The French experience in application of probabilistic methodologies to the safety justification of Non Reactors Nuclear Facilities
G. FRAIZE, J.M. LANORE, Workshop OCDE/CSNI/WGOE/FCS « PSA of Non Reactors Nuclear facilities », Isssy le Moulineaux, France, 4-5 octobre 2004.
Safety justifications of the French facilities that are operated for the fuel cycle and research activities are based on the conventional deterministic approach. A strict management of the operating conditions and limits and periodic safety re-assessment completes this approach. This approach was considered in reference to the extreme variety of processes and risks to be addressed in the safety cases. For the final assessment of specific risks, basic probabilistic methods were used. Examples of optimisation of important systems configuration will be provided as they were finalized based on comparison of failure probabilities. For such cases, generic failure rates for the equipments have been used. The main provided examples are related to the UP3 project. These optimisations were performed under the framework of the deterministic approach (examples of cooling of HLW tanks or electric supply architecture) and defence in depth principle. So, in spite of very low overall failure probability, the design was completed by consequences mitigation means. Furthermore, HAZOP methodology is routinely implemented, if needed, for the complex systems such as mechanical devices or systems that can be important for safety. (Handling cranes, etc.). Taking into account the progress of probabilistic approaches, the introduction of such approaches based on the reactor field experience could be envisaged assuming that specific data and methods could be developed, validated and approved. Safety re-assessment procedures should provide a relevant framework as updated safety objectives could be agreed on during it. The paper will present and discuss the major technical and methodological issues to be addressed for assessing the adaptation of standard PSA to NRNF.