Solid-Core, Gas-Cooled Reactor for Space and Surface Power

Abstract

The solid‐core, gas‐cooled, Submersion‐Subcritical Safe Space (S∧4) reactor is developed for future space power applications and avoidance of single point failures. The Mo‐14%Re reactor core is loaded with uranium nitride fuel in enclosed cavities, cooled by He‐30%Xe, and sized to provide 550 kWth for seven years of equivalent full power operation. The beryllium oxide reflector disassembles upon impact on water or soil. In addition to decreasing the reactor and shadow shield mass, Spectral Shift Absorber (SSA) materials added to the reactor core ensure that it remains subcritical in the worst‐case submersion accident. With a 0.1 mm thick boron carbide coating on the outside surface of the core block and 0.25 mm thick iridium sleeves around the fuel stacks, the reflector outer diameter is 43.5 cm and the combined reactor and shadow shield mass is 935.1 kg. With 12.5 atom% gadolinium‐155 added to the fuel, 2.0 mm diameter gadolinium‐155 sesquioxide intersititial pins, and a 0.1 mm thick gadolinium‐155 sesquioxide coating, the S∧4 reactor has a slightly smaller reflector outer diameter of 43.0 cm, and a total reactor and shield mass of 901.7 kg. With 8.0 atom% europium‐151 added to the fuel, 2.0 mm diameter europium‐151 sesquioxide interstitial pins, and a 0.1 mm thick europium‐151 sesquioxide coating, the reflector’s outer diameter and the total reactor and shield mass are further reduced to 41.5 cm and 869.2 kg, respectively.