Uncertainty analysis of the China experimental fast reactor start-up tests based on refined calculation results

In this paper, the numerical calculations of China Experimental Fast Reactor (CEFR) start-up tests were performed by using SARAX code with the improved core model. The results of criticality, control rod worth, and reactivity effect were compared against the experimental data. The numerical results showed the SARAX code could be reliably used for CEFR. Moreover, the sensitivity of the k_eff value due to the change of input parameters was analyzed. At the same time, the uncertainty quantification of calculated k_eff value and control rod worth and detailed contribution to the total uncertainty were analyzed. For the reactor loaded with highly enriched UO₂ fuel, the uncertainty of k_eff value could reach more than 2%. Besides, the capture reaction of ²³⁵U contributed the most with a value of 1.91%. The uncertainty analysis of the control rod worth showed that the total uncertainty depended on the control rod layout rather than the composition.