XAFS analysis of Ni diffused in compacted bentonite

Takahashi, Hiroaki; Nemoto, Kazuaki; Tachi, Yukio; Katayama, Misaki*; Inada, Yasuhiro*

2012-Nendo Ritsumeikan Daigaku Sogo Kagaku Gijutsu Kenkyu Kiko Sentan Kenkyu Shisetsu Kyoyo Sokushin Jigyo Seika Hokokusho (Internet), 2 Pages, 2013/00

http://www.ritsumei.ac.jp/acd/re/src/kyoyo/seikahoukoku2012/R1228.pdf

The diffusion profiles of strongly sorbing nuclides such as Cm, Am, Ni, in a compacted bentonite show two parts with different slopes which cannot be fitted by simple one-dimensional diffusion model considering single species. The reason for this anomalous diffusion behavior is not understood. Some XANES spectral shape of Ni diffused in compacted montmorillonite, which is main content of bentonite, at relatively higher concentrated region exhibit slight broadening of a feature on the high-energy side of the white line. The broadening of a feature doesn't appear in the case of Ni aqueous solution and Ni-montmorillonite. These results indicate that the inner coordination geometry of the Ni(II) ion diffused in compacted montmorillonite at relatively higher concentrated region.

Sorption / diffusion data aquisition method development for high sorbing americium in compacted bentonite

Ishii, Yasuo; Takahashi, Hiroaki; Tachi, Yukio; Tomura, Tsutomu*; Nemoto, Kazuaki*; Okazaki, Mitsuhiro*

no journal, , 

Am(III) diffusion experiment were performed by reservoir depletion (RD) test method coupled with thin layer ID profile fitting in 0.1 or 0.5M NaCl / 0.05M NaHCO - bentonite (kunipia-F) system. The Kd values were also measured using batch technique in the same experimental conditions. In an ordinary ID profile acquisition cutting the bentonite by scraper, the compacted bentonite sample can be cut into 100 m thick slices. Using this technique, it was possible to divide the ID profile into 10 m and therefore, to analyze diffusion distance layer larger than 50 m.

Study of Ni diffusion mechanisms on compacted montmorillonite

Takahashi, Hiroaki; Nemoto, Kazuaki; Tachi, Yukio

no journal, , 

Ni(II) diffusion experiment and microstructure analysis in compacted water-saturated Na- and Ca-montmorillonite have been performed. Diffusion mechanism of Ni(II) in compacted montmorillonite has been studied by comparative analysis of Ni(II) diffusion profile, XRD analysis and XAFS analysis.

Matrix diffusion and sorption of Cs, Na, I and HTO in granodiorite; Laboratory results and their extrapolation to the in-situ condition

Tachi, Yukio; Ebina, Takanori*; Takahashi, Hiroaki; Nemoto, Kazuaki; Suyama, Tadahiro*; Martin, A.*

no journal, , 

Matrix diffusion and sorption of radionuclides in crystalline host rocks are key processes controlling safe geological disposal of radioactive waste. Diffusion and sorption parameters for Cs, Na, I and HTO were determined by laboratory experiments using granodiorite samples from the Grimsel Test Site, Switzerland. The De values derived were in the order Cs Na HTO I. The capacity factor and Kd values show the same trends. Depth profiles of Cs and Na obtained by abrasing samples after a diffusion period showed typical dual profiles. The results of in-situ long-term diffusion tests at GTS were interpreted by using GoldSim code and transport parameters based on laboratory results and their extrapolations to in-situ conditions. These model calculations could the in-situ LTD results of Cs and Na reasonably well, although it was difficult to interpret HTO results. Key findings from these comparative studies between laboratory experiments and in-situ LTD tests were discussed.

Radionuclide migration in single fracture of mudstone at Horonobe URL, 1; Laboratory experiments

Tachi, Yukio; Akagi, Yosuke*; Nemoto, Kazuaki; Matsumoto, Kazuhiro; Ishii, Eiichi

no journal, , 

To validate radionuclide migration model in single fractures in sedimentary rocks, the mudstone sample with single fracture from Wakkanai Formation at Horonobe Underground Research Laboratory was investigated. The migration behaviors of deuterated water, iodine and cesium were measured by series of laboratory experiments including batch sorption, through-diffusion and flow-through experiments.

Microbial populations stimulated by lanthanoids in groundwater of Pliocene diatomaceous mudstone of northernmost Japan

Amano, Yuki; Endo, Takashi; Nemoto, Kazuaki; Tachi, Yukio

no journal, , 

High-level radioactive waste (HLW) from nuclear power generation must be disposed in a safe manner for at least 100,000 years until the radiation dose is reduced to the levels of natural radiation dose in subsurface environments. Interaction of long-lived radionuclides with subsurface microorganisms has been studied to evaluate the effect of radionuclides migration in subsurface environments. However, the microbial activities and their mechanisms of radionuclide transformation are poorly understood. In this study, we investigated microbial populations stimulated by lanthanoids as analogue elements for actinides in natural systems. Groundwater samples collected from boreholes in the subsurface environment at Horonobe Underground Research Laboratory, Japan, were incubated anaerobically with lanthanoids. During the incubation experiments, concentrations of lanthanoids, total Fe, Fe, S were measured by absorption spectrophotometry and ICP-MS. Microbial community compositions were analyzed by next generation sequencing the V4 region of the 16S rRNA gene on an Illumina Miseq. Phylogenetic analyses obtained from the original and incubated groundwaters revealed that microbial populations were changed from the original one. The original groundwater showed diverse microbial community structure with the dominant phylotypes clustered within the phylum Firmicutes, Proteobacteria, and Chloroflexi. In the lanthanoids added systems, microorganisms related to Chlostridium, Georgfuchsia or Rodobacter spp. increased by the incubation. These results indicate that interaction between microorganisms and actinides may effect on radionuclide migration in HLW systems.

Radionuclide migration in single fracture of granodiorite at Grimsel Test Site, 1; Laboratory

Akagi, Yosuke*; Tachi, Yukio; Nemoto, Kazuaki; Martin, A.*

no journal, , 

To validate radionuclide migration model in single fracture in crystalline rocks, the granodiorite sample with single fracture from the Grimsel Test Site in Switzerland was investigated. The migration behaviors of tracers including cesium in fracture and matrix parts were evaluated quantitatively by series of laboratory experiments including batch sorption, through-diffusion and flow-through experiments.

Modeling of solutes transport at the Horonobe URL; In-situ tracer tests for fractures in fault zone

Takeda, Masaki; Ono, Hirokazu; Ishii, Eiichi; Tachi, Yukio; Nemoto, Kazuaki*

no journal, , 

JAEA has developed evaluation techniques for characterization of solute transport in the mudstone through laboratory and in situ tests. This study reports on results of in situ tracer tests implemented for fractures in fault zone at Horonobe Underground Research Laboratory (URL).

In situ diffusion experiment in mudstone at the Horonobe URL; Comparative study between in situ and laboratory tests

Tachi, Yukio; Takeda, Masaki; Ono, Hirokazu; Ito, Tsuyoshi*; Sato, Tomofumi*; Nemoto, Kazuaki*

no journal, , 

Existence and the role of subsurface biofilm in the deep sedimentary rock environment of the Horonobe area, Hokkaido, Japan

Amano, Yuki; Beppu, Hikari*; Endo, Takashi*; Nemoto, Kazuaki*; Sato, Tomofumi*; Thomas, B. C.*; Banfield, J. F.*

no journal, ,