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Tobita, Minoru*; Konda, Miki; Omori, Takeshi*; Nabatame, Tsutomu*; Onizawa, Takashi*; Kurosawa, Katsuaki*; Haraga, Tomoko; Aono, Ryuji; Mitsukai, Akina; Tsuchida, Daiki; et al.
JAEA-Data/Code 2022-007, 40 Pages, 2022/11
JAEA-Data-Code-2022-007.pdf:1.99MB
Radioactive wastes generated from nuclear research facilities in Japan Atomic Energy Agency are planning to be buried in the near surface disposal field. Therefore, it is required to establish the method to evaluate the radioactivity concentrations of radioactive wastes until the beginning of disposal. In order to contribute to this work, we collected and analyzed concrete, ash, ceramic and brick samples generated from JRR-3, JRR4 and JRTF facilities. In this report, we summarized the radioactivity concentrations of 24 radionuclides (
H, 
C, 
Cl, 
Ca, 
Co, 
Ni, 
Sr, 
Nb, 
Tc, 
Ag, 
I, 
Cs, 
Ba, 
Eu, 
Eu, 
Ho, 
U, 
U, Pu, 
Pu, 
Pu, 
Am, 
Am, 
Cm) which were obtained from radiochemical analysis of the samples in fiscal years 2020-2021.
Sanada, Yukihisa; Munakata, Masahiro; Mori, Airi; Ishizaki, Azusa; Shimada, Kazumasa; Hirouchi, Jun; Nishizawa, Yukiyasu; Urabe, Yoshimi; Nakanishi, Chika*; Yamada, Tsutomu*; et al.
JAEA-Research 2016-016, 131 Pages, 2016/10
JAEA-Research-2016-016.pdf:20.59MB
By the nuclear disaster of Fukushima Daiichi Nuclear Power Station (FDNPS), Tokyo Electric Power Company (TEPCO), caused by the East Japan earthquake and the following tsunami occurred on March 11, 2011, a large amount of radioactive materials was released from the NPS. After the nuclear disaster, airborne radiation monitoring using manned helicopter was conducted around FDNPS. In addition, background dose rate monitoring was conducted around Sendai Nuclear Power Station. These results of the aerial radiation monitoring using the manned helicopter in the fiscal 2015 were summarized in the report.
Tanigawa, Masafumi; Mukai, Yasunobu; Tobita, Hiroshi; Kurata, Noritaka*; Kobayashi, Nozomi*; Takase, Misao*; Makino, Risa; Ozu, Akira; Nakamura, Hironobu; Kurita, Tsutomu; et al.
56th Annual Meeting of the Institute of Nuclear Materials Management (INMM 2015), Vol.1, p.693 - 701, 2016/00
no abstracts in English
He Alternative Neutron Detectors (ASAS), 2; Results of ASAS measurement testTanigawa, Masafumi; Mukai, Yasunobu; Kurita, Tsutomu; Makino, Risa; Nakamura, Hironobu; Tobita, Hiroshi; Ozu, Akira; Kureta, Masatoshi; Seya, Michio
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-36-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2015/12
Against the background of the serious shortage of He gas, design and development of a new detector equipped ZnS/
B
O
ceramic scintillation neutron detectors in JAEA, with the support of the government (the Ministry of Education, Culture, Sports, Science & Technology). The design of the alternative He detector is referred from INVS (INVentory Sample assay system (HLNCC (High Level Neutron Coincidence Counter) type)) which is being used for the verification of MOX powder etc. and is named it as ASAS (Alternative Sample Assay System). In order to prove the Pu quantitative performance as an alternative technology, several measurement tests and comparison test with INVS were conducted using ASAS. In these tests, evaluation of fundamental performance (counting efficiency and die-away time) and uncertainty evaluations were implemented. As a result, although fundamental performance of ASAS was not achieved to the one of INVS, we could confirm that ASAS has almost the same Pu quantitative performance including measurement uncertainty as that of INVS.
