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Journal Articles

Current status of decommissioning and waste management at the Ningyo-Toge Environmental Engineering Center

Ohashi, Yusuke; Shimaike, Masamitsu; Matsumoto, Takashi; Takahashi, Nobuo; Yokoyama, Kaoru; Morimoto, Yasuyuki

Nuclear Technology, 209(5), p.777 - 786, 2023/05

https://doi.org/10.1080/00295450.2022.2145136
 Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)

At the Ningyo-Toge Center, technical development related to uranium refining conversion and enrichment has been completed, and decommissioning of these facilities has begun. The error between the quantity of dismantled materials estimated from the facility design drawings and the actual quantity of dismantled materials was minimal when averaging over the entire Uranium Refining and Conversion Plant and Uranium Enrichment Engineering Facility, which results indicated that the preliminary estimate of the quantity of dismantled materials for decommissioning was reasonable. Most of the dismantled materials, which have no contamination history and are properly managed were able to be carried out to recyclers as non-radioactive waste (NR). In addition, the possibility of evaluating the uranium concentration of clearance level in dismantled objects was confirmed through gamma-ray measurement tests using mock-up waste.

JAEA Reports

Radiation environment account before dismantling the conversion facilities; Evaluation of the uranium inventory and air dose rate in the dismantling facilities, 2

Takahashi, Nobuo; Yokoyama, Kaoru; Morimoto, Yasuyuki; Shimaike, Masamitsu; Ikegami, Sohei; Sugitsue, Noritake

JAEA-Technology 2010-003, 92 Pages, 2010/06

JAEA-Technology-2010-003.pdf:10.76MB

At the reprocessed uranium conversion facilities, Hydration and Conversion room-1,2,3, Dehydration and Conversion room-1,2, Dry process filter room have been dismantled according to the schedule, in 2009 fiscal year. The $$gamma$$-ray measurement had been carried out before dismantlement to evaluate the radioactivity inventory. As a result, the uranium recovery work was forecasted for reasonable dismantlement. In addition, the feature nuclide affecting the results of the measurement on the air dose was evaluated. Additionally, as the waste data, $$gamma$$-ray analysis results are shown.

JAEA Reports

Radiation environment account before dismantling the conversion facilities; Evaluation of the uranium inventory and air dose rate in the dismantling facilities

Shimaike, Masamitsu; Yokoyama, Kaoru; Ikegami, Sohei; Takahashi, Nobuo; Sugitsue, Noritake

JAEA-Technology 2009-020, 55 Pages, 2009/06

JAEA-Technology-2009-020.pdf:2.0MB

At the conversion facility, 48Y homogenization treatment equipment (cylinder processing room), UO$$_{3}$$ pneumatic dispatch equipment (fluoride precipitation process room), gas trapping and filling equipment (cold trap room and UF$$_{6}$$ filling room) and the second grade UF$$_{4}$$ drying equipment (UF$$_{4}$$ feed chamber and UF$$_{4}$$ treatment room) are scheduled to be dismantled, in 2008 fiscal year. The $$gamma$$-ray measurement intended for the equipment was done before dismantlement and the radioactivity inventory was evaluated. As a result, the part that the uranium recovery had to be executed was forecast for reasonable dismantlement. Additionally, the reprocessed uranium was used at the conversion facility, so the feature nuclide affecting the air dose was evaluated. In addition, $$gamma$$-ray analysis results are organized for using as the waste data and the radionuclide distribution data in the process.

JAEA Reports

Influence evaluation of spent bed material in the conversion facilities; Evaluation of the external exposure caused by removing the spent bed material in the conversion facilities

Takahashi, Nobuo; Yokoyama, Kaoru; Ikegami, Sohei; Shimaike, Masamitsu; Sugitsue, Noritake

JAEA-Technology 2009-002, 51 Pages, 2009/03

JAEA-Technology-2009-002.pdf:5.71MB
JAEA-Technology-2009-002(errata).pdf:0.24MB

At the conversion facility, dismantlement and removal of the equipment are executed according to the decommissioning plan. The radioactivity of the spent bed material discharged along with the reprocessed uranium conversion is high. So, there is concern that the external exposure caused by the dismantlement of the spent bed material storage is high. Therefore, the uranium isotopic analysis using the $$gamma$$-ray measurement intended for the spent bed material was done, and the external exposure at site boundary was evaluated. As a result, the external exposure at site boundary is low. The external exposure caused by dismantlement work was evaluated, and the points to remember for dismantlement of the spent bed material storage are considered.

JAEA Reports

Technology development of system chemical decontamination using iodine heptafluoride gas; Evaluation of IF$$_{7}$$ treatment condition and uranium decontamination result

Ema, Akira; Yokoyama, Kaoru; Nakatsuka, Yoshiaki; Shimaike, Masamitsu; Sugitsue, Noritake

JAEA-Technology 2008-037, 50 Pages, 2008/06

JAEA-Technology-2008-037.pdf:3.15MB

In the centrifugation method uranium enrichment plant, the UF$$_{6}$$ gas was supplied for a long term. The main uranium compounds are estimated to the middle fluorides UFx(4$$leqq$$x$$leqq$$=5). This middle fluoride is changed to UF$$_{6}$$ and IF$$_{5}$$ gas again by the reaction with IF$$_{7}$$. Using this reaction, the uranium compound in the plant was decontaminated. The IF$$_{7}$$ treatment tests were executed to the plant in four treatment conditions. It is necessary to clarify the relation between IF$$_{7}$$ treatment condition and decontamination results for the best treatment condition setting. Therefore, the decontamination development is evaluated using the result of the weight measurement of recovery UF$$_{6}$$ and IF$$_{5}$$ gas, the $$gamma$$-ray measurement, and the ICP-MS analysis at the IF$$_{7}$$ treatment tests. Then the technical knowledge to clarify the decontamination characteristic features is accumulated for analyzing the treatment trend, the treatment time, decontamination level and variation of the decontamination level.

Oral presentation

Decommissioning project of uranium conversion plant, 2; Evaluation of the nuclide composition in the spent bed material and the external exposure

Takahashi, Nobuo; Shimaike, Masamitsu; Morimoto, Yasuyuki; Ikegami, Sohei; Sugitsue, Noritake

no journal, , 

no abstracts in English

Oral presentation

Decommissioning project of uranium conversion plant, 3; Evaluation of the nuclide composition in the cold trap and the external exposure

Shimaike, Masamitsu; Takahashi, Nobuo; Morimoto, Yasuyuki; Ikegami, Sohei; Sugitsue, Noritake

no journal, , 

no abstracts in English

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