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Journal Articles

Decomposition behavior of gaseous ruthenium tetroxide under atmospheric conditions assuming evaporation to dryness accident of high-level liquid waste

Yoshida, Naoki; Ono, Takuya; Yoshida, Ryoichiro; Amano, Yuki; Abe, Hitoshi

Journal of Nuclear Science and Technology, 57(11), p.1256 - 1264, 2020/11

https://doi.org/10.1080/00223131.2020.1780991

Times Cited Count：8 Percentile：71.58(Nuclear Science & Technology)

Emphasis has been placed on the behavior of ruthenium (Ru) in the evaporation to dryness accident due to the loss of cooling functions (EDLCF) of high-level liquid waste in fuel reprocessing plants. It is because Ru would form volatile compounds such as ruthenium tetroxide (RuO $_{4}$ ) and could be released into the environment with other coexisting gasses such as nitric acid (HNO $_{3}$ ), water (H $_{2}$ O). To contribute to the safety evaluation of this accident, we experimentally evaluated the decomposition and chemical change behavior of the gaseous RuO $_{4}$ (RuO $_{4}$ (g)) under the various atmospheric conditions: temperature and composition of coexisting gasses. As a result, the behavior of the RuO $_{4}$ (g) was diverse depending on the atmospheric conditions. In the experiments with the dry air or H $_{2}$ O vapor, decomposition of RuO $_{4}$ (g) was observed. In the experiment with the mixed gas which containing HNO $_{3}$ , almost no decomposition of the RuO $_{4}$ (g) was observed, and chemical form of the RuO $_{4}$ (g) was retained.

Journal Articles

Research development of separation for nuclear fuel reprocessing and reduction of hazardous substance in high level radioactive waste

Sasaki, Yuji

Kagaku Kogaku, 84(9), p.425 - 427, 2020/09

The reduction of waste volume and hazardous substance though separation methods concerning atomic energy must be requested. As disposal methods or temporary measures, geological disposal, transmutation and interim storage are proposed. In order to perform effectively the disposal methods, the development of separation method of aimed elements is indispensable. Here, the new separation method of U and Pu from spent nuclear fuel and minor actinide separation and fission products from high level radioactive waste are explained.

JAEA Reports

Evaluation of decay heat value from high-level liquid waste; Data for safety assessment of partitioning process

Morita, Yasuji; Tsubata, Yasuhiro

JAEA-Data/Code 2019-015, 45 Pages, 2020/01

JAEA-Data-Code-2019-015.pdf:2.09MB

Decay heat from radioactive elements in high-level liquid waste (HLLW) and separated solutions in partitioning process was evaluated as a basic data for safety assessment of partitioning process. In the evaluation of HLLW from spent UO $_{2}$ fuel burned-up to 45 GWd/t in light water reactor, decay heat value from fission products decreased as the cooling period become longer but heat from actinides, Am and Cm, was almost constant until 50-year cooling. Decay heat density in solutions of Am, Cm and rare earth elements and of Am and Cm without concentration for volume reduction does not exceed the heat density of HLLW, but the concentration should be required to minimize the scale of the partitioning process. Separated solution of Am and Cm must be concentrated to convert the two elements to a solid state to make fuel for transmutation, and the decay heat density of the concentrated solution of Am and Cm is 10 times higher compared with the Pu solution of same element concentration. Higher burn-up UO $_{2}$ fuel and MOX fuel in light water reactor and minor-actinide-recycled MOX fuel in fast reactor were also considered and the evaluated decay heat was compared among the spent fuels.

Journal Articles

Effect of seawater on corrosion of SUS316L in HAW under -ray irradiation

Ambai, Hiromu; Nishizuka, Yusuke*; Sano, Yuichi; Uchida, Naoki; Iijima, Shizuka

QST-M-2; QST Takasaki Annual Report 2015, P. 90, 2017/03

https://repo.qst.go.jp/records/73804

The spent fuel stored in the storage pools at the Fukushima Daiichi Nuclear Power Plant of Tokyo Electric Power Company Holdings, Inc. is exposed with the environment containing seawater components, owing to the injection of seawater into the storage pools. Therefore, during reprocessing, it is expected that the spent fuel will be contaminated with seawater components, and the influence of seawater on reprocessing needs to be investigated. We conducted the corrosion tests of the HAW storage tanks under -ray irradiation, and revealed that no significant effect of seawater components was emerged.

Journal Articles

Development of mechanistic entrainment correlation in accident of evaporation to dryness by boiling of reprocessed high-level liquid waste

Yoshida, Kazuo

Nihon Genshiryoku Gakkai Wabun Rombunshi, 14(1), p.40 - 50, 2015/02

https://doi.org/10.3327/taesj.J14.022

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents to occur caused by the loss of cooling function at a fuel reprocessing plant. In this case, some amount of non-volatiles fission products (FPs) will be transferred in form of mists to the vapor phase in the tank, and could be released to the environment. Therefore, the quantitative estimation of transfer rate is one of the key issues in the assessment of the accident consequence. To resolve this issue, a mechanistic correlation of entrainment rate with upward vapor velocity has been developed based on the data obtained from the experiments using simulated and actual HLLW.

Journal Articles

Solvent extraction of alkaline earth metal ions by diglycolic amides from nitric acid solutions

Tachimori, Shoichi; Suzuki, Shinichi; Sasaki, Yuji; Apichaibukol, A.

Solvent Extraction and Ion Exchange, 21(5), p.707 - 715, 2003/09

https://doi.org/10.1081/SEI-120024552

Times Cited Count：48 Percentile：75.63(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

An Innovative chemical separation process (ARTIST) for treatment of spent nuclear fuel

Sasaki, Yuji; Suzuki, Shinichi; Tachimori, Shoichi*; Kimura, Takaumi

Proceedings of GLOBAL2003 Atoms for Prosperity; Updating Eisenhower's Global Vision for Nuclear Energy (CD-ROM), 4 Pages, 2003/00

no abstracts in English

JAEA Reports

Studies on actinide separation process from high-level liquid waste (Joint research)

Morita, Yasuji; Tachimori, Shoichi; Koma, Yoshikazu*; Aoshima, Atsushi*

JAERI-Research 2002-017, 20 Pages, 2002/08

JAERI-Research-2002-017.pdf:1.32MB

The present report describes the results of a joint study between Japan Nuclear Cycle Development Institute (JNC) and Japan Atomic Energy Research Institute (JAERI) on actinide separation process from high-level liquid waste. The purpose of the joint study is to point out common subjects in process development by an overall evaluation of each actinide separation process: TRUEX/SETFICS Process studied in JNC and DIDPA Extraction Process studied in JAERI. The result of the evaluation showed that both processes have common subjects to be studied in sub-processes such as treatment step for spent solvent or DTPA waste solution and solvent washing step for recycling, although the main process is different from each other. It is necessary to develop the sub-processes and to test the whole process including the sub-processes. Two essential requirements: the cost reduction and the minimization of secondary wastes, are very important in future research and development for more rational and effective actinide separation process.

JAEA Reports