A. Taguchi

A. Takada

H. Funakoshi

K. Kotoh

K. Munakata

K. Wada

M. Tanaka

N. Akata

S. Moriyama

T. Kawano

T. Sugiyama

Y. Morita

Sugiyama,  T.

Takada,  A.

Morita,  Y.

Kotoh,  K.

Moriyama,  S.

Funakoshi,  H.

Munakata,  K.

Wada,  K.

Taguchi,  A.

Kawano,  T.

Tanaka,  M.

Akata,  N.

NIFS-Repository (National Institute for Fusion Science)

Magnetically conﬁned nuclear fusion research is nowin new stage to produce D-T burning plasma towardDEMO and fusion reactor. Linear divertor plasma simu-lators (LDPS), generating high density plasma in steadystate, have contributed so much to the basic understand-ing of SOL/divertor plasmas and plasma-wall interac-tion. Understanding of hydrogen isotope retention inplasma-facing materials is key to sustain long and/orsteady state plasma in next generation fusion devices,such as ITER and DEMO.Recently it has been revealed by Hatano et al. thathydrogen isotope retention in tungsten (W) increasesdramatically due to irradiation defects introduced byneutron irradiation. Neutron irradiation creates uniformdefects as a trap site in material, while ion beam ir-radiation mainly creates defects near material surface.It is necessary to study hydrogen isotope retention inneutron-irradiated materials under SOL relevant plasmacondition.In order to conduct plasma irradiation research withneutron-irradiated materials, new hot facilities havingLDPS are planned and under construction in US andEU. These facilities can handle neutron-irradiated mate-rials. However, in Japan, it is diﬃcult to construct newhot facility having LDPS. Alternative strategy to studyplasma-wall interaction of neutron-irradiated materialsshould be necessary.International Research Center for Nuclear MaterialScience, Institute for Materials (IMR), Tohoku Univ. hasa long history to conduct neutron irradiation tests us-ing nuclear reactors overseas (BR2) as well as in Japan(JMTR, JOYO, JRR-3). Many neutron-irradiated sam-ples already exist in IMR. We have developed a newLPDS with a dc plasma source composed of a zigzag-shaped LaB6 cathode and a water-cooled hollow cop-per anode. The developed LDPS, being able to producehigh density plasma more than 1019m−3 in steady state,is more compact in size and can be installed in limitedspace of existing laboratories. We are planning to in-stall the developed LPDS in a radiation-controlled areaof IMR for the purpose to investigate the eﬀect of neu-tron damage on the hydrogen retention characteristics.The LPDS is connected to the existing thermal des-orption spectroscopy (TDS) device as shown in Fig. 1.The sample carrier system is used to move the plasma-exposed samples from the vacuum chamber of the LPDSto the infrared heating equipment for TDS withoutbreaking vacuum. Fig. 2 shows a sample holder equippedin the LPDS. Neutron-irradiated sample (Φ 3.0x0.1) canbe mounted on the sample holder and the sample tem-perature can be controlled by air cooling within an accu-racy of 5 K. The sample holder can release the mountedsample in vacuum.Until the middle of 2014, we will ﬁnish constructingLPDS including the sample holder and the sample carriersystem in Nagoya Univ. After that, the device will moveto be installed in IMR, Tohoku University until the endof 2015.We believe that this facility will become a new re-search platform for study of plasma-radioactive materialinteraction.Fig. 1: Photo of the compact divertor plasma simulatorwith sample carrier system.Fig. 2: Design of sample holder with air cooling.The presentations and publications from this col-laborative research are listed below:1) N. Ohno, M.Takagi, S. Kajita, N. Matsunami, A.Sagara, M. Tokitani, H. Kurishita, T. Shikama, N.Yoshida, 4th Int. Workshop on Plasma Material In-teraction Facilities for Fusion Research, 2013, OakRidge, USA.2) H. Kurishita, M. Hatakeyama, M. Narui, S. Matuso,T. Shikama, N. Ohno, et al., 23rd International TokiConference (ITC-23), 2013. Toki, Japan, P1-59. Detritiation of huge amount of tritiated water and safety improvement by reducing the tritium inventory are still important developing challenges for DEMO fuel cycle. In the present study, we adopted water-hydrogen chemical exchange and cryogenic pressure swing adsorption (PSA) as technologies of hydrogen isotope separation. The purposes of study are development of high-efficient adsorbent and catalyst applied to the above technologies, and development of devices for hydrogen isotope separation with its high-efficient operating procedures.  