Abstract
Phase IV of BEMUSE Program is a necessary step for a subsequent uncertainty analysis. It includes the simulation of the reference scenario and a sensitivity study. The scenario is a LBLOCA and the reference plant is Zion 1 NPP, a 4 loop PWR unit. Thirteen participants coming from ten different countries have taken part in the exercise. The BEMUSE (Best Estimate Methods plus Uncertainty and Sensitivity Evaluation) Program has been promoted by the Working Group on Accident Management and Analysis (WGAMA) and endorsed by the Committee on the Safety of Nuclear Installations (CSNI). The paper presents the results of the calculations performed by participants and emphasizes its usefulness for future uncertainty evaluation, to be performed in next phase. The objectives of the activity are basically to simulate the LBLOCA reproducing the phenomena associated to the scenario and also to build a common, well-known, basis for the future comparison of uncertainty evaluation results among different methodologies and codes. The sensitivity calculations performed by participants are also presented. They allow studying the influence of different parameters such as material properties or initial and boundary conditions, upon the behaviour of the most relevant parameters related to the scenario.
Highlights
Models and codes are an approximation of the real physical behaviour occurring during a hypothetical transient, and the data used to build these models are known with certain accuracy
Phase IV of BEMUSE Program is a necessary step for a subsequent uncertainty analysis
The BEMUSE (Best Estimate Methods plus Uncertainty and Sensitivity Evaluation) Program has been promoted by the Working Group on Accident Management and Analysis (WGAMA) and endorsed by the Committee on the Safety of Nuclear Installations (CSNI)
Summary
Models and codes are an approximation of the real physical behaviour occurring during a hypothetical transient, and the data used to build these models are known with certain accuracy. One of the goals of computer code models of Nuclear Power Plants (NPP) is to demonstrate that these are designed to respond safely at postulated accidents. The analyses can either use conservative or best-estimate (BE) codes. Science and Technology of Nuclear Installations (i) The conservative codes contain assumptions to try to cover unknown uncertainties. These assumptions are often unphysical and lead to predictions that could be worse than reality. (ii) BE codes are designed to model all the relevant processes in a physically realistic manner. A calculation with a BE code is considered the best approach of what is more likely to occur. It is necessary to evaluate the uncertainty of the estimation
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