Uncertainty and sensitivity analysis for a nuclear power plant Large Break Loss of Coolant Accident (LB-LOCA) in the context of OECD BEMUSE programme

The second comparative exercise performed as part of BEMUSE (Best Estimate Methods - Uncertainty and Sensitivity Evaluation) Programme, was devoted to Nuclear Power Plant (NPP) application. The BEMUSE programme has been promoted by the Working Group on Analysis and Management of Accidents (WGAMA) and endorsed by the Committee on the Safety of Nuclear Installations (CSNI). The programme was divided into two main steps. The first step was to perform an uncertainty and sensitivity analysis related to the LOFT L2-5 test, and the second step was to perform the same analysis for a Nuclear Power Plant Large Break Loss of Coolant Accident (LB-LOCA). The second step, also known as Phases IV and V, started in May 2006 and was finished in September 2009. Phase IV of BEMUSE Program is connected with previous Phase II, being a necessary step for an uncertainty analysis: the simulation of the reference scenario and sensitivity analysis. The selected plant was Zion 1 NPP, a 4 loop PWR unit. Thirteen participants coming from ten different countries have taken part in the Phase IV of the program. Phase V main objective was to obtain uncertainty bands for the maximum cladding temperature (time trend), upper plenum pressure (time trend), maximum peak cladding temperature (scalar), 1st peak cladding temperature (scalar), 2nd peak cladding temperature (scalar), time of accumulator injection (scalar), time of complete core quenching (scalar). Fourteen groups from twelve organizations and ten countries have participated in BEMUSE Phase V. Both Phases IV and V compared procedures with experience gained in the previous step of the programme. (author)