Leaching of Actinides from Nuclear Waste Glass: French Experience

Abstract

Results are presented for a large number of aqueous leach tests on glass specimens doped with 237Np, 238Pu, 239pu, 241Am or 244Cm. The effects of the leaching mode (static or dynamic), temperature and environmental materials are discussed. The amount of actinides contained in the alteration film is characterized by the retention factor RF = NL(B)/NL(act). The neptunium retention factor ranged from 1 to 10 depending on the test conditions; for plutonium and americium, the retention factor varied from 6 to 1300.In general, the retention factor increased with the temperature. The very important influence of the environmental materials shows that there is competition for actinide retention between the alteration film and the surrounding materials, but in every case the amount of ca activity released into solution is very low.

The effects of the glass surface area/solution volume ratio on glass corrosion: A critical review

“…It was concluded from these tests that the alteration layer formed on R7T7 glass effectively retained Pu, Am, and Cm, although Np was not significantly retained by the layers under these test conditions [249]. This is consistent with the higher solubility of neptunium. …”

“…Notice also that the technetium is not completely depleted in the alteration layers. The retained technetium may have been reduced to the less soluble Tc 4 + state during formation of the glass, though this is only speculation.The corrosion of R7T7 glasses doped with 237 Np, 2 39 Pu, or 24 1 Am has been measured in leach tests with R7T7 glass run 70 days in deionized water at room temperature [249]. These tests were conducted with daily renewal of the leachant, which prevented accumulation of glass corrosion products The extent of corrosion was small in these tests, and only thin surface layers were observed.…”

Naturally-Occurring Zirconolites - Analogues for the Long-Term Encapsulation of Actinides in Synroc

“…a radiolysis surface mechanism, cannot be ruled out. Previous work on glass leaching has indicated this phenomenon [17], but it was not possible to ascertain whether the enhanced leaching was due to interactions between the α-activity and the water or the teflon sample container.…”

Characterization and Performance of Fluidized Bed Steam Reforming (FBSR) Product as a Final Waste form

“…In the FBSR final waste form the radionuclide release (Cs and Re) is retarded preferentially to the matrix element, Na, release (Table V) or conversely, Na is released from one of the phases preferentially compared to the nosean phase which retains the Re. This finding is noteworthy because the Hanford specification for Na release for vitrified waste forms is an indicator for the congruent release of Tc 99 since Na and B and Tc 99 are all released at similar stoichiometric rates (congruently) from vitrified waste forms [10,11,15,16,17,18,19,20,21,22,23,24].…”