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Journal Articles

Formation of organically bound deuterium at each growing stage of rice

Atarashi-Andoh, Mariko; Kumakura, Yasuharu*; Amano, Hikaru; Fukui, Masami*

Fusion Science and Technology, 48(1), p.771 - 774, 2005/07

 Times Cited Count:2 Percentile:80.59(Nuclear Science & Technology)

Uptake of tritium by food plants is an important pathway in transferring tritium to the human body. Plants take up tritium as the form of water and a part of tritiated water (HTO) is converted to organically bound tritium (OBT). The formation of OBT in plants depends on the growth stage when the contamination occurs. Potted rice plants were exposed to deuterated water vapor, as a substitute for HTO vapor, for 4 h at 5 different times during the grain ripening period to estimate the influence of the growth stage on the formation and retention of organically bound deuterium (OBD) in rice. The plants were grown outside before and after the exposure experiments and were exposed to deuterated water vapor in a laboratory in a small chamber equipped with controllers of temperature, humidity and light intensity.The mass of OBD in grain at harvest showed the highest value when the exposure was carried out in the early stage of the ripening period. When the exposure was carried out after 26 day from the heading, the increase of OBD in the grain was a little.

Journal Articles

International benchmark activity of tritium measurement of blanket neutronics

Ochiai, Kentaro; Verzilov, Y. M.; Nishitani, Takeo; Batistoni, P.*; Seidel, K.*

Fusion Science and Technology, 48(1), p.378 - 381, 2005/07

 Times Cited Count:7 Percentile:51.21(Nuclear Science & Technology)

To evaluate the measurement accuracy of the tritium production from $$^{6}$$LiLi(n,t)$$^{4}$$He reactions, an international benchmark program was initiated again under the frame work of an IEA fusion neutronics subtask from 2003. JAERI, ENEA and Technical University of Dresden (TUD) are participating in the activity. This program consists of the calibration of the tritium measurement systems and the verification of the measurement accuracies of the tritium production from $$^{7}$$Li(n,nt)$$^{4}$$He and $$^{6}$$LiLi(n,t)$$^{4}$$He reactions. We have completed the calibration of the measurement system with tritium standard water (HTO) and blind HTO samples. From the results, the scattering of the calibration was within 1.5 %.

Journal Articles

Methods for tritium production rate measurement in design-oriented blanket experiments

Verzilov, Y. M.; Ochiai, Kentaro; Nishitani, Takeo

Fusion Science and Technology, 48(1), p.650 - 653, 2005/07

 Times Cited Count:7 Percentile:51.21(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Tritium recovery from solid breeder blanket by water vapor addition to helium sweep gas

Kawamura, Yoshinori; Iwai, Yasunori; Nakamura, Hirofumi; Hayashi, Takumi; Yamanishi, Toshihiko; Nishi, Masataka

Fusion Science and Technology, 48(1), p.654 - 657, 2005/07

 Times Cited Count:3 Percentile:73.37(Nuclear Science & Technology)

Adding some amount of hydrogen to the helium sweep gas is effective for tritium extraction from blanket, but it causes permeation of tritium to a cooling system. In the design study of a demonstration reactor in JAERI, tritium leakage has been estimated to be about 20% of bred tritium under typical sweep gas conditions. If these tritiums are recovered under the ITER-WDS condition, tritium leakage limitation has to be less than 0.3% of typical case. Water vapor addition to the sweep gas is effective not only for blanket tritium extraction but also for permeation prevention. The reaction rate of isotope exchange is larger than the case of H$$_2$$, and the equilibrium constant is also expected to be about 1.0. When the H/T ratio is 100, tritium inventory of breeder material is larger than the case of H$$_2$$ addition. However it is not so large. In case of H$$_2$$O sweep, separation of tritiated water from helium seems to be easyer, but the process that changes HTO to HT is necessary.

