RAPID model to predict radial burnup distribution in LWR UO2 fuel

The RAPID (RAdial power and burnup Prediction by following fissile Isotope Distribution in the pellet) model was developed to predict the radial distribution of power, burnup and fissionable nuclide densities in the LWR UO2 fuel pellets to be used in the fuel performance analysis code. It considers the specific radial variations of the neutron reactions of all the fissionable nuclides as functions of burnup and 235U enrichment in the pellet. Comparison of the RAPID prediction with the measured data of the irradiated fuels and the predicted results by other codes showed good agreement, and therefore, the RAPID model can be used for UO2 fuel of up to 10 w/o 235U enrichment and 150 MWD/(kg U) pellet average burnup under the LWR environment.