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Journal Articles

Degassing behavior of noble gases from groundwater during groundwater sampling

Nakata, Kotaro*; Hasegawa, Takuma*; Solomon, D. K.*; Miyakawa, Kazuya; Tomioka, Yuichi*; Ota, Tomoko*; Matsumoto, Takuya*; Hama, Katsuhiro; Iwatsuki, Teruki; Ono, Masahiko*; et al.

Applied Geochemistry, 104, p.60 - 70, 2019/05

 Times Cited Count:0 Percentile:100(Geochemistry & Geophysics)

no abstracts in English

Journal Articles

Evaluation of $$delta^{2}$$H and $$delta^{18}$$O of water in pores extracted by compression method; Effects of closed pores and comparison to direct vapor equilibration and laser spectrometry method

Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Miyakawa, Kazuya

Journal of Hydrology, 561, p.547 - 556, 2018/06

 Times Cited Count:1 Percentile:82.47(Engineering, Civil)

no abstracts in English

Journal Articles

An Evaluation of the long-term stagnancy of porewater in the neogene sedimentary rocks in northern Japan

Nakata, Kotaro*; Hasegawa, Takuma*; Oyama, Takahiro*; Ishii, Eiichi; Miyakawa, Kazuya; Sasamoto, Hiroshi

Geofluids, 2018, p.7823195_1 - 7823195_21, 2018/01

 Times Cited Count:3 Percentile:44.62(Geochemistry & Geophysics)

A groundwater scenario is one of the scenario for safety assessment of geological disposal of high-level radioactive waste. In the safety assessment for groundwater scenario, the slow groundwater flow for a long-term should be an important factor. In the present study, study on stability of groundwater in the Koetoi and Wakkanai formations of Neogene marine based sedimentary rock at the Horonobe area, Hokkaido was performed by investigating the isotopes of chlorine and helium, and the stable isotopes of water. As the results, the stability of groundwater in deeper part of the Wakkanai formation was suggested due to no direct evidence of meteoric water intrusion during the uplift since ca. 1 Ma. Contrary, the groundwater both in the Koetoi formation and the upper Wakkanai formation would be unstable because the meteoric water intrusion was suggested by paleohydrogeological condition and the results of groundwater dating. Likely the Horonobe area, the accurate dating of groundwater would be difficult due to the complex effects of upward and mixing water derived from diagenesis in the thick sediment formation. However, a comparative procedure using both the results of groundwater dating and paleohydrogeological information would be useful for general evaluation of groundwater flow conditions for the long-term (i.e., check the possibility for long-term stability of groundwater).

JAEA Reports

Gas composition related to the Horonobe Underground Research Laboratory Project

Miyakawa, Kazuya; Tamamura, Shuji*; Nakata, Kotaro*; Hasegawa, Takuma*

JAEA-Data/Code 2016-021, 60 Pages, 2017/03

JAEA-Data-Code-2016-021.pdf:3.87MB
JAEA-Data-Code-2016-021-appendix(CD-ROM).zip:0.45MB

The Japan Atomic Energy Agency has been involved in ongoing research in the Horonobe area for the purposes of geoscientific research, and research and development (R&D) on technologies to be used for the geological disposal of high-level radioactive waste. The chemistry of groundwater and dissolved gas from deep boreholes has been obtained since H13 fiscal year for R&D on technologies related to geological characterization. Horonobe Research Institute for the Subsurface Environment (H-RISE) has investigated a resources development on promoting effective use of coal bed buried in Hokkaido including the Horonobe area using microbial communities. The data of dissolved gas from the Horonobe groundwater have also been obtained along with the microbiological research by H-RISE. Central Research Institute of Electric Power Industry (CRIEPI) has conducted R&D on technology of groundwater geochronology which is one of technologies to be used for the geological disposal, and noble gas data from the Horonobe groundwater have been obtained by CRIEPI. This report shows a data set which comprises gas data obtained from the Horonobe underground research project during the period from H13 fiscal year to H27 fiscal year.

