Soterium Space & Sea · Waste
Epitaxial Vitrification: Locking Waste into Glass and Crystal
Locking radioactive waste inside stable glass and crystal.
Nuclear Waste Management RGB
The most trusted way to hold radioactive waste for the long term is to melt it into glass. The waste is mixed with glass-forming minerals, heated until it flows, and poured into steel containers, where it cools into a solid that traps radioactive elements inside its structure. In Washington State, at Hanford, this is now happening at industrial scale.
Glass has limits, though. It can only absorb so much waste before unwanted crystals form, sink and clog the melter, and its disordered structure is not the strongest possible cage. Epitaxial vitrification is our name for a different approach: rather than fighting crystals, plant the right ones on purpose. Tiny seed crystals, kept evenly spread through the waste by a high zeta potential, could guide durable mineral cages to grow around the most dangerous elements, inside a protective glass. This page explains the idea, the proven science it builds on, and what would have to be shown before anyone should trust it.
- The approach
- Glass plus deliberately grown crystals, known as a glass-ceramic
- Epitaxy
- New crystal growing in step with the lattice of a seed
- Key lever
- The zeta potential of seed particles in the waste slurry
- Glass today
- Hanford has vitrified waste since October 2025, at about 2,100 °F
- Status
- A Soterium concept built on proven pieces, not yet tested as a whole
The starting point
Why waste becomes glass
Glass is a frozen liquid. Its atoms form a tangled network without the strict pattern of a crystal, which lets it dissolve a remarkable mix of elements into one solid. That flexibility is why vitrification has become the standard for the most hazardous liquid wastes.
Takes almost anything
Dozens of elements from the waste can be locked into a single glass, turning tanks of liquid and sludge into a compact solid that won't leak or slosh.
Crystals that sink
Push in too much waste and some elements, especially nickel, iron and chromium, form spinel crystals in the melt. In high-level waste melters these can settle and pile up. In one study, layers in nickel-rich glasses reached about 10.5 millimetres in only 20 days, enough to risk plugging the outlet that pours the glass.
Strong enough for forever?
Some radioactive elements, like plutonium and other actinides, stay dangerous for tens of thousands of years. Certain natural minerals have held similar elements stable for geological time, which raises the question of whether crystals could be the better cage.
The idea
Grow the cage on purpose
A glass-ceramic is glass with crystals grown inside it on purpose. Researchers have shown that this kind of material can combine the advantages of glass and ceramic while avoiding their weaknesses. Minerals such as zirconolite are studied as hosts because their crystal structures can hold actinides tightly.
Crystals follow a template
When a small crystal is placed in a glass, new crystal of the same kind can grow outward from it, copying its atomic pattern. In a 1991 Penn State study, glass seeded with albite crystals grew new albite by epitaxy at 1,000 °C, while unseeded glass and glass seeded with a mismatched material did not crystallise at all under the same conditions.
Many small beats few large
Research on crystal-tolerant waste glasses found that some particles, including noble metals and hematite, seed many small crystals instead of a few large ones. Smaller crystals stay suspended and are less likely to pile up in the melter.
Heat as a dial
A 2017 study of zirconolite-based glass-ceramics showed that crystal size and arrangement can be tuned with temperature, time and a two-stage heating schedule, giving smaller, more evenly spread crystals.
Where zeta potential comes in
Spreading the seeds evenly
Before it reaches the melter, the waste is a slurry: solid particles suspended in a salty, alkaline liquid. Seeds added to that slurry are only useful if they stay apart. Clumped seeds would grow clumped crystals, leaving some parts of the glass protected and others not.
The zeta potential is the electric charge a particle carries into the liquid around it. Beyond roughly ±30 millivolts, particles usually repel each other strongly enough to stay dispersed. Near zero, they clump.
Tank waste is salty
Salt shrinks the charged shield around each particle and lets particles clump. Studies of aluminium minerals from Hanford-type waste found that calcium caused clumping at roughly a hundredth of the concentration needed with sodium.
pH, salt and surfaces
Zeta potential can be raised by adjusting pH, limiting troublesome ions, or choosing seed materials and surface coatings that keep a strong charge in the waste's chemistry.
A slurry that behaves
How the slurry flows, foams and settles already matters to melter operators. Well-dispersed particles make a feed that is more predictable to pump and mix.
