Continuous temperature representation and feedback in coupled RMC/CTF

With increasing computing power, coupled Monte Carlo (Mc) and thermal-hydraulic (Th) codes become more attractive to provide the high fidelity multi-physical solutions. In the traditional coupling, the pin volume average temperature was used in neutronics codes (either deterministic codes or Monte Carlo codes), assuming that the temperature profile across a fuel pin is spatially flat. Such simplification can reduce the computational complexity, but also leading to non-negligible bias. Different models were proposed to calculate the effective Doppler temperature. However, most of these models were empirical and problem dependent. In this paper, the continuously varying temperature distribution were used to model the temperature profile within the fuel pin, without any division of sub pin regions and empirical weighting coefficient. The continuous temperature method was based on the on-the-fly temperature dependent cross sections treatment. This new method agree well with the reference by sub pin regions division. Then the continuous temperature method was applied to the coupling of Monte Carlo code RMC and subchannel codes CTF, to provide the continuous temperature feedback for intra-pellet temperature. The coupling codes was used to simulate the problem 6 of Vera Benchmark. Results show that the continuous temperature method can give more accurate result than the pin average feedback assumption in coupling calculations. (Author)