Outcome of the EU Nuclear Safety Stress Tests

Outcome of the EU Nuclear

Safety Stress Tests

Andrej Stritar

Chairman, ENSREG

ENSREG – who are we?

European Scene

• In European Union …• … there are almost 150

power reactors…• …in 15 EU member

countries,• producing ~1/3 of all

electricity in EU

We must keep them operating safe!

Before 2000

Country 1

Operator

RulesRegulator

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RulesRegulator

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RulesRegulator …

E. CommissionDGTREN

• Nuclear Safety was only national responsibility

WENRA, a voluntary club

• “Bottom up” approach to harmonisation

E. CommissionDGTREN

WENRA – nuclear regulators

Regulator

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Country 1

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RulesRegulator

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ENSREG – after 2007

• “Top down” advisory body

ENSREG – 27 EU regulators + EC

Country 1

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RulesRegulator

Country 2

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RulesRegulator

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RulesRegulator …

E. CommissionDGTREN

E. CommissionDGTREN

Regulator

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What is now better?

ENSREG – 27 EU regulators + EC

Country 1

Operator

RulesRegulator

Country 2

Operator

RulesRegulator

Country 3

Operator

RulesRegulator …

E. CommissionDGTREN

WENRA – nuclear regulators

WENRA Reference Levels

Nuclear Safety Directive, RW Directive,Stress Tests

Nightmare of 11 March 2011

Nightmare of 11 March 2011

• Beneficial conversion of mass to energy turned into a disaster

• The feedback loop for assuring perfection has failed!

• Trust of the society was lost!

Regulators

Operators

MediaDOUBT

CONFIDENCEPERFECTION

•G

Public

ELECTRICITY

TRUST

DOUBT

Stress Tests were about restoring confidence and regaining trust by further improving nuclear safety

Why Fukushima has happened?

• Tsunami is a very rare natural disaster.• It was underestimated during the design,

there was not enough knowledge about it.• Safety margins were too small.• Uncertainty of our understanding of

natural phenomena should have been compensated by bigger conservatism – higher protective dikes!

Fukushima concerns

The main lessons learned from Fukushima were actually the main objectives of our

Stress Tests:

• Did we properly take into account uncertainties of all potential external hazards?

• Are our plants robust enough, are safety margins big enough?

• Are we able to cope even with extremely low probability events?

EU response to Fukushima

Stress Tests

• 11 March: Fukushima accident occurs• 24 – 25 March: European Council Requests

– Stress tests to be developed by European Nuclear Safety Regulators Group (ENSREG), the Commission and WENRA

– Safety of all EU plants should be reviewed

– Scope of review developed in light of lessons learned from Japan

– Assessments conducted by national Authorities

– Assessments completed by a peer review

Development of Stress Test Methodology

• Methodology drafted by WENRA in April• Agreed to by ENSREG in May• On 25 May 2011 ENSREG including the

European Commission published the ENSREG declaration that described EU Stress Tests methodology

Stress Test Implementation

15. 8. 2011 Operators submitted progress

reports

15. 9. 2011 National progress reports submitted

31. 10. 2011 Operators submitted final reports

8. 12. 2011 EU Council informed about progress

31. 12. 2011 Final National reports submitted

The Peer Review Process

The process

• WENRA prepared first draft in June

• Task Force formed in July

• Involvement of stakeholders

• Number of meetings and discussions

• The Methodology endorsed by ENSREG on 12 October

The process

• The Peer Review Board• Three topical reviews in parallel, January

and February 2012– Initiating Events– Loss of Safety Functions– Severe Accident Management

• 17 country visits in 6 parallel groups,March 2012

• About 80 experts involved• ENSREG Report + 17 Country Reports

Milestones

• EU Council expected the final report in June 2012

• EC needed the report from ENSREG by end of April

• Peer Review started on 1 January• Majority of work was done in

February/March• The report was finalised in April

Main Results of the Peer Review

General conclusion over Europe

• Significant steps taken in all countries to improve safety of plants

• Varying degrees of practical implementation– Regulatory systems– Extent of programs

