The European stress tests

Current situation

From 22 to 26 April 2013, ENSREG and Germany jointly organised a workshop during which the participating states presented the state of implementation of the results of the European stress test and laid out their plans of measures. Lessons were drawn from the nuclear accident in Fukushima, necessary measures have been implemented or will be implemented with ambitious targets over the next years. The participants were in favour of carrying out peer reviews of their action plans in two to three years. ENSREG approved the final report of the workshop in late May and published it on its website on 10 June. The results of the workshop were also presented at the ENSREG Safety Conference in June 2013.

1. Comprehensive risk and safety assessment of nuclear power plants in the European Union

Immediately after the nuclear disaster in Fukushima, Commissioner for Energy Oettinger invited all EU ministers for energy and representatives of nuclear regulators and industry to consultations in Brussels on 15 March 2011. At this meeting, all participants agreed on comprehensive safety assessments for nuclear power plants in the European Union. Switzerland and Ukraine, too, declared their willingness to participate in these stress tests. 

On 24 and 25 March 2011 the European Council declared that the "safety of all EU nuclear plants should be reviewed on the basis of a comprehensive and transparent risk and safety assessment (stress tests)". The European Nuclear Safety Regulators Group (ENSREG) drew up scope, modalities and time frame for the EU stress tests and published these specifications on 13 May 2011. On 11 October 2011 ENSREG adopted the detailed requirements for contents and format of the reports and the procedure for the peer reviews which were then carried out in spring 2012.

2. The stress test

The stress tests are a review of nuclear power plants being conducted in light of the events in Fukushima. The test comprises a review of plant design and an assessment of robustness. The review is based on three scenarios, or priority issues, which are reviewed independently of the probability of occurrence:

i) initiating events:

  • earthquakes,
  • flooding and
  • extreme weather conditions

ii) loss of safety functions:

  • successive loss of power systems
  • loss of ultimate heat sink and
  • combination of both incidents

iii) severe accidents management:

  • measures against and management of loss of core cooling function,
  • measures to ensure containment integrity after core melt and measures against and management of loss of cooling function in spent fuel pool cooling
  • report on results of the stress test

The reports submitted by operators in line with ENSREG requirements form the basis for the national reports. The first part of these reports describes the location of sites and the characteristics of the installations, the extent of probabilistic safety analyses including essential results and an overview of key safety systems. The second part of the reports contains chapters on the different scenarios, each outlining general Länder requirements on design bases, the design of the individual installations and a compliance check. The safety margins beyond the design are identified, and it is assessed in which case a loss of functions, for example of core cooling, could be expected. This is done to assess the installation's robustness in case of extreme scenarios. The national report summarises the licensees' reports and the evaluation of the regulators of the respective states and draws a conclusion on current designs and the robustness of installations. A report on the progress of the stress tests had to be submitted by 15 September 2011. The deadline for the final national report was 31 December 2011. The Federal Environment Ministry sent the report to the European Commission on time. The reports of all member states can be accessed on the ENSREG website. German power plant operators published their stress test reports on their own websites. The links are available in the Annex to the German national report. 

The national reports of all participating countries were the basis for the peer reviews in March and April 2012. The results of the peer review of Germany are available in the Annax to the full report of ENSREG and the European Commission.

3. The EU stress test in Germany

The Federal Environment Ministry, the competent Länder regulators and the operators of nuclear power plants in Germany agreed on the modalities of the EU stress test for German nuclear power plants on 30 June 2011. This date is also the reference date for the state of the 17 German nuclear power plants in operation, irrespective of the moratorium or expiration of operation permits from 6 August 2011 for 8 of the installations under the 13th Act amending the Atomic Energy Act. 30 June 2011 is also the reference date for the state of the nuclear power plant Obrigheim, which is being dismantled, but where fuel elements are still stored. 

In Germany, the EU stress test was carried out in addition to the safety review by the Reactor Safety Commission (RSK). It revealed that in terms of the three central aspects (external hazards, loss of power and coolant failure, accident management measures) conservative and stringent design requirements had been realised at the time of construction. The RSK had already established that with reference to specific aspects, German facilities demonstrated a high resistance to stress. The German report on the EU stress test pointed out aspects that could be improved, especially with regard to emergency response, but also with regard to enhancing safety. These aspects have since been improved in all German plants. In addition to the above-mentioned topics and the impact of accidents in neighbouring installations, the German report also included RSK statements on man-made hazards such as plane crashes, off-site gas explosions or terrorist attacks. The content therefore goes beyond the framework laid down by the EU.

4. Peer reviews of stress test

For the review process following the national reports, teams of technologically experienced representatives of regulators from participating states were established. The review consisted of an evaluation of the respective national report, thematic hearings and missions to participating countries. In February 2012, the topical peer reviews were carried out. On this occasion, teams of experts critically reviewed member states' results on the three priority issues. This was done in the European Commission's buildings in Luxembourg. 

The results of the three topical peer reviews were incorporated into the country reviews in March and April. The country reviews took place in the country subject to the respective review. They gave an overview of the overall situation in the respective country. Country reviews also included a visit to a nuclear power plant, where the measures discussed were explained at the site. The country review reports include recommendations on improvements, for instance changes to installations, retrofits or further investigations. Germany's country review took place in Bonn from 19 to 23 March 2012 with a visit to the Grafenrheinfeld nuclear power plant. 

