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Journal Articles

Sorption of Sn and Nb on montmorillonite at neutral to alkaline pH

Ishidera, Takamitsu; Okazaki, Mitsuhiro*; Yamada, Yoshihide*; Tomura, Tsutomu*; Shibutani, Sanae*

Journal of Nuclear Science and Technology, 60(5), p.536 - 546, 2023/05

The distribution coefficient (${it K$_{d}$}$) value of radionuclides is an important parameter in the radionuclide migration analysis in the safety assessment of the geological disposal of high-level radioactive waste. The ${it K$_{d}$}$ values must be extensively evaluated especially under conditions where they might be decreased to improve the reliability of safety assessment. In this study, the pH dependence of the ${it K$_{d}$}$ values for Sn and Nb on montmorillonite was evaluated using batch sorption experiments at neutral to alkaline pH, which might be caused by the leaching of cementitious materials and the corrosion of carbon steel. The ${it K$_{d}$}$ values were determined in the range 8 $$<$$ pH $$<$$ 12 by the experiments and were found to decrease with increasing pH. A model calculation using a thermodynamic sorption model was conducted on the measured pH dependence of the ${it K$_{d}$}$ values. Two different sorption sites were required to describe the pH dependence of the ${it K$_{d}$}$ values of Sn in the model calculation, whereas one sorption site was considered predominant in the sorption of Nb.

JAEA Reports

Assessment report of research and development activities in FY2021; Activity of "Research and Development on Geological Disposal of High-level Radioactive Waste" (Post- and pre-review report)

Geological Disposal Research and Development Department

JAEA-Evaluation 2022-007, 81 Pages, 2022/11

JAEA-Evaluation-2022-007.pdf:2.06MB
JAEA-Evaluation-2022-007-appendix(CD-ROM).zip:37.06MB

Japan Atomic Energy Agency (JAEA) consulted the advisory committee, "Evaluation Committee on Research and Development (R&D) Activities for Geological Disposal of High-Level Radioactive Waste", for post- and pre-review assessment of R&D activities on high-level radioactive waste disposal in accordance with "General Guideline for the Evaluation of Government Research and Development (R&D) Activities" by the Cabinet Office, Government of Japan, "Guideline for Evaluation of R&D in Ministry of Education, Culture, Sports, Science and Technology" and JAEA's "Regulation on Conduct for Evaluation of R&D Activities". In response to JAEA's request, the Committee reviewed mainly the progress of the R&D project on geological disposal, the relevance of the project outcome and the efficiency of the project implementation during the period of the current and next plan. This report summarizes the results of the assessment by the Committee with the Committee report attached.

Journal Articles

Diffusion of acetic acid, butyric acid, and butanol in compacted montmorillonite

Ishidera, Takamitsu

Journal of Radioanalytical and Nuclear Chemistry, 330(1), p.149 - 158, 2021/10

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

Journal Articles

Surface complexation of Ca and competitive sorption of divalent cations on montmorillonite under alkaline conditions

Sugiura, Yuki; Ishidera, Takamitsu; Tachi, Yukio

Applied Clay Science, 200, p.105910_1 - 105910_10, 2021/01

 Times Cited Count:5 Percentile:53.59(Chemistry, Physical)

Journal Articles

Sorption behavior of U and Np on zeolite

Ishidera, Takamitsu; Tachi, Yukio; Akagi, Yosuke*; Ashida, Takashi

Progress in Nuclear Science and Technology (Internet), 5, p.221 - 224, 2018/11

In Fukushima Daiichi Nuclear Power Station, radionuclides are removed from contaminated water by the decontamination system using zeolite. In this study, sorption properties of U and Np on zeolite were investigated by batch sorption experiments to obtain fundamental information for predicting the radionuclides inventory. High distribution coefficients were observed for U in the simulated sea water diluted 10 times by deionized water. In contrast, low distribution coefficient of U was observed in simulated sea water. Low distribution coefficients were observed for Np independent of simulated sea water concentration. Batch sorption experiments of U carried out as functions of sodium ion and total inorganic carbon concentration suggested that the distribution coefficient of U was strongly affected by the total inorganic carbon concentration. This result suggests that aqueous species of radionuclides and their sorption behavior need to be considered to estimate the inventory of radionuclides in zeolite.

