Colloidal Plutonium at the OU 7-13/14 Subsurface Disposal Area: Estimate of Inventory and Transport Properties

This document reports an estimate of the fraction of plutonium buried at the Subsurface Disposal Area likely to be in the form of particulate Pu02 and provides an estimate of the size distribution of the particulates to quantify the amount of colloidal plutonium. As a colloid, particulate Pu02 could be transported more rapidly than soluble species of plutonium and therefore must be considered in evaluating the potential for groundwater contamination by plutonium. An estimated 3.7 % (41.9 kg) of plutonium from Rocky Flats Plant shipments are in a particle-size range of less than 1 pm and could migrate as colloids. Evaluation of the statistical uncertainties provides a 95 % upper confidence-limit estimate of 4.9 % (55.5 kg) of colloid-size plutonium. This report summarizes a review of current literature on colloidal transport to provide an analysis of the potential for colloidal Pu02 to be mobilized by infiltrating water under the geochemical and hydrological conditions expected at th