Major actinide diffusion (U, Pu) in oxidised zirconium. Application to nuclear fuel cladding tubes

Nuclear fuel devices of Pressurised Water Reactors are composed of uranium oxide pellets which are enclosed in zircaloy cylinders. During reactor operation, major actinides are created among which plutonium 239. Further on, energy deposition of fission recoils leads to sputtering of uranium and plutonium onto the inner surface of the cladding material. Thus, sputtered Pu and U ions start to migrate outwards. Experiments to investigate the migration process were performed at the Institut Laue Langevin (Grenoble) on the Lohengrin mass spectrometer. A model is proposed to deduce an apparent uranium and plutonium diffusion coefficient in zirconia (ZrO2) from the energy distribution broadening of a selected fission product.