Utilizing neutronics modelling to predict changing Pu ratios in UO2 in the presence of Th

• Published in: Progress in nuclear energy (New series) Vol. 137; p. 103762
• Main Authors: Evitts, L.J., Gilbert, M.R., Middleburgh, S.C., Lee, W.E., Dahlfors, M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-07-2021; Elsevier BV
• Subjects: Advanced fuels; Isotopes; MOX; Neutronics modelling; Nuclear forensics; Nuclear fuel elements; Nuclear fuels; Nuclear reactors; Plutonium; Plutonium fingerprints; Pressurized water reactors; Reactors; Rods; Studies; Thorium-based fuels; Uranium dioxide; Neutronics modelling; Advanced fuels; Nuclear forensics; Thorium-based fuels; Plutonium fingerprints
• ISSN: 0149-1970; 1878-4224
• DOI: 10.1016/j.pnucene.2021.103762

The isotopic fractions of plutonium produced in a reactor are of significant value as nuclear forensic signatures, and the mechanisms of their production and alteration should be investigated thoroughly. A series of neutronics calculations were made on a typical UO2 PWR setup, introducing (Th, U)O2 MOX rods gradually, to investigate how the presence of Th affects the 240Pu/239Pu and 242Pu/239Pu ratios in the remaining UO2 fuel rods. A relationship is found that links the percentage change in these ratios, with the burnup and Th content in the configuration. In an extreme case, it was found that the presence of Th may increase the ratio of 242Pu/239Pu by as much as 3.5% at low burnup.
•Historically, the isotopic fraction of plutonium may be used as a fingerprint of the reactor type.•Homogeneous thorium-based fuels have an unknown divergence from known fingerprints.•A fingerprint is derived from neutronics calculations based on thorium content.