements.

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FEASIBILITY STUDIES FOR FIN5

• As a preparatory step for FIN5 (later Olkiluoto 3), TVO carried out in cooperation with corresponding vendors feasibility studies for three BWR designs (ABWR, BWR90+, SWR1000) and for three PWR designs (AP1000, EPR, VVER1000) in 1998-2000.

• One of the main goals of the feasibility studies was to find out discrepancies between the plant designs and the Finnish safety requirements.

• Several presentations on each plant design were made for STUK.

• None of the original designs was licensable in Finland as such without design modifications.

• Needed modifications in each design were drafted.

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DECISION IN PRINCIPLE ON FIN5

• In TVO’s application (Nov. 2000) for the Decision In Principle (DIP) for FIN5, the plant designs studied in the Feasibility Studies were presented as possible alternatives to be constructed.

• STUK made a preliminary safety assessment on each design and ended up to the following general statement:

“The preliminary safety assessment of STUK has not brought up matters, which would prove that the plant options, presented in the application for a decision in principle, could not be made to fulfill the Finnish safety regulations. None of the presented options does, however, meet all the requirements as such. The nature and/or extent of the necessary modifications vary considerably by plant types.“

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FIN5 BIDDING PROCESS

• TVO prepared the technical Bid Invitation Specifications (BIS) based on the European Utility Requirements (EUR) document.

• The safety related requirements were modified to be consistent with the Finnish requirements.

• The safety related parts of the draft BIS was send for review to STUK . STUK’s comments were taken into account in the final BIS.

• TVO send the BIS to the Bidders in September 2002, received the bids in March 2003, evaluated the bids and signed the turnkey delivery contract on the EPR in December 2003.

• Several three party meetings (Bidder/TVO/STUK) arranged during the bid evaluation phase in order to find out the licensability of the proposed designs.

FIN5 BIS

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EXAMPLES OF EPR SAFETY FEATURES

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EXAMPLES OF EPR DESIGN CHANGES FROM FEASIBILITY STUDY TO CONTRACT

• Outer reactor containment and safety system buildings were strengthened to provide protection against airplane crash

• Inner containment was equipped with steel liner to ensure its adequate leak tightness

• Design features for severe accident management were improved (molten core management, hydrogen management, high pressure melt prevention)

• primary circuit loops were provided pipe whip restraints designed to restrict leak flow area in case of large LOCA

• in addition to the two diverse digital reactor protection systems, most important protection signals have hard wired back up

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Public Communication

Emergency Preparedness

Expert Services

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STUK’S ORGANISATION Figures indicate staff number at the end of 2008.Total 361.

DG's office

Administration, Internal Services and Information Management

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Non-ionising Radiation

Nuclear Waste and Materials Regulation

Nuclear Reactor Regulation

Radiation Practices Regulation

Research and Environmental Surveillance

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99

44

97

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61

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ORGANIZATION OF NUCLEAR REACTOR REGULATION DIVISION

Regulation

Security

Management Support

Structures and Components Projects and OperationalSafety

Reactor and SafetySystems

Risk Assessment

Electrical andAutomation Systems

Radiation Protection

Nuclear Facilities andSystems

Director Lasse Reiman

Deputy Directors:Marja-Leena Järvinen

Pentti Koutaniemi

MechanicalEngineering

Civil Engineering

ManufacturingTechnique

Organisations andOperation

Projects

Department Services

Director

Deputy Directors

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NUMBER OF PERSONS AT THE NUCLEAR REACTOR REGULATION DIVISION (end of each year)

61 6268

76

8388 86

99

0

20

40

60

80

100

120

2001 2002 2003 2004 2005 2006 2007 2008

nu

mb

er

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EDUCATIONAL LEVEL OF STUK’S STAFFat the end of 2008

DoctorPhD11.9 %

Licentiate4.8 %

Diploma engineerMSc45.8 %

EngineerLower universitydecree12.5 %

Technicians9.8 %

Basic education4.8 %

Vocational school10.4 %

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TECHNICAL SUPPORT OF STUK

• STUK has tight relations to national and international Technical Support Organizations (TSOs), such as

Technical Research Centre of Finland (VTT) IRSN (France) ISaR (Germany)

• TSOs are contracted to make independent confirmatory analysis or experimental research on topics requiring specific in-depth knowledge.

• STUK has co-operation arrangements with several foreign regulatory bodies, such as

ASN (France), NRC (USA) Rostechnadzor (Russia), SSM (Sweden)

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SCIENTIFIC SUPPORT OF STUK

• National nuclear safety research has been organized since the 1980’s into research programs with 3-4 years duration.

• Programs are planned and conducted in co-operation between Ministry, STUK, utilities, research institutes and universities.

• The present program SAFIR2010 includes 33 research projects covering the following areas:

1. Organization and human factors2. Automation and control room3. Fuel and reactor physics4. Thermal hydraulics5. Severe accidents6. Structural safety of reactor circuit7. Construction safety

8. Probabilistic safety analysis (PSA)

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CONCLUSIONS

• The nuclear legislative framework in Finland has a long history and has been updated when needed.

• STUK has a competent staff and effective relations to support organizations to develop safety requirements, to assess nuclear power plant designs and to achieve effective regulatory control of nuclear plant construction and operation.

• Generally, there is mutual understanding and respect between STUK and the licensees. A frank and open relationship is beneficial for tackling safety issues in order to achieve and maintain a high level of safety.

• The safety requirements imposed by STUK have influenced considerably to the design of the plants in operation and under construction in Finland.

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THANK YOU FOR YOUR ATTENTION!