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The effect of matrix oxidation on diffusion and trapping of gas atoms in (Th, U)O(2) was studied. Krypton was ion-beam implanted into the (Th, U)O(2) and its release in air was measured. Trapping of gas atoms during migration had been observed in pure ThO(2) at the implantation doses selected. Before implantation, the specimens were annealed at 1400 C in either air or hydrogen to remove polishing damage. Kr release was measured in air at temperatures increasing from 700 C to 1500 C. The H(2)-annealed (Th,U)O(2) stoichiometric at the time of implantation, became oxidised early in the heat treatments. The Kr release from these oxidised specimens showed only mild or weak trapping. The fractional release was significantly larger than that from ThO(2) which showed much stronger trapping at the corresponding doses. This enhanced release was in line with theoretical predictions of a lowered solution energy of noble gases in the anion-excess oxide. Specimens oxidised before implantation suffered uranium depletion at the surface by preferential vaporisation. As a result, the release from the pre-oxidised specimens showed strong trapping behaviour.

Additional information

Authors: OGAWA T, JAERI, Naka-gun, Ibaraki-ken (JP);VERRALL R A, Atomic Energy of Canada Ltd., Chalk River Nuclear Laboratories, Ontario (CA);LUCATA P G, Atomic Energy of Canada Ltd., Chalk River Nuclear Laboratories, Ontario (CA);MATZKE H-J, JRC Karlsruhe (DE)
Bibliographic Reference: Article: Solid State Ionics, Vol. 49 (1991) pp. 211-216
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