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Journal Articles

A Study on self-terminating behavior of sodium-concrete reaction, 2

Kawaguchi, Munemichi; Miyahara, Shinya; Uno, Masayoshi*

Journal of Nuclear Science and Technology, 55(8), p.874 - 884, 2018/08

 Times Cited Count:3 Percentile:44.17(Nuclear Science & Technology)

As parts of severe accident studies in sodium-cooled fast reactor, experiments were performed to investigate the termination mechanism of sodium-concrete reaction (SCR). In the experiment, the reaction time was controlled to investigate the distribution change of sodium (Na) and the reaction products in the pool and around the reaction front. In the results, the Na around the reaction front decreased from the enough amount with the reaction time. The concentrations were 18-24 wt.% for Na, and 22-18 wt.% for Si after the termination. From the thermodynamics calculations, the stable materials around the reaction front comprised more than 90 wt.% solid products such as Na$$_{2}$$SiO$$_{3}$$, and no Na. Further, the distribution of Na and reaction products could be explained by a steady-state sedimentation-diffusion model. At the early stage of SCR, the reaction products were suspended as particles in the Na pool because of the high H$$_{2}$$-generation rate. As the concrete ablation proceeds, they start settling down due to the decreased H$$_{2}$$-generation rate, thereby allowing SCR termination. It was concluded that SCR termination was caused by the sediment of the reaction products and the lack of Na around the reaction front.

Journal Articles

Oxidation characteristics of lead-alloy coolants in air ingress accident

Kondo, Masatoshi*; Okubo, Nariaki; Irisawa, Eriko; Komatsu, Atsushi; Ishikawa, Norito; Tanaka, Teruya*

Energy Procedia, 131, p.386 - 394, 2017/12

 Times Cited Count:2 Percentile:11.38

The chemical behaviors of lead (Pb) based coolants in the air ingress accident of fast reactors were investigated by means of the thermodynamic considerations and the static oxidation experiments for Pb alloys at various chemical compositions. The results of the static oxidation tests for lead-bismuth (Pb-Bi) alloys indicated that Pb was depleted from the alloy due to the preferential formation of PbO in air at 773K. Pb-Bi oxide and Bi$$_{2}$$O$$_{3}$$ were formed after the enrichment of Bi in the alloys due to the Pb depletion. The oxidation rates of the alloys were much larger than that of the steels, and became larger with higher Pb concentration in the alloys. The compatibility of Pb-Bi alloys with stainless steel was worse when the Pb concentration in the alloys became low, since the dissolution type corrosion was promoted by the Bi composition in the alloy. The Pb-Li alloys were oxidized as they formed Li$$_{2}$$PbO$$_{3}$$ and Li$$_{2}$$CO$$_{3}$$. Then, Li was depleted from the alloy.

JAEA Reports

Application of FORNAX-A

Aihara, Jun; Ueta, Shohei; Nishihara, Tetsuo

JAEA-Technology 2015-040, 32 Pages, 2016/02


Original FORNAX-A is a calculation code for amount of fission product (FP) released from fuel rods of pin-in-type high temperature gas-cooled reactors (HTGRs). This report is for explanation what calculations become possible with minor changed FORNAX-A.

Journal Articles

Evaluation of tritium confinement performance of alumina and zirconium for tritium production in a high-temperature gas-cooled reactor for fusion reactors

Katayama, Kazunari*; Ushida, Hiroki*; Matsuura, Hideaki*; Fukada, Satoshi*; Goto, Minoru; Nakagawa, Shigeaki

Fusion Science and Technology, 68(3), p.662 - 668, 2015/10

 Times Cited Count:7 Percentile:35.04(Nuclear Science & Technology)

