Authors:Dong-Yong Chung, Eung-Ho Kim, Young-Joon Shin, Jae-Hyung Yoo, and Jong-Duk Kim
The formation of precipitates by hydrazine was experimentally examined in the simulated high level liquid waste (HLLW), which was composed of 9 elements (Nd, Fe, Ni, Mo, Zr, Pd, Ru, Cs, Sr). Palladium was precipitated over 90% above 0.05M of hydrazine concentration and at 2M HNO3, while all of the other elements were hardly precipitated. The elements of Pd and Zr were precipitated 93% and 70% in the simulated solution in which the concentrations of Zr and Mo were decreased from 0.069M to 3.45·10–3M and 6.9·10–3M, respectively, and the acid concentration was decreased to about 0.5M after denitration. In a Pd solution of 0.5M and 2M HNO3, the precipitation yield of Pd increased with hydrazine concentration and reached over 98% at 0.1M. The precipitation yield of Pd at 0.5M HNO3 was higher than at 2M HNO3. The Pd precipitate, formed by adding hydrazine to an acidified solution, was an amorphous compound consisting of Pd, hydrazine, nitrate and hydrate.
Authors:Dong-Yong Chung, Eung-Ho Kim, Young-Joon Shin, Jae-Hyung Yoo, Cheong-Song Choi, and Jong-Duk Kim
The decomposition rate of oxalate by hydrogen peroxide has been investigated by a KMnO4 titration method. The rate equation for decomposition of hydrogen peroxide in the aqueous phase is 1n([H2O2]/[H2O2]0)=–k1·t, where k1=0.2, for [H+]<2M, k1=0.2+0.34([H+]–2), for [H+]>2M. As the acidity increases over 2M, an acid catalysis effect appeard. The new rate equation proposed for the decomposition of oxalate by hydrogen peroxide is
The rate constant for decomposition of oxalate, k2, increased with nitric acid concentration and the effect of hydrogen ion concentration was expressed as k2=a[H+]n, where the values fora andn were a=1.54, n=0.3 at [H+]<2M, a=0.31, n=2.5 at [H+]>2M, respectively.
Authors:Kwang-Wook Kim, Jae-Won Lee, Dong-Young Chung, Eil-Hee Lee, Kweon-Ho Kang, Kune-Woo Lee, Kee-Chan Song, Myung-June Yoo, Geun-Il Park, and Jei-Kwon Moon
This work studied a way to reclaim uranium from contaminated UO2 oxide scraps as a sinterable UO2 powder for UO2 fuel pellet fabrication, which included a dissolution of the uranium oxide scraps in a carbonate solution with hydrogen peroxide
and a UO4 precipitation step. Dissolution characteristics of reduced and oxidized uranium oxides were evaluated in a carbonate solution
with hydrogen peroxide, and the UO4 precipitation were confirmed by acidification of uranyl peroxo–carbonate complex solution. An agglomerated UO4 powder obtained by the dissolution and precipitation of uranium in the carbonate solution could not be pulverized into fine
UO2 powder by the OREOX process, because of submicron-sized individual UO4 particles forming the agglomerated UO4 precipitate. The UO2 powder prepared from the UO4 precipitate could meet the UO2 powder specifications for UO2 fuel pellet fabrication by a series of steps such as dehydration of UO4 precipitate, reduction, and milling. The sinterability of the reclaimed UO2 powder for fuel pellet fabrication was improved by adding virgin UO2 powder in the reclaimed UO2 powder. A process to reclaim the contaminated uranium scraps as UO2 fuel powder using a carbonate solution was finally suggested.