Nuclear power plays a key role in sustainable energy generation, offering a long-term solution with its extended operating life and low greenhouse gas emissions. As of 2025, nuclear energy supplies approximately 10% of the world’s electricity, with 440 power reactors operating across 31 countries.1
Beyond power generation, nuclear technology is also starting to play a vital role in medical diagnostics, industrial processes, and space exploration. With growing demand for reliable, clean energy, the sector continues to expand, with new reactors under construction worldwide.2 However, nuclear waste disposal remains a critical challenge, requiring innovative solutions to ensure long-term safety.
Vitrification and the Growing Importance of Nuclear Waste Management
High-level nuclear waste (HLW) is the most hazardous by-product of nuclear energy production, consisting primarily of spent nuclear fuel and its reprocessed liquids. Its long-lived isotopes and high radiation levels pose significant environmental and health risks, requiring robust containment strategies.3,4
As unstable isotopes decay, HLW continuously emits heat and radiation, making secure storage essential to prevent environmental contamination.4 Certain radionuclides, such as the actinides plutonium and curium, have extremely long half-lives, necessitating immobilization techniques that ensure stability for thousands of years.3 Others, like Technetium-99 and Iodine-129, are highly soluble in water, increasing the risk of groundwater infiltration if not properly contained. These challenges demand a waste form that offers long-term durability, leach resistance, and mechanical stability under repository conditions.
Vitrification—the process of turning waste into glass—has emerged as one of the most effective containment methods for HLW.4 Unlike dilution or surface storage, vitrification permanently traps hazardous materials within a stable glass matrix, preventing their release into the environment. Additionally, vitrified waste is compact, insoluble, and well-suited for secure long-term storage and disposal.
Glass Selection in Nuclear Waste Immobilization
Selecting the right glass composition is critical for the success of vitrification. Borosilicate and phosphate-based glasses are the two primary materials used for HLW immobilization.
Borosilicate glass is favored for its high chemical durability, low thermal expansion, and capacity to incorporate a wide range of radionuclides.3 It has been the standard choice in countries like France, the UK, and the US, where large-scale vitrification facilities are in operation. Its success is largely due to its compatibility with various waste cations, well-characterized structure, and well-established processing technology.3
However, optimizing the waste loading—the percentage of waste incorporated per unit volume of glass—while ensuring the final product remains stable and processable remains a persistent challenge in vitrification processes. While increasing waste loading reduces overall storage costs and processing time, it requires precise control over the glass formulation to prevent crystallization or phase separation.
Optimized borosilicate glass is generally well suited for this purpose, but certain waste components present in HLW, such as molybdenum and noble metals, have low solubility in the borosilicate matrices, limiting how much can be incorporated, and its utility as a universal HLW matrix.
Expanding Vitrification Strategies Through Customizable and Alternative Glass Solutions
While borosilicate glass has long been the standard for HLW vitrification, its limitations in incorporating certain waste components have driven the exploration of alternative glass formulations. Phosphate-based glasses (e.g., iron phosphate, alumino phosphate) present a promising alternative to traditional borosilicate glass for the immobilization of HLW, particularly in the management of actinides, lanthanides, and other elements that are poorly soluble in borosilicate.
These phosphate glasses offer enhanced degradation resistance and superior tolerance to radiation, making them ideal for managing complex waste streams.3 In particular, phosphate-based formulations are highly relevant for next-generation reactor technologies, such as molten salt reactors. These reactors, which utilize liquid fuel salts, produce waste compositions that are rich in fluorine and differ significantly from those of conventional reactors, thus limiting the types of glasses that can effectively immobilize this type of waste.5
Phosphate glasses also stand out for their ability to better accommodate halide-rich waste streams. These glasses can be processed at lower temperatures, reducing volatility, and can accommodate higher salt loading, making them an attractive solution for waste from advanced reactor designs. 5 For example, fast breeder reactors, which generate waste with high concentrations of plutonium and actinides, require non-silicate glass forms capable of accommodating these elements without compromising long-term integrity.
Leading Innovation in Nuclear Waste Vitrification
MO SCI is pioneering the development of advanced glass formulations that improve waste loading and long-term performance while addressing the limitations of traditional glass forms. By focusing on customizing glass compositions to suit specific waste characteristics, MO SCI is helping to ensure that vitrification remains a scalable and effective solution for HLW disposal, supporting the transition to next-generation reactor technologies.
For further information on nuclear waste management solutions, please contact us today.
References and Further Reading
- World Nuclear Association. Nuclear Power in the World Today [Updated 6 Jan 2025]. Available from: https://world-nuclear.org/information-library/current-and-future-generation/nuclear-power-in-the-world-today#:~:text=Nuclear%20energy%20now%20provides%20about,in%20about%20220%20research%20reactors.; (Accessed on 3 Mar).
- Hyatt NC, Ojovan MI. (2019) Special Issue: Materials for Nuclear Waste Immobilization. Materials (Basel);12(21).
- Bohre A, Avasthi K, Pet’kov VI. (2017) Vitreous and crystalline phosphate high level waste matrices: Present status and future challenges. Journal of Industrial and Engineering Chemistry;50:1-14.
- Sanito RC, Bernuy-Zumaeta M, You SJ, Wang YF. (2022) A review on vitrification technologies of hazardous waste. J Environ Manage;316:115243.
- Riley BJ, McFarlane J, DelCul GD, Vienna JD, Contescu CI, Forsberg CW. (2019) Molten salt reactor waste and effluent management strategies: A review. Nuclear Engineering and Design;345:94-109.