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Tomita, Yutaka; Morihira, Masayuki; Tamaki, Yoshihisa*; Nishimura, Kazuhisa*; Shoji, Shuichi*; Kihara, Yoshiyuki; Kase, Takeshi; Koizumi, Tsutomu
JAEA-Research 2006-088, 95 Pages, 2007/01
JAEA-Research-2006-088.pdf:23.02MB
JAEA has developed sphere-pac fuels in the feasibility study on commercialized FBR cycle systems as one of the candidates for low decontamination TRU fuels. Optimization of the fabrication condition for coarse spheres, development of an improved external gelation process, and examination of peculiar problems for the low decontamination fuel were carried out in Phase II. The results are shown as follows. (1) Fabrication condition of coarse spheres was optimized. (2) Feasibility of the improved external gelation process was confirmed. (3) Rare earth elements did not bring any problem for the characteristic of spheres and fabrication condition. (4) Radiation resistant data of the feed solution was acquired. Results of tests show the feasibility of the external gelation process for the low decontamination TRU fuel microsphere fabrication.
Tomita, Yutaka; Morihira, Masayuki; Kihara, Yoshiyuki; Tamaki, Yoshihisa*
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 4 Pages, 2005/10
High economic competitiveness and low environmental impact are required for advanced FBR cycle systems. Sphere-pac fuel has been considered as promising fuel systems, due to its inherent advantage in remote operation, dustfree fuel fabrication process and cost reduction. Japan Nuclear Cycle Development Institute (JNC) has been investigated the external gelation process for sphere-pac fuel. In this report, the result of the sphere fabrication test by the external gelation process is reported.
Huang, X.*; Mashimo, Tsutomu; Ono, Masao; Tomita, Takeshi; Sawai, Tomotsugu; Osakabe, Toyotaka; Mori, Nobuo*
Journal of Applied Physics, 96(3), p.1336 - 1340, 2004/08
Times Cited Count：11 Percentile：42.77(Physics, Applied)Mega-gravity field experiments were performed on the Bi
Sb
(atomic percent) alloy and pure Bi below their melting points, to investigate the change in crystalline state. For the alloy centrifuged at 191-205 
C, no change in composition was observed, and the grain sizes of the crystals decreased from several mm to tens of 
m, while no distinct change in grain size was observed for the centrifuged pure Bi. The alloy centrifuged at 220-240 C consisted of two regions with different morphologies-fine-grained crystals with grain sizes around tens of m in the low gravity region, and large crystals with grain sizes several mm long and hundreds of m wide along the direction of gravity in the high gravity region, where sedimentation of atoms was confirmed. The large crystals with hexagonal structures were formed by preferential crystal growth roughly along the c axes, and a large strain that increased as the gravitational field increased existed inside these crystals. Formation of this anomalous crystal state might be correlated with the sedimentation of atoms.
Morihira, Masayuki; Ozawa, Takayuki; ; Suzuki, Masahiro; Shigetome, Yoshiaki; Kihara, Yoshiyuki; Kono, Shusaku
JNC TN8400 2004-014, 193 Pages, 2004/07
JNC-TN8400-2004-014.pdf:24.52MB
The collaboration project concerning sphere-pac fuel among JNC, Swiss PSI (Paul Scherrer Institut) and Dutch NRG (Nuclear Research and Consultancy Group) is in progress.Final target of the project is comparative irradiation tests of Sphere-pac fuel in the HFR (High Flux Reactor) in Petten in the Netherlands with pellet type fuel and vipack fuel. Total 16 fuel segments (8 pins) of these three types of fuel are planned to be irradiated. Two sphere-pac fuel segments contain 5%Np in addition to 20%Pu-MOX. Other segments contain no Np. Fabrication of irradiation test pins was completed till May 2003 in PSI. After transportation of the fuel pins to Petten, two times of irradiation were performed in January to March in 2004 and now post irradiation tests are in progress. Later two irradiations will be done till the autumn in 2004.This report summarized the basic plan, fuel design, and fabrication of irradiation test pins concerning this collaboration project.
