Research of Failure Modes and Mechanisms of Space Reactor Reactivity Control System

The reactivity control system of space reactors plays a crucial role in enabling long-life missions under challenging environmental stresses, including large temperature differences, high vacuum, vibration shocks, and radiation fields. Maintaining the system during such missions is nearly impossible, demanding extremely high system reliability. In this paper, we explore the design characteristics of reactivity control systems used in major space reactors from the United States and the Soviet Union. Additionally, we analyze the four main environmental stresses encountered throughout the full mission life of space reactors, namely temperature, vacuum, mechanical, and irradiation stresses. These different environmental stresses impose various independent or interrelated damage mechanisms on the reactivity control system. We further investigate the failure mechanisms, such as thermal effects, cold welding in vacuum, mechanical impacts, and particle irradiation, organizing the potential failure modes of the reactivity control system. The findings presented here serve as a reference for future studies aimed at enhancing the overall reliability of the space reactors.