Calculation of Adjoint-Weighted Kinetics Parameters in OpenMC Using the Iterated Fission Probability Method

New capabilities to compute adjoint-weighted kinetics parameters have been developed, tested, validated, and made available in OpenMC, an open-source Monte Carlo particle transport code. The effective delayed neutron fraction βeff and the effective generation time Λeff are calculated using the iterated fission probability (IFP) method. Effective kinetics parameters produced with OpenMC are compared to a prior work performed with a developmental branch of OpenMC and other results from Serpent and MCNP based on several benchmark cases from the ICSBEP (International Criticality Safety Benchmark Evaluation Project). Overall, the results are in good agreement with a maximum difference in βeff of 25 pcm and 2.7% for Λeff.The results of the new IFP implementation are also compared to design data used in theoretical kinetics models for the ARE (Aircraft Reactor Experiment) and the Molten Salt Reactor Experiment (MSRE) when the fuel is not circulating. Reasonable agreement was obtained for both experiments with a maximum difference in βeff of 54 pcm and 13.4% for Λeff.This new feature is fully compatible with shared- and distributed-memory parallelism. The impact of the new implementation on code performance was verified to be minimal when IFP was not used with a maximum relative difference of 0.2% in peak memory usage and 0.8% in execution time for the model considered. When using the new IFP feature, the code performance scaled with the number of processes and threads, as expected.