Effect of preparation conditions and storage time on characteristic and rheological properties of carbonate slurries

Kato, Tomoaki; Yamagishi, Isao

JAEA-Technology 2023-018, 53 Pages, 2023/11

JAEA-Technology-2023-018.pdf:2.6MB

In the decommissioning of Fukushima Daiichi Nuclear Power Station, radioactive carbonate slurry waste was generated using the Advanced Liquid Processing System (ALPS) pretreatment and temporarily stored in a high integrity container (HIC). In 2015, overflow of supernatant from HIC estimate as bubble retention in the carbonate slurry was discovered, increasing the need for a safety assessment of the carbonate slurry stored the HIC (HIC slurry). In this study, a carbonate slurry (simulated slurry) was prepared according to the Mg/Ca mass ratio in the ALPS inlet water of the HIC slurry which overflew the HIC. The effects of reaction time during the pretreatment process, suspended solids concentration (SS concentration), and settling time on the particle composition, morphology and rheological properties of the slurry were investigated. Evaluating the effect of reaction time and concentration process on chemical properties in slurry production, the effect of the reaction time was not confirmed in the simulated slurry that had undergone the concentration process, and slurry prepared at SS concentration of 150 g/L was composed of formless particles have a particle diameter of 0.4 m or less. We also investigate the effect of SS concentration on sedimentability, decrease in SS concentration by dilution with processing solution contributed to an increase in the initial slurry settling velocity. Furthermore, two different flow characteristics were observed depending on the settling time, suggesting that the slurry at the initial settling time has non-Bingham flow properties, whereas it changes to Bingham flow properties as the settling time becomes longer. In addition, yield stress was increased with settling time, and this yield stress was found to be exponentially proportional to the density of the slurry. These results provide knowledge to estimate the current state of HIC slurry and are expected to contribute to the safety assessment.

Application of radiation to wastewater treatment

Arai, Hidehiko

Genshiryoku Kogyo, 41(7), p.36 - 40, 1995/00

http://ci.nii.ac.jp/naid/40001073660

no abstracts in English

Characterization of sludge generated from decontamination device in Fukushima Daiichi NPS

Hinai, Hiroshi; Sato, Daisuke; Shibata, Atsuhiro; Myodo, Masato; Koma, Yoshikazu; Nomura, Kazunori

no journal, , 

We have been analyzing and characterizing the contaminated water generated in Fukushima Daiichi Nuclear Power Station (NPS) and secondary waste of the contaminated water treatment system for investigation of their waste management. As one of the contaminated water treatment system, Decontamination Device was operated from June until September 2011. The operation of this device generated secondary waste of sludge that have a high dose rate. In this device, the contaminated water was mixed with several reagents to remove some radioactive nuclides. As the result, the sludge was generated as a complex of chemically stable substances. This sludge has been stored in a concrete pit and is required to transport to another place of the site and treat for further storage. For the purposes and upcoming disposal, a small amount of the sludge was analyzed for its radioactivity, particle size distribution and others. For radiochemical analysis, the sludge was successfully dissolved into solutions and was measured for its radioactivity composition; the main nuclides were Sr-90 and Cs-137. The concentration of Sr-90 (6.6E7 [Bq/cm]) was about 10 times higher than that of Cs-137 in the sludge. And small amount of Pu-238 as alpha-ray emitting nuclide was determined. The sludge mainly contained small particles of 10 micro meter or less in diameter. The rate of sedimentation and behavior of mixing also investigated.