Journal Articles

Evaluation of tritium behavior in the epoxy painted concrete wall of ITER hot cell

Nakamura, Hirofumi; Hayashi, Takumi; Kobayashi, Kazuhiro; Nishi, Masataka

Fusion Science and Technology, 48(1), p.452 - 455, 2005/07

 Times Cited Count:2 Percentile:80.59(Nuclear Science & Technology)

Tritium behavior released in ITER hot cell has been investigated numerically. Tritium behavior was evaluated by a combined analytical methods of a tritium transport analysis with the one dimensional diffusion model in the multi-layer wall (concrete and epoxy paint) and a tritium concentration analysis with the complete mixing model by the ventilation in the hot cell under the simulated hot cell operational conditions. As the results, tritium concentration in the hot cell volume decreases rapidly from 300 DAC (Derived Air Concentration) less than 1 DAC in several days after removing the tritium release source. Tritium inventory in the wall is estimated to be about 0.1 PBq for 20 years operation. On the other hand, Tritium permeation through the epoxy painted concrete wall will be negligible. Finally, as to the effect of epoxy paint on the tritium permeation and inventory, it is found that the epoxy paint can reduce tritium inventory by about two orders of magnitude relative to bare concrete wall.

Journal Articles

The Oxidation performance test of detritiation system under existence of CO and CO$$_{2}$$

Kobayashi, Kazuhiro; Terada, Osamu*; Miura, Hidenori*; Hayashi, Takumi; Nishi, Masataka

Fusion Science and Technology, 48(1), p.476 - 479, 2005/07

 Times Cited Count:10 Percentile:39.15(Nuclear Science & Technology)

To construct the ITER with high safety and acceptability, it is necessary to establish and to ensure the tritium safe handling technology. The performance of the detritiation system at the off-normal events has not been confirmed well. To obtain performance data of detritiation system at the off normal events, the detritiation experiment was performed at TPL/JAERI using a scaled detritiation system for the oxidation performance test. The detritiation system consists of two oxidation catalyst beds (473K and 773K) and a molecular sieve drying absorber. Basic performance of the detritiation system for hydrogen and methane in air was evaluated under maximum ventilation flow rate. Obtained oxidation efficiency was more than 99.99% for hydrogen in the catalyst bed of 473K and more than 99.9% for methane in the 773K one, respectively. It was confirmed that these performances were maintained even under carbon dioxide , carbon monoxide if oxygen remained in the process gas.

Journal Articles

Radiochemical reactions between tritium molecule and carbon dioxide

Shu, Wataru; Ohira, Shigeru; Suzuki, Takumi; Nishi, Masataka

Fusion Science and Technology, 48(1), p.684 - 687, 2005/07

 Times Cited Count:2 Percentile:80.59(Nuclear Science & Technology)

As part of a series of studies on radiochemical reactions that may take place in the fuel processing systems of a future D-T fusion machine like the ITER, reactions of tritium molecule (T$$_{2}$$) and carbon dioxide (CO$$_{2}$$) were examined by laser Raman spectroscopy and quadrupole mass spectrometry (QMS). Both T$$_{2}$$ and CO$$_{2}$$ decreased rapidly in the first 30 minutes after mixing, and then the reactions between them became much slower. As the predominant products of the reactions, carbon monoxide (CO) and tritiated water (T$$_{2}$$O) were found in gaseous phase and condensed phase, respectively. However, there existed also some solid products that were thermally decomposed to CO, CO$$_{2}$$, T$$_{2}$$, T$$_{2}$$O, etc. during baking at 150$$^{circ}$$C and 250$$^{circ}$$C.

Journal Articles

Tritium release behavior from JT-60U vacuum vessel during air exposure phase and wall conditioning phase

Isobe, Kanetsugu; Nakamura, Hirofumi; Kaminaga, Atsushi; Higashijima, Satoru; Nishi, Masataka; Konishi, Satoshi*; Nishikawa, Masabumi*; Tanabe, Tetsuo*

Fusion Science and Technology, 48(1), p.302 - 305, 2005/07

 Times Cited Count:2 Percentile:80.59(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Evaluation of tritium permeation from lithium loop of IFMIF target system

