Development of Glass-based Nuclear Waste forms for Legacy and Future Waste Streams

Arumala  Josiah Lere-Adams

doi:10.7273/000007410

The management and long-term containment of nuclear waste remain central challenges in ensuring the sustainability of nuclear energy and mitigating its environmental impact. This doctoral research focuses on the development glass-based waste forms designed to immobilize volatile radionuclides and optimize vitrification processes for high-level radioactive waste. By integrating glass chemistry with ceramic phase engineering, this work presents a comprehensive approach to addressing two critical issues: the sequestration of iodine-129 (I-129) from off-gas treatment and the control of crystallization in nuclear waste vitrification. This thesis is structured to provide a systematic exploration of these challenges, beginning with an in-depth review of the fundamental principles of nuclear waste immobilization, glass science, and ceramic phase formation. The first major study investigates the development of composite waste forms incorporating aluminosilicate ceramic phases for the retention of I-129. A caustic scrubber simulant was employed to capture iodine, which was then immobilized using low-temperature glass binders composed of ZnO-Bi2O3-based and Na2O-B2O3-SiO2 systems. Through thermal processing and material characterization, the study assesses the crystallization behavior of sodalite and other relevant phases, evaluating their effectiveness in ensuring long-term iodine containment and chemical durability. The second major study focuses on the vitrification of nuclear waste within the Hanford Tank Waste Treatment framework, with particular emphasis on risk reduction strategies for the Direct Feed Low-Activity Waste (DF-LAW) Vitrification Plant. This research examines the crystallization behavior of simulated waste glasses under varying thermal conditions, particularly the formation of SnO2 and ZrO2 crystalline phases, which can affect the stability and durability of the final waste form. By analyzing alkali mobility and its influence on phase separation, this study provides insights into optimizing glass compositions to achieve completely amorphous melts before thermal cycling, thereby enhancing waste form performance. Throughout this thesis, experimental methodologies, material synthesis techniques, and analytical characterization methods are presented in detail, followed by a discussion of the key findings and their implications for nuclear waste management. The conclusions drawn from this research contribute to the broader goal of advancing nuclear waste immobilization strategies, ensuring the long-term stability of high-performance vitreous waste forms, and supporting the continued development of safe and sustainable nuclear fuel cycle operations.

Development of Glass-based Nuclear Waste forms for Legacy and Future Waste Streams

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