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Journal Articles

Experimental study on modeling of Pu sorption onto quartz

Hemmi, Ko; Walker, A.*; Yamaguchi, Tetsuji

Radiochimica Acta, 109(7), p.539 - 546, 2021/07

 Times Cited Count:0 Percentile:0.01(Chemistry, Inorganic & Nuclear)

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, ${it K}$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 $$equiv$$SOTh(OH)$$_{4}$$$$^{-}$$ and $$equiv$$SOThOH(CO$$_{3}$$)$$_{2}$$$$^{2-}$$, 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 $$equiv$$SOM(OH)$$_{4}$$$$^{-}$$ and $$equiv$$SOMOH(CO$$_{3}$$)$$_{2}$$$$^{2-}$$ for Pu(IV) with smaller ionic radii than Th(IV). The Pu(IV) sorption model was developed as $$equiv$$SOPu(OH)$$_{3}$$ and $$equiv$$SOPu(OH)$$_{4}$$$$^{-}$$. In addition, data of Pu(IV) sorption onto muscovite was obtained in order to be compared with data for quartz.

Journal Articles

Consideration on modeling of Nb sorption onto clay minerals

Yamaguchi, Tetsuji; Ohira, Saki; Hemmi, Ko; Barr, L.; Shimada, Asako; Maeda, Toshikatsu; Iida, Yoshihisa

Radiochimica Acta, 108(11), p.873 - 877, 2020/11

 Times Cited Count:0 Percentile:0.01(Chemistry, Inorganic & Nuclear)

Journal Articles

Evaluation of thermal strain induced in components of Nb$$_{3}$$Sn strand during cooling

Suwa, Tomone*; Hemmi, Tsutomu*; Saito, Toru*; Takahashi, Yoshikazu*; Koizumi, Norikiyo*; Luzin, V.*; Suzuki, Hiroshi; Harjo, S.

IEEE Transactions on Applied Superconductivity, 28(3), p.6001104_1 - 6001104_4, 2018/04

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Journal Articles

Analysis on the effect of forest decontamination on reducing the air dose rate using the three-dimensional transport code MCNP

Hemmi, Ko; Yamaguchi, Tetsuji; Takeda, Seiji; Kimura, Hideo

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 24(1), p.3 - 14, 2017/06

Conditions of contaminated sources and ranges of forest decontamination that significantly reduce the air dose rate in residential areas were investigated by means of a sensitivity analysis related to the decontamination of the forest contaminated by radiocesium deriving from the accident at Fukushima Daiichi Nuclear Power Station. The contaminated sources including $$^{134}$$Cs and $$^{137}$$Cs were assumed to be a layer of sedimented organic matter (the A$$_{0}$$ layer) and surface soils (the A$$_{1}$$ layer). The air dose rates were calculated using the three-dimensional Monte Carlo transport code MCNP. A slope number of the forest, angles, state of contaminant distribution, radiocesium content in the forest soils, decontamination ranges, distance from the forest boundary to an evaluation point, and height at the evaluation point were adopted as the parameters. The decontamination of a litter (A$$_{0}$$) layer within the distance of 20 m from the forest boundary was revealed to be effective in reducing the air dose rate when the source distribution was homogeneous. The air dose rates were significantly reduced by the decontamination of the A$$_{0}$$ layer within a distance of 40 m from the forest boundary on condition that the radiocesium content of the A$$_{0}$$ layer was larger than that of the A$$_{1}$$ layer and the source distribution was non-homogeneous, such as the forest areas beyond 20 m from the forest boundary, which were more heavily contaminated than those within 20 m.