Journal Articles

The FeSe$$_{2}$$(cr) solubility determined by solubility experiments of Se co-existing with Fe

Doi, Reisuke; Uchikoshi, Keiji*; Beppu, Hikari*

Journal of Nuclear Science and Technology, 53(10), p.1554 - 1562, 2016/10

 Times Cited Count:3 Percentile:28.38(Nuclear Science & Technology)

To determine log K$$^{0}$$ for FeSe$$_{2}$$(cr) dissolution reaction, solubility experiments of Se co-existing with Fe were performed. Temperature was maintained at 348 K. Se concentration as a function of equilibration periods indicated that Se concentrations were similar at different equilibration periods. Only FeSe$$_{2}$$(cr) was detected as the Se solid phase by XRD analysis of the equilibrated precipitates. $$E_{rm h}$$ and pH of the equilibrated suspensions ranged from -188.6 to -4.9 mV vs. SHE and 6.00 to 8.76, respectively. Se$$_{4}$$$$^{2-}$$ and Fe$$^{2+}$$ are thermodynamically stable in this region. Interpretations using SIT model showed that the relationship between $$E_{rm h}$$ and the measured concentrations could be interpreted well when in the following equation n = 0.50$$pm$$0.01 and log K $$^{0}$$ = -17.24$$pm$$0.31 : 4Fe$$_{n}$$Se(cr) = 4nFe$$^{2+}$$ + Se$$_{4}$$$$^{2-}$$ + (8n - 2)e$$^{-}$$. The logK$$^{0}$$ value calculated from the available thermodynamic data agrees with that determined here.

Journal Articles

Diffusion and retention behaviour of Cs in illite-added compacted montmorillonite

Ishidera, Takamitsu; Kurosawa, Seiichi*; Hayashi, Masanori*; Uchikoshi, Keiji*; Beppu, Hikari*

Clay Minerals, 51(2), p.161 - 172, 2016/05

 Times Cited Count:4 Percentile:14.18(Chemistry, Physical)

The sorption and diffusion behavior of Cs in illite-added compacted montmorillonite was investigated by through-diffusion experiment. The obtained distribution coefficient of Cs for the illite-added compacted montmorillonite was several times larger than that for the montmorillonite without illite, while no increase of effective diffusion coefficient was observed for the illite-added compacted montmorillonite. The dominant sorption site of Cs on illite is considered to be the frayed edge site (FES) considering the Cs concentration in this experiment. Therefore, the surface diffusion of Cs sorbing on the FES on illite surface was considered to be negligible in compacted montmorillonite.

Journal Articles

Distribution of Cs and Am in the solution-bentonite colloids-granite ternary system; Effect of addition order and sorption reversibility

Iijima, Kazuki; Tomura, Tsutomu*; Tobita, Minoru*; Suzuki, Yasuyuki*

Radiochimica Acta, 98(9-11), p.729 - 736, 2010/11

 Times Cited Count:2 Percentile:17.51(Chemistry, Inorganic & Nuclear)

Distribution behavior of Cs and Am in the synthetic groundwater-bentonite colloids-granite ternary system was investigated. Radionuclide sorbed onto the bentonite colloids is desorbed by addition of granite, indicating that the sorption of Cs and Am onto the bentonite colloids are reversible. The sorption model based on cation exchange and surface complexation reaction considering high edge site density for bentonite colloids is applicable to explain the sorption behavior of Am and Cs in the ternary system.

Journal Articles

Reversibility and modeling of adsorption behavior of cesium ions on colloidal montmorillonite particles

Iijima, Kazuki; Tomura, Tsutomu*; Shoji, Yoshiyuki*

Applied Clay Science, 49(3), p.262 - 268, 2010/06

 Times Cited Count:37 Percentile:71.17(Chemistry, Physical)

Sorption and desorption behavior of Cs onto montmorillonite colloids was investigated. The ion exchange and surface complexation model can successfully reproduce the sorption and desorption behavior of Cs. Conditioning montmorillonite in higher Cs concentration than 0.005M causes decrease of interlayer distance which may lead to fixation of Cs in the interlayer. Sorption reversibility of Cs on montmorillonite colloids can be expected in this study due to lower Cs concentration than 0.0001M.