Consistency of approaches in European countries

• Global consistency over Europe in identification of:– Strong features– Weaknesses– Measures to increase robustness

Measures to increase robustness of plants

• Significant measures to increase robustness already decided or considered, such as:– Additional mobile equipment– Hardened fixed equipment– Improved severe accident management with

appropriate staff training

• Details available in Country Reports and Main Report

Example: New equipment in Krško NPP

Pumps

Portable fire system

Additional connection points

Portable external diesel generators

Assessment of natural hazards and margins

• Recommendation no.1:– WENRA, involving the best available

expertise from Europe, should develop guidance on natural hazards assessments, including earthquake, flooding and extreme weather conditions, as well as corresponding guidance on the assessment of margins beyond the design basis and cliff-edge effects.

Periodic safety review

• Peer review demonstrated efficiency of periodic safety reviews – Maintain and improve safety and

robustness of plants– Specially relevant, in the context of the

peer review, for protection of installations against external hazards

Periodic safety review

• Recommendation no. 2:– ENSREG should underline the

importance of periodic safety review. In particular, ENSREG should highlight the necessity to re-evaluate natural hazards and relevant plant provisions as often as appropriate, but at least every 10 years.

Containment integrity

• Fukushima disaster highlighted once again the importance of the containment function

• Last barrier to protect people and the environment against radioactive releases

• Issue already considered as follow-up of previous accidents and possible improvement already identified


• Recommendation no. 3:– National regulators should consider

urgent implementation of the recognized measures to prevent containment integrity.


• Measures vary depending upon the design of the plants

• For water cooled reactor, they include equipment, procedure and accident management guidelines to:– Depressurize primary circuit to prevent high

pressure core melt– Prevent hydrogen explosions– Prevent containment overpressure

Prevention of accidents resulting from natural hazards and limiting

their consequences

• Preliminary lessons learned from Fukushima: Necessary increase of defense in depth to take into account severe accidents resulting from extreme natural hazards exceeding design basis or current safety requirements applicable to plants


their consequences

• Such situation can result in:– Devastation and isolation of site– Event of long duration– Unavailability of numerous safety

systems– Simultaneous accidents in several

plants, including their spent fuel pools– Radioactive releases


their consequences

• Recommendation no. 4:– National regulators should consider

necessary implementation of measures allowing prevention of accidents and limitation of their consequences in case of extreme natural hazards


their consequences

• Typical measures:– Bunkered equipment including

instrumentation and communication means– Mobile equipment protected against extreme

natural hazards– Emergency response centers protected

against extreme natural hazards and radioactive releases

– Rescue teams and equipment rapidly available to support local operators

Follow-up

• Most actions are being prepared and implemented by operators and national regulators

• Special Task Force is preparing EU action plan to be endorsed by ENSREG on 3 July

What is still missing?

• The Security Track of EU Stress Tests was conducted in parallel.

• During the year the issue of off-site emergency preparedness has proven to deserve even more attention.

• Long term ENSREG action plan is being prepared.

Global Impact

• EU Stress Tests became a global model

• Directly used in some countries (Japan, UAE, South Africa, Russia)

• Important reference for all the others, including IAEA

What next?

• Stress Test campaign is over!• All lessons learned and actions to be done will

be included in our normal working processes.• Majority has to be done by operators and

national regulators.• Common technical issues will be dealt by

WENRA.• ENSREG’s special Task Force is preparing our

action plan.• Additional plant visits will be organised after

proper objectives are defined.

Proper focus

• Stress Tests were about the– design of plants and – mitigation of accidents.

• Equally or more important is – operational safety.

The focus of operators and regulators must be properly balanced between these three cornerstones of nuclear

safety!

Documents

Outcome of the EU Nuclear Safety Stress Tests