Calculation of Radial Distribution of ²³⁸U Resonance Absorption Cross Section in Fuel Pin with Non-uniform Temperature Profile

To precisely predict the resonance absorption cross section of ²³⁸U in the fuel pin with non-uniform temperature profile, a resonance calculation method based on solving the ultra-fine-group slowing-down equation was proposed. Using the temperature perturbation model, the impact on the radial spectrum of the fuel pin from the non-uniform temperature profile was decomposed to the independent impact on the spectrum from each radial sub-region, thus the prediction of the radial resonance absorption cross section with non-uniform temperature profile was achieved. Numerical results show that, using the results from MCNP5 code as the reference, the accuracy of the temperature perturbation model on the ²³⁸U resonance absorption cross section is better than that of the conventional method using uniform collision probabilities, and the relative deviation of the resonance absorption cross section is under 2%. Therefore, the temperature perturbation model proposed is suitable for resonance absorption cross section calculation of ²³⁸U in the scenario of non-uniform temperature profile.