Core neutronic design of small modular molten salt reactor for submarine propulsion

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Abstract
Molten salt reactor (MSR) shows great promise as a Generation IV nuclear reactor concept with high thermal-electric conversion efficiency, inherent safety features, and online reprocessing capability. During operation, the molten salt reactor MSR does not require a long refueling shutdown owing to online fuel reprocessing, making it suitable for watercraft propulsion. This paper presents the neutronic design of the 250 MWt iso-breeder MSR concept for submarine propulsion. The reactor is fueled with LiF-BeF2-ThF4-233UF4 salt with a virtual one-and-a-half fluid configuration. The MSR core is moderated with beryllium oxide and equipped with a high-density graphite reflector to improve neutronic. All calculations on the reactor core design were performed using MCNP6.2 code with ENDF/B-VII.0 neutron cross-section library. As a part of the neutronic analysis, the calculated parameters were the effective multiplication factor (), temperature coefficient of reactivity (TCR), and breeding ratio (BR). The value of ± 1.005 was obtained using Th : U ratio of 98.42% : 1.58%. The TCR value was obtained at -2.56 pcm/K, while the BR value was 1.057. These initial values indicate that the marine propulsion MSR can achieve iso-breeding with inherent safety characteristics. By using MSR design, it is hoped that the submarines will be able to reach significantly longer operational range than its Diesel-powered counterpart..

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