Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Miura, Takatomo; Kudo, Atsunari; Koyama, Daisuke; Obu, Tomoyuki; Samoto, Hirotaka
Proceedings of 12th International Conference on Nuclear Criticality Safety (ICNC2023) (Internet), 10 Pages, 2023/10
Tokai Reprocessing Plant (TRP) had reprocessed 1,140 tons of spent fuel discharged from commercial reactors (BWR, PWR) and Advanced Thermal Reactor "Fugen" from 1977 to 2007. TRP had entered decommissioning stage in 2018. In order to reduce the risk of High Active Liquid Waste (HALW) held at the facility, the vitrification of HALW is given top priority. HALW generated from reprocessing of spent fuel contains not only fission products (FPs) but also trace amounts of uranium (U) and plutonium (Pu) within the liquid and insoluble residues (sludge). Under normal conditions, concentrations of U and Pu in HALW are very low so that it can not reach criticality. Since FPs with high neutron absorption effect coexists in HALW, even if the cooling function is lost due to serious accident and HALW evaporates to dryness, it is considered that criticality would not been reached. In order to confirm this estimation quantitatively, criticality safety evaluations were carried out for the increase of U and Pu concentrations by evaporation of HALW to the point of dryness. In this evaluation, infinite multiplication factors were calculated for each of solution system and sludge system of HALW with respect to the concentration change through evaporation to dryness. It is confirmed it could not reach criticality. The abundance ratios of U, Pu and FPs were set conservatively based on analytical data and ORIGEN calculation results. Multiplation factors for two-layer infinite slab model of solution and sludge systems of HALW were also calculated, and it was confirmed it could not reached criticality. In conclusion, the result was gaind that there could be no criticality even in the process through evaporation to dryness of HALW in TRP.
Suzuki, Kazuyuki; Hatanaka, Akira; Samoto, Hirotaka; Suwa, Toshio; Tanaka, Kosuke; Tanaka, Yukiyoshi
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 6 Pages, 2011/12
The properties of the sludge in dissolver vessels from the reprocessing of ATR-MOX and ATR-UO
fuels were investigated on the pilot-plant scale at the Tokai Reprocessing Plant (TRP). This sludge is mainly composed of platinum-group elements, zircaloy fragments, and post-precipitates from the dissolver solution. The sludge deposited on the dissolver causes difficulties such as pipe clogging. The characteristics of the sludge collected from the dissolver vessels, which affect the reprocessing operation, were revealed through chemical composition analysis using ICP-AES, and XRD. It was confirmed that the major component of the sludge was zirconium molybdate, and no significant differences between ATR-MOX and ATR-UO fuels were observed in terms of the sludge compositions. In order to gain further understanding of the properties of the sludge, the distributions of Pu and other trace elements were EPMA.
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.
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.
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
Tanigawa, Masafumi; Matsuki, Takuya; Yasuda, Takeshi; Tsutagi, Koichi; Samoto, Hirotaka; Sekine, Megumi; Suzuki, Satoshi*; Kitao, Takahiko; Nakamura, Hironobu; Isomae, Hidemi
no journal, ,
no abstracts in English
Ouchi, Masayuki; Samoto, Hirotaka; Kishi, Yoshiyuki; Isobe, Hiroyasu; Yasuda, Takeshi; Yada, Yuji; Suzuki, Shohei; Tokoro, Hayate; Kusaka, Shota; Shoji, Keita
no journal, ,
Tokai Reprocessing Plant (TRP) retained nuclear materials such as spent fuel sheared powder, plutonium solution, and uranium solution due to TRP shift to decommissioning in anticipation of resuming reprocessing. Flush-out to sequentially remove these nuclear fuel materials was required for future decommissioning of equipment. U solution was denitrified to UO
powder as the final stage of flush-out, stored in the uranium storage. We performed inspections and training, simultaneously transferring technical knowledge to young engineers. Safe and stable processing was achieved by establishing conditions that could treat lower-concentration U solution and prevent nozzle clogging. Additionally, by denitrifying the diluted U solution in the feed tank, the washing waste was significantly reduced. Through these efforts, flush-out for TRP was successfully completed.
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.
Yanagibashi, Futoshi; Nagaoka, Shinichi; Isobe, Hiroyasu; Yasuda, Takeshi; Yada, Yuji; Suzuki, Shohei; Tokoro, Hayate; Kusaka, Shota; Shoji, Keita; Samoto, Hirotaka
no journal, ,
Tokai Reprocessing Plant (TRP) retained nuclear materials, such as low-concentration Pu solution due to TRP's shift to decommissioning in anticipation of resuming reprocessing. Pu solution required disposal as Flush-out before decontamination of equipment. Considering the operational range, the processing period, and the utilization after processing, Pu solution was transferred to high-active liquid waste tanks without evaporation or MOX conversion. During transferring, there was a critical risk due to Pu polymer formation caused by increasing in liquid temperature and decreasing in acid concentration. Based on past experience, U solution was mixed before transfer, and the acid concentration of the receiving tanks was adjusted. These measures prevented Pu polymer formation, ensured critical safety, and completed the disposal of low-concentration Pu solution.
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.
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.