The upgrade of intense pulsed neutron source (IPNS) through the change of coolant and reflector

The current intense pulsed neutron source (IPNS) depleted uranium target is cooled by light water. The inner reflector material is graphite and the outer reflector material is beryllium. The presence of H2O in the target moderates neutrons and leads to a higher absorption loss in the target than is necessary. D2O coolant in the small quantities required minimizes this effect. We have studied the possible improvement in IPNS beam fluxes that would result from changing the coolant from H2O to D2O and the inner reflector from graphite to beryllium. Neutron intensities were calculated for directions normal to the viewed surface of each moderator for four different cases of combinations of target coolant and reflector materials. The simulations reported here were performed using the MCNPX (version 2.1.5) computer program. Our results show that substantial gains in neutron beam intensities can be achieved by appropriate combination of target coolant and reflector materials. The combination of D2O coolant and beryllium inner and outer reflectors improves facility performance about 1.3 times. The purpose of this summary is to report our simulation and to recommend to change target coolant and inner reflector materials based on our simulation results.