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Meeting Materials Science & Technology 2019
Symposium Materials Issues in Nuclear Waste Management
Presentation Title Effect of Solution Chemistry on the Release Mechanism of Iodine from Iodoapatite Waste Form in Aqueous Environments
Author(s) Zelong Zhang, Jianwei Wang
On-Site Speaker (Planned) Zelong Zhang
Abstract Scope This study investigated the release mechanism of iodine in Pb9.85(VO4)6I1.75 to evaluate its long-term chemical durability. Leaching tests were conducted in different solutions: deionized water, pH buffers, and 0.1 mol/L of NaCl, Na2CO3, Na3PO4, and Na2SO4. Typically, a sample was leached in leachant, replaced every 24-hour, under 900.5C using a semi-dynamic protocol. Solution and surface characterization show the iodine release is subjected to both diffusion and dissolution processes and is highly sensitive to the solution chemistry: 1) in pH neutral solutions, iodine release is controlled by short-term diffusion via ion-exchange and long-term dissolution; 2) in acidic and basic solutions, dissolution dominates the iodine release; 3) in ion-rich solutions, iodine release is enhanced by rapid ion-exchange and increased ionic strength. In addition, we also observed secondary phases including: Pb2V2O7 from pH 4, Pb5(VO4)3Cl from NaCl, and Pb5(VO4)3OH from pH 10. This study provides implications for long-term disposal safety of nuclear waste.

OTHER PAPERS PLANNED FOR THIS SYMPOSIUM

Aerogels with Enhanced Gas Permeability and Mechanical Strength for use as Membranes in Radioiodine Capture
Dechlorination Methods and Ceramic Waste Forms for the Immobilization of Electrorefiner Salt
Disorder and Mass Transport in Model Waste Forms
Effect of Solution Chemistry on the Release Mechanism of Iodine from Iodoapatite Waste Form in Aqueous Environments
Electrical Properties of Nuclear Glasses
Energetics and Structure of Uranium-incorporated Iron Oxides
Impact of Redox on Crystallization Behavior of Spinel Crystals in HLW Borosilicate Glasses
Investigations into Physical and Chemical Characteristics of Nuclear Waste Glass Alteration Layers
Melt-Cast Ceramic Waste Forms: Laboratory Development and Scaled Demonstrations
Modeling of Carbonation Effects in a Cementitious Waste Form under Dry Environmental Conditions
Observations of Crystal Settling Behavior in a Full-Scale HLW Melter Mock-Up
Optimization of Frit Composition for Coupled Operation of the Defense Waste Processing Facility and Salt Waste Processing Facility at the Savannah River Site
P3-69: Corrosion Test Method Evaluation for Iodine Waste Forms
P3-70: Glass Pool Flow in a Joule-Heated, Laboratory-Scale Melter
P3-71: Multi-scale Structural Response of Pyrochlore Oxides to Swift Heavy Ion Irradiation
Predicting the Density of High-Level Waste Glass Compositions
The Influence of Reducing Conditions on the Stabilization of Iodine Containing Solid Secondary Wastes
The Relationship between Zeolite Type and Glass Dissolution Rate Resumption
Thermodynamics of Zeolite Precipitation in Stage III Glass Corrosion

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