Startup and Load-Following Transients of a Thermoelectric Space Reactor System with No Single Point Failure

Abstract

A space Nuclear Reactor Power System (NRPS) has been developed for avoidance of a single point failure in reactor cooling and energy conversion. The Sectored Compact Reactor (SCoRe) in this system is lithium-cooled and the reactor core is divided into six equal sectors with liquid metal heat pipes dividers. These sectors are neutronically, but not thermal-hydraulically, coupled. Each sector has its own primary and secondary circulating lithium loops, which are thermally coupled both in a SiGe Power Conversion Assembly (PCA) and in a Thermoelectric Conversion Assembly (TAC) that powers the electromagnetic pumps in the primary and secondary loops. Each secondary loop also has a separate, segmented radiator panel that is optimized for low specific mass and low liquid lithium inventory. The primary loops transport the thermal power generated in the reactor by fission in 1026 UN fuel pins (or 171 fuel pins per sector) to 6 PCAs that nominally supply a total of 111.5 kWe to the load at 450 VDC. A Dynamic simulation Model (DynMo-TE) has been developed and used to investigate the transient operation of the SCoRe-TE NRPS during startup from a fully-thawed condition initially at 600 K, to nominal steady-state operation at which the lithium coolant exits the reactor at only 1179 K. Also investigated is the response of the SCoRe-TE NRPS, following a 50% change in the electrical load demand.