Experimental evidence of Xe incorporation in Schottky defects in UO2

Abstract

Photoelectron spectroscopy and the electronic structure of the uranyl tetrachloride dianion: UO2Cl4 2−

Why a steady state void size distribution in irradiated UO2? A modeling approach

“…This suggests that the previously observed cavities may not contain gas and raises questions on the reality of the "homogeneous nucleation" alternative mechanism supposing bubbles nucleate when two gas atoms collide during the diffusion process. XANES analysis of samples similarly implanted with Xe ions proves the cavities are practically devoid of gas [1]. This conclusion was confirmed by irradiation with 4 MeV Au ions of UO 2 foils too thin to allow significant Au implantation: the same cavity pattern has been observed.…”

“…According to our simulation results, the TEM detects only a small part (1.7 %) of the defect clusters, which represents 10 % of the total vacancy volume ("porosity"). This means that if this model was in some way to be applied also to in-pile irradiation at low temperature (immobile cation vacancies), it is quite possible that the TEM observed cavities are devoid of Xe atoms because these atoms are likely to be trapped by the very small and abundant cavities as stated through XANES experiments [1].…”

“…None of these mechanisms appear to be well understood yet: for example 1) the ballistic term as calculated in [16] has been recently reevaluated and shown to be overestimated of a factor as large as 50 [22]; 2) the heterogeneous term has been evaluated by various CMD approaches whose conclusions do not agree [6,5]. Taking into account the mechanism described here and the fact that the "bubbles" could be devoid of gas atoms, in addition to a better account of point defects and small clusters for inpile irradiation situations might also help re-assess the relevance of the various re-solution models .…”

“…The purple squarish graph represents the experimental data[20], the light blue one is the raw histogram of the simulation results. Each smoothed graph presents the simulated size distribution that should be observed in a TEM image assuming1) various values R T EM for the optical resolution for cavities (which is not very well known) and 2) a 0.025 nm (∼ 2 pixels) uncertainty in the…”

First-principles study of fission gas incorporation and migration in zirconium nitride

“…For example, the most stable incorporation site of the fission gas Xe in uranium dioxide is the Schottky defect with three vacancies. 18 Therefore, we study the formation of N and Zr vacancy clusters and the Schottky defect in ZrN with respect to the vacancy distance. As shown in To study the stability of a divacancy with respect to its single vacancy, we calculated the bonding energy between the two single vacancies using Eq.…”