Experimental measurements for the first series of the modified stacy critical assembly with simple core configurations and experimental analysis using simplified computational models

Japan Atomic Energy Agency (JAEA) completed the modification of the STACY critical assembly and resumed operations in August 2024. The purpose of this study is to evaluate the applicability of experimental analysis results using representative Monte Carlo codes and nuclear data for cases with different moderation conditions and critical water heights in the STACY critical experiments. This paper presents the results of experimental measurements and experimental analyses using a simplified computational model for four representative simple symmetric core configurations. The results indicate that typical Monte Carlo calculation codes, combined with evaluated nuclear data, are applicable for analyzing experimental data. Although identifying the sources of slight uncertainty and quantifying their impact in STACY experiments remains a future challenge, the results support future applications in criticality safety research and nuclear data evaluation.