Deep Isolation’s nuclear waste repository method leverages directional drilling expertise to isolate spent nuclear fuel and high-level radioactive waste in horizontal drillholes located deep underground in suitable rock formations.

spent nuclear fuel assembly


Nuclear waste is composed of dense, compact pellets made of uranium dioxide and stored in a fuel assembly made of zirconium alloy that can hold 22,000 to 92,000 pellets.

When the fission energy in these pellets is spent, the assemblies along with their pellets are removed from the reactor and placed in cooling pools. After several years the radioactivity has decayed to the point where “dry” storage is possible; about one third of the current nuclear waste is stored in dry casks above ground at the nuclear reactor sites. This is considered to be “interim storage”; there is not yet any licensed location where the waste can be sent for long-term disposal.


Rather than creating large tunnels, Deep Isolation will place nuclear waste in narrow 18-inch horizontal drillholes in rock that has been stable for millions of years. No humans need to go underground.

The Deep Isolation nuclear waste repository begins with a vertical access drillhole extending thousands of feet deep and will then gently turn horizontal. Canisters containing nuclear waste would be stored in the deep horizontal section.

Benefits of this patented design:

  • One drillhole can store 5 years of waste from a Boiling Water Reactor (BWR) and 11 years of waste from a Pressurized Water Reactor (PWR).
  • Tilted horizontal drillhole offers excellent isolation from surface.
  • The drilling, placement, and retrieving techniques are standard and reliable.
  • Sites can be at or near power plants to minimize transportation.
Nuclear Waste Disposal Technology
Nuclear Waste Disposal Technology
Diagram of Deep Isolation's nuclear waste repository


A deep horizontal drillhole repository for high-level radioactive waste takes advantage of the exceptional isolation properties of geologic formations whose stability has endured for a million years or more.

Deep disposal would also be far below aquifers, in a region in which water has had no contact with the surface for a million years or more.

Deep, stable rock formations thousands of feet underground provide:

  • A billion tons of rock between the waste and the surface.
  • Extremely long time for waste to diffuse to the surface, even if it penetrates the engineered barriers, allows most radioisotopes time to decay naturally.

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Experience with oil and gas drilling shows that the drilling itself does not trigger earthquakes; the observed earthquakes from oil and gas fracking come from the high-pressure injection of liquid underground. There is no fracking performed with any of our technology. Compare the risks of fracking with the safety of the Deep Isolation solution.

The geology of the deep horizontal repository also offers natural protection against human intrusion and terrorist attempts.


Drill rig for the horizontal drillhole

Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes

Dr. Richard Muller introduces our method and issues pertaining to safety requirements.

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simulation of heat from a nuclear waste canister

Sealing of a Deep Horizontal Borehole Repository for Nuclear Waste

Investigative paper on the importance of borehole sealing on the safety of a deep horizontal borehole repository.

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Safety calculations graphic

Numerical Simulations in Support of a Generic Post-Closure Safety Analysis for a Horizontal Drillhole Repository

Preliminary safety calculations for the disposal of spent nuclear fuel in a generic deep horizontal drillhole repository published in the peer-reviewed journal, Energies, by MDPI. May 2020

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Patent image for horizontal drillhole

Deep Isolation Intellectual Property

Learn more about the Deep Isolation technology patents for storing hazardous material in a subterranean formation.

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