The Sorption of Uranium and Technetium on Bentonite, Tuff and Granodiorite

Abstract

A combined experimental and modelling study of the sorption of uranium and technetium on geological materials has been carried out as part of the PNC programme to increase confidence in the performance assessment for a high-level radioactive waste (HLW) repository in Japan. Batch sorption experiments have been performed in order to study the sorption of uranium and technetium onto bentonite, tuff and granodiorite from both equilibrated seawater and de-ionised water under strongly-reducing and non-reducing conditions.A preliminary study of the sorption of uranium on mineral surfaces in granodiorite has also been undertaken using a nuclear microprobe.Mathematical modelling using the geochemical speciation program HARPHRQ in conjunction with the HATCHES database has been carried out in order to interpret the results of the sorption experiments.

Binding mechanisms of radionuclides to cement

“…hematite was observed [13]. Baston et al [19] quantified Am sorption data using a surface complexation model, in which the main surface sites were >SiO -and >SiOCaOH, with Am hydroxide species assumed to be the sorbing species. Noshita et al [20], have found that Am is highly sorbed onto CSH gel, and they concluded that Am is anionic in cement.…”

Modeling of Groundwater Flow and Radionuclide Transport at the Climax Mine sub-CAU, Nevada Test Site

“…Several of the studies reported here were found through the Japan Nuclear Cycle Development Institute radionuclide sorption database Suyama and Sasamoto, 2004;Saito et al, 2007). Allard et al (1979); Koskinen et al (1985); Torstenfelt et al (1988); Aksoyoglu (1989); Suksi et al (1989);Ticknor (1994); Baston et al (1995); Sato et al (1997); Huitti et al (1998) Kamineni et al (1986); Pinnioja et al (1984);Nakayama, et al (1986); Suksi et al (1987); Kitamura et al (1999a) The studies that report radionuclide sorption data on granites other than the Climax stock can be sorted into two types. First, many of the references given in Table 5-13 are nuclear agency reports with an unknown and likely varying review process.…”

Measurement and modeling of the surface potential evolution of hydrated cement pastes as a function of degradation

“…Different modeling approaches have been developed in the literature to predict the behavior of radiocontaminants in cementitious media, such as solid solutions modeling [1,2] or surface complexation modeling (SCM) [3][4][5].…”

“…Other surface equilibria have also been suggested [4,5,9], with the resulting formation of >SiOCaOH, or (>SiO) 2 Ca.…”