Determination of alpha dose rate profile at the UO2/water interface

Abstract

ABSTRACTIn this paper, an evaluation of the alpha dose rate profile at the UO2/water interface is presented. The calculation is performed in spherical geometry by considering the position of alpha emitters in the material. Moreover it proceeds to an iterative way. The fuel matrix and water is divided in spherical layers of 0.1 μm of thickness. The alpha emitters have an average energy of 5.3 MeV corresponding to a maximum distance of 13.2 μm in UO2 matrix and 42 μm in water. The direction of emission and the energy deposition, described by the Bragg curve, in the nuclear fuel are also taken into account. It appears that the alpha dose rate strongly decreases towards the calculated maximum penetration depth in water namely 42 μm. The concentrations of oxidising and reducing species are largely higher at the UO2/water interface than in solution. This alpha dose profile is used as input file in a model coupling a radiolysis kinetic model and a diffusion model. This kind of calculation is particular suitable for HTR kernels which have a spherical form of few hundreds microns of diameters (200-500 μm).