STABILITY OF PLUTONIUM(VI) IN SELECTED WIPP BRINES

The redox stability of plutonium(VI) in WIPP brine was investigated by monitoring the oxidation state as a function of time using a combinat ion of absorption spectrometry, radiochemical counting and filtration. Studies were performed with Pu-239 and Pu-238 in four WIPP brines at concentrations between 10(-3) and 10(-8) M for durations as long as tw o years. Two synthetic brines, Brine A and ERDA-6, and two brines coll ected in the WIPP underground, DH-36 and G-Seep, were used. The stabil ity of Pu(VI) depended on the brine composition and the speciation of the plutonium in that brine. When carbonate was present, a stable Pu(V I)-carbonate complex was observed. In the absence of carbonate, Pu(VI) hydrolytic species predominate. These species had a wide range of sta bility in the brines investigated. The reported results will help defi ne the speciation of plutonium in WIPP brine and its potential for mig ration.