Abstract
This paper presents the latest work on the development of the gamma transport capability for the CASL neutronics code MPACT. MPACT is capable of performing pin-resolved neutronics calculations for full-core problems and the purpose of this project is to further expand its capability for gamma transport calculations at the same level of accuracy for potential applications of interests, such as gamma heating and gamma fluence calculations. The development of the gamma transport capability reuses many existing geometrical capabilities and neutronics solvers in MPACT, because essentially the same form of Boltzmann transport equation is solved. First, 2-D gamma transport is implemented in this work by leveraging the method of characteristics (MOC) sweeper. The HELIOS library is used to provide the neutron-induced gamma production and gamma interaction cross sections. The new gamma transport capability is verified with MCNP. Both the gamma spectrum of a pin cell problem and the gamma flux distribution of 2D assembly problems are consistent with reference calculations. A 2D quarter core case is qualitatively verified by comparing MCNP and MPACT predictions of the gamma flux and thermal neutron flux to confirm the gamma smearing effects.