Deep Isolation and NAC to develop horizontal repository design

Modular horizontal borehole repository could cut disposal costs in half compared to mined solution.

Nuclear waste start-up Deep Isolation has signed a cooperation agreement with NAC International to work on Deep Isolation’s design for canister storage and disposal in a horizontal repository.

Deep Isolation sees its innovative solution as a simpler, cost-effective, and flexible alternative to mined repositories such as Yucca Mountain in the US.

Berkeley-based Deep Isolation hopes to combine its patented designs for spent nuclear fuel and high-level waste storage and disposal solutions with NAC’s 20 years of experience as a leader in dry fuel storage technology.

“A partnership between an established corporation such as NAC and our company is a natural fit as it marries the agility and innovation of a start-up with the longevity and legacy of a large enterprise,” Deep Isolation VP Marketing and Communications, Zann Aeck, told Nuclear Energy Insider.

“Specifically, our partnerships combine innovation with existing best practices and global capacity and will allow us to build on existing capability and move forward more quickly than if we tried to do everything ourselves.”

This is the second strategic partnership that Deep Isolation has made in the last six months, following an agreement with engineering and construction company Bechtel National.

Under that agreement, Bechtel will provide support such as project management, financial/business and engineering capability for Deep Isolation’s sales in both domestic and international markets, including those with the US Department of Energy (DOE).

“In this highly regulated market, it’s critical to bring innovations in waste management through established industry leaders,” said Deep Isolation COO, Rod Baltzer.

“This partnership [with NAC] demonstrates the impact we are having in this industry and our ability to deliver a storage and disposal solution to governments looking for another option.”

Patented solution

Globally, there are around 450,000 metric tons of nuclear waste that have accumulated, and there is currently no operating disposal solution for commercial used nuclear fuel or high-level waste.

Finland’s waste management company Posiva laid the foundation stone for the world's first used fuel encapsulation plant Onkalo, at Olkiluoto, in October, with construction scheduled for completion in 2022. The permanent underground nuclear storage facility will store up to 6,500 tons of waste.

Deep Isolation has developed a patented solution using directional drilling, which was demonstrated to the public in January this year.

“Our solution brings differentiated benefits, both with regard to technology and also with regard to approach,” said Aeck. “Deep horizontal disposal would be located below aquifers and in a reducing environment in formations that can be shown to have been isolated from the biosphere for millions of years.

“They could potentially be located close to the reactors and interim storage facilities, minimizing transportation. No humans need to go underground, which gives considerable safety benefits.”

Deep Isolation’s concept consists of an array of deep horizontal drillholes bored into suitable rocks using off-the-shelf directional drilling technology. Waste is encapsulated in specialized corrosion-resistant canisters, which are placed end-to-end into the relatively small-diameter, cased and backfilled horizontal disposal sections of the drillholes.

The concept allows for consolidated waste disposal in a national or a few regional repositories or decentralized disposal in modular, smaller repositories located at or near the reactor sites or processing plants where the waste was produced.

“Over the long term, we expect that used fuel will be disposed of, but certain countries or waste streams may prefer storage in advance of disposal,” said Aeck. “Our solution does offer canister retrievability and therefore can be used for long-term, below-ground interim storage. The retrievability has been demonstrated successfully. As a disposal option, the canisters would not be retrieved and once the waste is emplaced, the drillhole would be backfilled and permanently sealed.”

Deep Isolation says disposal costs per ton of waste can be kept substantially lower than for mined repositories by its smaller size, reduced infrastructure needs and staged implementation. The waste could be retrieved using “fishing” technology.

Source: ‘Disposal of High-Level Nuclear Waste in Deep Horizontal Drillholes’ peer-reviewed white paper by Energies by Multidisciplinary Digital Publishing Institute (MDPI)

Disposal concept

In the proposed disposal concept, corrosion-resistant canisters containing unmodified fuel assemblies would be placed end-to-end in up to 50 cm diameter horizontal drillholes. Other high-level wastes can be disposed in small-diameter horizontal drillholes.

“Delays with nuclear repositories are a global problem,” adds Aeck. “As a society, we need to proactively move forward with disposal solutions and stop pushing the problem off to the next generation. It is vital to isolate nuclear waste deep underground where it cannot impact the biosphere. This can now be done, both for temporary storage and permanent disposal.”

According to Aeck, early research suggests disposal costs would be half of that compared to a mined repository. The savings would be even larger for countries with smaller inventories of used nuclear fuel. As the Deep Isolation solution is modular, the solution can be easily scaled.

Alternative to mining

Disposing of waste in deep shafts and boreholes was explored in a 1979 study commissioned by the US Atomic Energy Commission. Various studies conducted since then also suggested that deep vertical borehole disposal should be investigated as an alternative to mined repositories.

In the US, an underground repository has been delayed by political opposition and conflicting research studies since 1987, when Yucca Mountain was designated by Congress as a nuclear waste storage site. The Trump administration backs the plan, but the legislation faces major challenges.

A potential hurdle for Deep Isolation is that the US Nuclear Waste Policy Act currently does not allow a second repository for commercial spent nuclear fuel until the Yucca Mountain facility is completed.

“Deep Isolation provides a demonstrated nuclear waste storage and disposal solution that can be implemented modularly around the globe,” said Deep Isolation COO, Rod Baltzer. “Our solution can be customized for a country’s needs and specific waste inventory and includes feedback through a local stakeholder engagement process.”

Scott Birch