Boron isotopes reveal how nuclear waste glass slowly dissolves over time

A new study has uncovered how tiny differences in boron atoms can help scientists better predict the long-term behavior of glass used to store hazardous waste. The findings, published in Environmental and Biogeochemical Processes, could improve forecasts of how radioactive materials are released from storage over thousands of years.

Glass is often used to immobilize contaminants such as radionuclides and heavy metals, locking them safely inside a stable structure. However, when groundwater seeps into disposal sites, the glass can gradually dissolve. Understanding this process is crucial for ensuring the safety of geological waste repositories.

Researchers from Peking University, the University of Cambridge, and partner institutions used boron isotope “fingerprinting” to trace how boron moves within dissolving glass. By comparing two types of borosilicate glass, one containing magnesium and one without, the team discovered that the diffusion of boron atoms depends strongly on the glass composition and the time it has been exposed to water.

In laboratory experiments, the glasses were placed in pure water at 90 degrees Celsius for up to 112 days. Measurements of boron isotopes showed that at early stages, boron was released evenly from the glass surface. Over time, however, diffusion through an altered surface layer became a key mechanism controlling the release. In magnesium-bearing glass, the formation of secondary minerals slowed the dissolution, creating a dense, protective layer. In contrast, the magnesium-free glass developed a surface layer that offered little protection, allowing boron to continue diffusing out.

“Boron isotopes provide a sensitive and direct tracer of how waste glasses interact with water,” said lead author Thomas L. Goût. “They help reveal when the glass dissolves uniformly and when the process becomes controlled by diffusion through a transformed surface layer.”

The research offers a new approach for monitoring and modeling glass corrosion in environmental and nuclear waste management. By identifying how isotopic signatures change as glass ages, scientists can better estimate the long-term release of contaminants into groundwater systems.

This study demonstrates that isotope-based techniques can provide detailed insights into the complex reactions occurring within waste materials. Such knowledge is essential for designing safer storage strategies for nuclear and industrial waste in the coming centuries.

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Journal reference: Goût TL, Guo R, Misra S, Tipper ET, Bohlin MS, et al. 2025. Boron isotope tracers of diffusion during glass dissolution. Environmental and Biogeochemical Processes 1: e005  https://www.maxapress.com/article/doi/10.48130/ebp-0025-0004  

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About the Journal:

Environmental and Biogeochemical Processes is a multidisciplinary platform for communicating advances in fundamental and applied research on the interactions and processes involving the cycling of elements and compounds between the biological, geological, and chemical components of the environment. 

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