Uncertainty quantification and nuclear data adjustment of physical calculation parameters of lead-bismuth fast reactor core

<bold>background</bold>Uncertainty quantification and nuclear data adjustment of reactor core physical parameters can improve the calculation accuracy, thus improving the safety of reactor core design parameters. In recent years, domestic and foreign research institutions have developed a series of programs to analyze the sensitivity and uncertainty of core physical parameters, and use various methods to adjust the nuclear data to reduce the uncertainty of the calculation results.<bold>Purpose</bold>This study aims to conduct uncertainty quantification and nuclear data adjustment of the core physical parameters of the small lead-bismuth cooled fast reactor (SVBR), which holds broad prospects in the fourth generation nuclear energy technology.<bold>Methods</bold>Firstly, the SVBR was simplified, and the sensitivity analysis of critical reactivity, control rod value and power distribution were carried out by using NECP-SARAX and UNICORN programs. Then,138 groups of critical experimental devices were selected from the International Criticality Safety Benchmark Evaluation Project (ICSBEP) for uncertainty quantification. A similarity analysis was conducted between these 138 critical experiments and the SVBR. Finally, nuclear data adjustment was performed using the critical experiment devices with high similarity coefficients, with the isotopes ²³⁵U and ²³⁸U involved in the adjustment. The adjusted database was then applied to the back-substitution calculations.<bold>Results</bold>The selected critical experiment has a certain similarity with the SVBR. By using the adjusted nuclear data for back substitution calculations, the calculation uncertainty of critical reactivity is reduced from 2.59% to 0.496%, which improves the calculation accuracy.<bold>Conclusions</bold>It is verified in this study by back-substitution calculation that the uncertainty of the physical parameter calculation results after nuclear data adjustment has been significantly reduced, while the adjustments to the nuclear cross-sections are all smaller than the measurement errors. This indicates that the nuclear data adjustment can provide more reliable calculation results for the design of the lead-bismuth fast reactor and offers valuable reference for its design.