He Alternative Neutron Detectors (ASAS), 1; Design and fabrication of ASAS detectorOzu, Akira; Tobita, Hiroshi; Kureta, Masatoshi; Tanigawa, Masafumi; Mukai, Yasunobu; Nakamichi, Hideo; Nakamura, Hironobu; Kurita, Tsutomu; Seya, Michio
Kaku Busshitsu Kanri Gakkai (INMM) Nihon Shibu Dai-36-Kai Nenji Taikai Rombunshu (Internet), 9 Pages, 2015/12
Against the background of the serious shortage of He gas, the Japan Atomic Energy Agency (JAEA) has newly developed an alternative ZnS ceramic scintillation neutron detector for the safeguards, with the support of the government (MEXT). A demonstrator of plutonium inventory sample assay system (ASAS) has been also developed as an alternative HLNCC (High Level Neutron Coincidence Counter). The results from numerical simulations using Monte-Carlo code MCNPX showed that the fundamental performances of ASAS equipped with the 24 alternative neutron detectors, such as neutron detection efficiency and die-away time, equal to or higher than those of conventional HLNCC could be obtained. Here we present the inner mechanical structure of ASAS, together with the results of the simulating design.
Nakamura, Hironobu; Mukai, Yasunobu; Tobita, Hiroshi; Nakamichi, Hideo; Ozu, Akira; Kureta, Masatoshi; Kurita, Tsutomu; Seya, Michio
Proceedings of 37th ESARDA Annual Meeting (Internet), p.45 - 53, 2015/08
JAEA conducted an R&D project to develop a new type of neutron detector using ZnS/BO ceramic scintillator (as an alternative neutron detector to He-3) with support of Japanese government. The design of the JAEAs alternative system (ASAS: Alternative Sample Assay System using ceramic scintillator tubes) refers basically to the INVS (INVentory Sample assay system) which is the passive type of neutron assay system equipped total 18 He-3 tubes and capable of measuring the small amount of Pu in the MOX powder or Pu nitrate solution in a vial for nuclear material accountancy and safeguards verification. In order to prove the alternative technology and the performance instead of He-3 detector, and to establish Pu measurement capability, JAEA developed and fabricated ASAS equipped 24 alternative ceramic scintillator tubes (which is equivalent to the same counting efficiency of INVS) and demonstrated. The demonstration activity implemented the confirmation of reproducibility about sample positioning, optimization of detector parameters, counting statistical uncertainty, stability check and figure of merit (FOM) using Cf check source and actual MOX powder in PCDF (Plutonium Conversion Development Facility). In addition, performance comparison between the current INVS and the ASAS was also implemented. In this paper, we present demonstration results with design information with Monte-Carlo simulation code (MCNP).
Iijima, Kazuki; Tomura, Tsutomu*; Tobita, Minoru*; Suzuki, Yasuyuki*
Radiochimica Acta, 98(9-11), p.729 - 736, 2010/11
Times Cited Count：5 Percentile：34.72(Chemistry, Inorganic & Nuclear)Distribution behavior of Cs and Am in the synthetic groundwater-bentonite colloids-granite ternary system was investigated. Radionuclide sorbed onto the bentonite colloids is desorbed by addition of granite, indicating that the sorption of Cs and Am onto the bentonite colloids are reversible. The sorption model based on cation exchange and surface complexation reaction considering high edge site density for bentonite colloids is applicable to explain the sorption behavior of Am and Cs in the ternary system.
Oto, Tsutomu; Kimura, Tadashi; Miyauchi, Masaru; Nemoto, Nobuaki; Tobita, Kenji; Fukasaku, Akitomi; Takahashi, Kunihiro
JAEA-Review 2010-017, 21 Pages, 2010/07
JAEA-Review-2010-017.pdf:7.68MB
An integrity investigation of a Canal Expanded Joint was carried out as one of the integrity investigation of the JMTR reactor building related facilities and components, before the repair or replacement work of the JMTR related facilities that had begun in FY2007. The Canal Expanded Joint will be used for long-term after the JMTR restart. In the integrity investigation, the visual inspection, the performance test (Surface observations, Durometer hardness test) were investigated respectively and the integrity of the Canal Expanded Joint was confirmed. In order to use the Canal Expanded Joint continuously for long-term, it is important for maintaining the integrity of the Canal Expanded Joint by the periodical maintenance and the repairing work including that has been conducted up to now.
Miyauchi, Masaru; Kimura, Tadashi; Oto, Tsutomu; Nemoto, Nobuaki; Tobita, Kenji; Fukasaku, Akitomi; Takahashi, Kunihiro
JAEA-Review 2010-008, 106 Pages, 2010/06
JAEA-Review-2010-008.pdf:8.89MB
An integrity investigation was carried out for the JMTR Concrete Structure (Vent Stack, Trench, Canal Building, Filter Bank), which was the concrete structure and would be used for the long-term after JMTR restart, before the repair or replacement work of the JMTR related facilities that had begun in FY2007. In the integrity investigation, the concrete surface deterioration, the rebound number (nondestructive strength test), compressive strength using drilled concrete core test piece, the static modules of elasticity, the carbonation depth, the reinforced bar corrosion and the chloride ion content were investigated respectively and the integrity of concrete was confirmed. After the investigation, repair works such as re-painting of the Vent Stack and Trench were carried out from the viewpoint of prevention of flaking off, floating of the painting and the thinning due to the investigation results. In order to use the JMTR concrete structure continuously for long-term, it is important for maintaining the integrity of a concrete structure by the periodical maintenance and the repairing work including the building outer-wall surface painting that has been conducted up to now.
