Preconceptual nuclear design of a 50 kWth heat pipe cooled micro molten salt reactor (micro-MSR)

Abstract

Micro Reactors with power below 10 MW can offer many benefits for ocean or space exploration with their favorable characteristics, such as low specific mass, long-lasting life, highly flexible power supply and strong environment adaptability. The heat pipe cooled micro molten salt reactor (micro-MSR) which is an innovative concept combining molten salt reactor and heat pipe technology, is proposed in this work and furthermore, a 50 kWth version of micro-MSR is designed. The main neutronic characteristics, including the neutron spectrum, reactivity control with control drums inserted in the radial reflector, temperature reactivity coefficient (TRC), neutron flux, power deposition, and neutron balance are provided and discussed, respectively. The diameter and height of the designed core are about 0.69 m and 0.96 m, respectively, and the total mass of the core is merely about 1.3 tons, which is desirable for application in space, ocean and remote, off-grid locations. Meanwhile, an analysis of reactivity worth and interference effects of control drums are performed, which indicates that the reactivity control can be achieved by using the control drums. The results of TRC that governs the inherent safety of the micro-MSR demonstrate the feasibility of a self-actuated shutdown mechanism owing to a sufficiently negative TRC of about −13.91 pcm/K. A design of radiation shield mainly for effective protection of the electronic components is provided and it is found that a 47 cm thickness of shield can limit the neutron and gamma dose to the permissible range. Additionally, the performance of the heat pipes (HPs) in the core is evaluated, and the results indicate that the heat transfer capacity of the HP is great enough to ensure the cooling of the fuel salt in the core.