An efficient evaluation of depletion uncertainty for a GBC-32 dry storage cask with PLUS7 fuel assemblies using the Monte Carlo uncertainty sampling method

Abstract

It is important to evaluate an accurate depletion uncertainty resulting from the limitation of a computer code on accuracy in nuclear depletion calculations from the viewpoint of burnup credit with axial burnup distributions. In this work, the bias and bias uncertainty in keff resulting from the uncertainty in the calculation of isotopic concentrations are assessed using the Monte Carlo sampling method for a generic 32 PWR-assembly burnup credit cask loaded with the PLUS7 assemblies discharged from Hanbit Nuclear Power Plant Unit 3 in South Korea. In addition, an efficient method with the two-way ANOVA is suggested to obtain reasonably accurate values of total depletion uncertainties resulting from the isotopic uncertainties with reduction of Monte Carlo criticality calculations. Finally, the reasonable total depletion uncertainties in keff for 10, 30, and 40 GWD/MTU were efficiently estimated to be 0.011866, 0.013175, and 0.014262, respectively, with 100 Monte Carlo criticality calculations, which have about 1.6, 2.1, and 2.4% discrepancies, respectively, from the ones obtained with 200 calculations. The one for 50 GWD/MTU was efficiently estimated to be 0.030811 with 120 Monte Carlo criticality calculations, which has about 3.6% discrepancy from the one obtained with 200 calculations. Thus, these uncertainties showed good agreements with the uncertainties obtained from 200 nuclear criticality calculations.