the european stress test for nuclear power plants

Assessment methods and data

The “Stress test“ does not comply with qualified and comprehensible methods of technical studies and review practices.

The scope of the assessment will require answering new questions. These new questions partly rely on existing documents and partly on new investigations, inspections, assessments and calculations. New documents will be generated. ENSREG requires a classification of the documents:

“Documents referenced by the licensee shall be characterized either as:

  • validated in the licensing process
  • not validated in the licensing process but gone through licensee's quality assurance program
  • none of the above.”28

The “specifications” set the limited timeframe of two and a half months for the operator’s first report and one month for the nuclear authority to check it29. It is to be expected that a lot of safety relevant documents will be classified in the second or third category. This will significantly weaken the confidence in the used data and - as follows - in the report. 

Considering the limited time schedule the “specifications” accept so called “engineering judgments” whenever there is no time for orderly founded assessments30. The judgment of an engineer depends on many factors, on his/her experience, on his/her “questioning attitude” and on other subjective factors, especially on his/her subjective perception of the acceptance of risks.31 It is therefore not a basis for a comprehensible and safety-oriented method for the evaluation of the considered risks.

On the other hand it is completely out of scope for a nuclear authority to check the operator’s report within one month. Considering usual practice it would take at least two years to come to a founded judgment.32

28 Fn.4, page 5 (downloadable document)

29 This is the time schedule for the first report that will be the basis for the report to the EU Council deliberations in December 2011. It is not to be expected that the results of the final report will differ significantly from the first report that is expected in April 2012. The first report will strongly predetermine the second one.

30 Fn. 4, page 2 (downloadable document)

31 Lorenzo Strigini, Engineering judgment and safety and its limits: What can we learn from research in psychology, City University, London 2002

32 The legally mandatory periodic safety assessment in Germany takes not less than two up to five years or more for one plant.