Doppler broadening of neutron elastic scattering kernel in Tripoli-4®

Recent works have pointed out some relevant shortcomings of the so called ‘Sampling of the Velocity of the Target nucleus’ (SVT) algorithm, which is currently used in most Monte Carlo codes for the Doppler broadening of the elastic scattering kernel. To overcome these limitations, which affect resonant nuclei such as 238U, and whose consequences in pincell criticality calculations can amount to a drop of several hundred pcm, the Doppler Broadening Rejection Correction (DBRC) and the Weight Correction Method (WCM) have been proposed. In this work, we illustrate the implementation of DBRC and WCM in the Tripoli-4® Monte Carlo code. Several validation tests are discussed, and the impact of using DBRC or WMC to replace SVT is analyzed in detail in static as well as burnup calculations for UOX and MOX pincells, and in a PWR full-core simulation.

► DBRC and WCM algorithms are implemented in Tripoli-4.
► The effects of resonant Doppler broadening on static and burnup criticality calculations is analyzed.
► The differential contributions of distinct isotopes are singled out.