The simulation of I & C in accident analyses of nuclear power plants

The BEPU (Best Estimate Plus Uncertainty) approach constitutes a valuable and, under some circumstances, an unavoidable tool to demonstrate the safety of NPP (Nuclear Power Plants). Within the licensing process of the Atucha II PHWR (Pressurized Heavy Water Reactor) the BEPU approach has been followed for issuing the Chapter 15 of the FSAR (Final Safety Analysis Report). Namely, the BEPU approach replaced the classical conservative approach for issuing the Atucha II PHWR FSAR Chapter 15. The key steps of the entire process are basically two: (a) the selection of PIE (Postulated Initiating Events) and, (b) the analysis of each PIE by best estimate models supported by uncertainty evaluation. Otherwise, key elements of the approach are: (1) availability of qualified computational tools including suitable uncertainty method; (2) demonstration of quality of any calculation result; (3) achieving the acceptability and endorsement by the licensing authority. The key features of the BEPU approach are discussed in a companion paper. The present paper is concerned with the planning of the analyses at the item (b). The need to simulate the performance of the I & C (Instrumentation and Control) system is demonstrated.