Development and use of level 1 PSA at IRSN
Titre du congrès :PSA 2008 - International Topical Meeting on Probabilistic Safety Assessment and Analysis
Ville du congrès :Knoxville
Date du congrès :07/09/2008
Beginning with the early '90 the IRSN developed and used the PSA for French Nuclear Power Plants. IRSN is the support organization for the French Safety Authority (ASN) and in the frame of its missions the in-house development of PSA allowed gaining valuable knowledge on nuclear safety, beyond the probabilistic analysis area. This constituted in the same time a particularly deep independent analysis of the PSAs developed by the licensee (EDF). The main formal use of PSA is its using as a support for the Periodic Safety Review (PSR). Every 10 years, the level of safety of the plants of a given type is assessed. The licensee uses its own PSA to demonstrate the acceptability of the achieved safety level, and to identify the safety improvements, the conclusion being verified by IRSN using its own in-house developed PSA. The PSA is playing an important role in the frame of EPR safety assessment. The PSA is used to support the optimization of the Technical Specification, some methods to take into account the plant state changing transition risk and the shut-down risk being under discussion with EDF. Day-to-day the PSA is used as a tool for TechSpecs exemption analyses and for other regulatory activities. The PSA is used for the precursor's analysis and for the development of the safety indicators. The paper presents examples of PSA insights as well as examples of use of PSA by IRSN for diverse safety assessment activities.