Behavior of Host Materials with Surrogates of the Rare Earth–Actinide Fraction under Ion Irradiation

Аннотация

The behavior of rare earth titanate phases of monoclinic and orthorhombic symmetry under ion irradiation was studied. Three samples contain a set of rare earth elements (REE), and in one sample the high-level waste (HLW) is simulated by neodymium. The samples were prepared by sintering at 1400°С or cold crucible induction melting followed by melt crystallization. The samples were irradiated with 1-MeV Kr²⁺ ions at temperatures in the range 298–1023 K on a tandem installation consisting of an ion accelerator and a transmission electron microscope. The critical amorphization doses for the samples at 298 K were (1.5–2.5) × 10¹⁴ ion cm^–2. These values correspond to those for monoclinic titanates Nd₂Ti₂O₇ and La₂Ti₂O₇, are close to those for REE–Ti pyrochlores and brannerite, and are lower by an order of magnitude than those for zirconolites at the same irradiation mode. The critical amorphization temperature of the phases studied (900 K) is comparable to that of Nd₂Ti₂O₇ (920 K), but higher than that of La₂Ti₂O₇ (840 K). Close radiation resistance of the REE₂Ti₂O₇ and REE₄Ti₉O₂₄ phases in which the rare earth elements are represented by a mixture of elements similar in composition to their set in spent nuclear fuel and liquid HLW from its reprocessing or solely by Nd confirms the assumption that Nd is a suitable surrogate for the whole rare earth–actinide fraction.