Tritium production utilizing nuclear reactions by neutron and lithium in a high-temperature gas-cooled reactor is attractive for development of a fusion reactor. From viewpoints of tritium safety and production efficiency, tritium confinement technique is an important issue. It is known that alumina has high resistance for gas permeation. In this study, hydrogen permeation experiments in commercial alumina tubes were conducted and hydrogen permeability, diffusivity and solubility was evaluated. By using obtained data, tritium permeation behavior from an Al$$_{2}$$O$$_{3}$$-coated Li-compound particle was simulated. Additionally, by using literature data for hydrogen behavior in zirconium, an effect of Zr incorporation into an Al$$_{2}$$O$$_{3}$$ coating on tritium permeation was discussed. It was indicated that the majority of produced tritium was released through the Al$$_{2}$$O$$_{3}$$ coating above 500$$^{circ}$$C. However, it is expected that total tritium leak is suppressed to below 0.67% of total tritium produced at 500$$^{circ}$$C by incorporating Zr fine particles into the inside of Al$$_{2}$$O$$_{3}$$ coating.

Journal Articles

Study on operation scenario of tritium production for a fusion reactor using a high temperature gas-cooled reactor

Kawamoto, Yasuko*; Nakaya, Hiroyuki*; Matsuura, Hideaki*; Katayama, Kazunari*; Goto, Minoru; Nakagawa, Shigeaki

Fusion Science and Technology, 68(2), p.397 - 401, 2015/09

 Times Cited Count:1 Percentile:86.91(Nuclear Science & Technology)

To start up a fusion reactor, it is necessary to provide a sufficient amount of tritium from an external device. Herein, methods for supplying a fusion reactor with tritium are discussed. Use of a high temperature gas cooled reactor (HTGR) as a tritium production device has been proposed. So far, the analyses have been focused only on the operation in which fuel is periodically exchanged (batch) using the block type HTGR. In the pebble bed type HTGR, it is possible to design an operation that has no time loss for refueling. The pebble bed type HTGR (PBMR) and the block type HTGR (GTHTR300) are assumed as the calculation and comparison targets. Simulation is made using the continuous-energy Monte Carlo transport code MVPBURN. It is shown that the continuous operation using the pebble bed type HTGR has almost the same tritium productivity compared with the batch operation using the block type HGTR. The issues for pebble bed type HTGR as a tritium production device are discussed.

Journal Articles

Actively convected liquid metal divertor

Shimada, Michiya; Hirooka, Yoshihiko*

Nuclear Fusion, 54(12), p.122002_1 - 122002_7, 2014/12

 Times Cited Count:26 Percentile:13.78(Physics, Fluids & Plasmas)

Tungsten is considered to be the most promising material for divertor in a fusion reactor. Tungsten divertor can withstand the heat loads of ITER, but the heat loads of DEMO divertor is a challenge. Pulsive heat loads as those associated with disruption could melt tungsten targets. The surface would not be flat after subsequent resolidification, which would significantly deteriorate its heat handling capability. Furthermore, DBTT of tungsten is rather high: $$sim$$ 400$$^{circ}$$C, which would become even higher after neutron irradiation, possibly resulting in cracks in tungsten. Our proposal is to use liquid metal for the divertor target material and actively circulate it with $$j$$ $$times$$ $$B$$ force. A simplified analysis of mhd equation in a cylindrical geometry suggests that the engineering requirement is modest. This analysis suggests that this new divertor concept merits further investigation.

Journal Articles

Actively circulated liquid metal divertor (ACLMD)

Shimada, Michiya; Hirooka, Yoshihiko*; Zhou, H.*

Europhysics Conference Abstracts (Internet), 38F, p.O2.110_1 - O2.110_4, 2014/00

Tungsten is considered to be most promising candidate for divertor target material for fusion reactor. Although tungsten target can withstand the heat loads of ITER, the heat exhaust requirement for DEMO is much more demanding. Pulsive heat loads associated with disurption would melt the tungsten divertor target. Melting and subsequent resolidification will roughen the tungsten surface, significantly deteriorating the heat handling capability. Further, tungsten has a rather high DBTT (Ductile-Brittle-Transition temperature) of 400$$^{circ}$$C. Neutron irradiation would further increase the DBTT, which could result in cracks. In view of these issues, liquid metal divertor is proposed, which is actively circulated with the Lorentz force introduced through the electrodes in the liquid metal. A modest flow speed of 0.3 m/s seems to be adequate for the heat load exhaust of DEMO. A simple treatment of MHD equation in a cylindrical geometry suggests that the requirements on the current and voltage are modest if the ramp-up of current is made slowly (e.g. in a minute), implying that the this concept is worth further study.