Journal Articles

Evaluation of bending strain in Nb$$_{3}$$Sn strands of CIC conductor using neutron diffraction

Hemmi, Tsutomu*; Harjo, S.; Kajitani, Hideki*; Suwa, Tomone*; Saito, Toru*; Aizawa, Kazuya; Osamura, Kozo*; Koizumi, Norikiyo*

IEEE Transactions on Applied Superconductivity, 27(4), p.4200905_1 - 4200905_5, 2017/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Journal Articles

Sorption behavior of thorium onto granite and its constituent minerals

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Hemmi, Ko

Journal of Nuclear Science and Technology, 53(10), p.1573 - 1584, 2016/10

 Times Cited Count:4 Percentile:45.9(Nuclear Science & Technology)

The sorption behavior of thorium (Th) onto granitic rock and its major constituent were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. Distribution coefficients decreased with increased carbonate concentrations and showed the minimal value at pH 9-10. This sorption tendency was likely due to forming the hydroxide-carbonate complexes of Th in the solutions. The order of sorbability for Th was mica $$>$$ feldspar $$>$$ quartz = granite. The sorption behaviors of Th onto these minerals were analyzed by the triple-layer surface complexation model with the Visual Minteq computer program. The model calculations assuming the inner-sphere surface complexation of Th were able to explain the experimental results reasonably well. It was shown that the sorption behavior of Th onto granite can be explained primarily by the complexation with the surface sites of feldspar.

Journal Articles

Sorption behavior of thorium onto montmorillonite and illite

Iida, Yoshihisa; Barr, L.; Yamaguchi, Tetsuji; Hemmi, Ko

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.3 - 8, 2016/06

Thorium (Th)-229 is one of the important radionuclides for the performance assessment calculations for high-level radioactive waste repositories. The sorption behavior of Th onto montmorillonite and illite were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. The sorbability of montmorillonite was higher than that of illite. Distribution coefficients, $$K_{rm d}$$ (m$$^{3}$$ kg$$^{-1}$$), decreased with increased carbonate concentrations and showed the minimal value at around pH 10. The sorption behaviors of Th were analyzed by the non-electrostatic surface complex model with PHREEQC computer program. The model calculations were able to explain the experimental results reasonably well. The decreases of $$K_{rm d}$$ was likely due to the stabilization of aqueous species by hydroxo-carbonate complexations in the solutions.

Journal Articles

Development of evaluation procedure for critical current of periodically bent Nb$$_{3}$$Sn strand

Kajitani, Hideki; Ishiyama, Atsushi*; Agatsuma, Ko*; Murakami, Haruyuki; Hemmi, Tsutomu; Koizumi, Norikiyo

Teion Kogaku, 50(12), p.608 - 615, 2015/12

A cable-in-conduit (CIC) conductor using Nb$$_{3}$$Sn strand is applied to an ITER TF coil. The Nb$$_{3}$$Sn strand in the conductor is periodically bent due to electromagnetic force, which causes degradation of performance. This degradation should be evaluated to predict conductor critical current performance. In a past study, a numerical simulation model was developed to evaluate the superconductivity of a periodically bent single strand. However, this model is not suitable for application to strands in the conductor because of the extensive calculation time. The author thus developed a new analytical model with a much shorter calculation time to evaluate the performance of periodically bent strand. This new model uses the classical model concept of a high transverse resistance model (HTRM). The calculated results show good agreement with the test results of a periodically bent Nb$$_{3}$$Sn strand. This indicates that a more practical solution can be achieved when evaluating the performance of periodically bent strands. Thus, the model developed in this study can be applied to evaluate the performance of conductors incorporating many strands.

Journal Articles

Accuracy of prediction method of cryogenic tensile strength for austenitic stainless steels in ITER toroidal field coil structure

Sakurai, Takeru; Iguchi, Masahide; Nakahira, Masataka; Saito, Toru*; Morimoto, Masaaki*; Inagaki, Takashi*; Hong, Y.-S.*; Matsui, Kunihiro; Hemmi, Tsutomu; Kajitani, Hideki; et al.

