BOND OF RADIONUCLIDES WITH THE COLLOID OF UNDERGROUND WATERS LOCATED WITHIN THE KARACHAI CONTAMINATION PLUME

Author: Novikov A.P., Kalmykov O.V., Myasoedov B.F., Ivanov I.A., Rovny S.I.

Reference: Gazette “ВОПРОСЫ РАДИАЦИОННОЙ БЕЗОПАСНОСТИ“ (Issues on radiation safety), 2009

ISSN: 1816-9643

DOI:

Keywords: radionuclides, groundwater, colloids, migration

Abstract: Outcomes of the study are presented that concern bond strength of radionuclides with colloid particles of different sizes obtained from underground waters of the Karachai contamination plume. Using the method of photon-correlation spectroscopy, it was found out that the total content of colloid in deeper horizons is an order of magnitude higher than that in near-surface horizons. At that, an average particle radius also increases with depth. The main portion of Pu, Am, and Cm is bound with colloids (40-90 %). Portions of U and Np in the composition of colloid particles are smaller (2-20 %), and this fact determines their higher migration mobility in underground waters. An insignificant number of actinides is bond with large colloids with a size from 450 nm tо 200 nm. A significant part of actinides in water occurring at a depth of 40 m and deeper is in the fraction of colloid particles with a size from 200 nm tо 50 nm. In water of these horizons not more than 30 % of Pu and Am is bound with smaller size colloids (from 10 kDa tо 50 nm). As it gets closer to the surface, a number of actinides in the fraction of nano-particles (50 nm – 10 kDa) grows up to 50 %. Using the method of selective leaching, the bond strength of actinides with the colloid of underground waters from the Karachai contamination plume was investigated. Using the alpha-track analysis, it was shown that microdistribution of alpha-emitting radionuclides in the colloid is uniform. It was demonstrated that radionuclides, which are found in the colloid of underground waters sampled from three wells with various chemical composition, are in the forms that differ in the degree of their solubility. U and Np in colloid are bound only with highly soluble and mobile groups of compounds; these radionuclides were not identified in the sparingly soluble residue. While Pu and Am are, on the contrary, found in the colloid primarily in sparingly soluble forms. Am, to a greater extent, is bound with surface organo-metallic complexes. Pu was mainly found in the fraction of amorphous oxides.

URL: http://elibrary.ru/item.asp?id=11991986

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