Journal Articles

Cross-checking groundwater age by $$^{4}$$He and $$^{14}$$C dating in a granite, Tono area, central Japan

Hasegawa, Takuma*; Nakata, Kotaro*; Tomioka, Yuichi*; Goto, Kazuyuki*; Kashiwaya, Koki*; Hama, Katsuhiro; Iwatsuki, Teruki; Kunimaru, Takanori*; Takeda, Masaki

Geochimica et Cosmochimica Acta, 192, p.166 - 185, 2016/11

 Times Cited Count:4 Percentile:69.66(Geochemistry & Geophysics)

Groundwater dating was performed simultaneously by the $$^{4}$$He and $$^{14}$$C methods in granite of the Tono area in central Japan. Groundwater was sampled at 30 packed-off sections of six 1000-m boreholes. $$^{4}$$He concentrations increased and $$^{14}$$C concentrations decreased along a groundwater flow path on a topographic gradient. $$^{4}$$He ages were calculated by using the in situ $$^{4}$$He production rate derived from the porosity, density, and U and Th content of the rock, neglecting external flux. The linear relation between the $$^{4}$$He ages and the noncorrected $$^{14}$$C ages, except in the discharge area. Simultaneous measurements make it feasible to estimate the accumulation rate of $$^{4}$$He and initial dilution of $$^{14}$$C, which cannot be done with a single method. Cross-checking groundwater dating has the potential to provide more reliable groundwater ages.

Journal Articles

Comparison of $$^{14}$$C collected by precipitation and gas-strip methods for dating groundwater

Nakata, Kotaro*; Hasegawa, Takuma*; Iwatsuki, Teruki; Kato, Toshihiro

Radiocarbon, 58(3), p.491 - 503, 2016/09

AA2015-0781.pdf:0.96MB

 Times Cited Count:2 Percentile:83.85(Geochemistry & Geophysics)

Dissolved inorganic carbon (DIC) for $$^{14}$$C analysis of groundwater is usually extracted by a gas-strip or precipitation method. In this study, the certainty of the two methods for $$^{14}$$C dating were confirmed. DIC and $$^{14}$$C concentrations obtained by the gas-strip method were close to the theoretically predicted $$^{14}$$C value. Conversely, the $$^{14}$$C value obtained by the precipitation method always showed higher values than the predicted values. The difference in $$^{14}$$C value between gas-strip and precipitation methods was assumed to arise owing to contamination of modern carbon used in the precipitation method. The applicability of the precipitation method for groundwater should be considered carefully according to the DIC, $$^{14}$$C concentration of groundwater and purpose of the study being conducted.

Journal Articles

Cesium sorption and desorption behavior of clay minerals

Yokoyama, Shingo*; Nakata, Kotaro*; Suzuki, Shinichi

Nendo Kagaku, 54(1), p.28 - 35, 2015/08

no abstracts in English

Journal Articles

Shallow groundwater intrusion to deeper depths caused by construction and drainage of a large underground facility; Estimation using $$^{3}$$H, CFCs and SF$$_{6}$$ as trace materials

Hagiwara, Hiroki; Iwatsuki, Teruki; Hasegawa, Takuma*; Nakata, Kotaro*; Tomioka, Yuichi*

Nippon Suimon Kagakkai-Shi, 45(2), p.21 - 38, 2015/07

This study evaluates a method to estimate shallow groundwater intrusion in and around a large underground research facility (Mizunami Underground Research Laboratory - MIU). Water chemistry, stable isotopes ($$delta$$D and $$delta$$$$^{18}$$O), tritium ($$^{3}$$H), chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF$$_{6}$$) in groundwater were monitored around the facility (from 20 m down to a depth of 500 m), for a period of 5 years. The results show that shallow groundwater inflows into deeper groundwater at depths of between 200-400 m. In addition, the content of shallow groundwater estimated using $$^{3}$$H and CFC-12 concentrations is up to a maximum of about 50%. This is interpreted as the impact on the groundwater environment caused by construction and operation of a large facility over several years. The concomitant use of $$^{3}$$H and CFCs is an effective method to determine the extent of shallow groundwater inflow caused by construction of an underground facility.

