New Mineral Techniques to Immobilize Radioactive Technetium-99 Waste

Researchers at the University of Manchester have developed new ways to immobilize Technetium-99, a highly mobile radioactive byproduct that often escapes traditional containment efforts.

By integrating this isotope directly into the crystalline structure of specific minerals, scientists may have found a way to stop radioactive contamination from migrating through soil and water. This development addresses a critical vulnerability at legacy nuclear sites where Technetium-99—a byproduct of nuclear fuel production and reprocessing—tends to move easily through the environment.

The work, detailed in two separate papers published in Environmental Science & Technology, offers two distinct chemical pathways for stabilization. One method focuses on liquid waste effluents, while the other targets contaminated groundwater and land.

“We’re not simply removing technetium from the effluent; we’re locking it up directly into a mineral structure to provide much greater long-term stability,” said Samuel Shaw, a professor of environmental mineralogy at the University of Manchester.

Locking isotopes into mineral structures

The first breakthrough involves a technique to treat radioactive waste effluents by incorporating the isotope into layered double hydroxides (LDHs). These are a type of engineered environmental-remediation mineral.

In their study, “Reductive Incorporation of Technetium-99 in Fe(II)-Doped Layered Double Hydroxide,” investigators demonstrated that they could remove 99 percent of dissolved Tc-99 from a solution. The radioisotope was not just filtered out; it was incorporated directly into the mineral structure of the LDH during its formation.

This represents the first evidence of Tc-99 being incorporated into LDH, a material already used in various other environmental remediation tasks. According to the researchers, this process could be used to treat effluents generated during the daily operation of nuclear power plants or to create stable inorganic waste during the decommissioning of older facilities.

The University of Manchester is currently working with Sellafield through the Game Changers program to test if this tool can assist in the decommissioning of that specific legacy nuclear site.

Targeting groundwater with phosphate minerals

The second method addresses a different problem: the movement of contaminants through the earth itself. In a second study titled “Novel Pathways to Treat Radioactively Contaminated Land: Bisphosphonate Ligands Enhance 99Tc Sequestration by Phosphate Minerals,” researchers looked at how to stop the isotope in its tracks within groundwater systems.

The team evaluated the use of methylene diphosphonic acid (MDP), a compound typically used in nuclear medicine to bind short-lived medical radioisotopes to bone mineral. By forming a soluble complex of MDP with chemically reduced Tc-99, the researchers were able to use hydroxyapatite—a calcium phosphate mineral—to capture and bind 99 percent of the complex from a solution.

This experiment was conducted under environmental conditions that mimic those found at nuclear legacy sites. Further testing suggested the technique remains effective even in flowing groundwater conditions.

“This study demonstrates new ways of capturing and immobilizing technetium in stable minerals, helping to build the toolkit needed for the safe cleanup of nuclear legacy sites,” said Callum Robinson, a radionuclide research associate at the University of Manchester.

The research involved a collaborative effort between the University of Manchester, the Pacific Northwest National Laboratory, and the Christie NHS Foundation Trust.

The high stakes of nuclear legacy cleanup

Stabilizing these isotopes is a major technical hurdle for environmental agencies. Because Tc-99 is so mobile, it poses a long-term risk to local water tables and ecosystems near decommissioned sites like Hanford in the United States or Sellafield in the United Kingdom.

While these mineral-based solutions show high success rates in laboratory settings, the practical application involves scaling these chemical processes to handle massive volumes of contaminated soil and water. The transition from controlled experiments to field-scale remediation remains a primary challenge for the industry.

The long-term goal for many of these remediation technologies is to align with the Waste Hierarchy, moving away from simple disposal and toward the creation of stable, manageable materials that prevent environmental leakage for generations.

Whether these engineered minerals can be deployed effectively across the vast, complex landscapes of global nuclear legacy sites remains to be seen.

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