Nuclear Data Assessment for Advanced Reactors

Abstract

Advanced reactor concepts being developed throughout the industry are significantly different from light-water reactor (LWR) designs with respect to geometry, materials, and operating conditions, and consequently, with respect to their reactor physics behavior. Given the limited operating experience with non-LWRs, the accurate simulation of reactor physics and the quantification of associated uncertainties are important for ensuring that the nuclear design for advanced reactor concepts include appropriate margins. Nuclear data are a major source of input uncertainties in reactor physics analysis. As part of a project sponsored by the US Nuclear Regulatory Commission at Oak Ridge National Laboratory (ORNL), key nuclear data relevant to reactor safety analysis in selected advanced reactor technologies 1 were identified, and their impacts on important key figures of merit were assessed based on (1) a review of available advanced reactor specifications, (2) analysis of previous studies performed at ORNL and other research institutions, and (3) sensitivity and uncertainty analyses performed for six selected benchmarks-three experimental and three computational-to quantify the impacts of the identified key nuclear data on several key metrics. This report summarizes the key nuclear data-nominal data and nuclear data uncertaintiesconsidering the most important nuclear reactions in the fuel and in various materials for the moderator, coolant, and structure of the considered advanced reactors.The major nominal missing data that were identified consist of thermal scattering data and 135m Xe cross section data for molten salt reactor (MSR) analysis. The identified major gaps with respect to nuclear data uncertainties are (1) the missing uncertainties in the thermal scattering data for high-temperature gas-cooled reactors and moderated MSR systems, and (2) the incomplete uncertainties on angular distributions, particularly for fast spectrum systems such as sodium-cooled fast reactors, fast molten salt reactors, and heat pipe reactors.Large uncertainties of reactions that are not commonly considered to be relevant in LWR studies were found to be significant for several advanced reactor systems. The large uncertainty of 238 U inelastic scattering in the fast energy range contributes significantly to large output uncertainties in all fast spectrum systems. The large uncertainty of 235 U (n,) in the fast energy range causes significant reactivity uncertainties in fast neutron spectrum systems that use 235 Uenriched fuel. A large uncertainty of 7 Li (n,) causes a large fraction of uncertainty in the output quantities investigated for MSR systems in which lithium is part of the salt. Special attention should be paid to differences in cross section and uncertainties of different evaluated nuclear data library releases. Significant differences were found in nuclear data that can lead to major differences in reactivity calculations, even for well-known nuclides. In particular, differences in 235 U, 238 U, and 239 Pu nominal and unce...

SCALE Modeling of the Sodium Cooled Fast-Spectrum Advanced Burner Test Reactor

“…Based on previous studies [2], the effect of nuclear data library changes is expected to be negligible for reactivity coefficients. Therefore, all other reactivity calculations presented in this section were performed only with ENDF/B-VII.1.…”

“…Although validation has been focused on water-moderated thermal spectrum systems, criticality validation also includes systems of intermediate and fast spectral conditions [28]. Previous SFR development and analysis efforts with SCALE included the analysis of the EBR-II [3] and the 1,000 MWth Advanced Burner Reactor benchmark [2], as well as the generation of MG nuclear data libraries specifically for SFRs [4] and fast reactors in general [10].…”

Key nuclear data for non-LWR reactivity analysis

“…These conclusions were drawn upon the fact the INL Design A is a fast spectrum system based on 235 U-enriched fuel. The top contributors of mixed U/TRU-fueled fast spectrum reactors (such as those assumed in SFRs) do not include 235 U (n,γ) as the dominant contributing reaction (Bostelmann et al, 2021b).…”

“…This paper provides a summary of key observations and conclusions obtained during this study, while providing just two examples to demonstrate how the computational analyses were performed. Detailed analysis results are available in a comprehensive technical report (Bostelmann et al, 2021b) issued by the NRC. It is noted that the study focused on systems with 235 U enriched or mixed uranium/plutonium fuel based on spent LWR fuel; 233 U-fueled systems were not considered here.…”

Neural Network Acceleration of Genetic Algorithms for the Optimization of a Coupled Fast/Thermal Nuclear Experiment

“…Nuclear data uncertainty is propagated to all nuclear-related figures of merit of reactors such as k-eff, void, temperature and power reactivity coefficients and reactivity worth's. In a recent assessment of the nuclear data needed for advanced reactors, it was found that for several nextgeneration reactors need better resolved nuclear data (Bostelmann, et al, 2021). For example, in a sensitivity analysis of the Advanced Burner Reactor 1000 MWth Reference Concept, it was shown that the uncertainty in important nuclear characteristics is driven by uncertainties in uranium, plutonium, iron and sodium.…”