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Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*
JAEA-Research 2023-001, 26 Pages, 2023/05
JAEA-Research-2023-001.pdf:1.61MB
An accident of evaporation to dryness by boiling of high-level radioactive liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into the atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. To resolve this issue, an analytical approach has been developed using computer simulation programs to assess the radioactive source term from those facilities. The proposed approach consists analyses with three computer programs. At first, the simulation of boiling behavior in the HLLW tank is conducted with SHAWED code. Next step, the thermal-hydraulic behavior in the facility building is simulated with MELCOR code based on the results at the first step simulation such as flowed out mixed steam flow rate, temperature and volatilized Ru from the tank. The final analysis step is carried out for estimating amount of released radioactive materials with SCHERN computer code which simulates chemical behaviors of nitric acid, nitrogen oxide and Ru based on the condition also simulated MELCOR. Series of sample simulations of the accident at a hypothetical typical facility are presented with the data transfer between those codes in this report.
Yamaguchi, Akinori*; Yokotsuka, Muneyuki*; Furuta, Masayo*; Kubota, Kazuo*; Fujine, Sachio*; Mori, Kenji*; Yoshida, Naoki; Amano, Yuki; Abe, Hitoshi
Nihon Genshiryoku Gakkai Wabun Rombunshi (Internet), 21(4), p.173 - 182, 2022/09
Risk information obtained from probabilistic risk assessment (PRA) can be used to evaluate the effectiveness of measures against severe accidents in nuclear facilities. The PRA methods used for reprocessing facilities are considered immature compared to those for nuclear power plants, and to make the methods mature, reducing the uncertainty of accident scenarios becomes crucial. In this paper, we summarized the results of literature survey on the event progression of evaporation to dryness caused by boiling of high-level liquid waste (HLLW) which is a severe accident in reprocessing facilities and migration behavior of associated radioactive materials. Since one of the important characteristics of Ru is its tendency to form volatile compounds over the course of the event progression, the migration behavior of Ru is categorized into four stages based on temperature. Although no Ru has been released in the waste in the high temperature region, other volatile elements such as Cs could be released. Sufficient experimental data, however, have not been obtained yet. It is, therefore, necessary to further clarify the migration behavior of radioactive materials that predominantly depends on temperature in this region.
Do, V. K.; Yamamoto, Masahiko; Taguchi, Shigeo; Takamura, Yuzuru*; Surugaya, Naoki; Kuno, Takehiko
Talanta, 183, p.283 - 289, 2018/06
Times Cited Count：10 Percentile：39.53(Chemistry, Analytical)We develop a novel analytical method employing liquid electrode plasma optical emission spectrometry for measurement of total cesium in highly active liquid wastes. Limit of detection and limit of quantification are 0.005 mg/L and 0.02 mg/L, respectively. The method is validated and applied to the real samples.
Morita, Yasuji; Asakura, Toshihide; Mineo, Hideaki; Hotoku, Shinobu; Uchiyama, Gunzo
JAERI-Conf 2005-007, p.25 - 30, 2005/08
Researches on process safety of reprocessing, development of an advanced reprocessing and partitioning of high-level liquid waste(HLLW) have been conducted in NUCEF - BECKY (Back-end Fuel Cycle Key Elements Research Facility), which has alpha-gamma concrete cells and many glove-boxes. This paper presents 10 year accomplishment of the above researches and future activities to be conducted in the field of separation process development.
Yamaguchi, Isoo*; Suzuki, Shinichi; Sasaki, Yuji; Yamagishi, Isao; Matsumura, Tatsuro; Kimura, Takaumi
JAERI-Tech 2005-037, 56 Pages, 2005/07
JAERI-Tech-2005-037.pdf:2.31MB
For the development of the reprocessing of spent nuclear fuels, the solvent extraction using the mixer-settler equipment is greatly available. This method has the advantages of the treatment of the large mass of materials and continuous operations. In case of the application of the mixer-settler devise, the precise calculation using the distribution ratio of metals in order to determine the metal concentration at each stage is indispensable. This calculation is performed in the development of ARTIST process. The metal concentration in each stage of ARTIST process is calculated by the simulation using excel software equipped with counter-current equations. This method is not taken into consideration of the change of acid concentration, therefore, we developed the new method to calculate the metal concentration even after acidity change. This method can calculate not only the metal concentration at each extraction step but also at each stage of mixer-settler. Using this calculation, we evaluated the optimum condition of solvent extraction in ARTIST process.
