AbstractCoffinite (USiO4, I41/amd, Z=4) is the major alteration phase of uraninite, UO2+x, under reducing conditions in natural uranium deposits. Thus, it is important to understand the radiation response of coffinite because it is an expected alteration product of the UO2 in spent nuclear fuel. In the present study, we conducted in-situ transmission electron microscopy (TEM) investigation of synthetic coffinite under 1 MeV-Kr2+ ion beam irradiation. The radiation-induced crystalline-to-amorphous transformation was observed in the synthetic nanocrystalline USiO4, with a critical dose of ∼ 0.27 displacements per atoms (dpa) for which full amorphization occurred at room temperature. The critical dose increases as rising irradiation temperature, and above the critical temperature (Tc), ∼ 608 K, coffinite cannot be amorphized. These results are compared with previous studies on the isostructural zircon (ZrSiO4, Tc=1000K) and thorite (ThSiO4, Tc>1100K), which indicates that synthetic coffinite is more stable to ion beam irradiation at elevated temperature.
In-situ TEM observation of microstructural evolution in 18Cr-ODS steel induced by electron beam irradiation