Tomita, Yutaka; Shigetome, Yoshiaki; Kihara, Yoshiyuki
Saikuru Kiko Giho, (24), p.1 - 10, 2004/00
JNC has carried out the joint research project with PSI in Switzerland and NRG in Netherlands.In this project, three types of fuel segments (sphere-pac segments, vipac segments and pellet segments) were fabricated by PSI. They have been irradiated under same irradiation condition to compare their performances in the High Flux Reactor. This report describes the fabrication of sphere-pac segments and vipac segments for irradiation tests.
Nakahara, Masaumi; Tomita, Yutaka; Nomura, Kazunori; Washiya, Tadahiro
no journal, ,
Concerning the purification technology of UNH crystallization, cesium plutonium nitrate was obtained and was estimated by colorimetry, XRD, TG data. These experiments show cesium plutonium nitrate product increases with nitric acid concentration in the solution. This complex of XRD patterns was almost agreed with Cs
U(NO
)
of that. When CsPu(NO) is heated for short periods, no change occurs up to 100 degrees C, after plutonium is oxidized to CsPuO(NO)
above 245 degrees C. This observed mass loss step for TG curve of cesium plutonium nitrate was about 10%.
Kaji, Naoya; Nakahara, Masaumi; Nakamura, Kazuhito; Shibata, Atsuhiro; Tomita, Yutaka; Washiya, Tadahiro; Kitajima, Takafumi; Koizumi, Tsutomu
no journal, ,
Solubility obtained from the latest crystallization tests using irradiated fuel and the tests implemented before using U or Pu/U are compared with the data showed by Hart. Based on the result, availability of the data to estimate crystallization ratio is considered.
Hinai, Hiroshi; Tomita, Yutaka; Nomura, Kazunori; Oyama, Koichi; Kitajima, Takafumi; Koizumi, Tsutomu
no journal, ,
no abstracts in English
Kumata, Masahiro; Tomita, Yutaka
no journal, ,
A big earthquake occured in the eastern Japan on March 11, 2011. Operation and maintenance activities just after the big earthquake in RN38, Takasaki, Japan would be presented.
Obata, Hiroki; Toyokawa, Takuya; Tomita, Takeshi; Kimura, Yasuhiko
no journal, ,
Hydrogen absorption to the fuel cladding is increase on the high burn-up fuel. The concentration of absorbed hydrogen causes the cladding embrittlement which might become the origination of fractures of the cladding. Therefore, it's important to measure the hydrogen volume in the cladding to estimate the safety margin of the irradiated cladding. In the previous method of hot vacuum extraction, the hydrogen is released and measured as the melting condition of the cladding. It cannot be evaluated the hydrogen volume only in the cladding metal phase. The hydrogen absorption in the cladding metal phase is strongly-correlated the cladding embrittlement. The two-step heating method has the benefit to measure the hydrogen in metal phase and oxide layer separately. The measuring method including the extraction temperature condition using unirradiated cladding will be reported.
Obata, Hiroki; Toyokawa, Takuya; Tomita, Takeshi; Kimura, Yasuhiko
no journal, ,
The amount of hydrogen absorbed to the fuel cladding increases by extended burnup fuel. The absorbed hydrogen that exceed solid solubility limit precipitates as the hydride phase. The high concentration of hydride causes the fuel cladding embrittlement which might become the origination of fractures of the cladding. Therefore, it is important to measure the hydrogen content in the cladding to estimate the safety margin of the irradiated cladding. Hydrogen is absorbed not only in the cladding metal phase, but in the oxide layer. To evaluate the embrittlement of the cladding, it is necessary to measure the hydrogen content in the cladding metal phase and oxide layer separately. Therefore, the two-step heating method can measure the amount of hydrogen in the metal phase and the oxide layer separately. This paper shows the technical review of measuring method including the technique for the determination of extraction temperature.
