Comparison of Measured and Monte Carlo Results for Neutron Beam Transmission Through an Irradiated Nuclear Fuel Assembly

This paper compares measured results with simulation results of neutron beam transmission through an irradiated fuel assembly. The main objective of the comparison is to establish the technical foundation for using Monte Carlo simulation to evaluate the feasibility of using neutron computed tomography for irradiated fuel assembly inspection. The measured results were obtained from an irradiated fuel assembly from the Experimental Breeder Reactor II (EBR-II), and the neutron beam was produced by the Argonne National Laboratory Neutron Radiography Reactor (NRAD). The measurements consist of a projection profile representing the relative neutron beam attenuation at a specific fuel assembly axial elevation obtained from digitized neutron radiography film. Simulation of the neutron beam and fuel assembly was performed using the Monte Carlo code MCNP5. Results presented include the measured beam attenuation projection profile, simulated neutron beam attenuation projection profiles, parametric study of simulation results, and comparison of the projection results. Comparison of the radiography-based measurement with the simulation results shows good agreement, thereby confirming that Monte Carlo simulation of neutron transmission through an irradiated fuel assembly using MCNP5 is a reliable method for evaluating the use of neutron computed tomography as a means of inspecting irradiated fuel assemblies.