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Journal Articles

Status of efforts for safeguards challenges by Ningyo-toge Uranium Enrichment Facility

Ishida, Tsuyoshi; Nakashima, Shinichi; Kondo, Shinji; Hayashibara, Kenichi; Yamada, Shigeki*; Okamoto, Ryo*; Nakamura, Hironobu

Dai-44-Kai Nihon Kaku Busshitsu Kanri Gakkai Nenji Taikai Kaigi Rombunshu (Internet), 4 Pages, 2023/11

no abstracts in English

JAEA Reports

Current status of a decommissioning project in the Enrichment Engineering Facility; Results in the second-half of the fiscal year of 2014

Matsumoto, Takashi; Takahashi, Nobuo; Hayashibara, Kenichi; Ishimori, Yuu; Mita, Yutaka; Kakiya, Hideyoshi

JAEA-Technology 2016-020, 80 Pages, 2016/11

JAEA-Technology-2016-020.pdf:17.8MB

The Enrichment Engineering Facility of the Ningyo-toge Environmental Engineering Center was constructed in order to establish the technological basis of plant engineering for uranium enrichment in Japan. Uranium enrichment tests, using natural and reprocessed uranium, were carried out from 1979 to 1989 with two types of centrifuges in the facility. According to the decommissioning plan of the facility, UF$$_{6}$$ handling equipment and supplemental equipment in these plants are intended to be dismantled by 2019 in order to make vacant spaces for future projects use, for example, inventory investigation, precipitation treatment, etc. This report shows the current state of the decommissioning project in the second-half of the fiscal year of 2014.

JAEA Reports

Stability of Uranium Complexes in Supercritical Fluids and their Effective Recovery(The joint research report about precedence basic engineering research)

Tomiyasu, Hiroshi*; Nomura, Mitsuo; Yamazaki, Hitoshi; Hayashibara, Kenichi

JNC TY6400 2004-004, 18 Pages, 2004/07

JNC-TY6400-2004-004.pdf:0.65MB

This study has been performed to establish a method to recover uranium from uranium containing NaF and CaF2 wastes without forming any secondary wastes. For this purpose the use of supercritical carbon dioxide was primarily considered. Although TBP has been generally used with supercritical carbon dioxide to extract uranium, the use of TBP was ruled out in the present study because of the formation of secondary wastes due to phosphorous oxides. Among a variety of ligands, we have choused acetylacetone as a ligand for the extraction of uranyl ion. Acetylacetone is a strong chelate ligand, which dose not gives any solid residual after vaporization. As a matter of fact, our experimental result indicates that acetylacetone is a stronger ligand for uranyl ion compared with TBP., because uranyl TBP complex is replaced by acetylacetonate resulting in the formation of acetylaetonate complex. Experiments were carried out to recover uranium from the NaF waste by use of supercritical carbon dioxide containing acetylacetone, and it was found that uranium was only partly extracted to carbon dioxide phase. This might be attributed to the strong uranium fluoride complexes and also to the distribution of uranium to the inside of NaF pellets. In order to recover uranium from the NaF waste, another method was also carried out as follows: dissolve NaF waste by hot water, then add NaOH to the solution as to form the precipitation of uranium hydrolyzed species, where uranium can be recovered at high yield using centrifugation, and finally the addition of ethanol yields the NaF powder. In conclusion, the recovery of uranium from fluoride wastes seems to be difficult by the method using supercritical carbon dioxide; however, we have established a new method to recover both uranium and NaF in high yield.

JAEA Reports

Recovery and Reuse of Uranium from Radioactive Carbon Dioxide (The joint research report about precedence basic engineering research)

Aihara, Masahiko*; Yanai, Shinjiro*; Shimazaki, Yohei*; Nomura, Mitsuo; Yamazaki, Hitoshi; Hayashibara, Kenichi

JNC TY6400 2004-003, 93 Pages, 2004/07

JNC-TY6400-2004-003.pdf:2.19MB

To run the nuclear fuel cycle safely, new treatment and disposal technologies of radioactive waste from the cycle must be developed. Super critical CO2 extraction attracts attention as a technology to recover the uranium in low level solid waste. In this paper it is proposed that use of carbonation of calcium oxide and decarbonation of calcium carbonate for the system which recovers and reuses high pressure carbon dioxide discharge form the super-critical process. Conducting the cycle reaction experiment at the high pressure of carbon dioxide with the calcium oxide absorbent, the reaction velocity analysis, the structural analysis of solid reactant, the numerical analysis of the reaction characteristic and the recover-reuse process were discussed. The rate of carbonation at about 2MPa was most rapid with the stable reaction conversion of about 0.4 through 5 cycles. In the range of these experiment conditions The solid reactant was observed consisting of about 1-10 mm particles of the aggregate of minute grains. It was found that a blockade of the void between the grains after carbonation at high pressure CO2 caused the reduction of conversion and rate of carbonation. The heat consumption of CO2 recovery for the recover-reuse system was estimated by use of the reaction analysis data.

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