Hemmi, Ko; Walker, A.*; Yamaguchi, Tetsuji
Radiochimica Acta, 109(7), p.539 - 546, 2021/07
Plutonium(IV) sorption onto quartz in carbonate solutions was systematically investigated under anaerobic conditions to analyze the sorption behaviors of Pu(IV) with a non-electrostatic model (NEM). Pu(IV) sorption data was obtained from batch sorption experiments as a function of pH and carbonate concentration. The Pu(IV) sorption onto quartz showed similar tendencies to Th(IV), which is considered to be chemically analogous as a tetravalent actinoid. The distribution coefficient, d, of Pu(IV) onto quartz showed inverse proportionality to the square of the total carbonate concentration under the investigated pH conditions of 8 to 11. The modeling study, however, revealed a Th(IV) sorption model, which is SOTh(OH) and SOThOH(CO), could not be applied to simulate the Pu(IV) sorption onto quartz. It was inferred that the electrostatic repulsion between negatively charged ligands limited the formation of SOM(OH) and SOMOH(CO) for Pu(IV) with smaller ionic radii than Th(IV). The Pu(IV) sorption model was developed as SOPu(OH) and SOPu(OH). In addition, data of Pu(IV) sorption onto muscovite was obtained in order to be compared with data for quartz.
Soler, J. M.*; Meng, S.*; Moreno, L.*; Neretnieks, I.*; Liu, L.*; Keklinen, P.*; Hokr, M.*; ha, J.*; Vetenk, A.*; Reimitz, D.*; et al.
SKB TR-20-17, 71 Pages, 2021/07
Task 9B of the SKB Task Force on Modelling of Groundwater Flow and Transport of Solutes in fractured rock focused on the modelling of experimental results from the LTDE-SD in situ tracer test performed at the sp Hard Rock Laboratory in Sweden. Ten different modelling teams provided results for this exercise, using different concepts and codes. Three main types of modelling approaches were used: (1) analytical solutions to the transport-retention equations, (2) continuum-porous-medium numerical models, and (3) microstructure-based models accounting for small-scale heterogeneity (i.e. mineral grains and microfracture distributions). The modelling by the different teams allowed the comparison of many different model concepts, especially in terms of potential zonations of rock properties (porosity, diffusion, sorption), such as the presence of a disturbed zone at the rock and fracture surface, the potential effects of micro- and cm-scale fractures.
Yamaguchi, Tetsuji; Ohira, Saki; Hemmi, Ko; Barr, L.; Shimada, Asako; Maeda, Toshikatsu; Iida, Yoshihisa
Radiochimica Acta, 108(11), p.873 - 877, 2020/11
Watanabe, Kosuke*; Matsuda, Shohei; Cuevas, C. A.*; Saiz-Lopez, A.*; Yabushita, Akihiro*; Nakano, Yukio*
ACS Earth and Space Chemistry (Internet), 3(4), p.669 - 679, 2019/04
The photooxidation of aqueous iodide ions (I) at sea surface results in the emission of gaseous iodine molecules (I) into the atmosphere. It plays a certain role in the transport of iodine from ocean to the atmosphere in the natural cycle of iodine. In this study, we determined the photooxidation parameters, the molar absorption coefficient (()) and the photooxidative quantum yields (()) of I, in the range of 290-500 nm. Through the investigation of the influence of pH and dissolved oxygen (DO) on (), the subsequent emission rates of I following the photooxidation of I in deionized water solution (pH 5.6, DO 7.8 mg L) and artificial seawater solution (pH 8.0, DO 7.0 mg L) were estimated. A global chemistry-climate model employed herein to assess the I ocean emission on a global scale indicated that the photooxidation of I by solar light can enhance the atmospheric iodine budget by up to 8% over some oceanic regions.
Soler, J. M.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; Svensson, U.*; Trinchero, P.*; Iraola, A.*; Ebrahimi, H.*; Molinero, J.*; et al.
