Helium thermal diffusion in a uranium dioxide matrix

A study of helium mobility in polycrystalline uranium dioxide

“…Another study whose results are difficult to compare quantitatively to those reported here is that of Roudil et al [7] although the methods applied and helium concentration ranges are very similar (ion implantation, annealing and NRA). However, only depth profiling prior to and following annealing was carried out which may be insufficient to capture the kinetics of the phenomena involved.…”

“…These may be put into four categories: actual differences in materials and/or material microstructures: grain or particle size, presence of grain boundaries, impurity or foreign element content, initial non-stoichiometry. the conditions under which the diffusion experiment is carried out (under vacuum: this study, [28,27,5]; under controlled oxygen partial pressure: [7]; at high pressure and in an inert gas environment: [2,3]). the overall strategy for introducing helium atoms in the samples (ion implantation: this study, [7]; radiogenic production: [27,5], high pressure and temperature infusion: [2,3,28,27]).…”

“…NRA can provide such data [6] and there has recently been a renewed interest in its use to characterise helium mobility [7,8] can be applied to provide both thermal desorption and depth profiling data [9], but never has this nuclear reaction been used in conjunction with a micro-analysis of the surface distribution of solid samples as in the present work. Helium release mechanisms from uranium dioxide polycristals is studied here and whenever possible helium diffusion quantified.…”

Spent fuel radionuclide source term model for assessing spent fuel performance in geological disposal. Part II: Matrix alteration model and global performance

“…In addition, irradiation defects will accumulate in fuel pellets and may also migrate towards grain boundaries which would also act as defects well. In order to be conservative, we therefore assume in a first approximation that grain boundaries may be permeable to water and slightly open [44]. They can therefore act as a preferential migration path.…”

Gas releases and rod internal pressure of BN-added UO2fuel

“…Helium behaviors in irradiated UO 2 and MOX fuel were investigated by different authors [15][16][17][18][19][20].…”