The proposed “Stress test“ will not give a comprehensive and transparent risk assessment of the European plants. It is no basis for a judgment about the safety of the European nuclear power plants, especially not a basis for a safety ranking and therefore no basis with which to answer the question as to what nuclear risk should be tolerated in Europe and whether there are nuclear power plants that should be shut down. It will give nearly no information about the reliability of the protections measures of the plants to prevent the supposed failures of the safety systems. It will give nearly no information about all those other scenarios and serious events that could lead to the same safety challenges as the so far supposed extreme events. In particular the consequences of aeroplane crashes on nuclear power plants will not be regarded.
- the limited scope of the “Stress test”,
- the lack of clear assessment and acceptance criteria,
- the lack of harmonized assessment procedures and practices in the different member states
- and taking into account the interests of the involved experts of the utilities and nuclear authorities, including their technical support organizations
it should be expected that reports will be made mainly to demonstrate to the public how safely the plants are operating. Nevertheless the proposed “Stress test” could give more information and to some extent a first estimation of the ability of the individual plants to withstand a few important extreme external events (in particular earthquakes and floods).
Within this limited scope, and taking into account the deficiencies of the method and of the process, the report could give some new information on the robustness of individual plants, and on potential measures going beyond its design basis, in particular on:
- The identification of the step change in the event sequence under which the safety systems will fail completely (cliff-edge effects) and
- time limits until the failure threshold is reached
The proposed “Stress test“ therefore could be a first step towards an harmonized risk assessment of the European nuclear power plants.