Modeling Of AP1000 Nuclear Power Plant Lb-Loca Best Estimate Analysis And Uncertainty Study

In 1988, The Nuclear Regulatory Commission (NRC) approved the final version of a revised 10CFR50.46,"Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors", which allows the use of either conservative or realistic method for licensing LOCA analysis. At present, the LOCA analysis method used in China is conservative, while the realistic method used for considerable Nuclear Power Plants (NPPs) overseas, such as best estimate plus uncertainty (BEPU) method. The BEPU method becomes a trend worldwide, it is generally recognized that, realistic LOCA analysis method can offer larger PCT margin.This work contains the modeling of AP1000 Nuclear Power Plant DECLGB LB-LOCA best estimate analysis, based on the BE thermal hydraulic system code RELAP5/MOD3 platform, and the preliminary uncertainty study of AP1000 LB-LOCA.Firstly, the AP1000 NPP LB-LOCA best estimate analysis model based on RELAP5/MOD3 has been set up according to the related materials, and the applicability is checked through steady state test, transient calculation and sensitivity study on the settings of some input models and parameters.Further, based on the study of AP600 and other plants, Phenomena Identification and Ranking Table (PIRT) of AP1000 LB-LOCA has been initially established. And according to PIRT, the identification of"uncertain"input parameters which contribute significantly to peak cladding temperature (PCT) of AP1000 DECLGB LOCA, and with specified ranges and probability distributions of these parameters have been initiated. After that, based on nonparametric statistics method, the input sample of input parameters by using Random Simply Sampling (SRS) and Latin Hypercube Sampling (LHS) method has been generated, which are used for uncertainty calculation and sensitivity calculation separately.Finally, uncertainty and sensitivity calculation/analysis of PCT in AP1000 LB-LOCA is carried out. According to the results of sensitivity analysis, the parameters which have significant impact on PCT have been derived, and recalculation of uncertainty analysis conformed. At last, investigate the PCT characteristics of uncertainty and influence by comparing the upper limit of 95%/95% PCTs and their distribution, etc.