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Nakahira, Masataka; Takeda, Nobukazu
Hozengaku, 4(4), p.47 - 52, 2006/01
The technical structural standard for ITER (International Thermonuclear Experimental Fusion Reactor) should be innovative because of their quite different features of safety and mechanical components from nuclear fission reactors, and the necessity of introducing several new fabrication and examination technologies. Recognizing the international importance of Fusion Standard, Japan and ASME has started the cooperation development of the Fusion Standard. This paper shows the special features of ITER from view points of safety, design and fabrication, and proposes approach for development of the fusion standard.
Nakamura, Hirofumi; Nishi, Masataka; Sugisaki, Masayasu*
JAERI-Research 2003-018, 32 Pages, 2003/09
JAERI-Research-2003-018.pdf:1.32MB
Tritium transport behavior in materials, which is essential for the safety evaluation of the fusion reactor, has to be evaluated by either tritium properties or extrapolated value from protium or deuterium (D) to tritium (T) using the isotope effect theory. However, there are still some uncertainties on estimation of T behavior in materials, because there are only a few T transport properties data in materials, and it is not completely proven the application of the isotope effect theory to T due to the lack of T data. Therefore, in order to understand the tritium transport properties in materials, isotope effects on diffusion and surface recombination between T and D in/on nickel, whose hydrogen transport properties were well known, were investigated by comparing the obtained properties of T with those of D measured under the same conditions with the ion driven permeation method. Though obtained diffusion coefficient of T was larger than that of D, and activation energy of diffusion of T was smaller than that of D as the contrary to the classical diffusion theory, those were shown to be explained with a modified diffusion theory by introducing higher vibration temperatures in nickel than previous reported values. In addition, the isotope effect on surface recombination coefficient between D and T was shown to be explained using a modified solution model as well as diffusion.
Nakamura, Hirofumi; Nishi, Masataka; Morita, Kenji*
JAERI-Research 2003-016, 32 Pages, 2003/08
JAERI-Research-2003-016.pdf:5.5MB
As a part of the detritiation study from the fusion reactor materials, chemical state of tritium injected into Sr-Ce base oxide ceramic proton conductor, which is a candidate for a tritium recovery system, was investigated with thermal desorption method. The results indicated that the oxide has to be heated up over 1300K to remove tritium due to the OT bond formation in the oxide. On the other hand, tritium removal behavior from the oxide were also investigated by exposing to humid air, and the mechanism of tritium removal from the oxide was identified by the dependency of tritium removal amount and chemical state on the humidity. The results revealed that tritium removal rate by the air exposure was low, and that almost tritium was removed as the vapor form, which was attributed to the isotope exchange reaction between the OT bond on the surface and the protium in vapor. It was also found that small amount of tritium was removed as elemental form under the humid air exposure, which could be attributed to the solute tritium in the oxide and oxygen absorption to the oxygen deficit in the oxide. As a result, the difference of the detritiation mechanism exposed to the humid air on the chemical state of tritium in the oxide was clarified, and it could be a useful basic data for the optimization of detritiation method.
Suzuki, Satoshi; Ueda, Yoshio*; Tokunaga, Kazutoshi*; Sato, Kazuyoshi; Akiba, Masato
Fusion Science and Technology, 44(1), p.41 - 48, 2003/07
Times Cited Count：27 Percentile：85.28(Nuclear Science & Technology)no abstracts in English
Morita, Kenji*; Suzuki, Hironori*; Soda, Kazuo*; Iwahara, Hiroiku*; Nakamura, Hirofumi; Hayashi, Takumi; Nishi, Masataka
Journal of Nuclear Materials, 307-311(2), p.1461 - 1465, 2002/12
Times Cited Count：2 Percentile：17.15(Materials Science, Multidisciplinary)no abstracts in English
Atarashi-Andoh, Mariko; Amano, Hikaru; Ichimasa, Michiko*; Ichimasa, Yusuke*
Fusion Science and Technology, 41(3), p.427 - 431, 2002/05
In processes of tritium transfer in the environment, conversion of HTO to OBT in plant by photosynthesis is important for both aspects of monitoring and dose estimation. Because once OBT is formed in plant, it stays in the plant for longer time than HTO, and OBT is more harmful than HTO for human body. Conversion rate of HTO in plant leaf to OBT in plant edible parts in the open air were obtained for some plants (komatsuna, radish and cherry tomato) during the chronic HT release experiment at Chalk River in 1994. At the experiment, HT gas was released to the atmosphere at the cultivated site for 12 days continuously [1]. HTO and OBT concentration in cultivated plants were measured during the experiment. For plant leaves conversion rate of HTO to OBT was about 0.2 (% h
) but it varied with their growth stage. A chamber experiment in laboratory was also carried out for comparison.
Nakamura, Hirofumi; Hayashi, Takumi; Nishi, Masataka; Arita, Makoto; Okuno, Kenji*
Fusion Engineering and Design, 55(4), p.513 - 520, 2001/09
Times Cited Count：9 Percentile：56.34(Nuclear Science & Technology)no abstracts in English
Noguchi, Hiroshi
Nihon Genshiryoku Gakkai-Shi, 39(11), p.915 - 916, 1997/00
no abstracts in English
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Radioisotopes, 29(10), p.484 - 489, 1980/00
no abstracts in English
