High-fidelity multi-physics coupling study on advanced heat pipe reactor

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The advanced heat pipe cooled reactor is a potential candidate to generate nuclear power for space exploration, and exhibits strong neutron leakage and complicated multi-physics coupled effects. Traditional numerical methods based on single-field simulations do not adequately describe these interactive physical phenomena. It is thus necessary to apply high-fidelity multi-physics coupling simulations for the analysis and design of heat pipe reactors. In this work, a three-dimensional high-fidelity neutronics-thermo-elasticity multi-physics coupling code is developed for the heat pipe reactor, Kilowatt Reactor Using Stirling TechnologY (KRUSTY), based on the Monte Carlo method and the finite element method. The code combines existing open-source codes (OpenMC, Nektar++, SfePy) and implements the functional expansion tally method to perform data mapping between the Monte Carlo and the finite element method solver.An on-the-fly convergence criterion dedicated to the functional expansion tally method is developed based on statistical uncertainties and the L2 norm. This new criterion is shown to be unconditionally stable with various statistical uncertainties. Using the coupling code, high-fidelity coupling simulations are performed under different steady-state conditions, which provide insights to the physical phenomena of the reactor. The coupling results present same trends as the previous KRUSTY simulation, and illustrate that the feedback from thermal expansion is critical for capturing the negative reactivity feedback. The heat pipe analysis shows that a sufficient heat-removing margin for heat pipe failure accidents is guaranteed. The depletion coupling result shows that the burn-up effects are negligible for the reactor.