Objective ALTHOUGH A MAJOR RESEARCH EFFORT HAS BEEN UNDERTAKEN DURING THE LASTDECADE ON ACQUEOUS CORROSION OF NUCLEAR GLASSES (1) (2) OUR UNDERSTANDING OF THE BASIC CORROSION MECHANISM IS ESSENTIALLY PHENOMENOLOGICAL AND MANY IMPORTANT QUESTIONS REMAIN UNANSWERED. THIS UNDERSTANDING IS INDISPENSIBLE TO ENSURE THAT THE MECHANISMS TAKEN INTO ACCOUNT IN CORROSION MODELS CORRESPOND EFFECTIVELY TO THOSE GOVERNING THE LONG TERM RELEASE OF RADIONUCLIDES. THE EXPERIMENTS PROPOSED HERE ARE PARAMETER STUDIES OF SIMPLE GLASSWATER SYSTEMS DESIGNED TO INVESTIGATE THE EFFECTS OF SATURATION, LEACHING UNDER HYDROGHERMAL CONIDITONS, CORROSION AT THE INTERFACE LAYER, AND THE BEHAVIOUR OF TECHNETIUM AND ACTINIDES. R7T7 glass solubility was investigated in experiments with monolithic and powdered glass specimens at high surface area to volume ratios. A silicon concentration limit was obtained at 90 C, and pH related variations in this limit were determined. Very low corrosion rates were obtained under saturation conditions (from a few thousandths to a few 10 thousandths of the initial rate). The observed rates were not constant, however, but diminished as the surface area to volume ratio increased. It is, therefore, impossible to define a constant residual corrosion rate as an inherent glass property, or to specify an activation energy. Experiments at higher temperatures (150 and 250 C) also resulted in a constant corrosion rate under near saturation conditions, but this residual rate was a few per cent of the initial rate, indicating that the dissolution reaction affinity was relatively high at these temperatures. Investigation of the radionuclide containment properties in Volvic water confirmed that under oxidising conditions neptunium and technetium are leached at virtually the same rate as the glass matrix, while plutonium and americium mostly remain trapped in the gel layer that develops at the glass surface. Moreover, the leached plutonium is flocculated and quickly fixed in particle form after a few weeks.R7T7 glass solubility was investigated in experiments with monolithic and powdered glass specimens at high surface area to volume ratios. A silicon concentration limit was obtained at 90 C, and pH related variations in this limit were determined. Very low corrosion rates were obtained under saturation conditions: from a few thousandths to a few ten thousandths of the initial rate. The observed rates were not constant, however, but diminished as the surface area to volume ratio increased. It is therefore impossible to define a constant residual corrosion rate as an inherent glass property, and even less to specify an activation energy. Experiments at higher temperatures (150 and 250 C) also resulted in a constant corrosion rate under near saturation conditions, but this residual rate was a few percent of the initial rate, indicating that the dissolution reaction affinity was relatively high at these temperatures. Investigation of the radionuclide containment properties in Volvic water confirmed that under oxidising conditions neptunium and technetium are leached at virtually the same rate as the glass matrix, while plutonium and americium remain for the largest part trapped in the gel layer that develops at the glass surface. Moreover, the leached plutonium is flocculated and quickly fixed in particle form after a few weeks.B1. INVESTIGATION OF THE APPARENT SOLUBILITY LIMIT OF SON 68 GLASS FOR DIFFERENT SA/V VALUES. (ARE THE STEADY-STATE CONCENTRATIONS IN SOLUTION RELATED TO THE GLASS ITSELF, TO THE GEL OR TO NEWLY FORMED CRYSTALLINE PHASES) B2. HYDROTHERMAL LEACHING AND ANALYSIS OF THE CRYSTALLINE PHASES FORMED BETWEEN 50 C AND 250 C. B3. EXAMINATION OF THE INTERFACE OR IONIZATION LAYER BETWEEN THE SURFACE LAYERS AND THE SOUND UNDERLYING GLASS. B4. DETERMINATION OF THE CONCENTRATION PROFILES IN THE SURFACE LAYERS FOR THE PRINCIPAL ACTINIDES. B5. FILTRATION STUDY OF THE PHYSICOCHEMICAL FORM IN WHICH PLUTONIUM IS FOUND IN THE LEACHATES. B6. INVESTIGATION OG TECHNETIUM BEHAVIOUR. Fields of science natural scienceschemical sciencesinorganic chemistrytransition metalsengineering and technologymaterials engineeringnatural scienceschemical sciencesinorganic chemistrymetalloidsnatural scienceschemical sciencesnuclear chemistryradiation chemistry Programme(s) FP1-RADWASTOM 3C - Research and development programme (Euratom) on the management and storage of radioactive waste, 1985-1989 Topic(s) Data not available Call for proposal Data not available Funding Scheme CSC - Cost-sharing contracts Coordinator Commissariat à l'Energie Atomique (CEA) EU contribution No data Address Centre d'Études Nucléaires de la Vallée du Rhône Cité de Marcoule 30205 Bagnols-sur-Cèze France See on map Total cost No data
