Characterisation of UO2 Spent Nuclear Fuel Samples containing Gd2O3 using Serpent2

The degree of enrichment in uranium dioxide (UO2) nuclear fuels has evolved to the extent that the associated excess reactivity at reactor start-up requires additional compensation through the addition of gadolinium(III) oxide (Gd2O3). However, due to the increasing presence of Gd2O3, the accurate prediction of the isotopic evolution and power throughout irradiation cycles has a more significant impact on the fuel performance. Nevertheless, to date there have been no studies that have assessed the predictive capabilities of the SERPENT-2 fuel depletion code for low-doped UO2-Gd2O3 fuel samples. Therefore, this master’s thesis models selected UO2-Gd2O3 Spent Nuclear Fuel (SNF) samples and compares them with experimental results from destructive radiochemical analyses in order to assess the predictive capabilities of SERPENT-2. The simulation models incorporate fuel sample design data and reactor operational histories from the Spent Fuel Isotopic Composition 2.0 database, which was developed by the Organisation for Economic Co-operation and Development: Nuclear Energy Agency. The eight selected SNF samples originate from the Japanese Pressurised Water Reactors (PWRs) Takahama-3 and Ohi-2. After running the simulations, the nuclide inventory predictions were compared utilising the ‘C/E-1’ representation. For both PWRs, the calculated results were in good agreement with the experimental results. Therefore, in the scope of validating PWR samples in which Gd2O3 is more prevalent, the SERPENT-2 fuel depletion code can be utilised.