Stress tests nuclear installations

Soon after the Fukushima Daiichi accident on the 11th of March 2011 the European Council decided that all operating 143 nuclear power plants in the European Union were to carry out a complementary safety analysis CSA (also called stress test). The CSA from the Borssele nuclear power plant, the only one in the Netherlands, had a positive result: the power plant complies with all safety requirements and it has safety margins on top of these. Still the CSA indicated some possible further improvements which are being implemented at present.

Lessons learned from the accident and the CSA’s performed at the different power plants are or will be fed back into the international and national regulations for existing and new NPP’s and are or will be implemented at the NPP’s worldwide in order to prevent such an accident anywhere in the future.

Specification of the CSA (stress test)

In addition to the periodic safety assessments that are usually carried out, the CSA shall reveal the robustness of the NPP’s against extreme external events or combinations thereof.

The technical specification of the CSA were agreed upon by the organisation of the European Nuclear Regulators (Western Nuclear Regulators Association, WENRA and the the European Nuclear Safety Regulators Group, ENSREG).

The CSA was required to consider the robustness of nuclear power plants against:

  • Extreme natural hazards:
    Earthquake, Flooding, Extreme weather conditions (cold, heat, snow, ice, storms, tornado's, heavy rain and other extreme natural circumstances.Loss of electrical power
  • Loss of ultimate heat sink
  • Severe accident management

In The Netherlands the analysis was required to consider also human induced events such as shipwreck, explosions, airplane crash.

Netherlands: CSA also at other nuclear installations

The Netherlands decided to carry out a CSA also at the other nuclear installations.

  • Nuclear installations in Petten (High Flux and Low Flux Research Reactors);
  • Research Reactor of the Technical University in Delft;
  • The central radioactive waste storage facilities of COVRA in Nieuwdorp;
  • The uranium enrichment factory of Urenco in Almelo.

The results of the CSA at the other nuclear facility are presently only published on the Dutch website of ANVS.

Results of the CSA of the Borssele nuclear power plant

The CSA report of the Borssele power plant was finalized by the licence holder by the end of October 2011 and sent to the Dutch authorities who used it as a basis for the National Report.

The CSA report has been assessed by different independent experts, amongst others from the KFD (Kernfysische Dienst), one of the organisations that are merged into the current Authority for nuclear safety and radiation protection, ANVS. The conclusion of the National Report is that the Borssele nuclear power plant fully complies with the safety requirements and it has safety margins on top of these. Still, further improvements are possible and should be implemented.

The National Rapport has been sent to the Dutch Parliament and to the European Commission for the peer review process. It is also published on the website of ENSREG.

Peer review CSA

National experts from regulatory bodies and technical support organisations (TSO) from all EU countries (plus a few more on a voluntary basis, like Switzerland and Ukraine) have peer reviewed all National Reports. The peer review consisted of the following steps:

  • Written questioning and answering (January 2012)
  • Presentation and discussion of the reports (February 2012)
  • Site visits to one nuclear power plant per country (March-April 2012)
  • Publication of Ensreg Peer Review Report

The conclusions drawn earlier by the Dutch regulator about the Borssele plant were confirmed This appears from the final national peer review report and the ENSREG peer review report .

Implementation of the improvement measures

The CSA report, the National Report and the ENSREG review report also contain recommendations and suggestions for measures to further enlarge safety margins at the Borssele plant . These measures include technical, organisational and procedural improvement and extension of studies (e.g. on extreme flooding). The Borssele power plant has set up an improvement plan which has been agreed upon by the authorities, and is now being executed. Implementation of the measures will be finalized by end of 2017.

The licensee sends progress reports to the ANVS every three months. The ANVS carries out different supervision activities to verify the implementation of the measures according to the plan.

National Action Plans

Improvement measures in each country are described in a National Action Plan which is regularly updated and reviewed by the European Nuclear Regulators, to monitor implementation according to plans.

A National Action Plan contains, next to the measures at the power plants, also measures to be undertaken by the regulator, such as revision of regulations etc. A first peer review meeting of the National Action Plans was held in April 2013 followed by a second one in April 2015.

Peer review reports following these meetings have been published on the internet (e.g. ENSREG website). In The Netherlands these reports have also been sent to Parliament.