Journal Articles

The Integral experiment on beryllium with D-T neutrons for verification of tritium breeding

Verzilov, Y. M.; Sato, Satoshi; Ochiai, Kentaro; Wada, Masayuki*; Klix, A.*; Nishitani, Takeo

Fusion Engineering and Design, 82(1), p.1 - 9, 2007/01

 Times Cited Count:7 Percentile:49.29(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Diffusion of tritium in intermetallic compound $$beta$$-LiAl; Relation to the defect structure

Sugai, Hiroyuki

Solid State Ionics, 177(39-40), p.3507 - 3512, 2007/01

The diffusion coefficient and its activation energy (116.3 $$pm$$ 11.7 kJ/mol) of tritium in an intermetallic compound $$beta$$-LiAl are determined at temperatures from 700 to 848 K. Though the present result for the diffusion coefficient is almost the same as that reported previously, the present result for the activation energy turns out nearly twice of that (64.9 $$pm$$ 3.8 kJ/mol). The present result for the activation energy is consistent with the systematics that an increase of lithium concentration in Al-Li systems increases the activation energy, but the previous result is not. Furthermore, a consideration of the crystal structure and defect structure suggests that tritium diffuses and is impeded by the attractive interaction with lithium atom at lithium sublattices.

Journal Articles

Diffusion of tritium in intermetallic compound $$beta$$-LiAl; Relation to the defect structure

Sugai, Hiroyuki

Solid State Ionics, 177(39-40), p.3507 - 3512, 2007/01

 Times Cited Count:3 Percentile:80.59(Chemistry, Physical)

The diffusion coefficients and its activation energy (103.7$$pm$$9.5 kJ/mol) for tritium in intermetallic compound $$beta$$-LiAl are determined at temperatures from 699 to 886 K. Though the present result for the diffusion coefficient is almost the same as that reported earlier, the activation energy turns out nearly twice of that (64.9$$pm$$3.8 kJ/mol) reported earlier. On the basis of the crystal structure and defect structure, the large activation energy of this study suggest that tritium diffuses interstitially and is impeded by an attractive interaction with lithium atoms in lithium sublattices.

Journal Articles

Progress of neutral beam injection system on JT-60U for long pulse operation

Ikeda, Yoshitaka; NBI Heating Group; NCT Design Team

Journal of the Korean Physical Society, 49, p.S43 - S47, 2006/12

There are two type of NBI systems on JT-60U. One is the positive ion-based NBI (P-NBI) to inject the beam energy of 80-85 kV. The other is the negative ion-based NBI (N-NBI) at the beam energy more than 350 keV. Recently the pulse duration of NBI system was required to extend up to 30 sec so as to study long pulse plasmas. The four P-NBI units, which tangentially inject neutral beam to plasma, were modified to extend the pulse duration up to 30 sec with 2 MW/unit at $$sim$$ 85 keV. The seven P-NBI units, each of which perpendicularly injects for 10 sec, were conducted to operate in series for the total pulse duration of 30 sec. The ion source of the N-NBI unit was also modified to reduce the heat load of the grid for 30 sec operation. The pulse duration was extended up to 25 sec, $$sim$$ 1 MW at the beam energy of 350keV. In the next step, further pulse extension of NBI up to 100 sec is planned for the modified JT-60U with superconducting coils (so called NCT). This paper reports the recent progress of the NBI system on JT-60U and the design study of the upgraded NBI system for NCT.