Journal Articles

Corrosion products from carbon steel formed in compacted bentonite under reducing conditions

Ishidera, Takamitsu; Xia, X.*; Idemitsu, Kazuya*; Kikuchi, Yoshio*

Journal of Nuclear Science and Technology, 45(8), p.763 - 772, 2008/08

 Times Cited Count:6 Percentile:40.16(Nuclear Science & Technology)

For safety assessment of high-level radioactive waste disposal, it is important to identify the forms of corrosion products migrating from overpack material into compacted bentonite. In this study, the carbon steel, which was previously corroded electrochemically under aerobic condition, was in contact with compacted Kunigel V1 and Kunipia F under reducing condition for 3-4 years at room temperature. The corrosion products migrating from carbon steel into compacted bentonites were investigated by the selective dissolution analysis, which can estimate the crystallinity of Fe-bearing compounds. The valence of iron in corrosion products was investigated spectrophotometrically. Furthermore, the alteration of smectite contained in compacted bentonite to Fe-smectite was analyzed by X-ray diffractometry (XRD). The results of selective dissolution and valence analysis suggested that the corrosion products in compacted bentonite were amorphous, non-crystalline or poorly ordered Fe(OH)$$_{2}$$ and Fe(OH)$$_{3}$$. In the XRD profiles, no diffraction peak suggesting the existence of Fe-smectite in the compacted bentonite was found. Therefore, the corrosion products in compacted bentonite were considered to have no effect on the alteration of smectite contained in Kunigel V1 and Kunipia F to Fe-smectite.

Journal Articles

Effect of sodium nitrate on the diffusion of Cl$$^{-}$$ and I$$^{-}$$ in compacted bentonite

Ishidera, Takamitsu; Miyamoto, Shinya*; Sato, Haruo

Journal of Nuclear Science and Technology, 45(7), p.610 - 616, 2008/07

 Times Cited Count:11 Percentile:59.25(Nuclear Science & Technology)

For safety assessment of TRU waste disposal, the effective diffusion coefficients ($$D$$$$_{e}$$) for CO$$_{3}$$$$^{2-}$$, Cl$$^{-}$$ and I$$^{-}$$ ions in compacted bentonite (Kunigel V1) were determined as a function of NaNO$$_{3}$$ concentrations from 0.01 to 5 mol/dm$$^{3}$$. The $$D$$$$_{e}$$ values increased from 10$$^{-12}$$ to 10$$^{-11}$$ m$$^{2}$$/s with increasing NaNO$$_{3}$$ concentration. The rock capacity factor $$alpha$$, indicative of the effective porosity, were also increased with increasing NaNO$$_{3}$$ concentration. The maximum $$alpha$$ values of 0.21 for Cl$$^{-}$$ ion and of 0.25 for I$$^{-}$$ ion at 5 mol/dm$$^{3}$$ NaNO$$_{3}$$ concentration were lower than the net porosity of compacted bentonite (0.40). Therefore, the increases in the $$D$$$$_{e}$$ values were interpreted by the decrease of anion exclusion effect. The $$D$$$$_{e}$$ values for Cl$$^{-}$$ and I$$^{-}$$ ions normalized by the diffusivities for diffusants in the bulk water were found to increase in proportion to the $$alpha$$ values on the log-log diagram. The maximum $$alpha$$ value for CO$$_{3}$$$$^{2-}$$ ion was higher than the net porosity. The high concentration of CO$$_{3}$$$$^{2-}$$ ion was also found in the concentration profile in compacted bentonite. This retention of CO$$_{3}$$$$^{2-}$$ ion was possibly accounted for by isotopic exchange of $$^{14}$$C with inactive carbon of calcite in Kunigel V1.

JAEA Reports

Sorption behavior of cesium onto bentonite and sedimentary rocks in saline groundwaters

Kitamura, Akira; Tomura, Tsutomu*; Sato, Haruo; Nakayama, Masashi

JAEA-Research 2008-004, 39 Pages, 2008/03

JAEA-Research-2008-004.pdf:3.0MB

Distribution coefficient of cesium onto bentonite and sedimentary rocks was determined in saline groundwaters. Distribution coefficient of cesium onto the solid phases was also determined in sodium chloride and potassium chloride solutions in order to elucidate sorption behavior of cesium. It was expected that the sorption behavior of cesium was regarded as ion exchange reactions with sorption sites of the solid phases from the results of dependencies of distribution coefficient on pH and ionic strength. It was found that only potassium ion was competed with cesium for the sorption onto sedimentary rocks, while both sodium and potassium ions was competed with cesium for the sorption onto bentonite. It was also found that sorption behavior of cesium onto sedimentary rocks was well described using a model on the sorption of cesium onto illite. The present study was performed in Tokai Works, Japan Nuclear Cycle Development Institute (one of the predecessors of JAEA) in FY 2002-2003.

