The neutronic characteristics of thermal molten salt reactor

Recently Molten Salt Reactor (MSR) gains more interest among nuclear researchers due to its promising competitiveness and safety features. ThorCon MSR (TMSR500) is this kind of reactor projected to be built in Indonesia. Due to a limited number of proven operating reactors and limited knowledge of reactor characteristics, several aspects have to be studied, such as neutronic features, material, fuel circulation, fuel management, etc. This paper reveals some important neutronic safety features of MSR, referring to ThorCon design, such as temperature reactivity feedback of fuel, moderator, and reflector. Void reactivity feedback and neutron energy spectrum behavior during voiding were also examined by performing MCNP6 calculations and nuclear data ENDF/B-VII. Full core geometry was modeled, and the drift effect was not taken into account. Neutron flux and power density distribution were also addressed. The purpose of this paper is to review the aforementioned important safety parameters by doing the Monte Carlo code calculations. The results indicated that the core induces negative reactivity feedback due to temperature increase in fuel and moderator, but positive for temperature increase in the reflector. The temperature reactivity coefficient of fuel, moderator, and reflector exhibited −5.82×10−3 (%dk/k)/°C, −9.68×10−4 (%dk/k)/°C, and +1.84×10−4 (%dk/k)/°C, respectively. The introduction of void in the core either as a result of boiling or pump cavitation would induce positive reactivity of +0.115 (%dk/k)/(%void). Overall, the temperature reactivity coefficients exhibited large negative, and there is a comfortable margin between the operating temperature to the boiling point that might prevent void generation due to fuel boiling.