Yokoyama, Sumi*; Takahashi, Tomoyuki*; Ota, Masakazu; Kakiuchi, Hideki*; Sugihara, Shinji*; Hirao, Shigekazu*; Momoshima, Noriyuki*; Tamari, Toshiya*; Shima, Nagayoshi*; Atarashi-Andoh, Mariko; et al.
Plasma and Fusion Research (Internet), 14(Sp.2), p.3405099_1 - 3405099_4, 2019/06
The Large Helical Device of the National Institute for Fusion Science started D-D experiments in 2017. To ensure the safety of the facility, it is important to develop evaluation methods for environmental tritium transfer. Tritiated water (HTO) in atmosphere and soil is transferred to plants, and organically bound tritium (OBT) is formed by photosynthesis. Prediction of OBT formation is important, because OBT accumulates in plants and causes dose through ingestion. The objective of this study is to estimate environmental tritium transfer using a simple compartment model and practical parameters. We proposed a simple compartment model consisting of air-soil-plant components, and tried to validate the model by comparison with a sophisticated model, SOLVEG. In this study, we plan to add wet deposition to the model and obtain parameters from measurements of soil permeability and tritium concentrations in air, soil and plants. We also establish rapid pretreatment methods for OBT analysis.
Maekawa, Fujio; Transmutation Expeimental Facility Design Team
Plasma and Fusion Research (Internet), 13(Sp.1), p.2505045_1 - 2505045_4, 2018/05
The partitioning and transmutation (P-T) technology has promising potential for volume reduction and mitigation of degree of harmfulness of high-level radioactive waste. JAEA is promoting development of the P-T technology by using an accelerator driven system (ADS). To facilitate the development, we have a plan to construct the Transmutation Experimental Facility (TEF) as one of experimental facilities of J-PARC (Japan Proton Accelerator Research Complex). TEF consists of two facilities: the ADS Target Test Facility (TEF-T) and the Transmutation Physics Experimental Facility (TEF-P). Recent progress in design and R&D efforts toward construction of J-PARC TEF will be presented.
Plasma and Fusion Research (Internet), 13(Sp.1), p.2505013_1 - 2505013_8, 2018/03
The pulsed spallation neutron source of Japan Proton Accelerator Research Complex (J-PARC) has been supplying users with high intensity and sharp pulse cold neutrons using the moderators with following distinctive features; (1) 100% para-hydrogen for increasing pulse peak intensity with decreasing pulse tail, (2) cylindrical shape with 14 cm diam.12 cm long for providing high intensity neutrons to wide neutron extraction angles of 50.8, (3) neutron absorber made from Ag-In-Cd alloy to make pulse width narrower and pulse tails lower. Actually, it was measured at a low power operation that high neutron intensity of 4.510 n/cm/s/sr could be emitted from the coupled moderator surface for 1-MW operation, and a superior resolution of d/d = 0.035% was achieved at a beamline (BL8) with a poisoned moderator, where d is the d-spacing of reflection. Towards the goal to achieve the target operation at 1-MW for 5000 h in a year, technical developments to mitigate cavitation damages on the target vessel with injecting gas micro-bubbles into mercury target and design improvement of target vessel structure to reducing welds and bolt connections as much as possible are under way.
Takei, Hayanori; Hirano, Koichiro; Tsutsumi, Kazuyoshi; Meigo, Shinichiro
Plasma and Fusion Research (Internet), 13(Sp.1), p.2406012_1 - 2406012_6, 2018/03
The Japan Proton Accelerator Research Complex (J-PARC) has a plan to build the Transmutation Physics Experimental Facility (TEF-P), in which a 400-MeV negative proton (H) beam will be delivered from the J-PARC linac. Since the TEF-P requires a stable proton beam with a power of less than 10 W, a stable and meticulous beam extraction method is required to extract a small amount of the proton beam from the high power beam using 250 kW. To fulfil this requirement, the Laser Charge Exchange (LCE) method has been developed. To demonstrate the charge exchange of the H, a preliminary LCE experiment was conducted using a linac with energy of 3 MeV in J-PARC. As a result of the experiment, a charge-exchanged H beam with a power of about 8 W equivalent and an accuracy of about 2% was obtained under the J-PARC linac beam condition.
