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<p>Understanding the long-term behavior of spent nuclear fuel is critical for safety assessments, and as new doped fuels are developed, additional data are needed to evaluate their performance under disposal conditions. This study presents results from a &gt; 4-year leaching experiment on irradiated Cr + Al-doped UO₂ (ADOPT) and standard UO₂ fragments under hydrogen overpressure in simplified groundwater. Extending previous data from the DisCo project, new samplings and post-leaching characterization are included. Concentrations of radionuclides of interest reached steady state or exhibited very low concentrations and slow release rates. Ultrafiltration confirmed colloid-associated species in the leachate. SEM-WDS revealed a ~ 10&#xa0;µm secondary phase on pre-leached fragments, enriched in oxygen and partially depleted in most radionuclides. Both fuels exhibited similar long-term behavior under reducing conditions in the presence of H<sub>2</sub>. Even when secondary phases were present initially, H<sub>2</sub> effectively suppressed matrix dissolution, as evidenced by stable radionuclide concentrations throughout the experiment.</p> Graphical abstract <p></p>

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Long-term leaching under H2 overpressure of irradiated ADOPT and UO2 fuel and post-test characterization

  • 期刊论文

  • 发表日期：

    2026年3月17日

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  • A. Barreiro-Fidalgo,
  • L. Z. Evins

摘要

Understanding the long-term behavior of spent nuclear fuel is critical for safety assessments, and as new doped fuels are developed, additional data are needed to evaluate their performance under disposal conditions. This study presents results from a > 4-year leaching experiment on irradiated Cr + Al-doped UO₂ (ADOPT) and standard UO₂ fragments under hydrogen overpressure in simplified groundwater. Extending previous data from the DisCo project, new samplings and post-leaching characterization are included. Concentrations of radionuclides of interest reached steady state or exhibited very low concentrations and slow release rates. Ultrafiltration confirmed colloid-associated species in the leachate. SEM-WDS revealed a ~ 10 µm secondary phase on pre-leached fragments, enriched in oxygen and partially depleted in most radionuclides. Both fuels exhibited similar long-term behavior under reducing conditions in the presence of H2. Even when secondary phases were present initially, H2 effectively suppressed matrix dissolution, as evidenced by stable radionuclide concentrations throughout the experiment.

Graphical abstract