Retention of hydrogen bubbles generated from water radiolysis in carbonate slurry

Ito, Tatsuya; Nagaishi, Ryuji; Kuwano, Ryo*

Nuclear Technology, 210(8), p.1427 - 1443, 2024/08

https://doi.org/10.1080/00295450.2023.2299893

The retention of hydrogen (H) bubbles generated by water radiolysis was quantitatively studied in a high-viscous suspension of carbonate slurry consisting of a mixture of suspended solid (SS) of magnesium and calcium precipitates under strongly alkaline conditions, like the radioactive wastes discharged from the coagulation sedimentation (co-precipitation) process at the multinuclide removal equipment in the Fukushima Daiichi Nuclear Power Station. The H retention properties were evaluated in two types of carbonate slurry with different hydrophilicity: the hydrophilic "current type" and the hydrophobic "return type". Then, their properties were compared with those in another suspension of clay suspension of bentonite. From the comparison between the amounts of chemical adsorption and HO in the slurry, it was confirmed that HO molecules must be shared among the SS particles, and this sharing formed the structural viscosity in the slurry, different from that in the clay suspension where electrostatic bonding between the fine clay minerals forms the viscosity. The retention of H bubbles in (by) the slurry was evaluated from the difference in the amount of H observed with and without stirring the slurry after Co -irradiation. From the comparison of the retention properties of the hydrophilic slurry, the hydrophobic slurry, the clay suspension, and treated water, it was suggested that H2 bubbles were retained not only by the structural viscosity but also by the steric hindrance in the hydrophilic slurry.

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.

Preparation of carbonate slurry simulating chemical composition of slurry in overflowed high integrity container and evaluation of its characteristics

Horita, Takuma; Yamagishi, Isao; Nagaishi, Ryuji; Kashiwaya, Ryunosuke*

JAEA-Technology 2021-012, 34 Pages, 2021/07

JAEA-Technology-2021-012.pdf:2.1MB
JAEA-Technology-2021-012(errata).pdf:0.18MB

Waste mainly consisting of carbonate precipitates (carbonate slurry) from the Advanced Liquid Processing System (ALPS) and the improved ALPS at the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Holdings, Inc. have been storing in the High Integrity Container (HIC). The supernatant solution of carbonate slurry contained in some of HICs were overflowed in April of 2015. The all of level of liquid in the HICs were investigated; however, almost of the HICs were under the level of overflow. The mechanism of overflow suggested to be depending on the difference of the properties of the carbonate slurry such as the retention/release characteristics of the bubbles. Therefore, in order to clarify the mechanism of leakage, the repeatability experiment was carried out by using simulated carbonate slurry. The simulated carbonate slurry was perpetrated by using the same cross-flow filter system of the actual ALPS. Moreover, the preparative conditions for the simulated carbonate slurry were the same as Mg/Ca concentration ratio in inlet water of the ALPS (raw water) and the ALPS operating conditions. The chemical characteristics of simulated carbonate slurries were revealed by ICP-AES, pH meter, etc. The density of the settled slurry layer tended to increase depending on the calcium concentration in the raw water. The bubble injection test was conducted in order to investigate the bubble retention/release behavior in the simulated carbonate slurry layer. The simulated carbonate slurry with high settling density, which was generated by high calcium concentration solution was revealed to retain the injected bubbles. Since the ratio of concentration calcium and magnesium during the carbonate slurry generation is assumed to affect the retention of bubbles in the slurry layer, the information on the composition of raw water is one of important factor for overflow of HICs.

Incorporation of U, Pb and rare earth elements in calcite through crystallisation from amorphous calcium carbonate; Simple preparation of reference materials for microanalysis

Miyajima, Yusuke*; Saito, Ayaka*; Kagi, Hiroyuki*; Yokoyama, Tatsunori; Takahashi, Yoshio*; Hirata, Takafumi*

Geostandards and Geoanalytical Research, 45(1), p.189 - 205, 2021/03

https://doi.org/10.1111/ggr.12367

Uncertainty for elemental and isotopic analyses of calcite by LA-ICP-MS is largely controlled by the homogeneity of the reference materials (RMs) used for normalization and validation. In order to produce calcite RMs with homogeneous elemental and isotopic compositions, we incorporated elements including U, Pb, and rare earth elements into calcite through heat- and pressure-induced crystallization from amorphous calcium carbonate that was precipitated from element-doped reagent solution. X-ray absorption spectra showed that U was present as U(VI) in the synthesized calcite, probably with a different local structure from that of aqueous uranyl ions. The uptake rate of U by our calcite was higher in comparison to synthetic calcite of previous studies. Variations of element mass fractions in the calcite were better than 12% 2RSD, mostly within 7%. The Pb/Pb ratio in the calcite showed 1% variations, while the U/Pb ratio showed 3-24% variations depending on element mass fractions. Using the synthetic calcite as primary RMs, we could date a natural calcite RM, WC-1, with analytical uncertainty as low as 3%. The method presented can be useful to produce calcite with controlled and homogeneous element mass fractions, and is a promising alternative to natural calcite RMs for U-Pb geochronology.

