Effects of Alpha Decay on the Properties of Actual Nuclear Waste Glass

Abstract

An accelerated experiment using the actinide doping technique was performed to investigate the effects of alpha decay on the properties of actual nuclear waste glass at high radiation doses. A fully radioactive borosilicate waste glass, containing the actual high-level radioactive liquid waste generated from the Tokai Reprocessing Plant of PNC, was prepared by JAERI, and a powder mixture of the ground fully radioactive glass and 244CmO2 was melted at 1200°C for 2 hrs. The radioactivity concentration of 244Cm was 1.0 } 1010 Bq/g-glass at the date of preparation. The homogeneity of curium-doped glass samples was confirmed by the density measurement, heat load measurement and alpha autoradiography. The properties of the irradiated samples were investigated by the mass spectrometer for helium determination, the optical microscope, the electron probe microanalyzer, the densitometer, the Soxhlet and MCC-1 leach testing apparatus. By measuring the amount of helium released from the curium-doped glass samples, more than 99% of helium remained in the matrix at room temperature. The density of the sample slightly decreased with the increase of cumulative alpha decays and the decrease of 0.77% was observed at a dose of 1.55 } 1018 alpha decays/g, corresponding to an equivalent age of 150000 yrs. Optical and scanning electron micrographs showed that no cracks were observed on all samples having up to a dose of 1.5 } 1018 alpha decays/g. The leach rates, based on weight loss, in both the Soxhlet (100°C, 7 days) and MCC-1 (90°C, 28 days) tests did not significantly change with alpha decay dose.

Irradiation stability of R7T7-type borosilicate glass

“…American 72-68 glass samples, which were subject to about 1% densification after 2 · 10 18 a/g [3], still contained all the helium generated [22,23]. In-pile irradiation studies based on the 10 B(n,a) 7 Li [21] nuclear reaction to simulate alpha decay effects revealed pores 0.2 lm in diameter, suggesting the presence of helium bubbles. However, the pores are observed in glass samples whether subject to swelling or densification.…”

“…The effects of alpha decay on the macroscopic properties of different glass compositions have been documented in the literature for doses of up to 5 · 10 18 alpha disintegrations per gram of glass [1][2][3][4][5][6][7]. To the best of our knowledge, however, only a few studies have addressed particular aspects of nuclear glass behavior when subjected to higher integrated doses [3,8,9].…”

Plutonium solubility and self-irradiation effects in borosilicate glass

“…The presence of heterogeneities (crystalline phases, demixing) could raise problems at the phase interfaces, for example due to differential swelling or stress corrosion. Relatively little work has been published concerning Pu or Pu surrogate solubility in borosilicate glass (Karraker, 1982;Hess et al, 1998;Eller et al, 1985;Matyunin and Jardine, 1998;Feng et al, 1999;Marples et al, 1981;Plodinec, 1979;Bates et al, 1995Bates et al, , 1996Bibler et al, 1996;Vienna et al, 1996;Mertz et al, 1998;Davis et al, 2003). Plutonium can generally be loaded in glass only in relatively small amounts, of the order of a few weight percent.…”

“…Considerable work has been done in recent decades to guarantee the long-term behavior of the glass used for conditioning high-level waste up to an integrated dose not exceeding 10 19 a g À1 (Mendel et al, 1976;Turcotte and Roberts, 1977;Roberts, 1980;Bibler, 1981;Marples, 1988;Matzke and Vernaz, 1993;Banba et al, 1995;Inagaki et al, 1993Inagaki et al, , 1992Weber and Roberts, 1983;Weber et al, 1997;Ewing et al, 1995). The principal source of radioactivity in this glass is a and b decay from the fission products, together with a decay from the actinides.…”

Effect of alpha radiation on the leaching behaviour of nuclear glass

“…Despite the numerous studies carried out to assess the impact of radiation on the properties of nuclear glasses, reviewed in [1][2][3], some issues are still controversial especially concerning the effect on the nuclear glass leaching behaviour. Although almost all the data concerning the effects of alpha radiation have been determined by standard Soxhlet leach testing, some discrepancies still exist [4][5][6][7][8][9]. Estimates of leach rates based on weight loss measurements may have underestimated the effects induced by alpha radiation, so it was generally considered that alpha radiation could increase the leach rate by up to a factor of ten [3].…”