Investigation into the effects of subsurface ice deposits on the shielding of fast spectrum nuclear reactors using Martian regolith

Graduation date: 2006As human exploration of space continues, eventually sights will be set on establishing a permanent manned habitat on the surface of Mars. The success of such a base will depend on many new and developing technologies. Low mass and high energy density power production units will be of paramount importance. Excluding the development of some new power generating technology the clearest viable option is nuclear power. One significant drawback to using a nuclear reactor for a power source is the heavy shielding that must be used to protect humans from the radiation field generated by the reactor. In order to minimize the shielding mass, taken from Earth to adequately shield the reactor, it may be possible to use Martian soil as the primary shielding material. Previous work has suggested that non-line-of-sight geometries between the reactor and the habitat will provide the greatest radiation protection to the crew. This feasibility study examines the shielding properties of two such geometries. The first shielding geometry attained by using is a small crater, where the second geometry uses a cavity drilled into the surface.\ud The 2001 Mars Odyssey observer data has been analyzed and it has been determined that between one and two meters below the Martian surface there exists a hydrogen rich layer. This study examines the effects that this hydrogen rich layer will have on the shielding properties of the two geometries. The shielding properties are evaluated based on a dose response comparison, where dose is estimated for phantoms placed in increasing distances from the reactors. Calculation in this study will be carried out using Monte Carlo N-Particle 5 (MCNP5), a stochastic radiation transport code