The process
From tank to glass-ceramic
Characterise
Measure the waste batch: its elements, salts, pH and the charge on its particles.
Disperse seeds
Add host-mineral seed crystals and tune the slurry so their zeta potential stays high and they spread evenly.
Melt and grow
Melt the feed with glass formers, then hold it at set temperatures so host crystals grow outward from the seeds and capture actinides.
Lock in
Cool the glass-ceramic in its steel container: crystals guarding the longest-lived elements, glass guarding the rest.
The other side of zeta
When stability becomes a hazard
The same charge that keeps seeds apart in the tank can work against us underground. A stable colloid, a particle small and charged enough to stay suspended, can travel far through groundwater and carry radioactive atoms with it.
Plutonium on the move
Scientists sampling groundwater at the Nevada Test Site found plutonium riding on colloidal particles. Its isotopic fingerprint traced it to an underground nuclear test about 1.3 kilometres away. Models that ignored colloids had underestimated how far it could travel.
Don't shed particles
A waste form must hold its contents in a solid that dissolves extremely slowly and doesn't release fine particles as it weathers. That is a core reason to put the longest-lived elements inside durable crystals.
Charge is a tool, not a virtue
High zeta potential is what we want in the slurry and exactly what we don't want around a buried container. Good engineering uses both sides of the same physics.
Where the world stands
The field in 2026
Hanford makes glass
Hanford's Low-Activity Waste Facility began vitrifying tank waste in October 2025 in two 300-ton melters. By late May 2026 it had turned more than 100,000 gallons into glass, a small start against roughly 56 million gallons stored in aging underground tanks a few miles from the Columbia River.
First containers in disposal
The first glass-filled stainless steel containers, each about 7 tons, were placed in Hanford's Integrated Disposal Facility. The plant remains in hot commissioning before full-scale operation is approved, and the High-Level Waste Facility is still being completed.
Crystal-tolerant glasses
National laboratory researchers are developing glass recipes that tolerate some crystals rather than avoiding them entirely, aiming to safely put more waste into each container.
Glass-ceramic waste forms
Zirconolite and related crystal hosts are being studied to immobilise actinides from advanced fuel recycling, the same streams that a molten salt waste reactor would leave behind.
Honest questions
What still has to be proven
Epitaxial vitrification combines proven pieces in a way that has not been tested as a whole. These are the questions it must answer plainly.
- Do the seeds survive? Seed crystals must stay dispersed in salty, alkaline slurry and then survive the melt long enough to template growth. Which materials can do both?
- Do the right elements end up in the crystals? The aim is to capture the longest-lived elements in the crystal hosts. That needs to be measured, not assumed.
- Radiation damage. Over thousands of years, radioactive decay can disorder a crystal's structure from the inside. How do the chosen hosts hold up?
- Melter safety. Any crystal grown on purpose must not settle and plug the melter. Is the crystal growth kept to the cooling stage, where it belongs?
- Long-term durability. Does the finished glass-ceramic release less to water, and fewer particles, than standard glass in accepted leaching tests?
- Consent. Do the communities near treatment and disposal sites, including Indigenous nations along the Columbia River, have a real voice in how this waste is handled?
Where Soterium fits
Closing the loop
We are not operating a vitrification plant. Our role is to study, explain and connect: to follow the field honestly and develop ideas like this one to the point where they can be properly tested.
What reactors leave
The residues left after a molten salt waste reactor burns long-lived elements are exactly what this approach aims to lock away.
Living shielding
Our work on radiotrophic fungi and Cladosporium sphaerospermum explores life that thrives around stored materials.
From waste to wetlands
Salt makes river clay clump and settle where rivers meet the sea, the same zeta physics that builds the mudflats behind our mangrove restoration work.
Using the warmth
Melters and cooling glass give off steady heat that pairs with our thermal flywheel storage ideas.
Keep exploring
Nuclear Waste Management
Further reading
- Over 100,000 gallons of Hanford tank waste turned to glass (US Department of Energy)
- Hanford places first vitrified waste containers in disposal cell (American Nuclear Society)
- Development of crystal-tolerant high-level waste glasses (OSTI)
- Epitaxial crystallization of seeded albite glass (Penn State)
- Crystal evolution in zirconolite-based glass-ceramics (White Rose Research)
- Migration of plutonium in groundwater at the Nevada Test Site (Nature)
- Zeta potential: an introduction (Malvern Panalytical)