Neutron radiation shielding with sintered lunar regolith

Abstract

Lunar regolith simulant is exposed to a fast neutron flux of a spallation source. The samples consisted of a set of as-received, traditionally sintered, and solar sintered JSC-2A lunar regolith simulant. Aluminium samples were also irradiated for comparison. The ChipIr beamline of the ISIS neutron and muon source was used to provide a flux of atmospheric-like neutrons. The shielding properties of the different samples were measured for transmission, by counting neutrons before and after the samples using fast neutron detectors. Monte-Carlo simulations were carried out concurrently. The simulations are in good agreement with measurements. Aluminium simulations have shown to be in better accordance with the experimental results, probably because less affected by systematic errors. As for regolith shielding, a sensitivity analysis showed the low impact of the variations in regolith composition on the shielding properties. The benchmark of the simulations has allowed an independent estimate of the required level of regolith shielding needed to cope with primary and secondary radiation emissions. For galactic cosmic rays a value > 200 g/cm2 is estimated to give >50% reduction in transmission. For solar particle events a few 10s of g/cm2 can reduce the dose by more than an order of magnitude.