On the preparation of nitrogen gas

n/

IRSN ageing PSA pilot study development

International audienceElectricité de France (EDF), which is the nuclear power operator in France, applied for the plants life extension up to 60 years. The acceptability of this application is analyzed by the French Safety Authority (ASN) and by IRSN, which is the technical support organization, in the light of safety objectives for new reactors. In this context, IRSN developed a pilot study based on IRSN 900 MWe internal events Level 1 PSA, in order to test the methods for modeling in the PSA the impact of the ageing and of the ageing management programs. This test model specifically takes into account the impact of the maintenance aspects on the components (replacement, test, preventive maintenance, etc.). The developed tools (the specific maintenance/ageing database and the PSA model) can be easily used to perform sensitivity studies, as for example to test the impact of different maintenance strategies on the core damage frequency

Fire PSA of the French PWR 900 MWe series Part 1: Detailed study of the critical zones

The Institute for Radioprotection and Nuclear Safety (IRSN) has developed a Fire Probabilistic Safety Assessment of the operating French 900 MWe PWR in order to organize into a hierarchy the items of equipments and the compartments, impacting the core melt frequency following a fire, and to reinforce deterministic safety analysis with functional analysis and realistic fire scenarios. The IRSN Fire PSA is composed of two stages: the first one concerns the selection of critical zones and the second one concerns the detailed study of the critical compartments, corresponding to the development of the fire scenarios and of the fire-induced core damage sequences. The first version of the IRSN Fire PSA has been updated by integrating the specificities of the Fire Action Plan, implemented by the utility on the French 900 MWe PWR. This study shows that four compartments are preponderant. The integration of the Fire Action Plan allowed decreasing the number of preponderant compartments. The integration of the symptom-oriented procedures and the removal of conservatisms should lead to a lower core damage frequency for these preponderant compartments. The results show that fire is not a negligible risk but the implementation of the Fire Action Plan has a significant positive impact on safety. © Carl Hanser Verlag

Fire PSA of the French PWR 900 MWe series Part 2: Special case of the control room

The PSA approach described in part 1 is also used to assess the core damage frequency due to a fire in the control room of a 900 MWe Nuclear Power plant. The specifics of the control room include the cable failure modes due to the fire (spurious order in particular), two different kinds of fire detection systems in the control room and the use of controls and instrumentation of the remote shutdown panel to reach the safe shutdown state if the control room has to be evacuated. This paper will focus on the detailed study of critical compartments and on the results and insights of this study. The purpose of this paper is also to present the methodology used to assess the core damage frequency due to a fire in the control room of a French Nuclear Power Plant, some qualitative results and the main insights further to the discussions with the utility. © Carl Hanser Verlag