Nuclear data sensitivity and uncertainty analysis of effective neutron multiplication factor in various MYRRHA core configurations

A sensitivity and uncertainty analysis was carried out to estimate the uncertainty in the neutron multiplication factor k(eff) and to identify the most important nuclear data for neutron induced reactions for criticality calculations of the latest MYRRHA designs. Sensitivity profiles, i.e. sensitivity to the nuclear data as a function of incoming neutron energy, were derived for both a critical and sub-critical core. They were calculated using codes that are based on different methodologies including stochastic and deterministic calculations (i.e. SCALE, MCNP and XSUN). The neutron induced nuclear data sensitivity analysis outlined the following quantities to be of special importance for the MYRRHA reactor concept: Pu-239(n,gamma) both in resonance and fast energy region, (n,f) fast, chi and nu fast; U-238(n,n') fast, (n,gamma) resonance and fast, (n,n) resonance and fast; Pu-240 nu fast; Pu-238(n,f) both resonance and fast; Fe-56(n,gamma) both resonance and fast. Differences of less than 4% between codes were obtained for these quantities, with few exceptions ((238)pu(n,f), U-238(n,n) and Fe-56(n,gamma) reactions). Nuclear data covariance matrices of different libraries (SCALE-6, COMMARA-2 and JENDL-4.0m) were used to derive the uncertainty in k(eff) based on the calculated sensitivities. This study reveals that the largest contributions to k(eff) uncertainty result from the uncertainty in the average prompt neutron fission multiplicity of Pu-238, in the U-238 inelastic scattering cross section and Pu-239 fission cross section, using the covariances from SCALE-6, COMMARA-2 and JENDL-4.0m, respectively. (C) 2016 Elsevier Ltd. All rights reserved.