Matsuhiro, Kenjiro; Nakamura, Hirofumi; Hayashi, Takumi; Nakamura, Hiroo; Sugimoto, Masayoshi

Fusion Science and Technology, 48(1), p.625 - 628, 2005/07

 Times Cited Count:4 Percentile:66.97(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Interlinked test results for fusion fuel processing and blanket tritium recovery systems using cryogenic molecular sieve bed

Yamanishi, Toshihiko; Hayashi, Takumi; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu; Uzawa, Masayuki*; Nishi, Masataka

Fusion Science and Technology, 48(1), p.63 - 66, 2005/07

 Times Cited Count:6 Percentile:56.05(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Tritium accounting stability of a ZrCo bed with "In-bed" gas flowing calorimetry

Hayashi, Takumi; Suzuki, Takumi; Yamada, Masayuki; Nishi, Masataka

Fusion Science and Technology, 48(1), p.317 - 323, 2005/07

 Times Cited Count:9 Percentile:42.93(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Study on tritium removal performance by gas separation membrane with reflux flow for tritium removal system of fusion reactor

Iwai, Yasunori; Yamanishi, Toshihiko; Hayashi, Takumi; Nishi, Masataka

Fusion Science and Technology, 48(1), p.456 - 459, 2005/07

 Times Cited Count:3 Percentile:73.37(Nuclear Science & Technology)

Addition of gas separation membrane process into usual tritium removal process from atmosphere in a room is attractive for fusion plants where a large amount of atmosphere should be processed. Therefore, the gas separation membrane has been studied. New concept of membrane separation with reflux flow is proposed in the present. Driving force of membrane separation is the difference of partial pressure through membrane. Hence, reflux of a part of gases at permeated side to feed side enhances driving force. Essential points of present discussion are as follows: (1) Reflux has plus effect of driving force enhancement and minus effect of feed flow increase, hence, there is the optimum. (2) Permeated-side pressure effects enhancement of tritium recovery strongly. (3) Effect of reflux becomes striking as the target species have higher permeability coefficient, therefore, it is favorable for tritium recovery because those of hydrogen gas and water vapor are much higher among atmosphere elements. In addition, application of reflux flow will realize scale reduction of expensive membrane module.

Journal Articles

Case study on unexpected tritium release happened in a ventilated room of fusion reactor

Iwai, Yasunori; Hayashi, Takumi; Kobayashi, Kazuhiro; Nishi, Masataka

Fusion Science and Technology, 48(1), p.460 - 463, 2005/07

 Times Cited Count:4 Percentile:66.97(Nuclear Science & Technology)

A code has been developed to investigate tritium behavior in a ventilated room at its accidental release. Purpose of present study is to; (1) investigate the effect of atmospheric exchange number on confinement at initial stage of tritium release; (2) investigate the effect of atmospheric exchange number on time necessary for release detection; (3) investigate the suitable location of exhaust ducts and monitors. Essential points of discussion are as follows: (1) Atmospheric exchange number is less influential in confinement. (2) Time until a monitor detects release depends on exchange number but it is within a few minutes in any case. Installation of a monitor in each duct placed uniformly in a room is effective for the prompt detection. (3) After closing the emergency isolation valve, a few hours are needed until the tritium concentration in a room reaches uniform. Released tritium forms plume and it migrates in a room by the eddy flow at its initial stage, so it is important not to discharge plume directly. Hence, it is effective to locate exhaust ducts with some distance from the wall.

Journal Articles

New conceptual design of a test module assembly for tritium permeation experiment

Ohira, Shigeru; Luo, G.; Nakamura, Hirofumi; Shu, Wataru; Kitamura, Kazunori*; Nishi, Masataka

Fusion Science and Technology, 48(1), p.621 - 624, 2005/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

A new conceptual design of a tritium permeation test module assembly was developed for demonstration tests using a strong plasma source constructed in TPL for simulation of practical tritium permeation in the real plasma facing components and validation of the models and codes for evaluation of tritium permeation. The target module, to be irradiated by the high flux plasma beam, consists of a multi-layer structure of a plasma facing material plate and a copper substrate with pressurized coolant cavity. Tests using a preliminary model of the target module has been performed to verify thermal and mechanical behavior of the bonded structure and to assess its structural integrity focused on the bonded interface under the cyclic heat loads. After the heat load testing, no visible defect and crack was observed around the bonded interfaces with magnifying glass, and its structural integrity was verified. Also the first tests using tritium plasma at TSTA/LANL with the preliminary model was performed and process to measured tritium permeated was established.

