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
• Nuclear Safety was only national
responsibility
E. Commission
DGTREN
Country 1
Regulator
Country 2
Regulator
Rules
Operator
Country 3
Regulator
Rules
Operator
Rules
Operator
…
WENRA, a voluntary club
• “Bottom up” approach to harmonisation
WENRA – nuclear regulators
E. Commission
DGTREN
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Country 1
Regulator
Country 2
Regulator
Rules
Operator
Country 3
Regulator
Rules
Operator
Rules
Operator
…
ENSREG – after 2007
• “Top down” advisory body
ENSREG – 27 EU regulators + EC
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Country 1
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Regulator
Country 2
Regulator
Rules
Operator
E. Commission
DGTREN
Regulator
Regulator
Regulator
E. Commission
DGTREN
Regulator
Regulator
Regulator
Country 3
Regulator
Rules
Operator
Rules
Operator
…
What is now better?
WENRA – nuclear regulators
ENSREG – 27 EU regulators + EC
E. Commission
DGTREN
WENRA Reference Levels
Nuclear Safety Directive, RW Directive,
Stress Tests
Country 1
Regulator
Country 2
Regulator
Rules
Operator
Country 3
Regulator
Rules
Operator
Rules
Operator
…
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
Media
DOUBT
DOUBT
Operators
TRUST
Public
CONFIDENCE
PERFECTION
•G
ELECTRICITY
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
Containment integrity
• Recommendation no. 3:
– National regulators should consider
urgent implementation of the
recognized measures to prevent
containment integrity.
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
Prevention of accidents resulting
from natural hazards and limiting
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
Prevention of accidents resulting
from natural hazards and limiting
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
Prevention of accidents resulting
from natural hazards and limiting
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!