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Spectrophotometric investigation of U(VI) chloride complexation in the NaCl/NaClO{sub 4} system

Conference ·
OSTI ID:20015854
Post closure radioactive release scenarios from geologic salt formation, such as the WIPP (Waste Isolation Pilot Plant) (USA) include hydrologic transport of radionuclides through a chloride saturated aquifer. Consequently, the understanding of actinide solution chemistry in brines is essential for modeling requiring accurate knowledge of the interaction between AnO{sub 2}{sup 2+} and chloride ions. Complexation constants of two U(VI) chloride species UO{sub 2}Cl{sup +} and UO{sub 2}Cl{sub 2}{sup 0} have been intensively studied for about 40 years using different methods. However, large uncertainties reflect the general difficulty in determining accurate stability constants of weak complexes. In order to model the behavior of U(VI) in brines, the authors studied the formation of its chloride complexes by UV-Vis spectroscopy as a function of the NaCl concentration at 25 C. The experiments were performed at constant ionic strength by varying the concentration ratio of NaCl and NaClO{sub 4}. Deconvolution resulted in single component absorption spectrum for UO{sub 2}Cl{sup +} and UO{sub 2}Cl{sub 2}{sup 0}. The apparent stability constants of UO{sub 2}Cl{sup +} and UO{sub 2}Cl{sub 2}{sup 0} are determined at different ionic strengths. The experimental data are used to parameterize using the SIT approach.
Research Organization:
Los Alamos National Lab., NM (US)
Sponsoring Organization:
US Department of Energy
DOE Contract Number:
AC04-94AL85000
OSTI ID:
20015854
Country of Publication:
United States
Language:
English