Helium behaviour in nuclear waste materials

Waste conditioning matrices like synthetic zirconolite (CaZrTi2O7) were fabricated and doped with either the short-lived alpha-emitters 238Pu or 244Cm, or with 239Pu to generate various amounts of helium and of alpha-damage. The samples were annealed in a Knudsen cell, and the helium desorption profiles interpreted in conjunction with parallel radiation damage and previous annealing behaviour studies. To understand the long term behaviour of spent nuclear fuel, UO2 samples doped with the alpha-emitters 233U, 238Pu have been investigated by transmission electron microscopy (TEM), by XRD and by thermal desorption spectroscopy. The release of helium has been explained by the recrystallization of amorphized zirconolite on one hand and partially during alpha-damage recovery in the case of the spent fuel. This study mostly highlights the correlation between restructuring of damaged materials and gas release