Uncertainty Studies of CANDU 37 Element Lattice Cells

Abstract

The uncertainty in fundamental nuclear data cross sections has been the focus of intense international activities though the OECD-NEA Uncertainty Analysis in Modelling Expert Group. However, the transfer of the knowledge and techniques from this largely LWR Expert Group to CANDU has been very limited, and hence the Canadian nuclear sector hasn't benefited fully from those activities. Better quantification of uncertainties throughout the reactor simulation process could lead to increased reactor outputs or larger margins to safety limits. In this work the effect of nuclear data perturbations on lattice level calculation outputs has been observed. It was found that the relative standard deviation of keff for the CANDU cell varies from 0.86% for fresh fuel to 0.65% for fuel at 10.2 MWd/kg. Reactivity calculations for variations in temperatures and densities were performed and relative standard deviations were found to range from 2.8% to 7.0%. Relative uncertainty in isotopic number densities of U²³⁵ and Pu²³⁹ was tracked and found to reach a maximum of 1.8% at the end of the irradiation cycle.