Colloid-facilitated plutonium transport is often found to be the dominant mechanism controlling its migration in the environment.  However, the form of Pu (intrinsic versus pseudo-colloid) and its stability is not well understood.  Accurate prediction of colloid-facilitated transport requires an understanding of the underlying mechanisms and rates that control the stability of colloidal plutonium.  In this study, we examine the stability of intrinsic Pu colloids relative to Pu-montmorillonite pseudocolloids.Dialysis membranes were used to segregate Pu intrinsic nano-colloids (2-5 nm) from montmorillonite colloids (>100 nm) and allow Pu aquo (<1 nm) species to establish equilibrium between both colloidal phases. Experiments were conducted at both room temperature and 80�C under atmospheric conditions. Using the dialysis membrane approach, we determined that Pu intrinsic nano-colloid formation is reversible, though dissolution is kinetically limited. The data suggest that Pu intrinsic nano-colloids will tend to dissolve in the presence of montmorillonite and yield Pu pseudocolloids.  The reversible nature of intrinsic colloid formation suggests that their migration may be limited. Prepared by LLNL under Contract DE-AC52-07NA27344.

Stability of plutonium colloids in the presence of montmorillonite clay at elevated temperatures-a novel approach

243rd National Meeting (2012)

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