Deep Isolation leverages recent advances in directional drilling to provide a safe and less expensive approach to the long term storage and disposal of nuclear waste.
Spent Nuclear Fuel
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.
Directional Drillhole Configuration
Rather than creating large tunnels, Deep Isolation will place nuclear waste in narrow (9 to 14-inch diameter) horizontal drillholes in rock that has been stable for millions of years. No humans need go underground.
The Deep Isolation repository begins with a 1-mile vertical access drillhole and will then gently turn horizontal. Canisters containing nuclear waste would be stored in the deep horizontal section.
Benefits of this patented design:
- One 2-mile long drillhole can store 8 years of waste from a BWR and 33 years of waste from a PWR.
- Tilted horizontal drillhole offers excellent isolation from surface.
- The drilling, placement, and retrieving techniques are standard.
- Sites can be near power plants to minimize transportation risks.
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 about a mile 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.
Safety is Paramount
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 pumping of waste water into storage facilities, something that we will not need to do since we are not fracking. Nor is there risk of exposure to the stored waste if an earthquake were to happen in the area from an unknown fault.
The geology of the deep horizontal repository offers a natural protection against human intrusion, terrorist attempts, and chain reactions caused by ground water intrusion.