Analytical Electron Microscopy Study of Colloids from Nuclear Waste Glass Reaction
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ANALYTICAL ELECTRON MICROSCOPY STUDY OF COLLOIDS FROM NUCLEAR WASTE GLASS REACTION E.C.BUCK, J.K.BATES, J.C.CUNNANE, W.L.EBERT,
X.FENG AND D.J.WRONKIEWICZ Chemical Technology Division, Argonne National Laboratory, 11-60439 ABSTRACT
An Analytical Electron Microscopy study of colloidal particles formed during reaction of waste glass has been performed. The effect of waste glass test parameters on colloid formation is examined. Characterization of phases present in the leachate of these tests has shown that layers spalled from the glass and precipitated phases are both sources of colloids in the leachate. Elements, such as uranium, have been found to concentrate within colloidal particles in the leachate. INTRODUCTION
Secondary phases forming on the surface of reacted waste glass have been characterized by Analytical Electron Microscopy (AEM) [1,2]. Small particles such as colloids may also be identified using this instrument [3]. This paper aims to demonstrate the use of the AEM in characterizing colloidal material in the leachates of waste glass tests and provide data on the conditions necessary for the formation of stable colloids. Colloids have the potential to increase the release of radionuclides from waste materials into the environment. Most studies on nuclear waste colloids have concentrated on the adsorption of actinides on groundwater colloids or hydrolysis of actinides leading to colloid formation [4,5]. The formation of both these types of colloids will be controlled by an initial solubility-ratedetermining step [6]. However, colloidal particles produced as a direct result of the alteration of the waste glass itself (i.e., via spallation), will not be dependent on such a step. This process has been shown to occur during simulated weathering of nuclear waste glass; the particles produced have been found to adsorb americium and plutonium [7,8]. EXPERIMENTAL
Unfiltered leachates were collected from a number of different waste glass tests. A small quantity of leachate was extracted shortly after the experiment was terminated and a drop of the leachate was wicked through a 'holey' carbon grid with ethanol, in a modification to the method described by Wells and Goldberg, who recently utilized the TEM to examine sea water colloids
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