the european stress test for nuclear power plants

No acceptance level for “robustness”


The European “Stress test“ shall demonstrate how robust the European nuclear power plants are.25 In the current discussion after the Fukushima accident the term “robustness” is used as the key expression for that what should be required. If you are robust you will never get ill even in bad weather and insufficient clothes. Robustness is meant as something that guarantees a certain kind of additional safety. But there is no definition in the international framework of safety rules or in the “Stress test” specifications, as to what additional level of safety should be achieved, what level of safety would justify saying that a plant is robust or should be backfitted considering the new requirements of the Fukushima accident or should be shut down. Therefore room will be given for incomprehensible and arbitrary assessments of the results of the “Stress test”. A transparent method must provide criteria defining what level of safety for a required basic level has to be achieved and what perhaps might be a level that justifies saying “it’s a robust plant” with additional safety features. 

The German Reactor Safety Commission has defined four levels of robustness, the basic level and three higher levels.26 

The basic level is chosen as a level that must be fulfilled by all operating plants, taking into account that all plants meet the licensing conditions and have realised all backfitting measures required by the authority. Each of the three levels of robustness defines a larger kind of safety-margin beginning with level 1 of robustness. Level 3 means that the plant is safe even under the defined extreme conditions. 

With the example of an earthquake the levels are defined as follows:27 

Basic level: the plant must be safe in the case of an earthquake that is to be expected with a probability of 10-5 per year. 

First level of robustness: the plant is safe in the case of an earthquake with an intensity of plus one. Accident management measures may be taken into account. 

Second level of robustness: the plant is safe in the case of an earthquake with an intensity of plus two. Accident management measures may be taken into account. 

Third level of robustness: the plant is safe in the case of an earthquake with an intensity of plus two even without considering accident management measures.





25 Id., page 6 (downloadable document)

26 German Reactor Safety Commission (RSK), Plant specific safety assessment of German NPP in the light of the Fukushima accident (German text, Anlagenspezifische Sicherheitsüberprüfung (RSKSÜ) deutscher Kernkraftwerke unter Berücksichtigung der Ereignisse in Fukushima-I (Japan), Berlin, 14.05.2011, http://www.bmu.de/energiewende/doc/47398.php

27 See id., page 23 (downloadable document)