SKB R-17-10, 153 Pages, 2019/01
The SKB Task Force is an international forum on modeling of groundwater flow and solute transport in fractured rock. The WPDE experiments are matrix diffusion experiments in gneiss performed at the ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing tracers was injected along a borehole interval. The objective of Task 9A was the predictive modeling of the tracer breakthrough curves from the WPDE experiments. Several teams, using different modelling approaches, participated in this exercise. An important conclusion from this exercise is that the modeling results were very sensitive to the magnitude of dispersion in the borehole opening, which is related to the flow of water. Focusing on the tails of the breakthrough curves, which are more directly related to matrix diffusion and sorption, the results from the different teams were more comparable. The modeling results have also been finally compared to the measured breakthroughs.
Tachi, Yukio; Ito, Tsuyoshi*; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*
Water Resources Research, 54(11), p.9287 - 9305, 2018/11
Effects of fine-scale surface alterations on radionuclide migration in fractured crystalline rocks were investigated by a comprehensive approach coupling a series of laboratory tests, microscopic observations and modelling, using a single fractured granodiorite sample from the Grimsel Test Site, Switzerland. Laboratory tests including through-diffusion, batch sorption and flow-through tests using five tracers indicated that tracer retention was consistently in the sequence of HDO, Se, Cs, Ni, Eu, and as well as showing the existence of a diffusion-resistance layer near the fracture surface, cation excess and anion exclusion effects for diffusion. Microscale heterogeneities in structural properties around the fracture were clarified quantitatively by coupling X-ray CT and EPMA. A three layer model including weathered vermiculite, foliated mica and undisturbed matrix layers, and their properties such as porosity, sorption and diffusion parameters, could provide a reasonable interpretation for breakthrough curves and concentration distributions near fracture surface of all tracers, measured in flow-through tests.
Pratama, M. A.; Takahara, Shogo; Hato, Shinji*
Hoken Butsuri, 52(3), p.200 - 209, 2017/09
The purpose of this study is to identify the significance of the change in the intestinal absorption rate values the ( value) to the change of dose coefficient as well as to provide a list of dose coefficients which each of the value corresponds to a specific intestinal absorption rate and age groups. In the range of 0-1, 10 different values of for 1 year, 5 years old, and adult group were chosen and used in a separate calculation by using, a biokinetic compartment model, DCAL. It was found that the lower values of intestinal absorption rate lead to a significant decrease of the committed effective coefficient for adult. Oppositely for children, the decrease of committed effective coefficient was not as significant. This study also suggests that the significance of dose coefficient change due to the variation of substantially depends on the biological half-life of the radionuclide and the mass of organs and tissues in human body.
Sasaki, Takayuki*; Ueda, Kenyo*; Saito, Takumi; Aoyagi, Noboru; Kobayashi, Taishi*; Takagi, Ikuji*; Kimura, Takaumi; Tachi, Yukio
Journal of Nuclear Science and Technology, 53(4), p.592 - 601, 2016/04
The influences of pH and the concentrations of Eu and NaNO on the sorption of Eu to Na-montmorillonite were investigated through batch sorption measurements and time-resolved laser fluorescence spectroscopy (TRLFS). The pH had a little effect on the distribution coefficients (Kd) in 0.01 M NaNO, whereas the Kd strongly depended on pH at 1 M NaNO. A cation exchange model combined with a one-site non-electrostatic surface complexation model was successfully applied to the measured Kd. The TRLFS spectra of Eu sorbed were processed by parallel factor analysis (PARAFAC), which corresponded to one outer-sphere (factor A) and two inner-sphere (factor B and C) complexes. It turned out that factors A and B correspond to Eu sorbed by ion exchange sites and inner-sphere complexation with hydroxyl groups of the edge faces, respectively. Factor C became dominant at relatively high pH and ionic strength and likely correspond to the precipitation of Eu(OH) on the surface.
