Senzaki, Tatsuya; Arai, Yoichi; Yano, Kimihiko; Sato, Daisuke; Tada, Kohei; Ogi, Hiromichi*; Kawanobe, Takayuki*; Ono, Shimpei; Nakamura, Masahiro; Kitawaki, Shinichi; et al.
JAEA-Testing 2022-001, 28 Pages, 2022/05
In preparation for the decommissioning of Laboratory B of the Nuclear Fuel Cycle Engineering Laboratory, the nuclear fuel material that had been stored in the glove box for a long time was moved to the Chemical Processing Facility (CPF). This nuclear fuel material was stored with sealed by a polyvinyl chloride (PVC) bag in the storage. Since it was confirmed that the PVC bag swelled during storage, it seems that any gas was generated by radiolysis of the some components contained in the nuclear fuel material. In order to avoid breakage of the PVC bag and keep it safety for long time, we began the study on the stabilization treatment of the nuclear fuel material. First, in order to clarify the properties of nuclear fuel material, radioactivity analysis, component analysis, and thermal analysis were carried out. From the results of thermal analysis, the existence of organic matter was clarified. Then, ion exchange resin with similar thermal characteristics was selected and the thermal decomposition conditions were investigated. From the results of these analyzes and examinations, the conditions for thermal decomposition of the nuclear fuel material contained with organic matter was established. Performing a heat treatment of a small amount of nuclear fuel material in order to confirm the safety, after which the treatment amount was scaled up. It was confirmed by the weight change after the heat treatment that the nuclear fuel material contained with organic matter was completely decomposed.
Zhou, Q.*; Saito, Takumi*; Suzuki, Seiya; Yano, Kimihiko; Suzuki, Shunichi*
Journal of Nuclear Science and Technology, 58(4), p.461 - 472, 2021/04
Ikeuchi, Hirotomo; Yano, Kimihiko; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 57(6), p.704 - 718, 2020/06
To suggest efficient process of the fuel debris treatment after the retrieval from the Fukushima Daiichi Nuclear Power Plant (1F), thorough investigation is indispensable on potential source of U in the fuel debris. Estimation on the fuel debris accumulated in the reactor pressure vessel is specifically important due to its limited accessibility. The present study aims to estimate the chemical forms of U in the in-vessel fuel debris, especially in the minor phases such as metallic phases, by performing the thermodynamic calculation considering the material relocation and changing environment during the accident progression in the 1F Unit 2. Input conditions for the thermodynamic calculation such as composition, temperature, and oxygen amount were assumed mainly based on the results of severe accident analysis. The chemical form of U varied depending on the local amount of Fe and O. In regions of low steel content, the U-containing metallic phase was dominated by -(Zr,U)(O), while regions of high steel content were dominated by Fe(Zr,U) (Laves phase). A few percent of U was transferred to the metallic phases under reducing conditions, raising challenging issues on the chemical removal of nuclear material from fuel debris.
Kitagaki, Toru; Ikeuchi, Hirotomo; Yano, Kimihiko; Brissonneau, L.*; Tormos, B.*; Domenger, R.*; Roger, J.*; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 56(9-10), p.902 - 914, 2019/09
Yano, Kimihiko; Kitagaki, Toru; Washiya, Tadahiro; Miyamoto, Yasuaki; Ogawa, Toru
Progress in Nuclear Science and Technology (Internet), 5, p.225 - 228, 2018/11
According to the roadmap for decommissioning of Fukushima Daiichi NPS, fuel debris retrieval will start from 2021, after a decade from fuel debris generation. Fuel debris will stay in the reactors until the end of defueling. In addition, it is not hard to anticipate that storage is necessary for fuel debris removed from reactors. In order to consider such a post-accident operation for fuel debris, it is indispensable to discuss the states and characteristics of fuel debris during several decades. Therefore, JAEA directed R&D strategy on mid- and long-term behavior of fuel debris tentatively and is making a start of fundamental studies on this issue in corporation with the domestic universities and other research institutes.
