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Journal Articles

Outline of decommissioning plan of Tokai Reprocessing Plant

Okano, Masanori; Akiyama, Kazuki; Taguchi, Katsuya; Nagasato, Yoshihiko; Omori, Eiichi

Dekomisshoningu Giho, (57), p.53 - 64, 2018/03

The construction of Tokai Reprocessing Plant (TRP) was initiated in June 1971, and its hot test using spent fuel started in September 1977. Thereafter TRP had been operated to reprocess 1,140 tons of spent fuel for approximately 30 years until May 2007, according to the reprocessing contract with domestic electric power companies. JAEA announced a policy of TRP in report of JAEA reform plan published in September 2014. The policy shows that TRP will shift to a decommissioning stage by economic reasons. Based on the policy, application of approval for TRP decommissioning plan was submitted to Nuclear Regulation Authority (NRA) in June 2017. This plan provides basic guidelines such as procedures for decommissioning and specific activities for risk reduction, and implementation divisions of decommissioning, management of spent fuels and radioactive wastes, decommissioning budget, and decommissioning schedule. The process of TRP decommissioning is planned to continue for approximately 70 years until the release of controlled areas of approximately 30 facilities.

Journal Articles

Volume reduction of cesium contaminated soil by magnetic separation; Pretreatment of organic matters

Horie, Hiroki*; Yukumatsu, Kazuki*; Mishima, Fumihito*; Akiyama, Yoko*; Nishijima, Shigehiro*; Sekiyama, Tomio*; Mitsui, Seiichiro; Kato, Mitsugu

Journal of Physics; Conference Series, 871, p.012102_1 - 012102_7, 2017/07

 Percentile:100

Journal Articles

Introduction to radioactive waste; Management of radioactive waste from operation and decommissioning of nuclear and other facilities, 2; Perspective radioactive waste management

Akiyama, Kazuki; Takahashi, Masanori; Tsukamoto, Masaki*; Miyauchi, Yoshihiro*; Wada, Hiroshi*

Nippon Genshiryoku Gakkai-Shi, 56(10), p.656 - 660, 2014/10

This report shows the yield of low-level radioactive wastes and high-level radioactive wastes at the nuclear power plant and reprocessing plant, and those detailed managements are reported.

Oral presentation

Synthesis of $$^{85}$$Sr@C60 by nuclear recoil using high energy neutrons

Miyashita, Yuka*; Akiyama, Kazuhiko*; Hatsukawa, Yuichi; Chiba, Kazuki*; Tadai, Tomohiro*; Sato, Yuta*; Kubuki, Shiro*

no journal, , 

Metallofullerene is one of promising material for the drug delivery system transporting useful encapsulated atoms, such as radioisotopes, with their characteristic cage-like structure. The methods to synthesize radioactive metallofullerenes are, for example, to irradiate cold metallofullerenes by thermal neutrons in a nuclear reactor and to prepare metallofullerene by an arc discharge method using radioisotopes created by an accelerator. However, the radioactive metallofullerenes synthesized these methods are including many amount of non-radioactive carriers and radioisotopes are dispersed into not only targeted fullerene species but also various kind of other species. In this study, we tried to synthesize radioactive metallofullerenes of carrier-free and single molecular species using the nuclear recoil technique by high energy neutron irradiation.

Oral presentation

Synthesis of endohedral 85-Sr metallofullerene by nuclear recoil using high energy neutron

Miyashita, Yuka*; Akiyama, Kazuhiko*; Hatsukawa, Yuichi; Tadai, Tomohiro*; Chiba, Kazuki*; Sato, Yuta*; Kubuki, Shiro*

no journal, , 

To obtain an endohedral metallofullerenes with high specific radioactivity using nuclear recoil phenomena, many experiments have been performed so far. However, production yield of metallofullerene by nuclear recoil using high LET radiation was found to be very small because radiation damages to targeted fullerene molecule were not negligible. In order to increase the yield of radioactive metallofullerenes, it is very promising to employ the recoil of nuclear reaction by fast neutron from the viewpoint of reducing the radiation damage. In this session, we will report the synthesis of $$^{85}$$Sr@C$$_{60}$$ using nuclear recoil of $$^{86}$$Sr (n,2n) $$^{85}$$Sr reaction by 14 MeV fast neutron. Mixture of C$$_{60}$$ with strontium salts such as Sr(NO$$_{3}$$)$$_{2}$$ and SrC$$_{2}$$O$$_{4}$$ were employed for the target materials. These samples were irradiated by fast neutron in Fusion Neutronics Source at Japan Atomic Energy Agency. After the irradiation, CS$$_{2}$$, aniline, and HCl$$_{aq}$$ were passed through the irradiated samples on the filter to dissolve C$$_{60}$$, Sr@C$$_{60}$$, and strontium salts, respectively. The $$gamma$$-ray from these solutions were measured by Ge detector. As a result, about 0.75% of radioactivity was observed in the aniline solution from SrC$$_{2}$$O$$_{4}$$ sample. This result strongly suggests that Sr@C$$_{60}$$ was efficiently produced by fast neutron irradiation of SrC$$_{2}$$O$$_{4}$$/C$$_{60}$$ target.

