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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.
Kudo, Atsunari; Kurabayashi, Kazuaki; Yanagibashi, Futoshi; Sasaki, Shunichi; Sato, Takehiko; Fujimoto, Ikuo; Obu, Tomoyuki
Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04
The Co-processing process is the extraction process to recover Pu/U mixed product solution with given Pu/U ratio for improving of nuclear proliferation resistance. In addition, Np is also recovered with U and Pu because Np is one of minor actinides and a long-lived radionuclide and Np has the extractability into TBP solvent. Development of its flowsheet achieves to decrease environmental effect of waste materials. The orientation of development about Co-processing process is to demonstrate of reprocessing the future spent fuels from a LWR, a LWR-MOX hybrid, and a FR-MOX with one cycle. We demonstrated by use of miniature reflux-type centrifugal contactors at the partitioning unit. The test conditions of the Pu/U ratio in the loaded solvents were 1%, 3%, and 5% considering the composition of spent fuels. We used the HAN as the reductant of Np (VI) for back extraction. The results of these tests were very good. We got the prospect of U, Pu, and Np Co-processing flowsheet.
Kudo, Atsunari; Nagaoka, Shinichi; Yanagibashi, Futoshi
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Kudo, Atsunari; Yanagibashi, Futoshi; Hoshi, Takahiro; Tada, Kazuhito; Sato, Takehiko; Fujimoto, Ikuo; Obu, Tomoyuki
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Hoshi, Takahiro; Nagaoka, Shinichi; Kudo, Atsunari; Ouchi, Masayuki; Isobe, Hiroyasu; Obu, Tomoyuki; Kurabayashi, Kazuaki
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Kudo, Atsunari; Yanagibashi, Futoshi; Tada, Kazuhito; Hoshi, Takahiro; Fujimoto, Ikuo; Obu, Tomoyuki
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Kurabayashi, Kazuaki; Kudo, Atsunari; Sato, Takehiko; Tada, Kazuhito*; Obu, Tomoyuki
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We are developing Np recovery with U and Pu in co-processing process (U and Pu co-recovery) because Np is one of minor actinides and a long-lived radionuclide. It is reported the flow sheet of U, Pu and Np co-recovery we set by MIXSET-X.
Kudo, Atsunari; Kurabayashi, Kazuaki; Yanagibashi, Futoshi; Sato, Takehiko; Fujimoto, Ikuo; Obu, Tomoyuki
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no abstracts in English
Kudo, Atsunari; Nagaoka, Shinichi; Kurabayashi, Kazuaki; Yanagibashi, Futoshi; Obu, Tomoyuki
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no abstracts in English
Sato, Takehiko; Kudo, Atsunari; Takeuchi, Masayuki
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The co-processing is a process with high resistance to nuclear proliferation that improves the PUREX process and performs co-recovery with Pu always accompanied by U. In order to improve the decontamination performance of fission products in its decontamination section, the extraction behavior of Tc coexistent with Pu was surveyed.