Tachi, Yukio; Suyama, Tadahiro; Yotsuji, Kenji; Ishii, Yasuo; Takahashi, Hiroaki*
CMS Workshop Lectures, Vol.21, p.241 - 250, 2016/00
Sorption and diffusion of radionuclides in argillaceous rocks are key processes in the safe geological disposal. The diffusion and sorption behavior of Ni(II), Am(III) and Se(IV) in mudstone from the Horonobe URL were investigated by experimental and modeling approaches. Effective diffusivities obtained by the through-diffusion experiments were in the sequence of Cs, Ni, HTO, I, Se(SeO), Am(Am(CO)) by comparison with the previous study. The distribution coefficient values were consistent with those obtained by batch sorption tests. These results were interpreted by the clay-based modeling approach coupling the thermodynamic sorption model assuming key contributions of clays (smectite and illite) and the diffusion model assuming the electrical double layer theory and the simplified pore model with size distribution. This clay-based model could provide reasonable account of observed trends and could be basically applicable for various radionuclides.
Soler, J. M.*; Landa, J.*; Havlova, V.*; Tachi, Yukio; Ebina, Takanori*; Sardini, P.*; Siitari-Kauppi, M.*; Eikenberg, J.*; Martin, A. J.*
Journal of Contaminant Hydrology, 179, p.89 - 101, 2015/08
Matrix diffusion is a key process for radionuclide retention in crystalline rocks. An in-situ diffusion experiment in granite matrix was performed at the Grimsel Test Site (Switzerland). Several tracers (HTO, Na, Cs) were circulated through a borehole and the decrease in tracer concentrations was monitored for 2.5 years. Then, the borehole section was overcored and the tracer profiles in the rock were analyzed. Transport distances in the rock were 20 cm for HTO, 10 cm for Na and 1 cm for Cs. The dataset was analyzed with diffusion-sorption models by different teams using different codes, with the goal of obtaining effective diffusivities (De) and rock capacity factors. There was a rather good agreement between the values from different teams, implied that De and capacity factors in the borehole damaged zone are larger than those in the bulk rock. However, HTO seems to display large discrepancies between measured and modeled results.
Kishida, Norio*; Murata, Toru*; Asami, Tetsuo*; Kosako, Kazuaki*; Maki, Koichi*; Harada, Hideo*; Lee, Y.*; Chang, J.*; Chiba, Satoshi; Fukahori, Tokio
AIP Conference Proceedings 769, p.199 - 202, 2005/05
Nuclear data for photonuclear reactions are required in the field of shielding design of high-energy electron accelerators and high-energy -ray therapy. The JENDL Photonuclear Data File was prepared by a working group on nuclear data evaluations for photonuclear reactions in Japanese Nuclear Data Committee. From a survey of many literatures, it is difficult to construct the photonuclear data file by using only measured data, since there are not sufficient experimental data. We were therefore evaluating with theoretical calculations based on statistical nuclear reaction models. The photonuclear cross sections that are to be contained in the file are as follows: photoabsorption cross sections, yield cross sections and DDX for neutrons, protons, deuterons, tritons, He-particles and alpha-particles, and isotope production cross sections. For the actinide nuclides, photofission cross sections are also included. The maximum energy of incident photons is 140 MeV and stored are the photonuclear data for 68 nuclides from H to Np.
Mineo, Hideaki; Goto, Minoru; Iizuka, Masaru*; Fujisaki, Susumu; Hagiya, Hiromichi*; Uchiyama, Gunzo
Separation Science and Technology, 38(9), p.1981 - 2001, 2003/05
no abstracts in English
Tanaka, Tadao; Mukai, Masayuki; Maeda, Toshikatsu; Matsumoto, Junko; Ogawa, Hiromichi; Li, S.*; Wang, Z.*; Wang, J.*; Guo, Z.*; Zhao, Y.*
JAERI-Research 2002-034, 20 Pages, 2002/12
Adsorption mechanisms and models of Sr(II), Np(V), Pu(IV) and Am(III) on the loess were investigated from their adsorption and desorption properties. The distribution coefficient of Sr and Np was 2 - 3 orders of magnitude smaller than that of Pu and Am. The adsorption of Sr and Np was mainly controlled by the ion exchange reaction. On the other hand, the adsorption of Pu and Am was mostly controlled by the selective chemical reactions with Fe and Mn oxyhydroxide/oxide and humic substances. On the basis of the experimental results, several types of adsorption models of the radionuclides, considering elemental concentrations, adsorption mechanisms and kinetics, were proposed for setting up the analytical systems of radionuclide migration in the loess media.
