Nuclear Data Uncertainty Quantification of High Flux Isotope Reactor Low-Enriched Uranium Design

The sensitivity analysis and uncertainty quantification studies have been performed in support of ongoing validation efforts to strengthen the understanding and confidence in the use of LEU core design study tools to predict core behavior and performance. The results of this sensitivity analysis reveal the top positive sensitivity contributions from ²³⁵U ν̅, ¹H (n, el.), ²³⁵U (n, f), ²⁷Al (n, el.), and ¹⁶O (n, el.). Meanwhile, the top negative sensitivity contributions are from ²³⁵U (n, γ)ǡ ²³⁸U (n, γ), ¹H (n, γ), ²⁷Al (n, γ), and ¹⁰B (n, α). Moreover, the uncertainty of the three HFIR LEU silicide cores is comparable-about 0.6 %Δk_eff/k_eff. It is similar to the uncertainty of the current HFIR HEU, which is also about 0.6 %Δk_eff/k_eff. To reduce the uncertainty, the accuracy of nuclear data for ¹H, ²⁷Al, ²³⁵U, and ²³⁸U must be improved. Finally, the similarity coefficient indicates that about 200 critical experiments can be leveraged for the design validation efforts of HFIR LEU. The trending analysis can be further explored in a future work to determine the bias and bias uncertainty of the HFIR LEU computational tool and nuclear data.