Tsuchiya, Harufumi; Kitatani, Fumito; Maeda, Makoto; Toh, Yosuke; Kureta, Masatoshi
Plasma and Fusion Research (Internet), 13(Sp.1), p.2406004_1 - 2406004_4, 2018/02
Recently, it has become important in the field of nuclear nonproliferation and nuclear security to quantify nuclear materials (NMs) of uranium and plutonium in nuclear fuel using a non-destructive assay (NDA) technique. Currently, there is no reliable NDA system to apply to nuclear fuels such as spent fuel, fuel debris and next generation fuel for nuclear transmutation. Accordingly, development of NDA techniques for quantification of NMs in those fuels is an urgent issue. Neutron resonance transmission analysis (NRTA) is one candidate that is applicable to the quantification of NMs. Utilizing pulsed neutron beams, NRTA analyzes the content of a sample by measuring neutron beams that are transmitted from the sample. It is one of the reliable NDA methods that are based on a neutron time-of-flight technique for accurately evaluating nuclear data such as total cross sections and resonance parameters. A present NRTA system generally requires a large electron linear accelerator to produce intense neutron beams. Therefore this is not so easy to apply to various facilities that are used to measure NMs. Given this situation, a compact NRTA system would be required for practical applications of a method to quantify NMs in various samples. In order to realize a compact NRTA system, we consider two types of system: one uses a D-T neutron generator with pulse width of 10 sec and the other a small electron linac with pulse width of 1 sec Assuming each system is applied to measurements of NMs in spent fuel, numerical calculations were carried out and the results showed that the pulse widths of neutron beam largely affect the NRTA measurements. In this presentation, we will talk about the NRTA technique and give a schematic design of a compact NRTA system. Then, comparing calculation results for a D-T tube with those for a small electron linac, we especially discuss how the pulse widths of neutron beams to be used for NRTA affect the measurement of NMs in nuclear fuel.
Wakai, Eiichi; Watanabe, Kazuyoshi*; Ito, Yuzuru*; Suzuki, Akihiro*; Terai, Takayuki*; Yagi, Juro*; Kondo, Hiroo; Kanemura, Takuji; Furukawa, Tomohiro; Hirakawa, Yasushi; et al.
Plasma and Fusion Research (Internet), 11, p.2405112_1 - 2405112_4, 2016/11
Nishikiori, Ryo; Kojima, Atsushi; Hanada, Masaya; Kashiwagi, Mieko; Watanabe, Kazuhiro; Umeda, Naotaka; Tobari, Hiroyuki; Yoshida, Masafumi; Ichikawa, Masahiro; Hiratsuka, Junichi; et al.
Plasma and Fusion Research (Internet), 11, p.2401014_1 - 2401014_4, 2016/03
One of critical issues for high-energy high-current beam acceleration in ITER and JT-60SA is the high voltage holding which is dominated by vacuum discharges. The past results suggest that vacuum discharge occurs beyond the threshold of the dark current. The dark current can be derived from F-N theory where electric field enhancement factor beta is included. Though, beta could only be evaluated from the experiment previously. Therefore, the method to decide beta without experiment is required. This time dark currents were measured at three different areas to compare beta in different electric field. As a result, the effective electric field E, where E is average electric field, were found to be almost constant for different areas although the beta is largely different. By applying E, beta can be evaluated analytically, leading to the analytical prediction of the dark current and voltage holding capability without the measurements.
Plasma and Fusion Research (Internet), 11, p.2403006_1 - 2403006_5, 2016/02
In this work, we address saturation mechanisms of decaying turbulence induced by the ion temperature gradient driven trapped electron mode. In the simulation, turbulent transport is quenched in the nonlinear quasi-steady phase, where temperature profiles exceeding linear critical temperature gradient parameters are formed. This kind of nonlinear critical temperature gradient is sustained by radial electric fields with strong shear, which is generated by corrugated density profiles. It is found that the density profile structure is related to electrons transport near low order mode rational surfaces, where non-adiabatic response of passing electrons becomes important.
Furukawa, Masaru*; Matsuyama, Akinobu; Okawa, Yushiro*
Plasma and Fusion Research (Internet), 11, p.1303003_1 - 1303003_4, 2016/02
Watanabe, Yoshiyuki; Iwakiri, Hirotomo*; Murayoshi, Norihiko*; Kato, Daiji*; Tanigawa, Hiroyasu
Plasma and Fusion Research (Internet), 10, p.1205086_1 - 1205086_2, 2015/12
In this paper, formation energy of isolated hydrogen atom in CrC has been theoretically investigated with atomistic calculation based on the density functional theory. The lowest calculated formation energy of a hydrogen atom is -0.48 eV with a trigonal bipyramidal configuration surrounded by five regular Cr lattice atoms. A comparison of the formation energy of hydrogen atom in bcc-iron may indicate that hydrogen atoms in F82H steel are more energetically favorable in CrC-based precipitate rather than Fe-based matrix, leading to an increase of the tritium retention in the precipitate.