Yoda, Osamu; Miyashita, Atsumi; *; *
JAERI-M 92-173, 27 Pages, 1992/10
no abstracts in English
Journal of Nuclear Science and Technology, 20(6), p.503 - 510, 1983/00
no abstracts in English
Soler, J. M.*; Martin, A. J.*; Lanyon, G. W.*; Havlov, V.*; Siitari-Kauppi, M.*; Tachi, Yukio
no journal, ,
An in-situ long-term diffusion (LTD) project has been performed at the Grimsel Test Site, Switzerland, to realistically evaluate matrix diffusion of radionuclides in crystalline rock with minimal disturbance to in-situ conditions. A second in situ diffusion experiment (monopole 2) has been performed. Predictive calculations for the monopole-2 experiment, based on results from monopole 1 or from through-diffusion experiments have been compared to monitoring data from the injection and observation boreholes. For the non-sorbing tracers (HTO, Cl), the diffusion parameters from the through-diffusion experiments provide a better match for the measurements, especially in the injection borehole. The initial drop in activities for Cs and Ba shows clearly the effect of sorption. Bulk rock parameters for Cs from monopole 1 seem to be applicable to monopole 2. However, Ba seems to sorb more strongly than expected.
Soler, J. M.*; Lfgren, M.*; Nilsson, K.*; Lanyon, G. W.*; Gylling, B.*; Vidstrand, P.*; Neretnieks, I.*; Moreno, L.*; Liu, L.*; Meng, S.*; et al.
no journal, ,
The GWFTS Task Force is an international forum in the area of modeling of groundwater flow and solute transport in fractured rock. The WPDE experiments are matrix diffusion experiments in gneiss performed at the ONKALO underground facility in Finland. Synthetic groundwater containing several conservative and sorbing radiotracers was injected along a borehole interval. The objective of Task 9A of Task Force was the predictive modeling of the tracer breakthrough curves from the WPDE experiments. Several teams, using different modeling approaches, participated in this exercise. An important conclusion from this exercise is that the modeling results were very sensitive to the magnitude of dispersion in the borehole opening, which is related to the flow of water. Focusing on the tails of the breakthrough curves, which are more directly related to matrix diffusion and sorption, the results from the different teams were more comparable.
Tachi, Yukio; Ito, Tsuyoshi; Akagi, Yosuke*; Sato, Hisao*; Martin, A. J.*
no journal, ,
The effects of heterogeneity at fracture surface on radionuclides migration in fractured crystalline rocks was investigated by laboratory migration experiments, microscopic observations and detailed modelling, using a single fractured granodiorite sample from the Grimsel Test Site (GTS), Switzerland. The tracer migration behaviors in fracture and matrix parts were evaluated by series of laboratory experiments including through-diffusion and flow-through experiments. Mineral distributions from fracture surface to matrix were evaluated by X-ray CT, and were validated by comparing the elemental mapping measured by EPMA. Based on the microscopic observations by X-ray CT and EPMA, the aperture and connectivity in fracture and minerals distribution near fracture surface were quantitatively evaluated. The heterogeneous multi-layered model assuming a weathered vermiculite zone, a foliated mica zone and rock matrix was possible to provide a reasonable interpretation for measured breakthrough curves of all tracers.
Tachi, Yukio; Ito, Tsuyoshi; Gylling, B.*
no journal, ,
The in-situ long-term sorption and diffusion experiment (LTDE-SD) at the Aspo Hard Rock Laboratory in Sweden provides valuable dataset to test the scaling approach from laboratory to in-situ condition. The scaling approach developed in the in-situ Long-Term Diffusion (LTD) project at Grimsel Test Site in Switzerland was tested for the LTDE-SD results as part of the SKB Task Force on modeling of groundwater flow and transport of solutes in fractured crystalline rocks. Our modelling approach could account reasonably overall trends for sorption and diffusion of 10 radionuclides, and was then evaluated as being applicable for a wider range of radionuclides and for more complex fracture systems.