Kimura, Tadashi; Oto, Tsutomu; Miyauchi, Masaru; Nemoto, Nobuaki; Tobita, Kenji; Fukasaku, Akitomi; Takahashi, Kunihiro
JAEA-Review 2010-001, 27 Pages, 2010/03
JAEA-Review-2010-001.pdf:18.81MB
In order to investigate an integrity of the UCL (Utility Cooling Line) elevated water tank to be used for a long term after the JMTR restart, investigation on the base of the UCL elevated tank, especially for the part which had a significant aged effect, was carried out before the refurbishment work of the JMTR related facilities which had begun in FY2007. In the integrity investigation, it was confirmed that some part of the base bolts had significant aged effects, there were no evidence of crack and false indication in the welding region though thinning were observed in some parts of the base plate and the surrounding plate. After the investigation, repair works such as re-painting of the UCL elevated water tank were carried out from the viewpoint of prevention of flaking off, floating of the painting and the thinning due to corrosion based on the investigation results. In order to maintain the integrity of the UCL elevated tank, the periodical maintenance and the repair works of the base of the UCL elevated tank are important for continuous use of it in future.
Kimura, Tadashi; Oto, Tsutomu; Miyauchi, Masaru; Nemoto, Nobuaki; Tobita, Kenji; Fukasaku, Akitomi; Takahashi, Kunihiro
JAEA-Review 2009-054, 73 Pages, 2010/03
JAEA-Review-2009-054.pdf:6.79MB
An integrity investigation was carried out for the JMTR reactor building, which was the concrete structure and would be used for the long-term after JMTR restart, before the repair or replacement work of the JMTR related facilities that had begun in FY2007. In the integrity investigation, the concrete surface deterioration, the rebound number (nondestructive strength test), compressive strength using drilled concrete core test piece, the static modules of elasticity, the carbonation depth, the reinforced bar corrosion and the chloride ion content were investigated respectively and the integrity of concrete was confirmed. In order to use the JMTR reactor building continuously for long-term, it is important for maintaining the integrity of a concrete structure by the periodical maintenance and the repairing work including the building outer-wall surface painting that has been conducted up to now.
Ebisawa, Hiroyuki; Hanakawa, Hiroki; Asano, Norikazu; Kusunoki, Hidehiko; Yanai, Tomohiro; Sato, Shinichi; Miyauchi, Masaru; Oto, Tsutomu; Kimura, Tadashi; Kawamata, Takanori; et al.
JAEA-Technology 2009-030, 165 Pages, 2009/07
JAEA-Technology-2009-030.pdf:69.18MB
The condition of facilities and machinery used continuously were investigated before the renewal work of JMTR on FY 2007. The subjects of investigation were reactor building, primary cooling system tanks, secondary cooling system piping and tower, emergency generator and so on. As the result, it was confirmed that some facilities and machinery were necessary to repair and others were used continuously for long term by maintaining on the long-term maintenance plan. JMTR is planed to renew by the result of this investigation.
Ueta, Shohei; Tobita, Tsutomu*; Sawa, Kazuhiro; Tomimoto, Hiroshi; Kozawa, Takayuki; Inoi, Hiroyuki; Umeda, Masayuki
JAEA-Research 2008-096, 34 Pages, 2009/01
JAEA-Research-2008-096.pdf:10.12MB
The temperature monitors for fuel blocks in high temperature gas reactors during operation are being developed. The temperature monitors consist of alloy wires, with various melting points, sealed in quarts capsules. The temperature can be evaluated in the range from 600 to 1400 
C with 22 types of the temperature monitors. The temperature monitors have been irradiated by the capsule in JMTR, and then, PIEs such as X-ray radiograph and EPMA have been carried out. As the results of the PIE, it was estimated that the temperature monitors can be used up to 90 days at 1100 C, or up to 50 days at 1300
1350 C.
Konomura, Mamoru; Ogawa, Takashi; Okano, Yasushi; Yamaguchi, Hiroyuki; Murakami, Tsutomu; Takaki, Naoyuki; Nishiguchi, Youhei; Sugino, Kazuteru; Naganuma, Masayuki; Hishida, Masahiko; et al.