Journal Articles

Practical approach to decontamination of radioactive cesium-contaminated matter in agricultural region by improved wet classification and use of geomaterials

Ito, Kenichi*; Miyahara, Hidetaka*; Ujiie, Toru*; Takeshima, Toshikatsu*; Yokoyama, Shingo*; Nakata, Kotaro*; Nagano, Tetsushi; Sato, Tsutomu*; Hatta, Tamao*; Yamada, Hirohisa*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 11(4), p.255 - 271, 2012/04

no abstracts in English

Journal Articles

Reduction of Neptunium(V) on Magnetite Surface

Kitamura, Akira; Nakata, Kotaro*; Tanaka, Satoru*; Tomura, Tsutomu*; Kamei, Gento

Saikuru Kiko Giho, (22), p.59 - 66, 2004/03

Redox reactions between neptunium(V) (Np(V)) and magnetite (Fe(II)1Fe(III)2O4) surface were investigated in N$$_{2}$$ gas atmosphere. A batch method was applied to the experiment. High-pure magnetite and a 0.1 M NaCl were mixed in a polypropylene tube, and pH, redox potential and concentration of dissolved neptunium were measured as a function of shaking time (from 1 hour to 7 days), temperature (298 K and 318 K) and liquid/solid ratio (20, 50 and 100 ml.g$$^{-1}$$). It was observed that the concentration of dissolved neptunium was reduced rapidly within a day, due to the reducing of Np(V) to Np(IV) and the precipitation of Np(IV). This result was shown typically when the magnetite/solution ratio and the temperature were high. The rate constant of the redox reaction and the activation energy for the rate constant were preliminarily obtained. It was suggested that the redox reaction was promoted by not only Fe(II) on magnetite surface but also Fe(II) inside the magnetite.

JAEA Reports

Mechanism of Redox Reactions of Actinide Ions on Solid/Water Interface

Tanaka, Satoru*; Nagasaki, Shinya*; Nakata, Kotaro*; Oda, Takuji*; Kameda, Jun*; Kamei, Gento; Tachi, Yukio

JNC-TY8400 2003-008, 88 Pages, 2003/05

JNC-TY8400-2003-008.pdf:1.29MB

Redox reactions between Cr(VI) and iron(II) chloride (FeCl2) and those between Cr(VI) and magnetite (Fe(II)1Fe(III)2O4) were observed as a preliminary study. According to the experimental results, it was suggested that the redox reactions were promoted more than the amount of Fe(II) on magnetite surface because of electron transfer from internal Fe(II) to magnetite surface. The results were quantitatively supported from quantum chemical calculations. Redox reactions between Np(V) and magnetite and the reduction of Np to tetravalent were observed, while those between Np(V) and FeCl2 were not observed obviously. It was observed that the reactions were promoted rapidly when the magnetite / solution ratio and the temperature were high, and the rate constant of the reactions was obtained. Furthermore, it was found that hydrogen gas and hydrogen ion were generated with crushing the quartz in an inert gas atmosphere.

Journal Articles

Sorption and reduction of Neptunium(V) on the surface of iron oxides

Nakata, Kotaro*; Nagasaki, Shinya*; Tanaka, Satoru*; Sakamoto, Yoshiaki; Tanaka, Tadao; Ogawa, Hiromichi

Radiochimica Acta, 90(9-11), p.665 - 669, 2002/12

 Times Cited Count:46 Percentile:5.99(Chemistry, Inorganic & Nuclear)

Sorption and desorption experiments of Np on magnetite and hematite under aerobic and anaerobic conditions were carried out to investigate the possibility of reduction of Np(V) to Np(IV) on the surfave of iron oxides including Fe(II). The results indicated that Np sorption mechanism on magnetite under anaerobic condition was completely different from that under aerobic condition. The evidence of the presence of Np(IV) on magnetite surface after sorption was obtained from the extraction experiment with TTA/xylene solution.

Journal Articles

Effect of temperature on the sorption of neptunium on magnetite

Nakata, Kotaro*; Nagasaki, Shinya*; Tanaka, Satoru*; Sakamoto, Yoshiaki; Tanaka, Tadao; Ogawa, Hiromichi

JAERI-Conf 2002-004, p.667 - 673, 2002/03

no abstracts in English

Journal Articles

Sorption and desorption kinetics of Np(V) on magnetite and hematite

Nakata, Kotaro*; Nagasaki, Shinya*; Tanaka, Satoru*; Sakamoto, Yoshiaki; Tanaka, Tadao; Ogawa, Hiromichi

Radiochimica Acta, 88(8), p.453 - 457, 2000/12

 Times Cited Count:13 Percentile:32.88(Chemistry, Inorganic & Nuclear)

Sorption kinetics of Np(V) on magnetite and hematite were investigated, and a sequential desorption method was applied to investigate changes in the chemical form of Np sorbed according to the amount of time they were in contact with the Np solution. It was found that the sorption process consists of fast sorption and slow sorption which reaches equilibrium in 1 h. From the results of sorption and desorption kinetics, it was concluded that the equilibrium between various chemical forms of sorbed Np was achieved in about 1 week, although the amount of sorbed Np reached an equilibrium in only 1 h.

