Effect of fluoride in NTS groundwaters on the aqueous speciation of U, Np, Pu, Am and Eu

Bruton, C J ; Nimz, G J

Lawrence Livermore National Laboratory

关键词: Isotopes;    Uranium;    Europium;    Neptunium;    Ambient Temperature;   

DOI  :  10.2172/15015136
RP-ID  :  UCRL-TR-210805
RP-ID  :  W-7405-ENG-48
RP-ID  :  15015136

美国|英语

来源: UNT Digital Library

【 摘 要 】

To address SNJV concerns that fluoride in Nevada Test site (NTS) groundwaters may impact radionuclide speciation and transport, NTS water quality databases were obtained and scanned for analyses with high fluoride concentrations (> 10 mg/L). The aqueous speciation of nine representative samples of these groundwaters with added trace amounts of uranium (U), neptunium (Np), plutonium (Pu), americium (Am) and europium (Eu) was then calculated with the computer code EQ3NR assuming a temperature of 25 C, using currently available thermodynamic data for these species. Under conditions where U(VI), Np(V), Pu(IV), Am(III) and Eu(III) dominate, F complexes are insignificant (<1 mole %) for U, Np, Pu and Am. Eu-F complexes may be significant in groundwaters that lack bicarbonate, possess pH values less than about 7 at ambient temperatures, or contain F in extremely high concentrations (e.g. > 50 mg/L). The objective is to evaluate the extent to which fluoride in NTS groundwaters complex U(VI), Np(V), Pu(IV), Am(III) and Eu(III). The approach used is to screen existing databases of groundwater chemistry at NTS for waters with high fluoride concentrations and calculate the extent to which fluoride complexes with the nuclides of interest in these waters.