Reduction of Plutonium (VI) Species in Brine.

The reduction and oxidation state stability of Pu(VI) in brine was investigated in the presence of MgO, organics, aqueous Fe&sub2+;, and iron coupons. This was an extension of long-term studies to evaluate the effects of these constituents on Pu(VI) in brine that had been stable for over two years in the absence of reducing agents under anoxic conditions. The addition of these constituents, in all cases, resulted in a net reduction of Pu(VI). That reduction, not sorption, occurred was confirmed by edge-position analysis of the XANES spectra of the Pu precipitates. Fe coupons, i.e., zero valent iron, was the most effective in reducing Pu(VI) and led to essentially complete reduction in < 200 hours. These data show that reduction, even in the presence of significant radiolysis, is the likely path for Pu(VI) when iron is present under anoxic conditions. [ABSTRACT FROM AUTHOR]