Experimental and numerical study to optimize a design of passive moderator cooling system of an advanced nuclear reactor.

• Simulation of reactor and 1/10th scaled model of Passive Moderator Cooling system. • 1D numerical simulation using RELAP5/MOD3.2 of coupled natural circulation loop. • Validation of scaling philosophy was performed for a transient scenario. • Comparison of simulation results with experimental data. • Design optimization studies of Passive Moderator Cooling system. The passive moderator cooling system (PMCS) for the Advanced Heavy Water Reactor is one of the passive systems incorporated to enhance safety of the reactor. The PMCS comprises of a coupled natural circulation loop, with a Gravity-driven-water pool as the ultimate sink and a shell and tube heat exchanger as the coupling component. Previously (Pal et al., 2016), a scaled experimental facility for PMCS was setup. In this work, validity of scaling theory was verified using 1D thermal-hydraulic code (RELAP5/MOD3.2) and simulations were compared with experimental data. Finally, PMCS was simulated for various geometrical parameters, e.g. elevation difference and pipe diameters, in an attempt to optimize the design. A good agreement with experimental data (within ± 8%), except for initial 2 h, was observed in RELAP/MOD3.2 code simulation to scaled experimental facility because of internal recirculations within Calandria being more prominent than overall circulatory flows in the passive loops. [ABSTRACT FROM AUTHOR]