Physics Procedia, 67, p.536 - 542, 2015/07

 Times Cited Count:2 Percentile:68.84

Japan Atomic Energy Agency (JAEA) has developed the tensile strength prediction method at liquid helium temperature (4K) using the quadratic curve as a function of the content of carbon and nitrogen in order to establish the rationalized quality control of the austenitic stainless steel used in the ITER superconducting coil operating at 4K. ITER is under construction aiming to verify technical demonstration of a nuclear fusion generation. Toroidal Field Coil (TFC), one of superconducting system in ITER, have been started procurement of materials in 2012. JAEA is producing materials for actual product which are the forged materials with shape of rectangle, round bar, asymmetry and etc. JAEA has responsibility to procure all ITER TFC Structures. In this process, JAEA obtained many tensile strength of both room temperature and 4K about these structural materials, for example, JJ1: High manganese stainless steel for structure (0.03C-12Cr-12Ni-10Mn-5Mo- 0.24N) and 316LN: High nitrogen containing stainless steel (0.2Nitrogen). Based on these data, accuracy of 4K strength prediction method for actual TFC Structure materials was evaluated and reported in this study.

Journal Articles

Distribution coefficients of iodine and tin on granodiorite and tuffaceous sandstone specimens

Hemmi, Ko; Yamaguchi, Tetsuji; Iida, Yoshihisa

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 22(1), p.3 - 10, 2015/06

Iodine and tin are important elements in performance assessment of geological disposal of radioactive wastes. Sorption experiments of iodine were carried out under varying nitrate concentration with a range of 0 to 5 mol dm$$^{-3}$$ at neutral pH range in order to determine the distribution coefficient of iodine was zero or non-zero value. The experimental results with estimated statistical errors showed non-zero values for tuffaceous sandstone except for NaNO$$_{3}$$ concentration 0.5 mol dm$$^{-3}$$. Non-zero values were also obtained under NaNO$$_{3}$$ concentrations higher than 0.5 mol dm$$^{-3}$$ for granodiorite. Sorption experiments of tin were carried out at high pH range in order to check whether the distribution coefficient of tin decreases significantly with pH as a result of formation of anionic hydrolysis species of tin. The distribution coefficients of tin on granodiorite decreased from 9.79$$times$$10$$^{-2}$$ m$$^{3}$$ kg$$^{-1}$$ at pH10.4 to 2.46$$times$$10$$^{-3}$$ m$$^{3}$$ kg$$^{-1}$$ at pH12.4. The distribution coefficient of tin on tuffaceous sandstone was about one order of magnitude higher (about 2$$times$$10$$^{-2}$$ m$$^{3}$$ kg$$^{-1}$$) than that of granodiorite at pH around 12.4.

Journal Articles

Non-destructive examination of jacket sections for ITER central solenoid conductors

Takahashi, Yoshikazu; Suwa, Tomone; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200904_1 - 4200904_4, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

The Japan Atomic Energy Agency (JAEA) is responsible for procuring all amounts of Central Solenoid (CS) Conductors for ITER, including CS jacket sections. The conductor is cable-in-conduit conductor (CICC) with a central spiral. A total of 576 Nb$$_{3}$$Sn strands and 288 copper strands are cabled around the central spiral. The maximum operating current is 40 kA at magnetic field of 13 T. CS jacket section is circular in square type tube made of JK2LB, which is high manganese stainless steel with boron added. Unit length of jacket sections is 7 m and 6,300 sections will be manufactured and inspected. Outer/inner dimension and weight are 51.3/35.3 mm and around 90 kg, respectively. Eddy Current Test (ECT) and Phased Array Ultrasonic Test (PAUT) were developed for non-destructive examination. The defects on inner and outer surfaces can be detected by ECT. The defects inside jacket section can be detected by PAUT. These technology and the inspected results are reported in this paper.

Journal Articles

Behavior of Nb$$_{3}$$Sn cable assembled with conduit for ITER central solenoid

Nabara, Yoshihiro; Suwa, Tomone; Takahashi, Yoshikazu; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Sakurai, Takeru; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; et al.

