Abstract
This study evaluates the impact of depletion chain files on the isotopic prediction accuracy of OpenMC using post-irradiation examination data from five BWR 9×9-9 fuel samples irradiated in Fukushima Daini Unit 1. Six depletion chain files—ENDF/B-VII.1, ENDF/B-VIII.0, ENDF/B-VIII.1, JEFF-4.0, JENDL-5, and CASL—were assessed using a nodal power correction method. All chain files show good agreement (within 10% bias) for U-236, U-238, Pu-240, Pu-242, Pu-238, Nd-143–146, Nd-148, Eu-153, Pm-147, Sm-147, Mo-95, Ru-101, Rh-103, and Cs-133. ENDF/B-VII.1 exhibits higher errors in U-235 prediction, likely due to missing destruction pathways. ENDF/B-VIII.1 shows the widest Pu-239 bias range (37.47%). Nd-142 remains a consistent outlier across all chains, with large negative biases and biases attributed to isobaric interference. Eu, Gd, and Tc-99biases are largely chain-file independent. JENDL-5 shows poor performance for Pm-147 and Sm-154 due to additional production channels and differing fission yield contributors, including minor actinides. It also produces an anomalous overprediction for Sm-149 (∼+28%). JEFF-4.0 provides the best agreement for Ag-109 due to enhanced reaction pathways. Overall, JEFF-4.0 and ENDF/B-VIII.1 demonstrate the most consistent performance, supporting their application in BWR depletion analyses while highlighting areas for further chain file refinement.