Comparison of Bias and Uncertainty of ENDF/B-VII with ENDF/B-VI for Spent Fuel Criticality Analysis

Accurately evaluating the criticality of spent fuel storage rack is of importance to the analysis for the safety of the fuel storage rack and the reliability of shielding design. Because of this request for assessment, the Monte Carlo simulation has been an appropriate approach in the criticality analysis to estimate due to its general geometry modeling capability, correct representation of transport effects and continuous energy cross sections. The benchmark problem cases were selected from the International Handbook of Evaluated Criticality Safety Benchmark Validation Experiments (IHECSBE) by considering the typical PWR specifications such as the use of LEU and square-shape lattice structure of fuel assembly. Bias and uncertainty evaluation of MCNP6.1 with ENDF/B-VII using criticality safety benchmark experiments had been performed. The criticality validation calculation shows that the bias is 0.00265 with having uncertainty 0.01033. Also, the effective multiplication factors are in a range of 0.98094 to 1.00903 and all calculation results are within 2% difference with those of experiment values. Therefore, the MCNP6.1 with ENDF/B-VII are appropriate to evaluate the typical PWR criticality safety analysis. This result will be applied in criticality analysis of spent fuel storage rack.