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Curti, E.*; Aimoz, L.*; Kitamura, Akira
Journal of Radioanalytical and Nuclear Chemistry, 295(3), p.1655 - 1665, 2013/03
Times Cited Count：34 Percentile：89.47(Chemistry, Analytical)
Se is a major dose-determining redox-sensitive nuclide in safety analysis of radioactive waste disposal sites. In aqueous solutions, selenium forms soluble anionic species (Se
O
and Se
O
) that hardly sorb on negatively charged surfaces of common host-rock minerals. However, Se is known to have a strong affinity with sulphides and interacts with pyrite, a common minor mineral of argillaceous rocks being considered as host rocks for radioactive waste repositories in Switzerland etc. In this study, we present micro- and bulk X-ray spectroscopy data (
-XRF, -XANES, and EXAFS) showing that, under nearly anoxic conditions, dissolved SeO and SeO sorb directly onto the pyrite surface and are subsequently reduced to Se
with increasing ageing time (up to 8 months). These results suggest that the mobility of Se released from radioactive waste could efficiently be reduced through uptake on the pyrite surface followed by transformation into a sparingly soluble reduced form.
2
C as a function of solution composition; An Experimental 
Ba and 
Ra tracer studyCurti, E.*; Fujiwara, Kenso; Iijima, Kazuki; Tits, J.*; Cuesta, C.*; Kitamura, Akira; Glaus, M. A.*; M
ller, W.*
Geochimica et Cosmochimica Acta, 74(12), p.3553 - 3570, 2010/06
Times Cited Count：132 Percentile：92.88(Geochemistry & Geophysics)Uptake tests with Ba and Ra sorption experiments were carried out under the T, p and pH conditions and with the same aqueous solutions on barite suspensions. The Ba tests served to determine recrystallization rates, from which the amounts of barite recrystallized as a function of reaction time could be determined. They also showed that recrystallization was almost complete at the end of the experiments and that tracer distribution was homogeneous in the crystals, implying full thermodynamic equilibrium between solid and aqueous solution. With this information, it was possible to evaluate the Ra uptake experiments in terms of solid solution thermodynamics.
Fujiwara, Kenso; Iijima, Kazuki; Tomura, Tsutomu*; Tobita, Minoru*; Suzuki, Yasuyuki*; Tits, J.*; Curti, E.*
no journal, ,
no abstracts in English
Fujiwara, Kenso; Tomura, Tsutomu*; Tobita, Minoru*; Tits, J.*; Curti, E.*
no journal, ,
Ra-226 is a safety-relevant radionuclide in performance assessments of high-level waste repositories and has thus been deserved special attention. The aim of the proposed study is to provide new key data on the interaction of Ra with calcite and witherite. In this study, the interaction of Ca with calcite and Ba with witherite was measured by using Ca-45 and Ba-133.
Kitamura, Akira; Curti, E.*; Aimoz, L.*
no journal, ,
A batch experiment was performed to investigate sorption of selenium(IV/VI) onto pyrite (FeS
). Polished chips of natural pyrite were reacted with selenium(IV/VI) solutions with pH 8
9 for 2 months at 80 C under N atmosphere. Micro X-ray Fluorescence (-XRF) maps and Micro X-ray Absorption Spectra (-XAS) were collected in suitable sample holders flushed with inert gas. Crashed grains of natural pyrite were also used for comparison with pyrite chips. It was found that equivalent sulfur was dissolved to solutions after selenium sorption, sorption of selenium onto pyrite was highly heterogeneous, and both tetravalent and hexavalent selenium were reduced to selenium(0) after sorption onto pyrite.
-XRF/XAS studyKitamura, Akira; Curti, E.*; Aimoz, L.*
no journal, ,
In the present study, the interaction of Se(IV,VI) species with pyrite under strictly anoxic conditions was investigated using micro X-ray spectroscopy (-XAS). Polished chips of natural pyrite (Navajun, Spain) were reacted with 10
M NaSe(IV)O or NaSe(VI)O solutions at 80C during two months. Micro X-ray Fluorescence (-XRF) maps and -XAS spectra were collected in suitable sample holders flushed with inert gas at the Swiss Light Source (X05 beamline), using a beam focused to roughly 1
1 m. A highly heterogeneous distribution of Se on the pyrite surface was observed on the -XRF maps. Several highly-concentrated Se spots of a few m size were detected, surrounded by areas with low and uniform Se-level distribution. Micro X-ray Absorption Near-Edge Spectra (-XANES) in both regions indicate that Se(IV) and Se(VI) were partially reduced to Se(0).
Fujiwara, Kenso; Tomura, Tsutomu*; Tobita, Minoru*; Suzuki, Yasuyuki*; Tits, J.*; Curti, E.*
no journal, ,
The aim of the proposed study is to provide new key data on the interaction of Ra with calcite, witherite and barite in the presence of selected clay materials Kunigel V1 bentonite representing the backfill, respectively host-rock, of the high-level waste repositories planned in Japan.