Oral presentation

Distribution of RN between colloid, rock and aqueous phases; Development of experimental system and application to Cs

Nakata, Kotaro*; Iijima, Kazuki; Tomura, Tsutomu*; Tobita, Minoru*

no journal, , 

In this study, a new experimental system has been developed to obtain the information on distribution of raidonuclide between aqueous, colloid and rock phases. Sorption, desorption and distribution experiments of Cs on smectite colloid and granite were carried out with new developed system. After confirmation of applicability of the developed system, Kd values were obtained in 3 phases coexist system. The results of desorption experiment indicated sorption of Cs on smectite colloid is reversible.

Oral presentation

JAEA-CRIEPI collaboration study on mass transport by groundwater in and around the Mizunami Underground Research Laboratory

Hama, Katsuhiro; Iwatsuki, Teruki; Hasegawa, Takuma*; Nakata, Kotaro*; Tomioka, Yuichi*; Goto, Kazuyuki*

no journal, , 

The dating of groundwater has been carried out by the measurement of radionuclides in groundwater in and around the Mizunami underground research laboratory.

Oral presentation

Distribution of Cs and Am in the solution-bentonite colloid-granite ternary system

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

no journal, , 

Batch type distribution experiments of Cs and Am in the solution-bentonite colloid-granite ternary system were carried out. Considering Na concentration, distribution coefficient of Cs on bentonite colloids obtained in the ternary system is similar to the calculated value using ion selectivity coefficient evaluated in the binary system. It indicates that the method to estimate the distribution behavior in the binary system is applicable to the ternary system in this case.

Oral presentation

Estimation of groundwater residence time based on $$^{4}$$He, $$^{36}$$Cl at Horonobe area, Hokkaido

Nakata, Kotaro*; Hasegawa, Takuma*; Iwatsuki, Teruki

no journal, , 

Groundwater residence time were inferred by $$^{4}$$He, $$^{36}$$Cl at Horonobe area, Hokkaido, Japan. Both estimated value based on $$^{4}$$He and $$^{36}$$Cl range from 2Ma to 10Ma for the groundwater deeper than -250m S.L. Those values correspond to sedimentation age of rock formations. This indicates the possibility that the groundwaters are in stagnant condition since sedimentation.

Oral presentation

Central Research Institute of Electric Power Industry - Japan Atomic Energy Agency Joint Research; A Study of the hydraulic properties and transport characteristics around the Mizunami Underground Laboratory Project

Hasegawa, Takuma*; Nakata, Kotaro*; Tomioka, Yuichi*; Goto, Kazuyuki*; Kashiwaya, Koki*; Hama, Katsuhiro

no journal, , 

The groundwater flow velocity is one of the important items in the safety assessment for the HLW disposal. Generally, it is too difficult to measure the groundwater flow velocity directly. Therefore, to determine the groundwater age by radio active isotopes are effective. However, there are some problems to apply the metrology to the natural samples. For example, because the ratio of Carbon isotope changes by dissolving of the carbonate mineral and resolving the organic materials, the development of the technique for correcting this is needed. In this study, the groundwater ages are measured by $$^{4}$$He and $$^{14}$$C, etc. and compared these results as a joint research with Central Research Institute of Electric Power Industry.

Oral presentation

Estimation of groundwater age containing uranine based on $$^{14}$$C in dissolved organics

Nakata, Kotaro*; Hasegawa, Takuma*; Kodama, Hiroki*; Miyajima, Toru*; Hama, Katsuhiro; Iwatsuki, Teruki

no journal, , 

We developed estimation method of groundwater age for uranine-contaminated groundwater sample by using $$^{14}$$C in dissolved organics. Uranine and natural dissolved organics was divided by DAX-8 resin. This method enables to infer the groundwater age contaminated by drilling fluids.

35 (Records 1-20 displayed on this page)