Deuterium Critical Assembly (DCA) Decommissioning work in 2013

Morita, Kenji; Morimoto, Makoto; Hisada, Masaki; Fukui, Yasutaka

JAEA-Technology 2015-037, 28 Pages, 2016/01

JAEA-Technology-2015-037.pdf:8.44MB

Deuterium Critical Assembly (DCA) achieved first critically in 1969 and used for research and development program of Advanced Thermal Reactor. To achieved the aim of facility, DCA decommissioning work started in 2002. Decommissioning schedule consists of 4 stages. The third stage, which is the main work (To dismantle and remove reactor vessel and main equipment), was started in 2008 and will be finished at 2023. This report describes DCA decommissioning work and data (Ability of cutting tools and Man-hours) in 2013.

Deuterium depth profiling in JT-60U W-shaped divertor tiles by nuclear reaction analysis

Hayashi, Takao; Ochiai, Kentaro; Masaki, Kei; Goto, Yoshitaka*; Kutsukake, Chuzo; Arai, Takashi; Nishitani, Takeo; Miya, Naoyuki

Journal of Nuclear Materials, 349(1-2), p.6 - 16, 2006/02

https://doi.org/10.1016/j.jnucmat.2005.06.019

Deuterium concentrations and depth profiles in plasma-facing graphite tiles used in the divertor of JT-60U were investigated by NRA. The highest deuterium concentration of D/C of 0.053 was found in the outer dome wing tile, where the deuterium accumulated probably through the deuterium-carbon co-deposition. In the outer and inner divertor target tiles, the D/C data were lower than 0.006. Additionally, the maximum (H+D)/C in the dome top tile was estimated to be 0.023 from the results of NRA and SIMS. OFMC simulation showed energetic deuterons caused by NBI were implanted into the dome region with high heat flux. Furthermore, the surface temperature and conditions such as deposition and erosion significantly influenced the accumulation process of deuterium. The deuterium depth profile, SEM observation and OFMC simulation indicated the deuterium was considered to accumulate through three processes: the deuterium-carbon co-deposition, the implantation of energetic deuterons and the deuterium diffusion into the bulk.

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

https://doi.org/10.13182/FST05-A1034

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.

CARS study of deuterium clusters stabilized in solid helium

Gordon, E. B.*; Kumada, Takayuki; Ishiguro, Masazumi; Aratono, Yasuyuki

Journal of Experimental and Theoretical Physics, 99(4), p.776 - 783, 2004/10

The solid Deuterium clusters for the first time isolated in a matrix of solid Helium have been investigated at T = 1.3K and P = 3 MPa by CARS (Coherent anti-Stokes Raman spectroscopy) technique. The Q1(J=0) and Q1(J=1) lines intensity, shape and positions have been studied as the functions of ortho- para content in the solid, as well as of clusters size. The strong effect of Raman scattering cross section sensitivity to the molecular environment nuclear spin state has been found in CARS; the ratio of probabilities for the scattering by para (J=1) and ortho (J=0) deuterium being equal to 1 in a gas is as high as 10,000 in nearly pure o-D2, whereas it is about 50 in spontaneous Raman scattering. This effect has been shown to give rise starting from cluster size corresponding to the phonon band onset.

Measurement of deuterium and tritium retentions on the surface of JT-60 divertor tiles by means of nuclear reaction analysis

Ochiai, Kentaro; Hayashi, Takao; Kutsukake, Chuzo; Goto, Yoshitaka*; Masaki, Kei; Arai, Takashi; Miya, Naoyuki; Nishitani, Takeo

Journal of Nuclear Materials, 329-333(Part1), p.836 - 839, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.292

no abstracts in English

Irradiation test on Mo- and W-mirrors for ITER by low energy deuterium ions

Sugie, Tatsuo; Kasai, Satoshi; Taniguchi, Masaki; Nagatsu, Masaaki*; Nishitani, Takeo

Journal of Nuclear Materials, 329-333(2), p.1481 - 1485, 2004/08

https://doi.org/10.1016/j.jnucmat.2004.04.248

In ITER, the effect of lower energy particle bombardment is important for mirrors located near the divertor where the low temperature plasma is formed. The test pieces of molybdenum mirrors and a tungsten mirror were irradiated by high flux and low energy (67-80 eV) deuterium ions using SLEIS (Super Low Energy Ion Source with High Ion Flux) facility at the temperature of around 100 C. The molybdenum mirror manufactured by sintering and melting the thin layer of the surface by electron beam in order to eliminate holes on the surface has a higher reflectivity before irradiation than the mirrors without melting the surface, but the reflectivity decreases rapidly with the irradiation fluence due to the generation of blisters on the mirror surface. The reflectivity of molybdenum mirror manufactured by sintering only did not decrease so significantly (less than 10 % at the fluence of 1.3 10 m). The molybdenum and tungsten mirrors manufactured by sintering without melting the surface have a potential for plasma facing mirrors in ITER.

