RELATIVISTIC KINEMATICS FOR PHOTONEUTRON PRODUCTION IN MONTE CARLO TRANSPORT CALCULATIONS

摘要

In this paper, an algorithm for the production of photon-induced neutrons is described. Relativistic two-body kinematics are used to derive exact expressions for the secondary energy and angle distribution of photoneutrons; this treatment is important in cases where the evaluated photonuclear data does not give an explicit energy distribution. Comparisons of the relativistic relations were made to approximations in MCNP5 and TRIPOLI-4, highlighting the magnitude of the error of those approximations. Finally, photon transport simulations including photoneutron production were carried out in both MCNP5 and MC21 and demonstrate generally good agreement between the two codes except for cases where relativistic effects are important.