Immobilizing Nuclear Waste with Borosilicate Glass

:: Tuesday, October 3, 2023 :: Posted By Maryam Moravej

Nuclear power is an appealing source of carbon-free electricity. But outstanding questions remain: What to do with nuclear waste? How can we permanently—and safely—dispose of radioactive materials?

One globally accepted solution involves immobilizing radioactive materials in glass, through a process called nuclear waste vitrification.

However, not all glasses are created equal. Glass compositions that incorporate borates (borosilicate glass) have unique characteristics that make them especially suitable for not only encapsulating nuclear waste but improving the efficiency of the vitrification process itself.

With refined borates, nuclear waste management companies can ensure the safe containment of radioactive materials and greatly reduce the risk of leaching into the environment.

How nuclear waste vitrification works

Nuclear waste vitrification is not a new process. It dates to the late 1970s when France found a way to contain waste from reprocessed fuel in a borosilicate glass (BSG) matrix.

The vitrification process starts by combining a pre-melted, pre-sized borosilicate frit with a slurry of nuclear waste. This mixture is concentrated in an evaporator then transferred to a glass melter where it’s heated and becomes vitrified waste.

From there, the newly formed glass melt is poured into a stainless-steel container where it is cooled, decontaminated, sealed. Eventually it will be moved for long-term storage at a geological repository or surface facility.

Benefits of borates

For nuclear waste companies, refined borates support critical goals such as:

  • Adhering to regulatory requirements
  • Sourcing process-compatible materials

Borate compounds impart multiple benefits throughout the nuclear waste vitrification process.

Lowers melting temperature

Saving energy is a priority in all industrial environments. Borates significantly lower required melting temperatures (by hundreds of degrees), while still dissolving a full spectrum of nuclear waste materials.

Lowering the melting temperature also helps reduce corrosion and damage to melting equipment, extending its lifespan.

Chemical compatibility

Borates are highly compatible and non-reactive with a range of elements, making them an excellent choice for waste streams that feature both alkaline and non-alkaline elements.


Durability is a major concern for nuclear waste management companies. A disposal container encapsulating radionuclides must withstand temperature changes, pressure, and other adverse conditions.

Borosilicate glass is known for its durability and resistance to corrosion. Its strength makes it a safe long-term containment option that reduces the risk of leaching.

Read more about borates in glass

Vitrifying? Consider Optibor and Boric Oxide

For nuclear waste vitrification, borates without sodium are the preferred choice. That’s because alkali oxides can negatively impact vitrified materials, leaving them more susceptible to leaching.

We offer two non-sodium borate products fit for this process:

  • Optibor®
  • Boric oxide

These borate products undergo a thorough refinement process to remove impurities that may negatively impact finished glass quality. Also, because traceability is critical to any nuclear application, you’ll lot and batch codes enabling you to verify your products conform to specifications.

Beyond the product level, U.S. Borax is an experienced nuclear energy industry partner. Our technical experts draw from a deep, research-backed knowledge base. As a company, we are invested in advancing ESG initiatives, including improving sustainability in glass manufacturing and related processes.

If you have any questions about how borates may add value to your vitrification process, contact our technical team.



U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 650 customers with more than 1,800 delivery locations globally. We supply around 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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