The EU stress tests were the first measure to achieve a joint review of all nuclear power plants in Europe through peer reviews. The activities provided insights in important safety characteristics and properties of European nuclear power plants and severe accident management to an entirely new extent. In total more than 500 person-years were invested in this unique and very successful process by all stakeholders. 

ENSREG adopted the results of the peer reviews in April 2012 (ENSREG Summary Report; Peer review report, Stress tests performed on European nuclear power plants). The final report was published together with the national reports of the 17 participating countries. A joint statement of ENSREG and the European Commission on the results of the stress tests, the peer reviews and further steps is available at the ENSREG website. 

5. ENSREG Action Plan

On 31 July 2012, ENSREG published the action plan Follow-up of the peer review of the stress tests performed on European nuclear power plants, which details activities at European level for the time after the EU stress tests. The action plan specified that national action plans should be drawn up and published by the end of 2012, and that these plans should be discussed by all participating countries in the spring of 2013. The member states were responsible for laying down the type and extent of measures for the individual nuclear power plants. Plans were also made for additional visits to installations in order to take stock of improvement measures already initiated due to the EU stress tests. These visits were carried out in September 2012. The corresponding reports were published on the ENSREG website under the title Follow-up fact finding site visits. In Germany, the Gundremmingen nuclear power plant was visited.

6. European Commission's report on stress test results

Commissioner for Energy Oettinger presented the report of the European Commission on the results of the stress test on 4 October 2012. In this report, the Commission evaluated the results of the stress tests and presented its plans for further developing European law on nuclear safety. The Commission did not coordinate the report with national regulators and presented the results of the stress test in the staff working document in in addition to the documents adopted jointly by ENSREG and the Commission. 

With regard to German power plants, the Commission noted the lack of severe accident manuals in the staff working document and the lack of seismic instruments as well as insufficient seismic designs. It should be noted, however, that severe accident manuals have been in place in all German nuclear power plants for many years. The guidelines that supposedly do not exist refer to additional on-site instructions which still have to be drawn up. The layout for any German power plant takes due account of site-specific design earthquakes. This also explains the variations in seismic instrumentation of the different installations. In contrast to the Commission's view, seismic instrumentation had not been not a subject of the stress test. However, it was an issue during the peer reviews.

7. Follow-up to EU stress tests

7.1 Follow-up in Germany, national action plan

The BMU asked the Reactor Safety Commission (RSK) to analyse the results of the EU stress test for German nuclear power plants and consider them during further consultations on possible safety improvements. The RSK adopted and published its Recommendations on 27 September 2012. The Federal Environment Ministry forwarded them to the competent Länder authorities. 

The RSK recommendations and the Gesellschaft für Anlagen- und Reaktorsicherheit's (GRS) information note, available since February 2012, were the basis for safety-related assessments and measures that had yet to be taken. The Federal Environment Ministry drew up the national action plan together with the regulators of the Länder on this basis and in line with ENSREG requirements. The action plan was submitted to ENSREG in English in late 2012 and published on its website. The German version of the action plan is available at the BMU Website. The action plan illustrates that all nuclear power plants have taken measures mainly in the area of severe accident management. Many of these measures have already been realised, others are being implemented within the framework of supervision procedures.

7.2 ENSREG workshop on national action plans

ENSREG organised a workshop headed by Germany from 22 to 26 April 2013 where all participating states outlined their plans and reported on the state of implementation of the stress test results. The aim was to have the states, while maintaining their national responsibility for nuclear safety, agree on a widely harmonised level of risk reduction regarding extreme events in nuclear power plants. 68 experts from 21 EU member states, Ukraine and Switzerland as well as 11 observers from three other countries (Armenia, Canada and Taiwan) and the IAEA participated in the workshop. Discussions were open but did not fail to touch on critical issues. The participants exchanged experience and addressed upcoming challenges for European countries. Using a transparent procedure it was shown that lessons could be learned from the nuclear accident in Fukushima and that the implementation of measures had already begun. ENSREG approved the final report of the workshop in late May and published it on its website on 10 June. A second workshop on national action plans was held in Brussels in April 2015. The goal of the workshop was a mutual exchange of information among participating countries on progress made in the implementation of measures and a discussion on technical and organisational measures to increase nuclear safety. The workshop showed that the implementation of the national action plans is already complete in many countries or will be complete in 2016 in other countries. Only few countries stated that the implementation would take more time than planned which means that in some individual cases the measures would first be implemented in plants in 2020. Progress made in the individual countries was discussed openly and constructively, but also with a critical eye. ENSREG published the summary report of the workshop.

7.3 Outlook

All European partners are convinced that the stress tests contributed to further improving nuclear safety of installations in Europe. It will be important to continue these joint discussions and mutual reviews among European partners. In future, mandatory topical peer reviews will be carried out every six years in Europe, during which European countries will have the opportunity to discuss certain nuclear safety issues and identify potential for improving the safety of their nuclear plants. The BMUV is active in various European bodies and groups, particularly ENSREG, and works towards the goal of all states achieving high standards of nuclear safety. The BMUV provides information on and discusses all issues relating to nuclear safety in nuclear installations close to borders in bilateral bodies with Belgium, France, Switzerland, the Czech Republic, the Netherlands and Austria. These bilateral talks also include the federal Länder that share a border with the respective country. The results of the stress tests were discussed in the Commission's working groups. The responsibility for the safe operation of installations, however, generally remains with the respective country.

Last updated: 20.07.2022

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