Pre-conceptual high temperature gas-cooled microreactor design utilizing two-phase composite moderators. Part I: Microreactor design and reactor performance

Abstract

In this work, an approach is demonstrated for designing a microreactor based on a High Temperature Gas-Cooled Reactor (HTGR) platform intended for use in remote regions or for emergency response. The pre-conceptual microreactor design generated in this study is based on the Idaho National Laboratory's High Temperature Gas-Cooled Test Reactor (HTGTR) point design. Major design changes to the HTGTR were made to transform the design to a microreactor based on constraints inspired by open literature information from the Office of Secretary of Defense (OSD)/Strategic Capabilities Office (SCO) Pele Program. The primary purpose of this study is to compare reactor performance by evaluating key figures of merit for systems employing two-phase composite moderators (magnesia matrix with either an entrained beryllium or hydride containing moderating phase) relative to a reference graphite moderated case. Design parameters were selected to maximize reactor cycle performance for a given microreactor design with additional performance metrics such as natural resource requirement and fuel cycle costs also calculated. Our results demonstrate that a microreactor design based on the HTGR can be achieved by implementing a high fuel density. By using two-phase composite beryllium- or hydride-based moderators instead of graphite, substantial improvements can be realized in the reactor cycle performance, natural resource utilization, and fuel cycle cost.