Behavior of fine particle originated from cement

Tanaka, Satoru*

JNC TJ8400 2000-003, 62 Pages, 2000/02

JNC-TJ8400-2000-003.pdf:11.88MB

For the safety assessment of radioactive waste disposal, it is important to elucidate the effect of colloids on radionuclide migration, which are released with dissolution of cementitious materials composing engineered barricr. In the previous work, we identified and characterized the colloidal particles in the solutions contacting cement hydrates, OPC and low-alkaline cement paste, and observed the release of the colloid particle. In the present work, we performed same experiments as the last year to confirm the reproducibility of the colloid release. We studied the leaching behavior of the colloid when OPC and low-alkaline cement past contact water flow. Furthermore, the effect of an alumina particle was studied, which is used as a barrier material for colloid migration. The following conclusions were derived: (1)In the solution contacting cement paste, the small amount of particles, which are considered as CaCO or silicate colloids were observed. Thus, the reproducibility of the last work was confirmed. (2)The leaching of colloid in the solution was confirmed by water flow through the cement paste. The concentration of particle was as low as 1010 mL. (3)Al0 powder, with the diameter of 200150m, was found to be effective to some extent as a barrier for a colloid migration from low-alkaline cement paste.

Effect of thorium concentration on ThO sol preparation under pH control by gaseous ammonia addition method

;

Journal of Nuclear Science and Technology, 24(9), p.748 - 758, 1987/09

https://doi.org/10.3327/jnst.24.748

no abstracts in English

Autocatalytic reaction of uranium reduction and formation of colloidal particles in a weakly acidic solution

Kitatsuji, Yoshihiro; Otobe, Haruyoshi; Kihara, Sorin*

no journal, , 

We have studied electrolytic redox behaviours of U ions under weak acidic conditions. UO is reduced to UO reversibly. The UO ion disproportionates to produce U and UO in an acid solution, and the reaction rate of the disproportionation is lower in weaker acidic solution up to pH ca. 2.1. It was found that reduction current of UO increased abruptly after the induction period of several minutes. Acceleration of UO reduction coincides to adsorption of reduction product on the electrode surface which was observed by the electrochemical quartz crystal microbalance. As a result of electrolytic reduction of UO to U(IV), black fine particles were formed both on the surface of the electrode and in the solution. The size of the U(IV)-containing particles formed in a solution of pH 2.5 was analysed to be ca. 10 nm. The particles in the colloid solution were filtered after aging the colloidal particles, and filtrate was analysed by X-ray diffraction measurement system. Characteristic diffraction peaks of XRD pattern of the U-containing particles can be assigned to be poorly crystallized UO of fluorite structure. These facts suggest that the aggregated U(IV) work as catalyst for the electrolytic reduction and the disproportionation of UO.