Response of zircon to electron and Ne{sup +} irradiation

Zircon (ZrSiO{sub 4}) is an actinide host phase in vitreous ceramic nuclear waste forms and a potential host phase for the disposition of excess weapons plutonium. In the present work, the effects of 800 and 900 keV electron and 1 MeV Ne{sup +} irradiations on the structure of single crystals of ZrSiO{sub 4} have been investigated. The microstructural evolution during the irradiations was studied in situ using a high-voltage electron microscope interfaced to an ion accelerator at Argonne National Laboratory. The results indicate that electron irradiation at 15 K cannot amorphize ZrSiO{sub 4} even at fluences an order of magnitude higher than that required for amorphization by 1.5 MeV Kr{sup +} ions. However, the material is readily amorphized by 1 MeV Ne{sup +} irradiation at 15 K. The temperature dependence of this amorphization is discussed in light of previous studies of radiation damage in ZrSiO{sub 4}