Benchmarking of the HTR-10 reactor's kinetic parameters: Effective delayed neutron fraction

A number of methods have been proposed to calculate the effective delayed neutron fraction using Monte Carlo codes. The present work aims at assessing the possibility of using the prompt method to calculate the effective delayed neutron fraction for the HTR-10 reactor. The prompt method in Monte Carlo codes is based on a simple assumption: negligibility of the effect of delayed neutrons on neutron flux shape and distribution. Hence one way to prove the applicability of the aforementioned would be to assess those effects. To this end, we modeled the HTR-10 reactor core using the MCNP4c code and extracted such parameters as the neutron spectrum and radial neutron flux distribution. These calculations were performed for two distinct core configurations, corresponding to the start-up and full power modes. Finally, the effective delayed neutron fractions were calculated and compared to previously reported values. Given the simplicity of the prompt method, the innate geometrical flexibility of Monte Carlo based neutronic simulation codes and the results obtained for the HTR-10, this combination method is proposed as an acceptable reactor core kinetic analysis tool for PBM-type reactors.