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Nishino, Saki; Okada, Jumpei; Watanabe, Kazuki; Furuuchi, Yuta; Yokota, Satoru; Yada, Yuji; Kusaka, Shota; Morokado, Shiori; Nakamura, Yoshinobu
JAEA-Technology 2023-011, 39 Pages, 2023/06
JAEA-Technology-2023-011.pdf:2.51MB
Tokai Reprocessing Plant (TRP) which shifted to decommissioning phase in 2014 had nuclear fuel materials such as the spent fuel sheared powder, the diluted plutonium solution and the uranium solution in a part of the reprocessing main equipment because TRP intended to resume reprocessing operations when it suspended the operations in 2007. Therefore, we have planned to remove these nuclear materials in sequence as Flush-out before beginning the decommissioning, and conducted removal of the spent fuel sheared powder as the first stage. The spent fuel sheared powder that had accumulated in the cell of the Main Plant (MP) as a result of the spent fuel shearing process was recovered from the cell floor, the shearing machine and the distributor between April 2016 and April 2017 as part of maintenance. Removing the recovered spent fuel sheared powder was conducted between June 2022 and September 2022. In this work, the recovered powder was dissolved in nitric acid at the dissolver in a small amount in order to remove it safely and early, and the dissolved solution was sent to the highly radioactive waste storage tanks without separating uranium and plutonium. Then, the dissolved solution transfer route was rinsed with nitric acid and water. Although about 15 years had passed since previous process operations, the removing work was successfully completed without any equipment failure because of the organization of a system that combines veterans experienced the operation with young workers, careful equipment inspections, and worker education and training. Removing this powder was conducted after revising the decommissioning project and obtaining approval from the Nuclear Regulation Authority owing to operating a part of process equipment.
Watanabe, Kazuki; Kimura, Norimichi*; Okada, Jumpei; Furuuchi, Yuta; Kuwana, Hideharu*; Otani, Takehisa; Yokota, Satoru; Nakamura, Yoshinobu
JAEA-Technology 2023-010, 29 Pages, 2023/06
JAEA-Technology-2023-010.pdf:3.12MB
The Krypton Recovery Development Facility reached an intended technical target (krypton purity of over 90% and recovery rate of over 90%) by separation and rectification of krypton gas from receiving off-gas produced by the shearing and the dissolution process in the spent fuel reprocessing at the Tokai Reprocessing Plant (TRP) between 1988 and 2001. In addition, the feasibility of the technology was confirmed through immobilization test with ion-implantation in a small test vessel from 2000 to 2002, using a part of recovered krypton gas. As there were no intentions to use the remaining radioactive krypton gas in the krypton storage cylinders, we planned to release this gas by controlling the release amount from the main stack, and conducted it from February 14 to April 26, 2022. In this work, all the radioactive krypton gas in the cylinders (about 7.1
10
GBq) was released at the rate of 50 GBq/min or less lower than the maximum release rate from the main stuck stipulated in safety regulations (3.710
GBq/min). Then, the equipment used in the controlled release of radioactive krypton gas and the main process (all systems, including branch pipes connected to the main process) were cleaned with nitrogen gas. Although there were delays due to weather, we were able to complete the controlled release of radioactive krypton gas by the end of April 2022, as originally targeted without any problems such as equipment failure.
