Capability of Mathematical Probability Tables to Treat Resonance Interference among Isotope

Document Type : Original Article

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Department of Engineering Physics, McMaster University, Canada

Abstract

In light water reactors, it is very important to consider the resonance self-shielding behavior of the cross-section, where the accuracy of the calculation method is related to the technique used to represent the self-shielding distribution. The impact of the self-shielding on one nuclide cross-section can depend strongly on the resonance cross-section of other nuclides in the composition, accordingly, the mutual resonance interference between different resonance isotopes should be considered. The advanced subgroup technique based on the mathematical probability tables can treat such effect, where the Ribon extended model (RIB) and the subgroup projection method (SPM) are available in DRAGON4 code. The calculations are performed for three PWR fuel types: UO2, ThO2-UO2, and PuO2-UO2, and the obtained results are benchmarked with the reference MCNP6 calculations. The main purpose of these studies is to investigate which isotopes can be included in the correlation model and the results indicate that the contribution of some isotopes may disturb other cross-sections leading to discrepancy from MCNP results. Consequently, those isotopes should be removed from the correlation model especially for the PuO2-UO2 fuel pin.

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