Decay heat analysis of VHTR cores by Monte Carlo core depletion calculation

In this study, a decay heat analysis was performed for prism type VHTR cores by combining Monte Carlo depletion calculation with McCARD code and the decay cooling calculation with ORIGEN-2 code. In the Monte Carlo depletion approach, the McCARD multi-cycle core depletion calculation was performed up to an equilibrium cycle, involving a great details of core geometry and material inventory. ORIGEN-2 performs only the decay cooling calculation with the full scope of ORIGEN-2 nuclides inventory provided by the McCARD depletion calculation. The accuracy of the decay heat analysis procedure developed in the previous work by using HELIOS and ORIGEN-2 codes was also verified. The HELIOS/ORIGEN-2 procedure showed a good accuracy for a short period of cooling time. However, a relatively large discrepancy between the two was observed for a long period of cooling time. As expected, the decay heat of a TRU fueled DB-MHR core was much higher than that of uranium fueled PMR200 core due to the fuel composition difference, which means that more attention for effective removal of the decay heat should be paid in designing the TRU fueled deep burn cores to ensure the safety of the deep burn core during the conduction cooling events.