Journal Articles

Development of a new fusion power monitor based on activation of flowing water

Verzilov, Y. M.; Nishitani, Takeo; Ochiai, Kentaro; Kutsukake, Chuzo; Abe, Yuichi

Fusion Engineering and Design, 81(8-14), p.1477 - 1483, 2006/02

 Times Cited Count:2 Percentile:81.41(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Analysis of sequential charged particle reaction experiments for fusion reactors

Yamauchi, Michinori*; Hori, Junichi*; Ochiai, Kentaro; Sato, Satoshi; Nishitani, Takeo; Kawasaki, Hiromitsu*

Fusion Engineering and Design, 81(8-14), p.1577 - 1582, 2006/02

 Times Cited Count:1 Percentile:89.22(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Design study of a neutral beam injector for fusion DEMO plant at JAERI

Inoue, Takashi; Hanada, Masaya; Kashiwagi, Mieko; Nishio, Satoshi; Sakamoto, Keishi; Sato, Masayasu; Taniguchi, Masaki; Tobita, Kenji; Watanabe, Kazuhiro; DEMO Plant Design Team

Fusion Engineering and Design, 81(8-14), p.1291 - 1297, 2006/02

 Times Cited Count:10 Percentile:39.1(Nuclear Science & Technology)

Requirement and technical issues of the neutral beam inejctor (NBI) is discussed for fusion DEMO plant. The NBI for the fusion DEMO plant should be high efficiency, high energy and high reliability with long life. From the view point of high efficiency, use of conventional electrostatic accelerator is realistic. Due to operation under radiation environment, vacuum insulation is essential in the accelerator. According to the insulation design guideline, it was clarified that the beam energy of 1.5$$sim$$2 MeV is possible in the accelerator. Development of filamentless, and cesium free ion source is required, based on the existing high current/high current density negative ion production technology. The gas neutralization is not applicable due to its low efficiency (60%). R&D on an advanced neutralization scheme such as plasma neutralization (efficiency: $$>$$80%) is required. Recently, development of cw high power semiconductor laser is in progress. The paper shows a conceptual design of a high efficiency laser neutralizer utilizing the new semiconductor laser array.

Journal Articles

Neutronics assessment of advanced shield materials using metal hydride and borohydride for fusion reactors

Hayashi, Takao; Tobita, Kenji; Nishio, Satoshi; Ikeda, Kazuki*; Nakamori, Yuko*; Orimo, Shinichi*; DEMO Plant Design Team

Fusion Engineering and Design, 81(8-14), p.1285 - 1290, 2006/02

 Times Cited Count:18 Percentile:20.63(Nuclear Science & Technology)

Neutron transport calculations were carried out to evaluate the capability of metal hydrides and borohydrides as an advanced shielding material. Some hydrides indicated considerably higher hydrogen content than polyethylene and solid hydrogen. The hydrogen-rich hydrides show superior neutron shielding capability to the conventional materials. From the temperature dependence of dissociation pressure, ZrH$$_{2}$$ and TiH$$_{2}$$ can be used without releasing hydrogen at the temperature of less than 640 $$^{circ}$$C at 1 atm. ZrH$$_{2}$$ and Mg(BH$$_{4}$$)$$_{2}$$ can reduce the thickness of the shield by 30% and 20% compared to a combination of steel and water, respectively. Mixing some hydrides with F82H produces considerable effects in $$gamma$$-ray shielding. The neutron and $$gamma$$-ray shielding capabilities decrease in order of ZrH$$_{2}$$ $$>$$ Mg(BH$$_{4}$$)$$_{2}$$ and F82H $$>$$ TiH$$_{2}$$ and F82H $$>$$ water and F82H.

Journal Articles

Nuclear technology and potential ripple effect of superconducting magnets for fusion power plant

Nishimura, Arata*; Muroga, Takeo*; Takeuchi, Takao*; Nishitani, Takeo; Morioka, Atsuhiko

Fusion Engineering and Design, 81(8-14), p.1675 - 1681, 2006/02

 Times Cited Count:3 Percentile:73.58(Nuclear Science & Technology)

In a fusion reactor plant, a neutral beam injector (NBI) will be operated for a long time, and it will allow neutron streaming from NBI ports to outside of the plasma vacuum vessel. It requires the superconducting magnet to develop nuclear technology to produce stable magnetic field and to reduce activation of the magnet components. In this report, the back ground of the necessity and the contents of the nuclear technology of the superconducting magnets for fusion application are discussed and some typical investigation results are presented, which are the neutron irradiation effect on Nb$$_{3}$$Sn wire, the development of low activation superconducting wire, and the design concept to reduce nuclear heating and nuclear transformation by streaming. In addition, recent activities in high energy particle physics are introduced and potential ripple effect of the technology of the superconducting magnets is described briefly.