Yamanaka, Atsushi; Hashimoto, Kowa; Uchida, Toyomi; Shirato, Yoji; Isozaki, Toshihiko; Nakamura, Yoshinobu
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 6 Pages, 2011/12
The Tokai Reprocessing Plant (TRP) adopted the PUREX method in 1977 and has reprocessed spent nuclear fuel of 1140 tHM (tons of heavy metals) since then. The reprocessing equipment suffers from various corrosion phenomena because of high nitric acidity, solution ion concentrations, such as uranium, plutonium, and fission products, and temperature. Therefore, considering corrosion performance in such a severe environment, stainless steels, titanium steel, and so forth were employed as corrosion resistant materials. The severity of the corrosive environment depends on the nitric acid concentration and the temperature of the solution, and uranium in the solution reportedly does not significantly affect the corrosion of stainless steels and controls the corrosion rates of titanium steel. The TRP equipment that handles uranyl nitrate solution operates at a low nitric acid concentration and has not experienced corrosion problems until now. However, there is a report that corrosion rates of some stainless steels increase in proportion to rising uranium concentrations. The equipment that handles the uranyl nitrate solution in the TRP includes the evaporators, which concentrate uranyl nitrate to a maximum concentration of about 1000 gU/L (grams of uranium per liter), and the denitrator, where uranyl nitrate is converted to UO
powder at about 320
C. These equipments are therefore required to grasp the degree of the progress of corrosion to handle high-temperature and high-concentration uranyl nitrate. The evaluation of this equipment on the basis of thickness measurement confirmed only minor corrosion and indicated that the equipment would be fully adequate for future operation.
Kuno, Takehiko; Nakamura, Yoshinobu; Okano, Masanori; Sato, Soichi; Watahiki, Masaru
Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 3 Pages, 2005/10
The elemental composition and amount of insoluble materials in highly active liquid waste (HALW) were measured at the Tokai Reprocessing Plant. To evaluate the composition of the insoluble material between the treatment and storage processes, samples from the evaporator and two vessels which differ in the storage period, were taken. The concentration of insoluble material evaluated by both its weight on filter paper after filtration as well as by filtration volume showed no difference for three different samples. Inductively coupled plasma atomic emission spectrometry and isotope dilution mass spectrometry were used to determine the elements in samples dissolved by sulfate fusion. Analytical data revealed that Zr and Mo were the main components of the insoluble material in three samples, but low levels of Rh, Ru and Pd were also present. These results suggest that most of insoluble material had re-precipitated from the HALW solution during the concentration process.
; ; Nakamura, Yoshinobu; ;
Proceedings of International Conference on Future Nuclear Systems (GLOBAL'97), 0 Pages, 1997/00
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; ; Nakamura, Yoshinobu; ;
Proceedings of International Conference on Future Nuclear Systems (GLOBAL'97), 0 Pages, 1997/00
None
Suzuki, Kazuyuki; Kikuchi, Hideki; Hata, Katsuro; Tanaka, Ken; Miyamoto, Masanori; Nakamura, Yoshinobu; Hayashi, Shinichiro
no journal, ,
no abstracts in English
Hata, Katsuro; Suzuki, Kazuyuki; Kikuchi, Hideki; Kogawa, Takayuki; Nakamura, Yoshinobu; Hayashi, Shinichiro
no journal, ,
no abstracts in English
Taguchi, Katsuya; Nagaoka, Shinichi; Yamanaka, Atsushi; Sato, Takehiko; Nakamura, Yoshinobu; Omori, Eiichi; Miura, Nobuyuki
no journal, ,
no abstracts in English
Suzuki, Kazuyuki; Nakamura, Yoshinobu; Hikita, Keiichi; Kogawa, Takayuki; Hayashi, Shinichiro
no journal, ,
The reprocessing plant dissolves Spent Fuels and it is a process to attract U and Pu after the removal of the Fission Products. Because dissolver is a tank with boiling nitric acid, there is it in the severe corrosion environment. Corrosion environment of the heat transfer surface is the severest. Therefore, the dissolver is made in High Chrome Nickel Steel in consideration of corrosion resistance. This paper reports a supersonic wave measurement method and corrosion rate of the dissolver.
Suzuki, Kazuyuki; Nakamura, Yoshinobu; Miyoshi, Ryuta; Sugai, Eiji; Hayashi, Shinichiro; Uchida, Toshitsugu*
no journal, ,
The pulse filter used by the dissolution and clarification process of the Tokai Reprocessing Plant uses the sintering metal powder filter. As for the sintering metal powder filter, being jammed is easy to occur by sludge. The basic examination of the sintering laminating wire mesh filter for the sintering metal powder filter was carried out.