i) Water-hydrogen chemical exchange A water detritiation system, which consisted of two liquid phase chemical exchange columns operated under the different temperature and pressure each other, was newly proposed. We call this system ‘Dual-Temperature Dual-Pressure Catalytic Exchange (DTDP-CE)’ hereinafter. An experiment device was built as shown in the left hand side of Fig. 1 in order to demonstrate DTDP-CE. The chemical exchange columns were both 55 mm in I.D. and 1 m in height. Kogel catalysts and Dixon gauze rings were mixed and randomly filled in the columns. The catalyst packing rate was set as 30 % in volume. The temperature and pressure can be controlled at constant values in the ranges 30-70 °C and 0.03-0.1 MPa, respectively, for the low-temperature low-pressure column, and in the ranges 70-140 °C and 0.1-0.5 MPa, respectively, for the high-temperature high-pressure column. Flow rates of hydrogen gas and feed water can be set at a maximum as 30 NL/min and 30 g/min, respectively. Experiments were started and the results will be reported in the near future.  ii) Catalyst for DTDP-CE Developing targets of a Pt-catalyst for DTDP-CE are improvement in heat resistance and lasting hydrophobicity under pressurized condition. A porous silica beads (Fuji silysia chemical Ltd., CARiACT Q-50 hydrophobic prototype) was used as a carrier. Its average pore diameter was 50 nm. The pore volume and specific surface area were measured as 1.0 cm3/g and 73 m2/g, respectively. The catalyst was prepared by impregnating the carrier with chloroplatinic acid followed by reduction with hydrogen. The catalyst performance for hydrogen atom exchange between water vapor and hydrogen gas was measured with tritiated water of 1 MBq/kg, and the overall mass transfer coefficient was obtained as 1.8 cm/s. The experimental and theoretical results obtained for the developments of high-efficient adsorbent and catalyst were reported in the literatures.1-6)   iii) Cryogenic pressure swing adsorption For the hydrogen isotope separation system in the deuterium-tritium fuel cycle protium removal is one of the most important issues, but complete separation of deuterium and tritium is not necessary required. Based on this point of view, we have been developed a cryogenic PSA process and its high-efficient operating procedure. An experiment device of a cryogenic pressure swing adsorption process with three adsorption columns was built as shown in the right hand side of Fig. 1. We call this device ‘Pressure Swing Multi-packed-column Adsorption Process (PSMAP) system’ hereinafter. The U-shaped adsorption columns were made of stainless steel, and those inner diameter and effective length of the adsorption bed were 23 mm and 92.4 cm, respectively. The synthetic zeolite of SZ-13X was chosen as an adsorbent according to the results of previous research. The device was controlled automatically and the three adsorption columns worked cyclically processes of evacuating desorption, priming carrier H2 replenishment and isotopic replacement adsorption, like a merry-go-round way. Experiments were started and the results will be reported in the near future. A preliminary experimental and theoretical results for the present study was reported in the literature.7)                Fig. 1. Snapshots of devices for hydrogen isotope separation: DTDP-CE (left), PSMAP (right).   1) K. Munakata, Surface Science, 616, pp. 1-11 (2013).  2) K. Munakata, K. Hara, T. Sugiyama et al., Fusion Engineering and Design, 88(9-10), pp. 2408-2412 (2013).  3) K. Munakata, Journal of Chemical Engineering of Japan, 46(7), pp. 444-449 (2013).  4) Y. Kawamura, Y. Iwai, K. Munakata et al., Journal of Nuclear Materials, 442, pp. S455-S460 (2013).  5) A. Taguchi, Y. Kato, Y. Torikai et al., Microporous and Mesoporous Materials, 179㸪pp. 217-223 (2013).  6) K. Kotoh, S. Moriyama, S. Takashima et al., Fusion Engineering and Design, 88, pp. 2223-2227 (2013).  7) S. Takashima, K. Kotoh, Fusion Engineering and Design, 88, pp. 2366-2368 (2013).   265§30. Development of Hydrogen Isotope Separation Technologies for DEMO Fuel CycleSugiyama, T., Takada, A., Morita, Y. (Nagoya Univ.), Kotoh, K., Moriyama, S., Funakoshi, H. (Kyushu Univ.), Munakata, K., Wada, K. (Akita Univ.), Taguchi, A. (Univ. Toyama), Kawano, T., Tanaka, M., Akata, N.

Development of Hydrogen Isotope Separation Technologies for DEMO Fuel Cycle

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Development of Hydrogen Isotope Separation Technologies for DEMO Fuel Cycle

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