One of the most intense multinational safety reviews of nuclear power, the post-Fukushima European stress tests process, is now winding up. Reports for 140 nuclear power plants in 17 countries (15 in the European Union plus Switzerland and Ukraine) were produced, and analysed by national regulators, which were in turn analysed in peer reviews by 70 experts under the European Nuclear Safety Regulators Group.
All of the countries included have taken 'significant steps to improve the safety of their plants,' said ENSREG's final report, released on 25 April. However, it noted that there was lots of variation among the various countries in their approach and in the degree of action taken so far. Action plans have already been or are soon to be defined for each country covered.
ENSREG said that European regulators should consider four main areas of safety improvement.
1. Standardise extension of safety margins beyond the design basis. Although the peer reviews found that the national reports were generally compliant with ENSREG guidance for earthquakes and flooding, national regulators were found to be inconsistent when it came to events that exceed the safety design-basis, and to assessments of cliff-edge effects, in which a relatively small change has a major effect. It has recommended that the Western European Nuclear Regulators Association (WENRA) develop guidance.
2. Plan to carry out another periodic safety review in 2021. ENSREG said that the peer review process has demonstrated the usefulness of carrying out a periodic safety review, particularly for natural hazards, and suggests it should be repeated every decade.
3. Start carrying out containment integrity protections now. The ENSREG report calls this a 'crucial' issue, and recommends that operators make improving the resilience of containment integrity an urgent priority.
4. Improve defences against natural hazards.
The report made two other recommendations, both of which fell outside the strict remit of its original mandate. First, it recommended a follow-up to check implementation of its guidance. Second, it recommended that European countries consider off-site emergency preparedness.
The latter point proved divisive at the ENSREG meeting on 25 April, according to a statement from chairman Andrej Stritar. Although an initiative for EU-wide harmonisation of off-site emergency preparedness has been proposed, the statement said that several members stressed the complexity of the issue, which involves diverse national authorities and responsibilities.
There was also disagreement about a review of national nuclear safety legislation. Although the UK, Luxembourg and Greece have presented their preliminary views, most ENSREG members stated that the time was not right to discuss the issue, the chairman's statement said.
At the meeting, the report and a public statement were endorsed by all countries' representatives, except that of Austria, which abstained. A public meeting to discuss the results of the tests is planned for 8 May in Luxembourg.
11 March 2011: Fukushima Daiichi earthquake and tsunami
24-25 March: European Council requests comprehensive safety and risk assessment of 140 reactors in EU
April: WENRA drafts preliminary stress test specifications
24 May: ENSREG and European Commission achieve consensus on stress test specifications1
1 October: Peer review specifications agreed
31 October: Deadline for final operator assessments
31 December: Regulators submit final national reports
1 January 2012: Peer review starts. Step 1: desktop review of national reports. 70 experts, nominated for three topical areas (safety: natural hazards, loss of safety systems, severe accident management).
17 January: ENSREG/peer review board host public meeting
5 February: Reviewers meet in Luxembourg for topical review
March: Country reviews begin. Three- to four-day visit by eight peer reviewers, including plant visit.
25 April: Peer review report endorsed
8 May: Second public meeting planned in Brussels