Journal Articles

Development of reliable diamond window for EC launcher on fusion reactors

Takahashi, Koji; Illy, S.*; Heidinger, R.*; Kasugai, Atsushi; Minami, Ryutaro; Sakamoto, Keishi; Thumm, M.*; Imai, Tsuyoshi

Fusion Engineering and Design, 74(1-4), p.305 - 310, 2005/11

 Times Cited Count:13 Percentile:31(Nuclear Science & Technology)

A new diamond window with the copper-coated edge for an EC launcher is developed. The diamond window is designed to cool its disk edge. Since Cu is coated at the entire edge, ingress of cooling water into a transmission line in case of failure on the edge is negligible. In addition, corrosion of Al blaze between the edge and the Inconel cuffs can be avoided. A 170GHz, RF transmission experiment equivalent to a MW-level transmission was carried out to investigate the capability of the edge cooling. The transmission power and pulse are 55kW and 3sec, respectively. Temperature increase was 45$$^{circ}$$C and alomost became constant. Thermal calculation with tan$$delta$$ of 4.4$$times$$10$$^{-4}$$ and thermal conductivity of 1.9kW/m/K agrees with the experiment. Since tan$$delta$$ of the diamond is much higher than the actual one (tan$$delta$$=2$$times$$10$$^{-5}$$), the temperature increase corresponds to that of 1MW transmission. It concludes that the Cu coating dose not degrade the edge cooling capability and improves the reliability of the diamond window.

Journal Articles

The HFR Petten high dose irradiation programme of beryllium for blanket application

Hegeman, J. B. J.*; Van der Laan, J. G.*; Kawamura, Hiroshi; M$"o$slang, A.*; Kupriyanov, I.*; Uchida, Munenori*; Hayashi, Kimio

Fusion Engineering and Design, 75-79, p.769 - 773, 2005/11

 Times Cited Count:23 Percentile:16.23(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Intelligible seminar of fusion reactors, 10; Remote maintenance robot for in-vessel components, Advanced robot technology for handling large-heavy components with high positioning accuracy

Shibanuma, Kiyoshi

Nippon Genshiryoku Gakkai-Shi, 47(11), p.761 - 767, 2005/11

In-vessel components such as blanket and divertor of the fusion reactor are activated by neutron produced during fusion reaction. Gamma radiation will be about 500 MGy/h in maximum after fusion reaction. When the components are failed or troubled in the vessel, the maintenence has to be carried out by the robot because the human cannot be close inside the vessel. The required functions and present R&D status of the typical robots applied to ITER are introduced as examples of robots maintaining the in-vessel components of the fusion reactor.

Journal Articles

N-NBI heating and current drive in JT-60U towards steady-state tokamak

Ikeda, Yoshitaka; Oikawa, Toshihiro; Ide, Shunsuke

Purazuma, Kaku Yugo Gakkai-Shi, 81(10), p.773 - 778, 2005/10

In steady-state tokamak fusion reactors, an efficient external current drive and a large fraction of the bootstrap current are required for non-inductive operation at low circulating power. NBI is a powerful and reliable actuator for current drive and heating. A negative ion-based NBI (N-NBI) with a high beam energy more than 350 keV has been installed in the JT-60U tokamak in order to study the NBI current drive and heating in an ITER relevant regime. This paper presents recent progress of N-NBI experiments and its system in JT-60U towards steady-state operation for ITER and tokamak fusion reactors.

327 (Records 1-20 displayed on this page)