Gas retention behavior of carbonate slurry under -ray irradiation

Motooka, Takafumi; Nagaishi, Ryuji; Yamagishi, Isao

QST-M-2; QST Takasaki Annual Report 2015, P. 95, 2017/03

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

We conducted ray irradiation test using simulated carbonate slurry to investigate the cause of stagnant water over the high integrity container (HIC). This test was performed at Co-60 irradiation facility in Takasaki Advanced Radiation Research Institute. We observed a rise in water level, air bubbles in the slurry, a supernatant when the carbonate slurry with 95 g/L density was irradiated by ray at a dose rate of 8.5 kGy/h. The cause of the rise in water level was regarded as the volume expansion by the gas retention of the carbonate slurry. It was suggested that the cause of stagnant water over the high integrity container might be the volume expansion by the gas retention.

Sorption behavior of thorium onto granite and its constituent minerals

Iida, Yoshihisa; Yamaguchi, Tetsuji; Tanaka, Tadao; Hemmi, Ko

Journal of Nuclear Science and Technology, 53(10), p.1573 - 1584, 2016/10

https://doi.org/10.1080/00223131.2016.1138901

The sorption behavior of thorium (Th) onto granitic rock and its major constituent were investigated by batch sorption experiments. Experiments were carried out under variable pH and carbonate concentrations. Distribution coefficients decreased with increased carbonate concentrations and showed the minimal value at pH 9-10. This sorption tendency was likely due to forming the hydroxide-carbonate complexes of Th in the solutions. The order of sorbability for Th was mica feldspar quartz = granite. The sorption behaviors of Th onto these minerals were analyzed by the triple-layer surface complexation model with the Visual Minteq computer program. The model calculations assuming the inner-sphere surface complexation of Th were able to explain the experimental results reasonably well. It was shown that the sorption behavior of Th onto granite can be explained primarily by the complexation with the surface sites of feldspar.

Influence of uranium enrichment on the etching rate of polycarbonate fission track detector containing uranium particles

Lee, C. G.; Iguchi, Kazunari; Esaka, Fumitaka; Magara, Masaaki; Sakurai, Satoshi; Watanabe, Kazuo; Usuda, Shigekazu

Nuclear Instruments and Methods in Physics Research B, 245(2), p.440 - 444, 2006/04

https://doi.org/10.1016/j.nimb.2005.11.002

The etching rates of fission track detectors made of polycarbonate containing uranium particles were measured after thermal neutron irradiation with fluence of 810 n/cm, in order to study the influence of uranium enrichment on the etching rate that was calculated from the weight loss by etching. There is a strong correlation between the etching rate of detector and the enrichment E of uranium particle: the former increases as the latter increases. Particularly, the etching rate per particle was proportional to E rather than E, which is probably due to the overlapping of fission tracks. The etching behaviors of detector revealed that the existence of two different etching rate regions, a nonlinear region in the beginning of etching process and a subsequent constant region, which was explained as the opening of fission tracks and the broadening of opened tracks, respectively.

Back-extraction of tri- and tetravalent actinides from diisodecylphosphoric acid (DIDPA) with hydrazine carbonate

Watanabe, Masayuki; Tatsugae, Ryozo*; Morita, Yasuji; Kubota, Masumitsu*

Journal of Radioanalytical and Nuclear Chemistry, 252(1), p.53 - 57, 2002/04

https://doi.org/10.1023/A:1015279519321

no abstracts in English

Solvent-washing process using butylamine in fuel reprocessing

Uchiyama, Gunzo; Fujine, Sachio; Maeda, Mitsuru

Nuclear Technology, 120(1), p.41 - 47, 1997/10

https://doi.org/10.13182/NT97-A35429

no abstracts in English

Solid-aqueous phase equilibria of uranium(VI) under ambient conditions

G.Meinrath*; ; Kimura, Takaumi; Yoshida, Zenko

Radiochimica Acta, 75(3), p.159 - 167, 1996/00

https://doi.org/10.1524/ract.1996.75.3.159

no abstracts in English