Journal Articles

Sorption behavior of americium onto bentonite colloid

Iijima, Kazuki; Shoji, Yoshiyuki*; Tomura, Tsutomu*

Radiochimica Acta, 96(9-11), p.721 - 730, 2008/00

 Times Cited Count:9 Percentile:52.88(Chemistry, Inorganic & Nuclear)

Distribution coefficients of Am onto bentonite colloid were evaluated under weak basic and low ionic strength conditions, in taking the influence of Am colloid into account. The obtained values are larger than those obtained for larger montmorillonite particles in literatures. It is attributed to one order of magnitude higher reactive site density of the bentonite colloid. Applicability of a relatively simple and generalized mechanistic sorption model to the bentonite colloid is also discussed.

JAEA Reports

Solubility Product of Np(IV) Hydrous Oxide

Fujiwara, Kenso; Kohara, Yukitoshi*; Mori, Takashi

JNC TN8400 2004-021, 32 Pages, 2004/12

JNC-TN8400-2004-021.pdf:0.44MB

In support of the performance assessment of geological disposal of high-level radioactive waste, solubility measurement of tetravalent neptunium (Np(IV)) hydroxide in reducing condition was performed. Np stock solution was reduced by using H$$_{2}$$gas and platinum black (catalyst). Solubility test were perfomed by oversaturation method. Sample solution of 1.0 M NaClO$$_{4}$$was spiked by the Np(IV) solution. The pHc value was adjusted around 3 with NaOH and HClO$$_{4,}$$and the sealed sample solution was standing at room tempreture (23 $$pm$$ 2$$^{circ}$$C) in the shaded box avoiding photo-oxidation. The concentration of Np(IV) was measured by alpha-spectrometry. The solubility decreased with increasing pHc. It can be seen that the hydrolysis species are predominantly formed with the slope of solubility. It can be seen that the hydrolysis species are predominantly formed with the slope of solubility. From the obtained results, the solubility product (K$$_{sp)}$$of Np hydroxide at I = 1.0 were determined. The experimental values were extrapolated to the standard state (I = 0) by using the specific interaction theory (SIT), and the solubility product of Np hydroxide was determined to be logKsp° = -56.2 $$pm$$ 0.3.

JAEA Reports

Sorption Behavior of Neptunium onto Smectite under Reducing Conditions in Carbonate Media

Kitamura, Akira; Tomura, Tsutomu*

JNC TN8400 2003-025, 67 Pages, 2003/03

JNC-TN8400-2003-025.pdf:1.48MB

The obtained distribution coefficient under reducing conditions was much larger than that under non-reducing conditions at low carbonate concentration. The distribution coefficient decreased with increasing the total carbonate concentration. The experimentally obtained distribution coefficient was analyzed by a least-squares fitting with free parameters of distribution coefficient of neptunium hydrolysis and carbonate complexes. Based on the analytical result, consideration of sorption behavior of neptunium, especially neptunium(IV) hydrolysis species and carbonatohydroxo complexes, was carried out, and a possibility of specific interaction of the neptunium(IV) species with the solid surface was pointed out.

Oral presentation

Corrosion products of carbon steel formed in compacted bentonite

Ishidera, Takamitsu; Xia, X.; Idemitsu, Kazuya*; Kikuchi, Yoshio*

no journal, , 

no abstracts in English

Oral presentation

Measurement of Np(IV) hydrolysis constants by a solvent extraction method

Fujiwara, Kenso; Kohara, Yukitoshi*

no journal, , 

no abstracts in English

Oral presentation

Sorption behavior of Am onto bentonite colloid

Iijima, Kazuki; Shoji, Yoshiyuki; Tomura, Tsutomu*

no journal, , 

Sorption behavior of Am onto bentonite colloid was investigated. The obtained distribution coefficients were larger than those evaluated by the calculation in which ion exchange and surface complexation reactions were assumed. It seems to be due to the higher site density of bentonite colloid for surface complexation compared with bulk bentonite.

Oral presentation

Sorption behavior of Am onto bentonite colloid, 2; Evaluation of sorption site density of bentonite

Iijima, Kazuki; Shoji, Yoshiyuki; Tomura, Tsutomu*

no journal, , 

Sorption site density of bentonite was investigated by acid titration. As a result, bentonite colloid is considered to have higher sorption site density than that of larger bentonite particle. Thus the high sorption site density, which has been supposed to lead to the large distribution coefficient of Am onto the bentonite colloid in the previous presentation, is experimentally proved.

Oral presentation

Measurement of Np(IV) hydrolysis constants by a solvent extraction method, 2

Fujiwara, Kenso; Kohara, Yukitoshi*

no journal, , 

no abstracts in English

48 (Records 1-20 displayed on this page)