Counter-permeation of deuterium and hydrogen through INCONEL 600

Takeda, Tetsuaki; Iwatsuki, Jin*

Nuclear Technology, 146(1), p.83 - 95, 2004/04

https://doi.org/10.13182/NT04-A3490

The objective of this study is to investigate the effect of the existence of hydrogen in a pipe outside on the amount of permeated deuterium through the pipe. It was found that the amount of permeated deuterium decreases with increasing the partial pressure of hydrogen in the pipe outside when the partial pressure of deuterium in the pipe is lower than 100 Pa and that of hydrogen in the pipe outside is higher than 10 kPa. The amount of permeated deuterium on counter permeation was predicted quantitatively by using an effectiveness factor for diffusivity of deuterium in metals and by taking into account the equilibrium state for hydrogen, deuterium and HD molecules on the metal surface. From the results obtained in this study, it is supposed that the amount of tritium transferred from the primary circuit of the HTTR to the hydrogen production system will be reduced by the existence of high-pressure hydrogen in the catalyst pipe of the steam reformer.

Application of glow discharges for tritium removal from JT-60U vacuum vessel

Nakamura, Hirofumi; Higashijima, Satoru; Isobe, Kanetsugu; Kaminaga, Atsushi; Horikawa, Toyohiko*; Kubo, Hirotaka; Miya, Naoyuki; Nishi, Masataka; Konishi, Satoshi*; Tanabe, Tetsuo*

Fusion Engineering and Design, 70(2), p.163 - 173, 2004/02

https://doi.org/10.1016/j.fusengdes.2003.11.001

In order to establish the effective and conventional in-vessel tritium removal method, glow discharge methods, usually used as wall conditioning, have been applied and examined in vacuum vessel of JT-60U for tritium removal characteristics and kinetics. Release rates of all hydrogen isotopes as well as hydrocarbons from JT-60U vacuum vessel induced by Glow Discharge Cleaning (GDC) with He and H were measured. Release characteristics of hydrogen isotopes were classified into three different release processes each of which is well described by a simple exponential decay with time. It was found that H GDC showed the superior hydrogen isotope release characteristics than the He GDC, probably because chemical processes, such as isotope exchanges assisted by the chemical sputtering process between discharged hydrogen and hydrogen isotopes plasma facing carbon tiles are enhanced by the H glow discharge. Based on the release kinetics observed in the present work, it is estimated that it will take several days to reduce tritium inventory in the surface area of JT-60U to a half by continuous H GDC at 573 K.

Deuterium effect on the subcritical limit for fissile-to-hydrogen ratio

Okuno, Hiroshi; Akiyama, Hideo*; Mochizuki, Hiroki*

Journal of Nuclear Science and Technology, 40(1), p.57 - 60, 2003/01

https://doi.org/10.3327/jnst.40.57

Low-level waste (LLW) drums are required to transport as fissile material if the current IAEA's Regulations for the Safe Transport of Radioactive Material are rigorously applied. This problem is a consequence that water contents of concrete in LLW drums contained deuterium (D) in quantities more than 0.1% of fissile material mass, therefore they are not excepted from packages containing fissile material. Consideration of differences in the absorption cross sections of light hydrogen and D shows that the relative increase in the neutron multiplication factor by a presence of D in natural water for hydrogen (H)-moderated systems is not larger than 0.015%. A numerical calculation confirms that the infinite multiplication factor of a mixture of U-metal and water in a U/H mass ratio of 5% increases proportionally to the D/H atomic ratio, and that its relative increase is less than 0.03% for the D/H atomic ratio of 0.015%. The limiting fissile-to-H mass ratio of 5% in the exception rule is concluded to be applicable to H-moderated systems including D in natural water.

In-situ observation of surface blistering in silicon by deuterium and helium ion irradiation

Igarashi, Shinichi; Muto, Shunsuke*; Tanabe, Tetsuo*; Aihara, Jun; Hojo, Kiichi

Surface & Coatings Technology, 158-159, p.421 - 425, 2002/09

no abstracts in English