Whole core transport analysis with the DTMC method in a small modular reactor

Abstract

Sensitivity tests are implemented to examine the numerical instability in the FMFD assisted MC simulation. The multiplication factor is highly biased and underestimated beyond the confidence level when small number of histories and/or node size is applied. The number of particles in the simulation is always limited, and too many histories per cycle can decline the efficiency of the calculation. Therefore, it is crucial to find a way to determine the appropriate generation size to ensure the accuracy and efficiency of the calculations. In addition, with the proper generation and node size, neutronic analysis is implemented in the SMR core to verify the numerical performance of the DTMC method. The DTMC method shows more reliable solution than the other MC solutions throughout the simulation. Although the cycle-wise computing time is longer in the DTMC method, the total computing time is shorter or similar due to the less number of inactive cycles. In short, the FOM is almost three times higher in the DTMC solution than the other MC solutions. As a future work, the algorithm will be further studied to determine the proper generation size for a reliable and efficient calculation. Moreover, the DTMC method should be validated in a larger scale reactor model in the continuous energy framework.