Journal Articles

Release behavior of hydrogen isotopes from JT-60U graphite tiles

Katayama, Kazunari*; Takeishi, Toshiharu*; Nagase, Hiroyasu*; Manabe, Yusuke*; Nishikawa, Masabumi*; Miya, Naoyuki; Masaki, Kei

Fusion Science and Technology, 48(1), p.561 - 564, 2005/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Retention of hydrogen isotopes in divertor tiles used in JT-60U

Hirohata, Yuko*; Shibahara, Takahiro*; Tanabe, Tetsuo*; Oya, Yasuhisa*; Arai, Takashi; Goto, Yoshitaka*; Masaki, Kei; Yagyu, Junichi; Oyaizu, Makoto*; Okuno, Kenji*; et al.

Fusion Science and Technology, 48(1), p.557 - 560, 2005/07

 Times Cited Count:3 Percentile:73.37(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Recovery of retained tritium from graphite tile of JT-60U

Takeishi, Toshiharu*; Katayama, Kazunari*; Nishikawa, Masabumi*; Miya, Naoyuki; Masaki, Kei

Fusion Science and Technology, 48(1), p.565 - 568, 2005/07

 Times Cited Count:1 Percentile:88.49(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Simulation of tritium spreading in controlled areas after a tritium release

Cristescu, I. R.*; Travis, J.*; Iwai, Yasunori; Kobayashi, Kazuhiro; Murdoch, D.*

Fusion Science and Technology, 48(1), p.464 - 467, 2005/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

A model to simulate tritium behaviour after a release into a confined ventilated volume has been developed. The model assumes that for the investigated cases, tritium behaviour can be characterized by solving the dynamic equations of motion (the compressible Navier-Stokes equations) coupled with the classical k-$$varepsilon$$ turbulence model to simulate the ventilation in the room and mass diffusion for tritium spreading. The GASFLOW-II fluid dynamics field code, developed through a Los Alamos National Laboratory (LANL) - Forschungszentrum Karlsruhe co-operation, was used as the computational tool to solve the equations that describe the processes. The numerical results have been validated with experimental data collected on the experimental facility (Caisson) at the Tritium Process Laboratory (TPL) Japan. Additionally an investigation of the influence of the obstacles to the tritium distribution inside the Caisson is presented.

Journal Articles

Tritium elimination system using tritium gas oxidizing bacteria

Ichimasa, Michiko*; Awagakubo, Sayuri*; Takahashi, Miho*; Tauchi, Hiroshi*; Hayashi, Takumi; Kobayashi, Kazuhiro; Nishi, Masataka; Ichimasa, Yusuke*

Fusion Science and Technology, 48(1), p.759 - 762, 2005/07

 Times Cited Count:6 Percentile:56.05(Nuclear Science & Technology)

There exists various kinds of HT oxidizing soil bacteria in the world, and we have conducted the investigation of HT oxidation activity of such bacteria. In the fusion facility where deuterium and tritium will be used as its fuel, the system is necessary to eliminate tritium from atmospheric air. General tritium elimination method is oxidation and dehumidification, and high temperature catalyst is used in the present system for oxidation. Application of the HT oxidation bioreactor, which can oxidize in room temperature, to this oxidation process has possibility to get higher tritium elimination efficiency, so we started to study the bioreactor. In the recent study, we can get high oxidation ratio of 85% in the processing conditions of 200 Bq/cm$$^{3}$$ as tritium concentration in air, 100 cm$$^{3}$$/min as flow rate and once-through processing using the Caisson Assembly for Tritium Safety Study (CATS) in JAERI. This result encourages this development study.

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