Oral presentation

Volume reduction of contaminated soil by superconducting magnetic separation technology

Akiyama, Yoko*; Yukumatsu, Kazuki*; Horie, Hiroki*; Mishima, Fumihito*; Sekiyama, Tomio; Mitsui, Seiichiro; Kato, Mitsugu; Nishijima, Shigehiro*

no journal, , 

A large amount of the contaminated soil has been removed in the process of off-site decontamination works in Fukushima prefecture and will be stored intensively at the interim storage facilities (ISF). According to the amended JESCO Law, the National Government shall take necessary measures for the final disposal outside Fukushima within 30 years from the start of the ISF. In order to optimize final disposal of the contaminated soil outside Fukushima, development of effective treatment techniques is indispensable. In this study, we have been investigating selective separation of paramagnetic 2:1 type clay minerals, which strongly absorb and fix Cs ions, by superconducting magnetic separation on silt/clay suspension as a separation technique. We conducted magnetic separation experiments of contaminated soil in Fukushima utilizing a superconducting magnet based on results of particle trajectory simulation for various particle size.

Oral presentation

Volume reduction of cesium contaminated soil by high gradient magnetic separation using superconducting magnet

Nishijima, Shigehiro*; Yukumatsu, Kazuki*; Horie, Hiroki*; Nomura, Naoki*; Akiyama, Yoko*; Mishima, Fumihito*; Sekiyama, Tomio; Mitsui, Seiichiro; Kato, Mitsugu

no journal, , 

The amount of Cs contaminated soil originating from decontamination work after the accident of Fukushima Dai-ichi Nuclear Power Plant is estimated as large as 20 million m$$^3$$ in maximum, and its volume reduction is required to optimize final disposal of the contaminated soil outside Fukushima pref. We have proposed a new method to reduce the volume of the contaminated soil by the combination of wet classification and high gradient magnetic separation (HGMS). In this study, we have been investigating selective separation of paramagnetic 2:1 type clay minerals and mica, which strongly absorb and fix Cs ions, by superconducting magnetic separation on silt/clay suspension as a volume reduction technique. We conducted magnetic separation experiments of contaminated soil in Fukushima utilizing a superconducting magnet based on results of particle trajectory simulation for various particle size.

Oral presentation

Volume reduction of Cs contaminated soil by magnetic force control

Nishijima, Shigehiro*; Akiyama, Yoko*; Yukumatsu, Kazuki*; Horie, Hiroki*; Mishima, Fumihito*; Sekiyama, Tomio*; Mitsui, Seiichiro; Kato, Mitsugu

no journal, , 

By the Fukushima Daiichi Nuclear Power Plant accident, a large amount of soil was contaminated by radioactive Cs, and effective volume reduction techniques have been required to optimize final disposal of the contaminated soil outside Fukushima pref. We focused on the phenomenon that Cs ions are strongly adsorbed on paramagnetic 2:1 type clay minerals, and tried to separate 2:1 type clay minerals selectively by the combination of classification and magnetic separation. In this study, we conducted magnetic separation experiments of actual contaminated soil in Fukushima utilizing a superconducting magnet, based on the simulated results of 2:1 type clay minerals with each particle size. Based on the result, we proposed a new method for volume reduction of Cs contaminated soil.

Oral presentation

Decommissioning for Tokai Reprocessing Plant

Akiyama, Kazuki

no journal, , 

Tokai Reprocessing Plant (TRP) started to reprocess in September 1977, and reprocessed approximately 1,140 tons of spent fuel. TRP which finished the role will do the decommissioning for the next approximately 70 years. We will dismantle facilities while performing risk reduction. And we will perform necessary technology development for decommissioning.

Oral presentation

Decommissioning of Tokai Reprocessing Plant (TRP), 2; Approach to the decommissioning schedule

Akiyama, Kazuki; Taguchi, Katsuya; Nagasato, Yoshihiko

no journal, , 

Tokai Reprocessing Plant is the chemical plant having approximately 30 facilities. Moreover TRP has the particularity that must start the decommissioning while treating radioactive waste. Especially it is important to vitrify high radioactive waste. JAEA worked out the decommissioning schedule for TRP having these particularities. In this presentation, the basic thought of 70-years-schedule is described.

Oral presentation

Decommissioning of Tokai Reprocessing Plant (TRP), 1; Outline

Taguchi, Katsuya; Hashimoto, Kowa; Akiyama, Kazuki; Nagasato, Yoshihiko

no journal, , 

The TRP had been operated to reprocess 1,140 tons of spent-fuel for approximately 30 years until May 2007. TRP finished the role of reprocessing, and it shift to a decommissioning stage. In this presentation, particularity and challenging-issues of TRP decommissioning are presented, before report a related consideration of TRP.

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