Conceptualization of the micro research reactor cooled by heat pipes (MRR-HP), part-II: safety analyses

Abstract

ABSTRACT The safety of the novel Micro Research Reactor cooled by Heat Pipes (MRR-HP) design is explored. This is achieved by developing a 3D thermal conduction model using STARCCM+ software, besides, coupling it with the 3D neutronics model for reactor dynamics. The MRR-HP has a unique design characteristic, which is the implementation of dual-sets of heat pipes (HPs) in the monolithic-block: Water-HPs for operation, and Potassium-HPs for accident/post-accident scenarios. Water-HPs cool the reactor effectively, allowing for maximum fuel temperature (K). However, water-HPs may suffer from: Loss-of-heat-Sink-Accident(LOSA), which may occur due to blackout, since it requires forced convective cooling in the condenser. Non-Condensable-Gases-Generation-Accident (NCGGA), due to radiolysis. These events cause significant melting in the monolithic-block and fuel rods after 3 and 6 hours, respectively. This paper proves the reliability of potassium-HPs as a passive countermeasure against LOSA and NCGGA, while natural convective cooling in the condenser is applied. Cold-state no-scram Reactivity-Insertion-Accident (RIA) scenarios with an insertion of 2.35$ are investigated, showing that no partial or significant melting occurs, due to the negative reactivity feedback of the MRR-HP. Besides, Potassium-HPs are essential in removing the decay heat, for warm-state RIA, after water-HPs dry out. This paper proves the robustness of the MRR-HP and encourages its utilization for remote operation.