Tomita, Yutaka; Kumata, Masahiro; Wakabayashi, Shuji; Kijima, Yuichi; Yamamoto, Yoichi; Oda, Tetsuzo
no journal, ,
Yamamoto, Yoichi; Kijima, Yuichi; Tomita, Yutaka
no journal, ,
This presentation summarizes JAEA's recent activities related to CTBT verification regime. To establish the global verification regime of CTBT for the nuclear tests, JAEA has been operating provisionally three facilities (two monitoring stations and one radionuclide laboratory) of the CTBT international monitoring system and a national data center for radionuclide monitoring. For the 6th nuclear test conducted by North Korea in September 2017, JAEA reported the analysis and evaluation results of data observed at the CTBT radionuclide monitoring stations to the national government etc. in a timely manner and thereby contributed to the evaluation by the national government based on the CTBT operation system in Japan. For the purpose of strengthening CTBTO's detection capability for nuclear tests, JAEA started new noble gas joint measurement project with CTBTO in Horonobe (Hokkaido) and Mutsu (Aomori) based on the Japanese government contribution in 2017.
Yamamoto, Yoichi; Kijima, Yuichi; Tomita, Yutaka
no journal, ,
As a member of the CTBT National Operation System of Japan (NOSJ), JAEA monitors and evaluates radionuclides derived from nuclear tests. For this purpose, Takasaki and Okinawa radionuclide stations, Tokai radionuclide laboratory, and a national data center already were put in place and have been operated. This presentation introduces outline of NOSJ and each facility, the response to a nuclear test event, JAEA's recent activities etc.
Yamamoto, Yoichi; Kijima, Yuichi; Tomita, Yutaka
no journal, ,
Based on repeated DPRK's nuclear tests, the Japanese government contributed funds for the noble gas measurement project in February 2017 for the purpose of strengthening CTBTO's detection capability for nuclear tests. The CTBTO decided to conduct measurements in Hokkaido and Tohoku regions of Japan for the time being, and to enhance JAEA with experiences and performance of measurements in Japan as the responsible organization. In response to this, the JAEA has installed two mobile noble gas measurement systems at Horonobe, Hokkaido and JAEA Ohminato site in Mutsu, Aomori, and been carrying out the joint measurement project with the CTBTO. The current status of this project will be presented.
Kijima, Yuichi; Yamamoto, Yoichi; Tomita, Yutaka
no journal, ,
Using the contribution from the Japanese government to the CTBTO for the purpose of strengthening of the CTBTO's detection capability for nuclear tests, the JAEA installed the Transportable Xenon Laboratories (TXLs) in collaboration with the CTBTO at Horonobe, Hokkaido and Mutsu, Aomori, and has been measuring radioxenon since 2018. Therefore, the measurements of radioxenon in Japan for monitoring nuclear tests are currently conducted at total 3 measuring points (Horonobe TXL, Mutsu TXL and Takasaki IMS station). In the past measurement results, the radioxenon isotopes with activity concentration above the background level were detected at these measuring points. The JAEA/NDC carried out the ATM analyses for the investigation of an emission source of the radioxenon isotopes for some detection cases. We report the measurement results of radioxenon and the ATM analysis results.
Yamamoto, Yoichi; Kijima, Yuichi; Tomita, Yutaka
no journal, ,
Radionuclide monitoring is the only way to judge whether the target explosion event was a nuclear test. Among the radionuclides produced by the nuclear explosion, the noble gases are particularly important because they are inert and more likely to leak to the ground rather than other substances in an underground nuclear test. Only 4 radioxenon isotopes as the noble gases are monitored for the CTBT verification. It was after the first nuclear test of North Korea in October 2006, when a radioxenon monitoring system installed at the Takasaki radionuclide monitoring station in Japan and the radioxenon monitoring has been carried out since January 2007. We report on the past observation results of the radioxenon at the Takasaki radionuclide monitoring station and the characteristics of radioxenon background.
Kijima, Yuichi; Yamamoto, Yoichi; Tomita, Yutaka
no journal, ,
The Japan Atomic Energy Agency installed transportable xenon laboratories (TXLs) supporting the CTBT Organization at Horonobe, Hokkaido and Mutsu, Aomori, respectively and has been measuring radioxenon since 2018. The measurement data from these two systems is expected to contribute in better understandings of the data measured at the radionuclide monitoring station at Takasaki a part of International Monitoring System for CTBT. The analyses of estimation of emission source location by atmospheric transport modelling (ATM) were carried out to investigate the emission source of the radioxenons detected at these measuring points. We report the measurement results of radioxenons at 3 measuring points and the ATM analysis results.
