Enlarge / A German nuclear power plant, which is currently partially closed. (credit: Getty Images )

In 2011, in the wake of the Fukushima disaster, Germany decided to shut down all of its nuclear power. The process was supposed to have ended last year, but it has been extended in response to energy uncertainties caused by the war in Ukraine. As a result, even though renewable generation in Germany continues to climb, the country's carbon emissions have only trended down slowly.

While there's no indication that the US will follow Germany down this path—the Biden administration is actively subsidizing nuclear plants to keep them open—the economics of nuclear power have led to a number of plant shutdowns. It's currently the second-most expensive major source of power, just ahead of offshore wind, with the costs of wind continuing to drop. So there's a significant chance that nuclear's contribution to the US grid will shrink.

A new analysis shows that a drop in nuclear power on the current US grid will mean enough additional pollution to cause over 5,000 deaths each year, and the burden of those deaths will fall disproportionately on Black Americans. But on a future grid where renewables are present at sufficient levels to offset the loss of nuclear, almost all of these additional deaths can be avoided.

Enlarge / An artist’s impression of a deep borehole for nuclear waste disposal by Sandia National Laboratories in 2012. Red lines show the depth of mined repositories: Onkalo is the Finnish one, and WIPP is the US DOE repository for defense waste in New Mexico. (credit: Sandia National Laboratories)

Deep Isolation , a company founded in 2016 and headquartered in California, launched a “ Deep Borehole Demonstration Center ” on February 27. It aims to show that disposal of nuclear waste in deep boreholes is a safe and practical alternative to the mined tunnels that make up most of today’s designs for nuclear waste repositories.

But while the launch named initial board members and published a high-level plan, the startup doesn’t yet have a permanent location, nor does it have the funds secured to complete its planned drilling and testing program.

Although the idea to use deep boreholes for nuclear waste disposal isn’t new , nobody has yet demonstrated it works. The Deep Borehole Demonstration Center aims to be an end-to-end demonstration at full scale, testing everything: safe handling of waste canisters at the surface, disposal, possible retrieval, and eventual permanent sealing deep underground. It will also rehearse techniques for ensuring that eventual underground leaks will not contaminate the surface environment, even many millennia after disposal.

Enlarge / An artist’s impression of a deep borehole for nuclear waste disposal by Sandia National Laboratories in 2012. Red lines show the depth of mined repositories: Onkalo is the Finnish one, and WIPP is the US DOE repository for defense waste in New Mexico. (credit: Sandia National Laboratories)

There’s one thing every planned permanent repository for spent nuclear fuel has in common: They're all underground mines.

Like any mine, a mined repository for nuclear waste is a complex feat of engineering. It must be excavated by blasting or a boring machine, it must keep the tunnels stable using rock supports, and it must have ventilation, seals, and pumps to handle groundwater and make it safe for people and machinery. Unlike a mine, however, a repository must also transport and entomb canisters of radioactive waste, and it must be engineered to exacting standards that ensure the tunnels will keep the canisters safe for many millennia.

There is an alternative idea that dispenses with most of those downsides: disposal in deep boreholes. But can they be both feasible and safe?

Enlarge / A tunnel in Finland’s nuclear waste repository. (credit: Posiva)

Even if all nuclear power plants were shut down today, there’s a mountain of radioactive waste waiting to be disposed of. Yet only Finland has an approved solution for nuclear waste disposal, while projects in the US , UK , and Germany have failed for decades, and progress is also slow in other countries . With growing calls to extend the life of existing nuclear power stations and build new ones, that mountain of radioactive waste sitting in temporary , vulnerable , and expensive storage will keep growing.

The challenge is daunting. “ High-level ” nuclear waste, which includes spent nuclear fuel, stays radioactive for hundreds of millennia , so a waste facility must keep it safely away from aquifers, violent weather, war, plane crashes, sea level rise, future ice sheets, volcanic activity, and even curious future humans for a time span that dwarfs all of previous human history.

Ultimately, it’s the geology of a proposed disposal site that determines if it's a safe place to entrust nuclear waste for millennia. We talked to people involved in the Finnish, US, and UK programs about what investigations of the rock and groundwater at those sites revealed about their suitability—or lack thereof.

Enlarge / The two reactors of the Diablo Canyon facility. (credit: Tracey Adams )

On Friday, California Governor Gavin Newsom sent a series of aggressive climate proposals to the state legislature. And, in a separate but related move, his administration is circulating potential legislation that would allow the state's last nuclear power plant to continue operating past its planned shutdown in 2025. The proposed legislation is remarkably complicated despite its seemingly simple goal and is already facing a backlash from environmental groups, yet it has to be passed by the end of the month when the current legislative session expires.

Big goals

California already has one of the most ambitious sets of climate goals among the US states. But Newsom's plan would accelerate the targets already in place. It would set 2045 as the latest date by which the state would reach net carbon neutrality and make that target legally binding. To make that easier, it would boost the 2030 greenhouse gas emissions cuts from 45 percent to 55 percent relative to the 1990 baseline.

As part of that, California will rapidly cut carbon emissions from electrical generation, with 90 percent clean energy in 2035, and 95 percent in 2040. Concurrently, it will put more areas in the state off-limits to oil extraction and start supporting carbon capture and sequestration.

Enlarge / NuScale's reactor-in-a-can. (credit: NuScale)

On Friday, the Nuclear Regulatory Commission (NRC) announced that it would be issuing a certification to a new nuclear reactor design, making it just the seventh that has been approved for use in the US. But in some ways, it's a first: the design, from a company called NuScale, is a small modular reactor that can be constructed at a central facility and then moved to the site where it will be operated.

The move was expected after the design received an okay during its final safety evaluation in 2020.

Small modular reactors have been promoted as avoiding many of the problems that have made large nuclear plants exceedingly expensive to build. They're small enough that they can be assembled on a factory floor and then shipped to the site where they will operate, eliminating many of the challenges of custom, on-site construction. In addition, they're structured in a way to allow passive safety, where no operator actions are necessary to shut the reactor down if problems occur.

Enlarge (credit: picture alliance | Getty Images)

Lindsay Krall decided to study nuclear waste out of a love for the arcane. Figuring how to bury radioactive atoms isn’t exactly simple—it takes a blend of particle physics, careful geology and engineering, and a high tolerance for reams of regulations. But the trickiest ingredient of all is time. Nuclear waste from today’s reactors will take thousands of years to become something safer to handle. So any solution can’t require too much stewardship. It’s gotta just work, and keep working for generations. By then, the utility that split those atoms won’t exist, nor will the company that designed the reactor. Who knows? Maybe the United States won’t exist either.

Right now, the US doesn’t have such a plan. That’s been the case since 2011, when regulators facing stiff local opposition pulled the plug on a decades-long effort to store waste underneath Yucca Mountain in Nevada, stranding $44 billion in federal funds meant for the job. Since then, the nuclear industry has done a good job of storing its waste on a temporary basis, which is part of the reason Congress has shown little interest in working out a solution for future generations. Long-term thinking isn’t their strong suit. “It’s been a complete institutional failure in the US,” Krall says.