IEEE Transactions on Applied Superconductivity, 25(3), p.4200305_1 - 4200305_5, 2015/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Journal Articles

Nuclear energy (Technical topic); Development of ITER toroidal field (TF) coil

Hemmi, Tsutomu; Kajitani, Hideki; Takano, Katsutoshi; Matsui, Kunihiro; Koizumi, Norikiyo

Yosetsu Gakkai-Shi, 83(6), p.497 - 502, 2014/09

JAEA, serving as the Japan Domestic Agency (JADA) in the ITER project, is responsible for the procurement of 9 TF coils. In the TF coil, the radial plate (RP) structure is selected to improve electrical and mechanical reliability of the electrical insulation. Since the superconductor is degraded by the bending strain of 0.1% after the reaction heat-treatment, the conductor is inserted into the RP after winding to D-shape and the heat-treatment. To insert the conductor into the RP, the winding and RP groove length must be controlled with accuracy of 0.02% (7 mm on the 1 turn of 34 m). Accordingly, the targets for solving this issue are as follows: (1) Development of manufacturing procedure of the RP; (2) Development of winding head to achieve highly accurate winding; (3) Estimation of the conductor elongation after the heat-treatment. Therefore, JAEA can establish manufacturing plan for the TF coil as a result of the R&D for these targets.

Journal Articles

Optimization of heat treatment of Japanese Nb$$_3$$Sn conductors for toroidal field coils in ITER

Nabara, Yoshihiro; Hemmi, Tsutomu; Kajitani, Hideki; Ozeki, Hidemasa; Suwa, Tomone; Iguchi, Masahide; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Koizumi, Norikiyo; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.6000605_1 - 6000605_5, 2014/06

no abstracts in English

Journal Articles

Investigation of strand bending in the He-inlet during reaction heat treatment for ITER TF Coils

Hemmi, Tsutomu; Matsui, Kunihiro; Kajitani, Hideki; Okuno, Kiyoshi; Koizumi, Norikiyo; Ishimi, Akihiro; Katsuyama, Kozo

IEEE Transactions on Applied Superconductivity, 24(3), p.4802704_1 - 4802704_4, 2014/06

 Times Cited Count:0 Percentile:0(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency (JAEA), as Japan Domestic Agency, has responsibility to procure nine ITER Toroidal Field (TF) coils. The TF coil winding consists of a Nb$$_{3}$$Sn Cable-In-Conduit conductor, a pair of joints and a He-inlet. The current capacity of 68 kA is required at the magnetic field of 7 T around the He-inlet region in the TF coil winding. During reaction heat-treatment, the compressive residual strain in Nb$$_{3}$$Sn cable is induced by the difference in the thermal expansion coefficients between the Nb$$_{3}$$Sn cable and stainless steel jacket. The strands bending in the Nb$$_{3}$$Sn cable of the He-inlet is anticipated since there is the compressive residual strain and a gap between the Nb$$_{3}$$Sn cable and the He-inlet to introduce SHE flow. If the strand is bent, the variation of mechanical behaviors, such as the elongation of He-inlet during the reaction heat-treatment and the thermally induced residual strain on the jacket around the He-inlet, are expected. To investigate the strands bending in the Nb$$_{3}$$Sn cable of the He-inlet, the following items are performed; (1) elongation measurement during reaction heat-treatment, (2) residual longitudinal strain measurement using strain gauges by sample cuttings, (3) nondestructive inspection on the cable and strands using high resolution X-ray CT, Detail of test results and investigation of the strands bending in the Nb$$_{3}$$Sn cable of the He-inlet are reported and discussed.

Journal Articles

Cabling technology of Nb$$_3$$Sn conductor for ITER central solenoid

Takahashi, Yoshikazu; Nabara, Yoshihiro; Ozeki, Hidemasa; Hemmi, Tsutomu; Nunoya, Yoshihiko; Isono, Takaaki; Matsui, Kunihiro; Kawano, Katsumi; Oshikiri, Masayuki; Uno, Yasuhiro; et al.