Kitagaki, Toru; Ikeuchi, Hirotomo; Yano, Kimihiko; Ogino, Hideki; Haquet, J.-F.*; Brissonneau, L.*; Tormos, B.*; Piluso, P.*; Washiya, Tadahiro
Progress in Nuclear Science and Technology (Internet), 5, p.217 - 220, 2018/11
Kitagaki, Toru; Yano, Kimihiko; Ogino, Hideki; Washiya, Tadahiro
Journal of Nuclear Materials, 486, p.206 - 215, 2017/04
Takeuchi, Masayuki; Yano, Kimihiko; Shibata, Atsuhiro; Sambommatsu, Yuji*; Nakamura, Kazuhito*; Chikazawa, Takahiro*; Hirasawa, Izumi*
Journal of Nuclear Science and Technology, 53(4), p.521 - 528, 2016/04
Hoshino, Takanori; Kitagaki, Toru; Yano, Kimihiko; Okamura, Nobuo; Ohara, Hiroshi*; Fukasawa, Tetsuo*; Koizumi, Kenji
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05
Washiya, Tadahiro; Yano, Kimihiko; Kaji, Naoya; Yamada, Seiya*; Kamiya, Masayoshi
Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 7 Pages, 2015/05
On March 11, 2011, a severe nuclear accident occurred at Tokyo Electric Power Company (TEPCO)'s Fukushima Daiichi Nuclear Power Plant (hereinafter called as F1). After the accident, the Council for the Decommissioning was established, mainly by the government and TEPCO, and a road map for the F1 decommissioning was drawn up. In the road map, the fuel debris removal from the reactors is scheduled to launch around 2020. In this study, the characteristics and technological issues of each potential treatment scenario were extracted, and the scenarios were prioritized in advance of formal evaluations in the future. The preliminary evaluation results show that long term storage and direct disposal have more positive aspects in terms of economic efficiency and radioactive waste generation. On the other hand, stabilizing processing, aqueous processing, and pyrochemical processing have been estimated to have more disadvantages in such aspects.
Ikeuchi, Hirotomo; Ishihara, Miho; Yano, Kimihiko; Kaji, Naoya; Nakajima, Yasuo; Washiya, Tadahiro
Journal of Nuclear Science and Technology, 51(7-8), p.996 - 1005, 2014/07
Ikeuchi, Hirotomo; Kondo, Yoshikazu*; Noguchi, Yoshihiro*; Yano, Kimihiko; Kaji, Naoya; Washiya, Tadahiro
Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.1349 - 1356, 2013/09
Yano, Kimihiko; Kitagaki, Toru; Ikeuchi, Hirotomo; Wakui, Ryohei; Higuchi, Hidetoshi; Kaji, Naoya; Koizumi, Kenji; Washiya, Tadahiro
Proceedings of International Nuclear Fuel Cycle Conference; Nuclear Energy at a Crossroads (GLOBAL 2013) (CD-ROM), p.1554 - 1559, 2013/09
Kitagaki, Toru; Hoshino, Takanori; Sambommatsu, Yuji; Yano, Kimihiko; Takeuchi, Masayuki; Igarashi, Takeshi*; Suzuki, Tatsuya*
Journal of Radioanalytical and Nuclear Chemistry, 296(2), p.975 - 979, 2013/05
Nakahara, Masaumi; Kaji, Naoya; Yano, Kimihiko; Shibata, Atsuhiro; Takeuchi, Masayuki; Okano, Masanori; Kuno, Takehiko
Journal of Chemical Engineering of Japan, 46(1), p.56 - 62, 2013/01
The influence of HNO concentration in the solution on the formation of CsPu(NO) was evaluated in the U crystallization process. The solubility of CsPu(NO) in a uranyl nitrate solution was found to decrease with increasing HNO concentration in the solution. In the U crystallization experiments with the dissolver solution of irradiated fast reactor fuel, CsPu(NO) formed with 6.5 mol/dm HNO concentration in the mother liquor, and the decontamination factor of Cs for the uranyl nitrate hexahydrate crystals was low. Meanwhile, CsPu(NO) did not precipitate with uranyl nitrate hexahydrate crystals under the condition of 4.0 mol/dm HNO concentration in the mother liquor, and Cs could be separated from the uranyl nitrate hexahydrate crystals.
