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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.
Samoto, Hirotaka; Kimura, Norimichi; Otani, Takehisa; Sugai, Eiji; Hayashi, Shinichiro
Proceedings of International Conference on Advanced Nuclear Fuel Cycle; Sustainable Options & Industrial Perspectives (Global 2009) (CD-ROM), p.458 - 463, 2009/09
JAEA has been developing technology to immobilize radioactive krypton gas to metal alloy by ion-implantation method as a stable storage technique of krypton gas recovered from a reprocessing plant. The characteristics of implantation of krypton gas and of krypton implanted alloy were investigated by the cold test performed so far. In this paper, we report the results of the hot immobilization test performed at the Krypton Recovery development Facility (hereafter called KRF) which is attached to the Tokai Reprocessing Plant (hereafter called TRP). In this test, we immobilized the radioactive krypton gas recovered from TRP by cryogenic distillation process of KRF and investigated the gas retention characteristics of the implanted alloy.
Samoto, Hirotaka; Kimura, Norimichi; Otani, Takehisa; Sugai, Eiji; Takahashi, Makoto; Hayashi, Shinichiro; Akutsu, Tomoyuki*
no journal, ,
Krypton is immobilized to metal alloy by ion-implantation and sputtering process. The retention characteristic of immobilized radioactive Kr with different storage temperature of the metal alloy is reported.
Sugai, Eiji; Terunuma, Hirotaka; Otani, Takehisa; Hikita, Keiichi; Hatanaka, Akira; Samoto, Hirotaka; Okano, Masanori; Hayashi, Shinichiro
no journal, ,
A dissolution test of the sludge gathered from the dissolver of Tokai Reprocessing Plant (TRP) was performed for the purpose of eliminating of the sludge, which deposited in the dissolver and clogged pipes equipped in the dissolver. In the result, the sludge consisted primarily of ZrMo
O
(OH)(HO) and was possible to eliminate at the rate of about 80% by using NaOH and HNO
reagent which was commonly-used in the PUREX process. From this experimental result, it is thought that the method of using NaOH and HNO reagent is effective method for the elimination of the sludge which deposited in the dissolver.
Kikuchi, Hideki; Suzuki, Kazuyuki; Sugai, Eiji; Hikita, Keiichi; Otani, Takehisa; Samoto, Hirotaka; Hayashi, Shinichiro
no journal, ,
About 6t the Fugen MOX type B fuels, whose Pu content rate is about 1.7%, were reprocessed on Tokai Reprosessing Plant(TRP) to the present. It was required to control plutonium(Pu) concentration of dissolution liquor because of the higher Pu content of the MOX fuels. There operational method to control Pu concentration by dilution has be established. And the amount of Pu, which was transferred to the highly radioactive liquid waste system with the residue from the clarification process, was investigated.
Sugai, Eiji; Kikuchi, Hideki; Hatanaka, Akira; Otani, Takehisa; Suzuki, Kazuyuki; Taguchi, Katsuya
no journal, ,
no abstracts in English
Otani, Takehisa; Suzuki, Kazuyuki; Hata, Katsuro; Kikuchi, Hideki; Nakamura, Daishi; Samoto, Hirotaka; Tanaka, Yukiyoshi
no journal, ,
The investigation of the behavior of krypton gas arising due to reprocessing of spent fuels has been performed at TRP. The whole amount of Kr gas transfers to the off-gas system through shearing and dissolution process, so it is applicable as an indicator to determine the progress of fuel dissolution. It is thought that the behavior of gaseous fission product, including Kr, in the spent fuels depends on burn-up and the type of spent fuels. In the reprocessing process, these deference are reflected to the migration rate of krypton gas between shearing off-gas system (SOG) and dissolver off-gas system (DOG). At TRP, four types of spent fuels (LWR; PWR, BWR and ATR; UO, MOX) were treated and examined about their release characteristics of krypton gas in order to understand the effect on burn-up and type of spent fuels. In this report, the results concerning the ATR-UO fuel and ATR-MOX fuel are discussed compared with the results of LWR fuel.
Otani, Takehisa; Takahashi, Makoto; Akutsu, Tomoyuki*; Kimura, Norimichi; Tanaka, Yukiyoshi
no journal, ,
Optimum geometry of electrodes, which were equipped at the top and bottom of the krypton gas immobilizing chamber, was investigated for improvement of the immobilizing capability with enlarged krypton gas immobilizing chamber.
Kuroda, Yasuji; Kurabayashi, Kazuaki; Otani, Takehisa; Tomiyama, Masahiro; Miura, Takatomo; Namatame, Toshihiro
no journal, ,
It was based on teachings of the Fukushima Daiichi Nuclear Power Plant accident, and the view and concrete measure against security were arranged supposing major accidents, such as all the power supply loss by the earthquake and tsunami, about decay heat removal, such as highly radioactivity waste fluid in the Tokai reprocessing facility, and plutonium solution, and the measure against hydrogen exhaust gas. Moreover, while verifying the validity of safety measures, an example of verification of the data used for safety evaluation was shown.