Correlated gammas using CGM and MCNPX

Abstract: Transport codes like MCNPX (Monte Carlo N-Particle eXtended) which are based primarily on experimentally derived data libraries at energies below approximately 100 MeV are reliable and predictive in transporting and producing neutrons and gammas. However, they are deficient in the microscopic sense because of the inability to produce correlated secondary particles. Neutrons will produce the average number of gammas at each collision regardless of the specific neutron reaction. Consequently, capture gammas may be produced by elastic collisions and inelastic gammas may be produced by capture. To remedy this deficiency the Cascading Gamma-ray and Multiplicity (CGM) V3.4 code has been integrated into MCNPX V2.7.0. The CGM code is based on Hauser–Feshbach and optical models. This paper details an overview of the CGM code integration into MCNPX followed by a test case highlighting the gamma spectrum and multiplicities from the CGM/MCNPX code. The test case provides gamma spectrum and multiplicities for the (n,γ) reaction on 56Fe using thermal neutrons. A second test case highlights gamma correlation for the (n,γ) reaction on 56Fe using thermal neutrons using three coincidence detectors. [Copyright &y& Elsevier]