Nakahara, Masaumi; Yano, Kimihiko; Shibata, Atsuhiro; Takeuchi, Masayuki; Okano, Masanori; Kuno, Takehiko
Procedia Chemistry, 7, p.282 - 287, 2012/00
For decontamination of Cs and Pu compound, CsPu(NO), precipitated in the U cooling crystallization method, solubility measurement of CsPu(NO) in a uranyl nitrate solution and a U crystallization experiments were carried out with the dissolver solution derived from irradiated fast neutron reactor core fuel. The solubility of CsPu(NO) in the uranyl nitrate solution decreased with decreasing temperature. In the crystallization experiments, the decontamination factors of Cs and Pu for uranyl nitrate hexahydrate crystal decrease with increasing the Cs concentration in the feed solution because CsPu(NO) formed in the course of U crystallization. Basic data were obtained for the formation behavior of CsPu(NO) in the U crystallization process.
Shibata, Atsuhiro; Yano, Kimihiko; Sambommatsu, Yuji; Nakahara, Masaumi; Takeuchi, Masayuki; Washiya, Tadahiro; Nagata, Masanobu*; Chikazawa, Takahiro*
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 6 Pages, 2011/12
JAEA has been developing a U crystallization process. The development targets were DFs of over 100, confirmation of mechanical performance of crystallizer, and so on. Fundamental data were obtained by beaker-scale experiments with actual dissolver solution. DFs for most of the FPs are improved by washing. However the formation of Pu-Cs double salt causes low DF of Cs. To confirm the mechanical performance of an annular type crystallizer and a crystal separator, some experiments were carried out. The crystallizer and the separator have good performance. However washing of UNH crystals by the separator did not have the intended effect for solid impurities. We discussed the application of crystal purification technology to improve the purity and selected KCP. UNH crystal purification tests were carried out using bench-scale KCP apparatus with simulated solid impurities. The purifier has good performance on the decontamination of not only liquid impurities but also solid impurities.
Washiya, Tadahiro; Tayama, Toshimitsu; Nakamura, Kazuhito*; Yano, Kimihiko; Shibata, Atsuhiro; Nomura, Kazunori; Chikazawa, Takahiro*; Nagata, Masanobu*; Kikuchi, Toshiaki*
Journal of Power and Energy Systems (Internet), 4(1), p.191 - 201, 2010/02
Japan Atomic Energy Agency (JAEA) and Mitsubishi Materials Corporation (MMC) are developing the crystallization process for elemental technology of FBR fuel reprocessing. The uranium (U) crystallization process is a key technology for New Extraction System for TRU Recovery (NEXT) process that was evaluated as the most promising process for future FBR reprocessing. We had developed an innovative crystallizer and fabricated an engineering-scale crystallizer and have carried out continuous operation test to investigate the stability of the equipment at steady and non-steady state conditions by using depleted uranium. As for simulating typical failure events in the crystallizer, crystal accumulation and crystal blockage were occurred intentionally, and monitoring method and resume procedure were tried and selected in this work.
Shibata, Atsuhiro; Yano, Kimihiko; Kamiya, Masayoshi; Nakamura, Kazuhito; Washiya, Tadahiro; Chikazawa, Takahiro*; Kikuchi, Toshiaki*
Nihon Genshiryoku Gakkai Wabun Rombunshi, 8(3), p.245 - 253, 2009/09
Behavior of Cs in U crystallization process of advanced aqueous reprocessing system was investigated with simulated dissolver solution. Beaker-scale U crystallization experiments were carried out with some simulated dissolver solutions. The results show that possibility of generation of CsNO,CsUO (NO) or Cs-FP complex salt is small. Precipitation experiments of Cs-U(IV) complex salts were also carried out with nitrate solution of U(IV) and Cs. It was found that Cs-U(IV) complex salt was precipitated in higher acidity than 5 mol/dm. It is suggested that Cs-Pu(IV) precipitates can be generated in the U crystallization process, under specific solution condition.