Effect of amorphization on isolation properties of actinide pyrochlore matrix

The effect of 244Cm decay (T 1/2 = 18 years) on the radiation and chemical stability of the pyrochlore Gd1.935Cm0.065TiZrO7 was examined. Irradiation leads to degradation of its structure. The amorphization dose at room temperature is 4.60 × 1018 α-decay g−1 (or 0.60 displacements per atom, dpa). It is close to the corresponding value at ion irradiation of phases of similar composition and three times higher as compared to titanium pyrochlores with 238Pu or 244Cm. The rate of Cm leaching from the initial ceramics is 1.7 × 10−2 g m−2 day−1, and after amorphization it increases to 4.7 × 10−2 g m−2 day−1. The critical temperature (330 K) corresponds to probable conditions in sites of underground waste disposal. Therefore, such matrix will not undergo amorphization at any irradiation doses and will preserve its isolation properties in a repository.