Optimized core design and shield analysis of a medium temperature heat pipe cooled reactor

•Core design of medium temperature heat pipe cooled reactor is conducted in detail.•Specific power of the core is further improved.•Neutronics analysis and shielding analysis are carried out by MCNP5 and ORIGEN coupling method.•Simplified control mechanism and high inherent safety of the core are ensured. Medium Temperature heat pipe cooled Reactor (MTR) is a new reactor concept proposed by Li et al. in (2022). Low enriched uranium zirconium hydride fuel and mercury heat pipe are introduced in MTR. The unique advantages of MTR have been verified (Li et al., 2022) and it is considered as a potential candidate for energy supply in decentralized markets. In this work, an optimized MTR core design is proposed with detailed neutronic analysis and evaluation on mercury heat pipe, reflector and control rod arrangement, further increasing the economic efficiency and mobility of MTR. Heat transfer limit of the improved heat pipe model is further increased, contributing to a great reduction on core volume. Reflector material and thickness are analyzed in detail for mass minimization. Core physics characteristics are analyzed for four control rod arrangement schemes. The control mechanism is further simplified with only 9 control rods involved in the normal regulation of the core. Core lifetime is far more than 10 years. High inherent safety of the core is ensured. Besides, preliminary design of the shielding system is also carried out. A shieling layer of 60 cm LiH and 20 cm Pb can reduce the total dose to less than 40 % of the design limits. The total mass of the optimized core is greatly reduced and its specific power is increased by 60 % compared with that of the previous design.