Measurement of HLW glass dissolution/alteration kinetics by using micro-reactor flow-through test method
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Measurement of HLW glass dissolution/alteration kinetics by using micro-reactor flow-through test method Y.Inagaki1, S.Mitsui2, H.Makigaki1, K.Idemitsu1, T.Arima1, T.Banba3, K.Noshita4 1 Department of Applied Quantum Physics & Nuclear Engineering, Kyushu University, Japan 2 Geological Isolation Research and Development Directorate, Japan Atomic Energy Agency, Japan 3 Nuclear Safety Research Center, Japan Atomic Energy Agency, Japan 4 Energy & Environmental Systems R&D Laboratory, Hitachi, Ltd, Japan ABSTRACT A new type of flow-through test method using micro-reactor was developed and applied to measurement of the dissolution/alteration kinetics for a Japanese type of simulated HLW glass, P0798. In this test method, a face of coupon shaped glass specimen (30mm x 10mm x 4mm size) is in contact with a micro-channel (20mm length, 2mm width, 0.16mm depth) constructed on a PTFE (Teflon®) plate, and a solution is injected into the inlet of micro-channel at a constant rate. The injected solution, which flows through the micro-channel reacting with the glass to the outlet, is retrieved at certain intervals to be analyzed for determination of the glass dissolution/alteration rate. After the test, the glass specimen removed from the micro-reactor is subjected to surface analyses. This test method has major features as follows, 1) any controlled solution condition can be provided over the test duration, 2) a relatively high S/V ratio can be provided by use of micro-reactor in spite of using coupon shaped glass specimen, which results in precise and consistent analyses of both the solution and the reacted glass surface, 3) the test apparatus is simple with compact size and easy operation, which allows a flexible setup of test conditions. By use of this test method the dissolution/alteration rate for P0798 glass was measured as a function of pH, temperature, and time, and the results indicated that this test method is applicable and suitable for evaluation of the dissolution/alteration kinetics. INTRODUCTION In assessing long-term performance of high-level radioactive waste glass (HLW glass) in geological disposal environments, measurement of the glass dissolution/alteration kinetics is needed to parameterize a mechanistic model used to determine the dissolution/alteration rate as a function of key environmental variables such as the solution composition, pH, temperature, flow rate, reaction progress and time. The measurement of glass dissolution/alteration kinetics is also needed to develop a greater understanding of the glass dissolution/alteration based on fundamental principles of physics, chemistry and thermodynamics for reliable modeling [1]. For the last 30 years several test methods have been applied to measurement of the glass dissolution/alteration kinetics, and these test methods can be categorized into two types, i.e., static test method and flow-through test method. Although both types have been applied to the measurement, the flow-through test method is adequate for measurement of the dissolution/ alteration rate as
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