An Analysis of Disassembling the Radial Reflector of a Thermionic Space Nuclear Reactor Power System

will be used to increase orbital altitude while conducting scientific measurements. At this high altitude, operational accidents should have no significant effect on the earth and its population. 2 Nonetheless, it is useful to explore noncredible events to bound the consequences and to provide information for a probabilistic risk assessment. The objective of this article is to assess the effect of the disassembly of the radial reflector of the TOPAZ-II reactor as well as to determine the minimum number of the radial reflector panels that need to be disassembled to shut down the TOPAZ-II reactor following a postulated reactivity initiated accident (RIA). In this RIA, the control drums, starting in the full-in position, are assumed to run out at their maximum speed of 1.4°/s to their full-out position and remain out. The Thermionic Transient Analysis Model (TITAM) 3‐9 is used to explore this noncredible accident, which is assumed to occur because of a malfunction in the drive mechanism of the control drums. In addition to the temperatures of the different core components (fuel, moderator, coolant, core support plates, and TFE electrodes), the reactivity excursion and feedback effects in the reactor core are calculated, before and after the disassembly of the radial reflector panels, as functions of time during the transient.