Uncertainty quantification of light-water-moderated and light-water-reflected cores with highly-enriched uranium fuel at Kyoto University Critical Assembly

ABSTRACT

A series of uncertainty quantifications are successfully conducted by the eigenvalue calculations, the uncertainty of criticality and reactivity, and the reduction of uncertainty using the KENO-VI code, the TSUNAMI-3D, the TSAR and the TSURFER modules of the SCALE code system, respectively. The eigenvalue calculations with KENO-VI provide noteworthy the discrepancy between experimental and numerical results of effective multiplication factor (k_eff), and the neutron spectrum dependence of k_eff in the light-water-moderated and light-water-reflected cores (C-cores) at the Kyoto University Critical Assembly (KUCA). In terms of TSUNAMI-3D, the discrepancy of k_eff is determined mainly by the uncertainty of uranium-235 (²³⁵U) fission spectrum (χ value) induced by the cross-section data, due to the use of highly-enriched uranium fuel in the KUCA C-cores. Also, the neutron spectrum dependence of k_eff is adequately understood from the effects of the uncertainty of hydrogen-1 capture, oxygen-16 elastic scattering, and aluminum-27 elastic and inelastic scattering reactions, in addition to the uncertainty of ²³⁵U fission spectrum. The reduction in the uncertainty of criticality and reactivity is interestingly achieved by the cross-section adjustment method provided in the TSURFER module, demonstrating the contribution of relevant nuclides and reactions of core components in the KUCA C-cores.

KEYWORDS:

• Uncertainty
• criticality
• reactivity
• highly-enriched uranium
• light-water moderators
• KUCA
• SCALE

Acknowledgments

The authors are grateful to all the technical staff at KUCA for their assistance during the experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

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