Water and Regolith Shielding for Surface Reactor Missions

This paper investigates potential shielding options for surface power fission reactors. The majority of work is focused on a lunar shield that uses a combination of water in stainless‐steel cans and lunar regolith. The major advantage of a water‐based shield is that development, testing, and deployment should be relatively inexpensive. This shielding approach is used for three surface reactor concepts: (1) a moderated spectrum, NaK cooled, Hastalloy/UZrH reactor, (2) a fast‐spectrum, NaK‐cooled, SS/UO2 reactor, and (3) a fast‐spectrum, K‐heat‐pipe‐cooled, SS/UO2 reactor. For this study, each of these reactors is coupled to a 25‐kWt Stirling power system, designed for 5 year life. The shields are designed to limit the dose both to the Stirling alternators and potential astronauts on the surface. The general configuration used is to bury the reactor, but several other options exist as well. Dose calculations are presented as a function of distance from reactor, depth of buried hole, water boron concentratio...