Delayed-gamma signature calculation for neutron-induced fission and activation using MCNPX. Part II: Simulations

In Part I, we presented the theory for the MCNPX Monte Carlo delayed-gamma emission feature. This feature permits the automated execution of radiation transport simulations of delayed-gamma emission spectra at discrete (line) energies created by the products of neutron fission and activation. To illustrate and help validate the new capability, calculated delayed-gamma emissions are presented in Part II for a model based on the Fisher and Engle (1964) experiment involving 235U irradiation by a Watt-fission neutron pulse. The simulated results are in good agreement with low-resolution measured data. Simulation results involving the Beddingfield and Cecil (1998)235U and 239Pu thermal-neutron irradiation are also presented. The structure of the high-resolution emission signature obtained using MCNPX is seen to be in good agreement with their experimental counterparts. We also show an activation result for 60Ni bombardment by 15-MeV neutrons. The simulation results help to illustrate the use and validity of the new MCNPX delayed-gamma capability.