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Semi-dynamic leach testing of densified silicon-based iodine waste forms
Amanda R Lawter1, Gemma G Clark1, Nancy Escobedo1
1Pacific Northwest National Laboratory (PNNL) 902 Battelle Boulevard, P.O. Box 999, MSIN P7-54 Richland WA 99352 USA matthew.asmussen@pnnl.gov +1 (509) 371-7223.
RSC Advances
|April 20, 2026
Summary
Nuclear waste iodine immobilization requires understanding iodine waste form (IWF) corrosion. This study tested IWF corrosion resistance, finding that processing methods and conditions like temperature and pH significantly impact iodine release rates for better disposal models.
Area of Science:
- Materials Science
- Nuclear Engineering
- Environmental Science
Background:
- Iodine immobilization in iodine waste forms (IWFs) is critical for nuclear waste disposal.
- A conceptual corrosion release model (CCRM) is needed to predict iodine release rates.
Purpose of the Study:
- To assess the corrosion resistance of different IWFs.
- To identify key parameters influencing IWF corrosion and iodine release for CCRM development.
Main Methods:
- Semi-dynamic leach tests on monolithic IWFs (silver-mordenite and silica aerogels) under varied conditions (temperature, pH, leachant replacement, etc.).
- Evaluation of hot isostatic pressing (HIP) and spark plasma sintering (SPS) processing effects on IWF stability.
Main Results:
- Spark plasma sintering (SPS) processed silica aerogels showed superior iodine retention compared to hot isostatic pressing (HIP) processed ones.
- Iodine dissolution rates decreased with lower temperatures, extended test times, and potentially with a common ion effect if leachant is not replaced.
- Corrosion susceptibility of silver-mordenite was influenced by HIP processing temperature and pressure.
Conclusions:
- Processing methods (SPS vs. HIP) and environmental conditions (temperature, pH, leachant replacement) significantly affect IWF performance.
- These findings provide crucial data for parameterizing a CCRM for nuclear waste repositories.
- Optimizing IWF processing and understanding environmental interactions are key for safe long-term iodine disposal.
