Corrosion and dissolution studies of UO₂ containing α-emitters

Abstract

Leaching / Radiolysis / XPS / alpha-doped UO 2 / PlutoniumSummary. Corrosion and dissolution of UO 2 doped with short-lived α-emitters, the so called α-doped UO 2 , was investigated in leaching experiments combined with X-ray Photoelectron Spectroscopy (XPS) analyses. These experiments are part of an ongoing set of tests aiming at evaluating the effects of α-radiolysis on the dissolution of the UO 2 spent fuel matrix when it will become exposed to groundwater in a deep final repository. Pellets of UO 2 containing ∼ 10 and ∼ 0.1 wt. % 238 Pu were used. These compositions simulate the α-radiation field of different types of commercial LWR spent fuel after different storage times. Undoped UO 2 pellets were also used as reference. Static sequential leaching experiments in demineralised water at room temperature under anoxic conditions confirmed that higher fractions of uranium are released in the case of α-doped materials compared with undoped UO 2 . Relatively large amounts of plutonium were found in the leachate of the materials doped with 238 Pu. Significant contributions to the total amount released of uranium were found in the rinse solutions of the leaching vessels.

Radionuclide behaviour in the near-field of a geological repository for spent nuclear fuel

“…Most experimental studies that investigate the effect of activity on SNF matrix dissolution kinetics focus on "old" spent nuclear fuel, which is dominated by α-emitters (e.g. [97,[115][116][117][118][119][120][121]. Poinssot et al reviewed the large experimental dataset and drew the following major conclusions on the SNF matrix dissolution kinetics [111,122,123]:…”

Radiation Effects on Materials Used in Geological Repositories for Spent Nuclear Fuel

“…Several different types of materials have been manufactured and tested in dissolution experiments. UO 2 doped with α-emitting nuclides [51][52][53][54][55][56][57][58] has been used to mimic the radiation field from spent nuclear fuel older than 1000 years. UO 2 has been doped with Pd particles [59,60] to mimic the effect of ε-phase particles (fission products forming noble metal inclusions in the fuel matrix) and with rare earth oxides [61][62][63] to mimic the effect of fission products forming oxides in the fuel matrix.…”

Radiolytic oxidation of UO2 pellets doped with alpha-emitters (238/239Pu)

“…Despite the 100-fold difference in the alpha activity of the two types of investigated specimen, no significant difference was observed in the dissolution behavior of uranium for the two doped materials. More recently, Cobos et al [7] showed a flux dependence between the uranium release in solution and the alpha activity of identical batches. Beyond the flux dependence, the behavior uranium in solution and the concentrations reached during tests performed without solution renewal also appear to be highly dependent on the series of experiments considered, even for batches of comparable activity alpha [14].…”

“…The reactivity of a polycrystalline UO 2 surface under alpha irradiation in contact with water has been widely investigated experimentally in recent years [1][2][3][4][5][6][7][8][9][10][11][12][13][14], motivated by the prospect of direct disposal of spent fuel in a deep geological repository. In this regard it is worth remembering that over the long term, alpha radiolysis of water, which produces oxidizing and reductive species, radicals (HO • , O 2…”

“…• external irradiation of a UO 2 /water interface by a He 2+ particle beam generated by a cyclotron [8,9] or using alpha sources [2][3][4]; • or the use of UO 2 matrices doped with alpha-emitters ( 238/239 Pu, 233 U) to reproduce the evolution of alpha activity in spent fuel in a nuclear waste repository [1,[5][6][7][10][11][12].…”