JNC TN9400 2004-035, 2071 Pages, 2004/06
JNC-TN9400-2004-035.pdf:76.42MB
The attractive concepts for Sodium-, lead-bismuth-, helium- and water-cooled FBRs have been created through using typical plant features and employing advanced technologies. Efforts on evaluating technological prospects of feasibility have been paid for these concepts. Also, it was comfirmed if these concepts satisfy design requierments of capability and performance presumed in the feasibilty study on commertialization of Fast Breeder Reactor Systems. As results, it was concluded that the selection of sodium-cooled reactor was most rational for practical use of FBR technologies in 2015.
Ueta, Shohei; Emori, Koichi; Tobita, Tsutomu*; Takahashi, Masashi*; Kuroha, Misao; Ishii, Taro*; Sawa, Kazuhiro
JAERI-Research 2003-025, 59 Pages, 2003/11
JAERI-Research-2003-025.pdf:2.53MB
In the safety design requirements for the High Temperature Engineering Test Reactor (HTTR) fuel, it is determined that "the as-fabricated failure fraction shall be less than 0.2%" and "the additional failure fraction shall be small through the full service period". Therefore the failure fraction should be quantitatively evaluated during the HTTR operation. In order to measure the primary coolant activity, primary coolant radioactivity signals the in safety protection system, the fuel failure detection (FFD) system and the primary coolant sampling system are provided in the HTTR. The fuel and fission product behavior was evaluated based on measured data in the rise-to-power tests (1) to (4). The measured fractional releases are constant at 2
10
up to 60% of the reactor power, and then increase to 710 at full power operation. The prediction shows good agreement with the measured value. These results showed that the release mechanism varied from recoil to diffusion of the generated fission gas from the contaminated uranium in the fuel compact matrix.
Sawa, Kazuhiro; Tobita, Tsutomu*
Nuclear Technology, 142(3), p.250 - 259, 2003/06
Times Cited Count：13 Percentile：63.76(Nuclear Science & Technology)The maximum burnup of the first-loading fuel of the HTTR is limited to 3.6%FIMA to certify its integrity during the operation. In order to investigate fuel behavior under extended burnup condition, irradiation tests were performed. The thickness of buffer and SiC layers of the irradiated fuel particles were increased to keep their integrity up to over 5%FIMA. The fuel compacts were irradiated in independent capsules at the HFIR of ORNL, and at the JMTR of JAERI, respectively. The comparison of measured and calculated (R/B)s showed that additional failures occurred in both irradiation tests. A pressure vessel failure model analysis showed that no tensile stresses acted on the SiC layers even at the end of irradiation and no pressure vessel failure occurred in the intact particles. The presumed failure mechanisms are additional through-coatings failure of as-fabricated SiC-failed particles or an excessive increase of internal pressure by the accelerated irradiation. The further study is needed to clarify the failure mechanism.
Ueta, Shohei; Tobita, Tsutomu*; Ino, Hiroichi*; Takahashi, Masashi*; Sawa, Kazuhiro
JAERI-Tech 2002-085, 41 Pages, 2002/11
JAERI-Tech-2002-085.pdf:2.66MB
no abstracts in English
-energy analysis system for fuel and fission gas behavior during High Temperature Engineering Test Reactor operationUeta, Shohei; Tobita, Tsutomu*; Takahashi, Masashi*; Sawa, Kazuhiro
JAERI-Tech 2002-055, 24 Pages, 2002/07
JAERI-Tech-2002-055.pdf:1.04MB
no abstracts in English
Sawa, Kazuhiro; Sumita, Junya; Ueta, Shohei; Takahashi, Masashi; Tobita, Tsutomu*; Hayashi, Kimio; Saito, Takashi; Suzuki, Shuichi*; Yoshimuta, Shigeharu*; Kato, Shigeru*
JAERI-Research 2002-012, 39 Pages, 2002/06
JAERI-Research-2002-012.pdf:3.12MB
no abstracts in English
Ino, Hiroichi*; Ueta, Shohei; Suzuki, Hiroshi; Tobita, Tsutomu*; Sawa, Kazuhiro
JAERI-Tech 2001-083, 46 Pages, 2002/01
JAERI-Tech-2001-083.pdf:6.31MB
no abstracts in English
