Controlled release of radioactive krypton gas

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 7.110 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.

Plutonium concentration conditioning method of dissolution liquor in reprocessing of MOX fuel of Fugen reactor

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.

Reinforcement of safety measures for the earthquake disaster of the Tokai Reprocessing Plant

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.

Dissolution test on the sludge of the dissolver

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 ZrMoO(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.

Studies on krypton immobilization technology using ion-implantation and sputtering process; Parametric study of electrode geometry of enlarged krypton gas immobilizing chamber

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.