Somewhere in Russia, 34 tons of surplus weapons-grade plutonium—enough material to make about 10,000 weapons—are awaiting disposal. Moscow was supposed to start destroying this stockpile, but has yet to begin, leaving a huge threat lurking in an unknown location. If even a tiny fraction of this material fell into terrorists’ hands, they could threaten nuclear terrorism around the world.

Yet, the plutonium’s continued existence isn’t Russia’s fault. It’s ours.

In 1998, Russia and the United States agreed that each would dispose of 34 tons of surplus plutonium, a major step toward nuclear nonproliferation. But in the years since, due to mistaken policy decisions, the U.S. hasn’t begun destroying its own stockpile—and that process isn’t going to start anytime soon. In turn, Russia hasn’t complied either while they wait for us, leading to the current stalemate.

The good news is that Russia still intends to uphold the deal—but only if the U.S. finds a credible way to dispose of its plutonium. On the current path, that may never happen. Both the Obama and Trump administrations have adopted a technique to dispose of our plutonium stockpile that Russia has already rejected, deeming it not credible.

Luckily, there is a third path, one that would provide significant economic benefits to the U.S. economy and one that Russia has already approved, ensuring that Moscow would finally dispose of its 34 tons of weapons-grade plutonium. It’s time for the Trump administration to abandon the failed Obama-era approach and chart a new course, one that can comply with the deal signed 20 years ago.

I have decades of experience with this issue: I was science adviser to the late Sen. Pete Domenici, who authored the original legislation codifying the 1998 U.S.-Russia agreement, and then served as a commissioner on the Nuclear Regulatory Commission. Under President Barack Obama, I served as the Energy Department’s top nuclear energy official.

Under the original agreement, the United States agreed to dispose of its plutonium by building a facility to make mixed plutonium-uranium reactor fuel—known as MOX fuel—to use in our commercial reactors. At the time, this path made sense since we anticipated a “nuclear energy renaissance,” which promised a growing need for reactor fuel.

But in the past two decades, the MOX proposal has become much less likely to work. First, that “nuclear energy renaissance” never happened. In fact, reactors are closing in many countries and there is so much cheap uranium that some of the world’s most productive mines have closed. Second, the facility to convert the plutonium into MOX fuel—originally scheduled to start operating in 2016—is years behind schedule and well over budget; its current completion date is at least a decade away. And even if the fuel facility is completed, domestic utilities are not interested in burning MOX fuel in their reactors because uranium is so cheap—unless the government pays them. In other words, for the MOX proposal to work, the government would have to pay to build and maintain the facility—and then pay utilities to actually burn the MOX fuel. Not a great business model!

Hoping to break this political and financial logjam, the Obama administration devised a new approach to get rid of its plutonium called “dilute and dispose.” Under this approach, the plutonium is blended with other waste and sent to a radioactive waste disposal facility, the Waste Isolation Pilot Project in New Mexico. “Dilute and dispose” renders a valuable resource totally worthless, but the Obama administration supported this option because it was cheaper than the MOX approach.

However, like the MOX proposal, this approach is unlikely to work. The biggest problem is that the WIPP doesn’t even have the capacity to complete its present mission and also dispose of the 34 tons of plutonium. Any new use of WIPP could crowd out other uses, potentially delaying the disposal of waste generated in the cleanup of former defense facilities. In addition, even if there was enough room, WIPP is not currently licensed to accept this additional material. Even worse, Russia already rejected this idea, both in the original negotiations and again last year, because it does not destroy the plutonium. In other words, even if the Trump administration successfully implemented the “dilute and dispose” option, Moscow likely wouldn’t dispose of its own 34 tons of plutonium.

Luckily, there’s another option. During the Obama administration, I argued vehemently that the dilute and dispose proposal was a poor choice and instead recommended disposing the plutonium as fuel in fast reactors, which effectively destroy the plutonium. I was overruled, but this idea remains the best chance to eliminate Russia’s dangerous stockpile of plutonium and realize other important national benefits.

Fast reactors are not new in the United States. In the 1950s, we built several fast reactors and demonstrated their impressive safety attributes, including proving that they could not melt down even with a complete loss of coolant. But through a combination of early safety issues and political decisions, the last fast reactor in the country shut down in 1993.

However, several U.S. companies—including TerraPower, which is funded by Bill Gates, General Atomics and General Electric—are exploring fast reactors because of their versatility and meltdown- proof operation; among other abilities, they can destroy nuclear waste, burn plutonium and generate electricity with higher efficiency than existing reactors. But the exploration process can take years, especially since any testing requires the use of existing Russian fast reactors. But if Washington financed a fast reactor to dispose of its plutonium stockpile, it would jump-start the development process by providing a fast reactor-testing platform in this country, a real benefit to many U.S. companies. Congress has recognized this opportunity as well, spending money in fiscal 2016 to develop a plan for an advanced reactor, such as a fast reactor.

Such a plan would also prevent the U.S. from falling behind on modern technologies as other nations, including France, Japan, China and India consider building their own fast reactors. At the very least, this proposal would ensure that the U.S. has enough operational experience with fast reactors to participate in global discussions on their safety and nonproliferation characteristics.

This plan has one downside: It would be more expensive than the dilute and dispose option since we’d have to build a new reactor. But unlike Obama’s plan, the fast reactor proposal would ensure that Russia disposes of its plutonium stockpile. In fact, Moscow intends to use its own fast reactors to destroy its plutonium. If we adopt a similar proposal, we would satisfy the original agreement, taking an important step toward nuclear nonproliferation and a safer world.

Peter Lyons worked at Los Alamos National Laboratory from 1969 until he became science adviser to Sen. Pete Domenici from 1997 to 2005. He was a commissioner on the Nuclear Regulatory Commission from 2005 to 2009 and assistant secretary for nuclear energy from 2011 to 2015. He now consults on nuclear energy and safety issues.

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