Implementation of Photonuclear Reactions in the Monte Carlo Transport Code TRIPOLI-4 and Its First Validation in Waste Package Field

Abstract

This paper presents the implementation of photonuclear reactions in the Monte Carlo transport code TRIPOLI-4. A complete coupling of neutron and photon transport is thus achieved by this feature which can be used with the electromagnetic shower option as well. The production of photoneutrons can occur when photon energy is above a threshold of a few MeV. The recent photonuclear data from the ENDF/B-VII library were chosen for this work. The conventions assumed for the reading of these data are first listed. The general algorithm of photon collision and its non analog part for photonuclear reactions sampling are then detailed. Analytical expressions used for the sampling of photoneutrons from an individual photonuclear reaction are also given. At last, a simulation of a waste package, involving a complete coupling of electron, positron, photon, and neutron transport, was carried out. The test case consists in an 11-MeV electron beam produced by an accelerator, generating high energy photons by Bremsstrahlung on a tungsten target, and then photoneutrons by photofission on an active filter embedded in the waste package. The results of the TRIPOLI-4 simulation are compared to MCNPX results and to measurement values. A good agreement is shown.