EU Stress Test: high safety level of Swiss nuclear power plants is confirmed

The experts of the European Nuclear Safety Regulators Group (ENSREG) have joined others in awarding good marks to Switzerland’s nuclear power plants. In their assessment of Switzerland’s National Report for the EU Stress Test, the EU experts conclude that Swiss nuclear power plants meet the international safety requirements in all areas, and Switzerland is even singled out for special praise regarding certain aspects.

In Brussels today, ENSREG (the European Nuclear Safety Regulators Group) approved and published the reports on individual countries by their teams of experts.
In the course of these peer reviews, the EU experts assessed the national reports that were submitted at the end of December 2011. Bojan Tomic, Head of the Peer Review Team which is responsible for Switzerland, summarised the outcome: “On the basis of the stress tests, the Swiss nuclear power plants displayed high safety margins and proved to be very robust. The reasons for this are good design concepts and back-fitting measures implemented over many years.”

The report on Switzerland places particular emphasis on the proactive approach of the Swiss Federal Nuclear Safety Inspectorate (ENSI) after Fukushima and on the Reitnau emergency storage facility, which was actually singled out for praise as a “good practice”. Special mention was made of the fact that the energy supply for Switzerland’s nuclear power plants has seven safety layers. Protection against loss of the ultimate heat sink (i.e. cooling of the  reactor) was also described as “outstanding”.

The international experts who reviewed the Swiss National Report on the EU Stress Test on behalf of the European Nuclear Safety Regulators Group (ENSREG) also accord special recognition to Switzerland’s exceptional efforts in connection with the analysis of seismic hazards. Regarding the topic of floods, the experts highlighted the “very good flood protection” at the Beznau nuclear power plant, which was inspected by the EU experts during their visit to Switzerland last March. Precautionary measures against severe accidents were also given good marks.

Recommendations only for the range beyond the design basis

No recommendations were formulated for Switzerland for the range within the design basis of the nuclear power plants. The experts only recommended a further review in respect of extreme weather conditions and hydrogen management in case of severe accidents which exceed the design basis.

“ENSI has already identified the need for further analysis in these areas, and has incorporated this requirement into the 2012 Fukushima Action Plan“, according to Rosa Sardella, Head of the Systems Supervision Area at ENSI. “The points singled out for examination by the experts who conducted the peer review are being added to the Action Plan and will be implemented within the schedule.” Summing up, ENSI Director Hans Wanner comments: “The EU Stress Test involved great effort for everyone who participated.”

“Nevertheless, it was worthwhile in the interests of further improvements to safety.” The stress test was of particular international interest and was significant because it was the first global undertaking of this sort in the nuclear sector, Wanner added.

Recommendations at European level

In the summary regarding the EU Stress Test, the teams of experts arrive at the conclusion that all the participating countries have implemented “important steps to improve the safety of nuclear power plants in their countries”. At the same time, the peers issued three recommendations at European level:

  • WENRA (the Western European Nuclear Regulators Association) should formulate guidelines for the assessment of natural hazards such as earthquakes, floods and extreme weather, including the evaluation of safety margins and cliff-edge effects, i.e. abrupt deteriorations in the condition of a plant due to minor changes in the plant or the impact parameters, for events beyond the design basis.
  • ENSREG (the European Nuclear Safety Regulators Group) should emphasise the importance of regular safety reviews. In particular, it should communicate the importance of periodic reviews of natural hazards and determinations of the plant’s condition at least every ten years.
  • Already recognised measures to protect containment integrity should be implemented rapidly.
  • Measures should be implemented to prevent accidents due to natural hazards, and to mitigate the consequences of such accidents.

“These recommendations offer an opportunity to continue improving the safety of nuclear power plants in Europe,” reports Hans Wanner. Switzerland will be actively involved in the ongoing work. “We have already implemented many of these recommendations in Switzerland,” Wanner notes. Thanks to Periodic Safety Reviews (PSR), all Swiss nuclear power plants already undergo a thorough inspection every ten years. The Reitnau emergency storage facility has reinforced emergency preparedness. The PEGASOS Refinement Project brings the seismic data into line with the latest developments in science and technology. And the Fukushima Action Plan makes provision for additional measures to improve safety, in connection with the containment as well as other aspects.


Stress test as a response to Fukushima

The EU Stress Test is the response of those European countries with their own nuclear power plants to the Fukushima reactor accident following the tsunami on 11 March 2011. On 1 June 2011, ENSI issued a ruling which required the operators of Swiss nuclear power plants to take part in the EU Stress Test. The EU Commission adopted a specification for the content and timeframe on 25 May 2011. Three topics are examined:

1. External events (earthquakes, flooding and extreme weather conditions)
2. Loss of power supply and ultimate heat sink
3. Emergency management

The operators submitted their reports to ENSI by 31 October 2011. ENSI reviewed the reports and processed them to produce the National Report which was delivered to the EU Commission on 31 December 2011. The peer review process was led by a team of seven senior supervision experts from EU countries and a senior manager from the EU Commission. The nuclear power plants in 15 EU countries as well as those in Switzerland and Ukraine were examined in the EU Stress Test. A total of over 80 experts from 24 EU countries took part in the peer review. The peer review process proceeded in three stages: the Desktop Peer Review, the Topical Peer Review and the Country Peer Review.

From 1 January 2012 onwards, the Desktop Peer Review entailed an initial review of the national reports. All the reviewers had access to all the national reports and they were able to submit written questions to the supervisory authorities. Over 2000 questions were asked in this way.

The two-week Topical Peer Review began on 5 February 2012 in Luxembourg, with meetings on the three topics. The review of the Swiss National Report took place on 9 and 10 February 2012. For each topic, this review included presentations of the results from the EU Stress Tests and back-fitting measures that had already been implemented, as well as specific topics (the PEGASOS project, and the establishment of the external emergency storage facility at Reitnau). Out of a total of some 140 questions that were submitted to ENSI, the Inspectorate answered the first 55 (i.e. those accorded the highest priority).

As the result of the Topical Peer Review, a Country Peer Review Draft Report was drawn up for each country, including a summary of the results obtained by the review team and a list of points (Open Issues) for further follow-up by the review team during the Country Peer Review. In addition, a Topical Peer Review Draft Report was drawn up for each topic, summarising the overall results across all countries from ENSREG’s perspective.
The Country Peer Review for Switzerland took place from 26 to 29 March 2012 in Switzerland and – at the request of the peer review team – included a visit to the Beznau nuclear power plant. ENSI and the operators gave detailed presentations of the points requiring clarification (Open Issues) and answered all the questions raised by the peer reviewers.


Tomorrow, ENSI will publish an interview here with Bojan Tomic, Head of the Peer Review Team responsible for Switzerland.