Terunuma, Hirotaka; Shimoyamada, Tetsuya; Kogawa, Takayuki; Kikuchi, Hideki; Miyoshi, Ryuta; Yokota, Satoru; Nakamura, Yoshinobu; Hayashi, Shinichiro
no journal, ,
We have developed dissolver cleaning device which can clean up sludge inside dissolver with high pressure water spray. The device has been applied to TRP dissolvers and the sludge has been cleaned up successfully. This allowed smooth solution transfer and stable operation of the dissolvers.
Hata, Katsuro; Suzuki, Kazuyuki; Miyoshi, Ryuta; Sugai, Eiji; Hikita, Keiichi; Nakamura, Yoshinobu; Hayashi, Shinichiro
no journal, ,
The pulse filter of the clarification process used the sintered metal powder filter at Tokai reprocessing plant. It is known that the sintered metal powder filter is easy to be clogged up by sludge. Therefore, we examined the filtration performance of the sintered laminated wire mesh filter which might substitute for the sintered metal powder filter.
Shirato, Yoji; Isozaki, Toshihiko; Kishi, Yoshiyuki; Isobe, Hiroyasu; Nakamura, Yoshinobu; Uchida, Toyomi; Seno, Shigeo
no journal, ,
no abstracts in English
Isozaki, Toshihiko; Shirato, Yoji; Tsutagi, Koichi; Yoshino, Yasuyuki; Uchida, Toyomi; Nakamura, Yoshinobu
no journal, ,
no abstracts in English
Tomiyama, Masahiro; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Shirato, Yoji; Nakamura, Yoshinobu; Kinuhata, Hiroshi*; Kodama, Takashi*; Nakano, Masanao*; Tamauchi, Yoshikazu*; et al.
no journal, ,
no abstracts in English
Tsutagi, Koichi; Yoshino, Yasuyuki; Aoyama, Kazuaki; Tomiyama, Masahiro; Uchida, Toyomi; Nakamura, Yoshinobu
no journal, ,
no abstracts in English
Kinuhata, Hiroshi*; Kodama, Takashi*; Nakano, Masanao*; Tamauchi, Yoshikazu*; Matsuoka, Shingo*; Tomiyama, Masahiro; Yasuda, Takeshi; Tsutagi, Koichi; Yoshino, Yasuyuki; Shirato, Yoji; et al.
no journal, ,
no abstracts in English
Takahashi, Naoki; Nakamura, Yoshinobu; Obu, Tomoyuki; Samoto, Hirotaka; Namatame, Toshihiro; Hoshi, Takahiro; Kurabayashi, Kazuaki; Mukai, Yasunobu; Kimura, Yuichi; Kurita, Tsutomu
no journal, ,
no abstracts in English
Yokota, Satoru; Hatanaka, Akira; Fujimori, Masahito; Shimoyamada, Tetsuya; Nakamura, Yoshinobu
no journal, ,
Three batch-type dissolvers in the Tokai Reprocessing Plant are a device for dissolving spent fuel. The dissolver is composed of one slab and two barrels (stainless steel 310s). Install a fuel basket (stainless steel 304L) in the barrel and accept the sheared spent fuel to dissolve it. The insoluble fuel cladding is taken out of the barrels with the basket. The dissolution time of operation for one batch is approximately 10 hours. During dissolution operation, nitric acid was added to the dissolver into the spent fuel in the basket with water. The solution was heated with steam. Corrosion failure has occurred in the past because the dissolver is exposed to a high corrosive environment (high temperature, high acid concentration). Therefore, we carry out the periodical wall thickness measurement of the barrel by the remote control. On the other hand, the wall thickness measurement of the fuel basket was carried out only once by destructive measurement at the time of renewal in 1999. The details of the corrosion tendency of the fuel basket are unknown, and it is urgent to establish a non-destructive measurement method by remote handling. Therefore, we examined the method of wall thickness measurement of the fuel basket and established the measuring technique.