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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.
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Nuclear Safeguards Technology 1986,Vol.1, p.341 - 352, 1987/00
no abstracts in English
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Nuclear Safeguards Technology,Vol.1, p.499 - 512, 1983/00
no abstracts in English
Sato, Fuminori; Horiguchi, Kenichi; Yamashita, Masaaki; Kojima, Junji
no journal, ,
no abstracts in English
Yamashita, Masaaki; Sato, Fuminori; Horiguchi, Kenichi; Kojima, Junji; Sakai, Etsuo*; Atarashi, Daiki*; Kadota, Hirofumi*
no journal, ,
no abstracts in English
Yamamoto, Masahiko
no journal, ,
The 9th UK-Japan Nuclear Industry Forum, hosted by UK Department for Business and Trade and the British Embassy in Japan, and supported by British Market Council, UK Nuclear Industry Association and the Japan Atomic Industrial Forum (JAIF), will be held at the Residence of the British Ambassador to Japan. In this forum, the current decommissioning status of the Tokai Reprocessing Plant will be presented.
Sano, Kyohei; Tameta, Yuito; Yamamoto, Masahiko; Akiyama, Kazuki
no journal, ,
In the HASWS decommissioning project, remotely operated vehicle(ROV) with UK field experience and lifters are considered for waste retrieval from wet cells. The previous tests revealed that identifying the ROV's umbilical via the operating camera installed at the cell was difficult in low-light conditions. To address this, new auxiliary lights were installed near the camera, and improved tools -including enhanced umbilical management systems and waste-grasping devices, and hook-were tested in a simulated environment. The added lighting significantly improved visibility, aiding cables identification. Furthermore, the upgraded tools reduced overall retrieval time, demonstrating improved safety and efficiency. The results support the applicability of the proposed system for future decommissioning operations.