Miki, Kazuhiro; Idomura, Yasuhiro
Plasma and Fusion Research (Internet), 10(Sp.2), p.3403068_1 - 3403068_4, 2015/07
We identify linear properties of the energetic-particle-induced geodesic acoustic mode (EGAM) using eigenmode analysis based on the gyrokinetic theory. From the perturbed gyrokinetic equation with energetic particles, we derive a dispersion relation of the EGAM. The behaviors of the roots vary depending on the safety factor. Taking into account of the finite-orbit-width (FOW) effects, we examine variations of the growth rates of the EGAM for various beam intensities. The analyses indicate that the FOW effects are small, within several percent of the growth rates, for experimentally relevant machine sizes.
Kitazawa, Sin-iti; Maruyama, Toshiyuki; Ogawa, Hiroaki; Itami, Kiyoshi; Casal, N.*
Plasma and Fusion Research (Internet), 10(Sp.2), p.3402044_1 - 3402044_4, 2015/04
Hiratsuka, Junichi; Hanada, Masaya; Umeda, Naotaka; Kojima, Atsushi; Kashiwagi, Mieko; Watanabe, Kazuhiro; Tobari, Hiroyuki; Yoshida, Masafumi
Plasma and Fusion Research (Internet), 10(Sp.2), p.3405045_1 - 3405045_4, 2015/04
To produce high current density ( 200 A/m), high-energy ( 1 MeV) negative ion beams for long pulse duration time (1 hour) for International Thermo-nuclear Experimental Reactor (ITER), the suppression of the direct interception of the negative ions with the grids has been carefully investigated with studying the deflection angle by aperture displacement technique. The non-linear dependence of the deflection angle appears at the aperture diameter of 14 mm on a steering control grid (SCG). From this dependence, the aperture diameter and the offset distance of the SCG has been designed to be 16 mm and 0.7 mm, respectively and tested in a prototype accelerator for ITER. Each of the beamlets on the multiple apertures is properly steered with compensation of the deflection due to the residual magnetic field in the accelerator and the grid power loading was significantly reduced. It resulted in a 10% enhancement of the accelerated beam current.
Narita, Emi*; Honda, Mitsuru; Hayashi, Nobuhiko; Urano, Hajime; Ide, Shunsuke; Fukuda, Takeshi*
Plasma and Fusion Research (Internet), 10, p.1403019_1 - 1403019_11, 2015/03
Maruyama, Takahito; Noguchi, Yuto; Takeda, Nobukazu; Kakudate, Satoshi
Plasma and Fusion Research (Internet), 10(Sp.2), p.3405010_1 - 3405010_4, 2015/02
Nuga, Hideo; Matsuyama, Akinobu; Yagi, Masatoshi; Fukuyama, Atsushi*
Plasma and Fusion Research (Internet), 10, p.1203006_1 - 1203006_2, 2015/01
Plasma and Fusion Research (Internet), 9, p.1203148_1 - 1203148_3, 2014/12
Ion temperature gradient (ITG) driven turbulence simulation with a transient edge temperature sink which is localized in the poloidal plane is performed using a global Landau-fluid code in the electrostatic limit. Pressure perturbations with = input by the edge sink, which are responsible for the nonlocal transport found in reduced magnetohydrodynamic (RMHD) simulation, are dissipated by the ITG turbulence in the core, where and are poloidal and toroidal mode numbers, respectively. Hence, the ITG turbulence tends to prevent the pressure perturbations connecting the core region with the edgeand thereby the nonlocal plasma response/transport of a kind observed in the RMHD simulation.
Sasa, Toshinobu; Oigawa, Hiroyuki
Plasma and Fusion Research (Internet), 9(Sp.3), p.4401113_1 - 4401113_5, 2014/10
The accelerator driver system concept proposed by JAEA and status of the research and development are introduced with the effects of nuclear transmutation technology. The role and function of the J-PARC Transmutation Experimental Facility which is indispensable to realize an accelerator driver systems, and the possibility of the multipurpose use of spallation neutrons is also explained.
Nakamura, Makoto; Tobita, Kenji; Someya, Yoji; Tanigawa, Hisashi; Gulden, W.*; Sakamoto, Yoshiteru; Araki, Takao*; Watanabe, Kazuhito*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.
Plasma and Fusion Research (Internet), 9, p.1405139_1 - 1405139_11, 2014/10
Key aspects of the safety study of a water-cooled fusion DEMO reactor is reported. Safety requirements, dose target, DEMO plant model and confinement strategy of the safety study are briefly introduced. The internal hazard of a water-cooled DEMO, i.e. radioactive inventories, stored energies that can mobilize these inventories and accident initiators and scenarios, are evaluated. It is pointed out that the enthalpy in the first wall/blanket cooling loops, the decay heat and the energy potentially released by the Be-steam chemical reaction are of special concern for the water-cooled DEMO. An ex-vessel loss-of-coolant of the first wall/blanket cooling loop is also quantitatively analyzed. The integrity of the building against the ex-VV LOCA is discussed.