Conceptual Design of a 3 MWTH Yttrium Hydride Moderated Heat Pipe Cooled Micro Reactor for Spacefaring Applications

Abstract

Micro reactors are gaining substantial interest worldwide due to their capabilities to deliver power to remote and decentralized areas, also their long fuel cycles which makes them more attractive compared to other energy sources. The goal of this project is to develop a conceptual design for a mobile micro reactor, suitable for space applications and decentralized markets. The requirements for this reactor design were that the reactor should fit in a 40 ft shipping container and that the reactor weight should be limited to 20 kg/kW-electrical, the desired power output of the reactor is 1 MWe which means that the reactor weight, including the reactor core and all the supporting systems, should be less than 20,000 kg. Different reactor designs were considered for this purpose, mainly, fast molten salt, thermal molten salt and heat pipe reactors. Metal hydride moderated heat pipe cooled reactors were found to best meet the size and weight requirements and hence were further investigated.

A conceptual design for a heat pipe cooled yttrium hydride moderated micro reactor was developed, different material options were discussed for moderator material. Key safety parameters were evaluated such as control devices reactivity worth, temperature reactivity coefficients and power distribution in the reactor core. Burnup calculation was performed to estimate the effective full power life time of the reactor generating. Code to code validation was conducted by performing burnup calculations using both MCNP and SERPENT Monte Carlo radiation transport codes. Temperature distribution in the reactor core was estimated by evaluating the heat transfer in the reactor core using STAR CCM+ multi-physics computational fluid dynamics (CFD) software. Finally, thermodynamic analysis of the power conversion system was performed to ensure realizing the required thermal efficiency and total weight of the system.

Original contributions of this study are the development of a new micro reactor conceptual design using low enriched uranium fuel that has smaller size and weight than other published micro reactors with similar power level, neutronics and thermal hydraulics models were developed to support the design of the new reactor. Moreover, an optimization for a closed Brayton cycle energy conversion system was performed. The energy conversion system is coupled with the reactor core to convert fission energy to electrical power.