Analysis of the SAFE-30 resistance-heated test data

The Heatpipe Power System (HPS) is one possible system that could produce near-term, low-cost space fission power. One of the main ways that it achieves these goals is by designing the system for inexpensive testing. Nuclear testing is often a long and expensive process. The HPS utilizes electrical resistance heaters to simulate the nuclear heat, which if done correctly can reduce development time and cost. The purpose of the SAFE-30 testing is to verify core thermal performance and to evaluate the usefulness of this type of resistance heated testing. The Safe Affordable Fission Engine (SAFE) is a derivative of the HPS designed for producing electricity in space. A 30 kWt SAFE model was built by Los Alamos National Laboratory and recently tested at the NASA Marshall Space Flight Center. The SAFE-30 had 12 heatpipes and 48 electrical heaters to simulate the nuclear fuel. The SAFE-30 tests that were done were regulated and monitored using approximately 84 thermocouples. The heaters were controlled using variable current and voltage, which made it possible to obtain a specific input power. Attaching water-jacket calorimeters to the heatpipes made it feasible to obtain the power output from the core using simple heat transfer calculations. These actual temperatures and power values were then compared to a computational model that uses nuclear data and thermal properties. Near the completion of testing, a Stirling engine was attached to the core heatpipes to verify thermal coupling and produce electricity. This paper describes how the tests were conducted and what pieces of hardware were used to model potential environments. (Author)