IEEE Transactions on Applied Superconductivity, 24(3), p.4802404_1 - 4802404_4, 2014/06

 Times Cited Count:20 Percentile:73.53(Engineering, Electrical & Electronic)

Japan Atomic Energy Agency (JAEA) is procuring all amounts of Nb$$_3$$Sn conductors for Central Solenoid (CS) in the ITER project. Before start of mass-productions, the conductor should be tested to confirm superconducting performance in the SULTAN facility, Switzerland. The original design of cabling twist pitches is 45-85-145-250-450 mm, called normal twist pitch (NTP). The test results of the conductors with NTP was that current shearing temperature (Tcs) is decreasing due to electro-magnetic (EM) load cycles. On the other hand, the results of the conductors with short twist pitches (STP) of 25-45-80-150-450 mm show that the Tcs is stabilized during EM load cyclic tests. Because the conductors with STP have smaller void fraction, higher compaction ratio during cabling is required and possibility of damage on strands increases. The technology for the cables with STP was developed in Japanese cabling suppliers. The several key technologies will be described in this paper.

Journal Articles

Progress of manufacturing trials for the ITER toroidal field coil structures

Iguchi, Masahide; Morimoto, Masaaki; Chida, Yutaka*; Hemmi, Tsutomu; Nakajima, Hideo; Nakahira, Masataka; Koizumi, Norikiyo; Yamamoto, Akio*; Miyake, Takashi*; Sawa, Naoki*

IEEE Transactions on Applied Superconductivity, 24(3), p.3801004_1 - 3801004_4, 2014/06

 Times Cited Count:6 Percentile:40.1(Engineering, Electrical & Electronic)

no abstracts in English

Journal Articles

Residual strains in ITER conductors by neutron diffraction

Harjo, S.; Hemmi, Tsutomu; Abe, Jun; Gong, W.; Nunoya, Yoshihiko; Aizawa, Kazuya; Ito, Takayoshi*; Koizumi, Norikiyo; Machiya, Shutaro*; Osamura, Kozo*

Materials Science Forum, 777, p.84 - 91, 2014/02

 Times Cited Count:2 Percentile:78.54

Journal Articles

Evaluation of inter-laminar shear strength of GFRP composed of bonded glass/polyimide tapes and cyanate-ester/epoxy blended resin for ITER TF coils

Hemmi, Tsutomu; Nishimura, Arata*; Matsui, Kunihiro; Koizumi, Norikiyo; Nishijima, Shigehiro*; Shikama, Tatsuo*

AIP Conference Proceedings 1574, p.154 - 161, 2014/01

 Times Cited Count:3 Percentile:86.67

Japan Atomic Energy Agency (JAEA), as Japan Domestic Agency, has responsibility to procure 9 ITER Toroidal Field (TF) coils. The insulation system of the ITER TF coils consists of 3 layers of insulations, which are a conductor insulation, a double-pancake (DP) insulation and a ground insulation, composed of multi-layer glass/polyimide tapes impregnated a resin. The ITER TF coils are required to withstand an irradiation of 10 MGy from $$gamma$$-ray and neutrons since the ITER TF coils is exposed by first neutron ($$>$$ 0.1 MeV) of 10$$^{22}$$ n/m$$^{2}$$ during the operation of 20 years in the ITER. Cyanate-ester/epoxy blended resins and bonded glass/polyimide tapes are developed as insulation materials to realize the required radiation-hardness for the insulation of the ITER TF coils. To evaluate the radiation-hardness of the developed insulation materials, the inter-laminar shear strength of glass-fiber reinforced plastics (GFRP) fabricated using developed insulation materials is measured as one of most important mechanical properties before/after the irradiation in a fission reactor of JRR-3. As a result, it is demonstrated that the GFRPs using the developed insulation materials have a sufficient performance to apply the ITER TF coil insulation.

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