Report Finds That ‘Advanced’ Nuclear Reactor Designs Are No Better Than Current Reactors—and Some Are Worse

Proposed Non-Light-Water Reactors Not Clearly Safer and Will Likely Take Decades to Achieve Reliable Commercial Operation

Published Mar 18, 2021

WASHINGTON (March 18, 2021)—A report released today by the Union of Concerned Scientists (UCS) analyzed the designs of a number of so-called “advanced” non-light-water nuclear reactors currently in development and found that they are no better—and in some respects significantly worse—than the light-water reactors in operation today.

The 140-page report, “Advanced” Isn’t Always Better, assesses the pros and cons of three main types of non-light-water reactors: sodium-cooled fast reactors, high-temperature gas-cooled reactors, and molten salt-fueled reactors. It rates them on three broad criteria: safety and security; nuclear proliferation and terrorism risks; and “sustainability,” which refers to how efficiently they use uranium and how much long-lived nuclear waste they generate.

“If nuclear power is to play a larger role to address climate change, it is essential for new reactor designs to be safer, more secure, and pose comparable or—better yet—lower risks of nuclear proliferation and nuclear terrorism than the existing reactor fleet,” says report author Dr. Edwin Lyman, a physicist and director of nuclear power safety at UCS. “Despite the hype surrounding them, none of the non-light-water reactors on the drawing board that we reviewed meet all of those requirements.”

The report takes a close look at unsubstantiated claims developers are making about their designs, which are largely based on unproven concepts from more than 50 years ago. With little hard evidence, they assert that their reactors have the potential to lower costs, reduce nuclear waste, burn uranium more efficiently, strengthen safety, and lower the risk of nuclear proliferation.

One of the proposed sodium-cooled fast reactors, TerraPower’s 345 megawatt Natrium, has received considerable media attention recently because TerraPower founder Bill Gates has been citing it during interviews about his new book, How to Avoid a Climate Disaster. In mid-February, Gates told 60 Minutes correspondent Anderson Cooper that the Natrium reactor will produce less nuclear waste and be safer than a conventional light-water reactor.

In fact, according to the UCS report, sodium-cooled fast reactors such as the Natrium would likely be less “uranium-efficient.” They would not reduce the amount of waste that requires long-term isolation in a geologic repository. They also could experience safety problems that are not an issue for light-water reactors. Sodium coolant, for example, can burn when exposed to air or water, and a sodium-cooled fast reactor could experience uncontrollable power increases that result in rapid core melting.

“When it comes to safety and security, sodium-cooled fast reactors and molten salt-fueled reactors are significantly worse than conventional light-water reactors,” says Dr. Lyman. “High-temperature, gas-cooled reactors may have the potential to be safer, but that remains unproven, and problems have come up during recent fuel safety tests.”

Timing is also an issue. Some developers promise that they can demonstrate, license and deploy their non-light-water reactors on a commercial scale as early as the end of this decade, enabling them to address the climate crisis in the near term. For example, last fall the Department of Energy (DOE) gave both TerraPower and X-Energy, developer of a high-temperature, gas-cooled “pebble-bed” reactor, $80 million grants to begin operating first-of-a-kind commercial units by 2027, most likely at the Columbia Generating Station site in Washington.

According to the report, if federal regulators require the necessary safety demonstrations, it could take at least 20 years—and billions of dollars in additional costs—to commercialize non-light-water reactors, their associated fuel cycle facilities, and other related infrastructure.

“One of the new reactor designs being considered, the ‘breed-and-burn’ reactor, has the most potential because it doesn’t require reprocessing—or recycling—spent nuclear fuel, which poses unacceptable proliferation risks,” says Dr. Lyman. “But the concept is still saddled with considerable technical obstacles and safety hazards due to the fact that fuel would remain in the reactor longer than in a light-water reactor, allowing fission gases and pressure to build.”

The report recommends that the DOE suspend its advanced reactor demonstration program until the Nuclear Regulatory Commission determines whether it will require full-scale prototype tests before licensing any designs for commercial deployment, which the report argues are essential. It also calls on Congress to require the DOE to convene an independent commission to review the technical merits of all proposed non-light-water reactors and only approve projects with a high likelihood of commercialization that are clearly safer and more secure than the current fleet. Finally, the DOE and Congress should consider spending more research and development dollars on improving the safety and security of light-water reactors, rather than on commercializing immature, overhyped non-light-water reactor designs.