By W.J. Hennigan
February 27, 2019

For decades, American presidents have sought a deal to disarm North Korea, only to be frustrated at every turn. At the center of these efforts is the sprawling nuclear research center at Yongbyon, where three reactors provide the country with the ability to make more nuclear warheads — or worse, peddle the material to third parties.

So it comes as little surprise that once again, as President Donald Trump and North Korean leader Kim Jong Un sit down for a second summit in Hanoi, Yongbyon has emerged as a vital element of any prospective deal.

The nuclear center, comprised of nearly 400 buildings peppered over 3.4 square miles, has been called the crown jewel of Pyongyang’s nuclear infrastructure. It’s believed that all of the nation’s plutonium is produced at the complex, along with highly enriched uranium and tritium, which is necessary to make a powerful thermonuclear weapon.

Although Pyongyang is a long way from giving up its nuclear weapons entirely, the diplomatic path toward that goal is more visible than it has been in years. Kim is aware that Yongbyon, which has been producing plutonium since 1986, is perhaps his biggest bargaining chip in negotiating relief from economic sanctions that have long crippled his country. He indicated he might be willing to accept limits on nuclear fuel production earlier this year during a national New Year’s address. And he told South Korean President Moon Jae-in last September he was open to shutting down at least one reactor.

But it will take more than a vague promise to show progress.

Arms control analysts warn that any agreement to shut down Yongbyon must be detailed with straightforward demands that can be verified by international inspectors who will have access to equipment, documents, and personnel to confirm compliance.

Siegfried Hecker, former director of the nuclear weapons design center at Los Alamos, N.M., and now a professor of management science and engineering at Stanford University, is one of the few foreigners to have toured Yongbyon. He witnessed 2,000 centrifuges capable of producing highly enriched, weapons-grade uranium. The facility, he said, has since doubled in size. “The bottom line is that shutting down and dismantling Yongbyon will eliminate the ability to produce more plutonium as well as tritium,” Hecker said. “It is highly unlikely that reactors exist anywhere else in North Korea. Dismantling Yongbyon will greatly limit highly enriched uranium production, but not end it.”

Dismantling the 5 megawatt plutonium production reactor represents a good start at the facility, he said, because “that would be easy to verify.”

However, North Korea has already twice agreed to shut down parts of the nuclear center, only to fire it back up again once relations soured.

The Agreed Framework signed by Washington and Pyongyang in 1994 called for Korea to halt nuclear-weapons development in return for two light-water nuclear power plants, from which it is difficult to generate the fissile material for bombs. In 2007, as a result of the so-called Six–Party Talks, Korea again agreed to shut down a reactor and invite the International Atomic Energy Agency (IAEA) inspectors for verification. A year later, Pyongyang publicly demolished a cooling tower at its main reactor. Once diplomatic relations deteriorated, however, it was restarted after the engineers devised a way to cool the reactor by pumping in water from a nearby river.

In both cases, Korea dismantled equipment but was able to quickly restart because the sensitive material, such as furnaces for fuel fabrication and reprocessing equipment, was close at-hand. “If we’re serious about stopping operations there, the sensitive equipment needs to be removed from North Korea this time,” said Jeffrey Lewis, an analyst with the James Martin Center for Nonproliferation Studies Middlebury Institute of Strategic Studies.

Moreover, any destruction of nuclear facilities must be inspected by IAEA, he said. Pyongyang shouldn’t be allowed off-the-hook from verification like their decision last year to blow up tunnels leading to an underground nuclear test site, which was only observed by international journalists. “Inspectors need to be allowed to do the forensic work to ensure compliance,” Lewis said.

Either way, delivering any sort of blow to Pyongyang’s sprawling missile and nuclear weapon infrastructure will take a herculean, years-long effort — the likes of which have never been seen before. No nation that has amassed such an arsenal has ever given it up. As a result, many arms control analysts are dubious of the Trump Administration’s stated goal of a “complete, verifiable and irreversible denuclearization” of the Korean Peninsula.

Yongbyon is the only known facility where North Korea produces weapons-grade material, but analysts believe it’s not alone. For instance, Lewis discovered another site at Kangson, just outside Pyongyang, using commercial satellite imagery.

“There are more facilities that we don’t know about,” Melissa Hanham, a non-proliferation expert and director of the One Earth Future Foundation’s Datayo Project. “Regardless of what happens in Hanoi, we will be living with a nuclear North Korea.”

She pointed out that any agreement should also acknowledge Pyongyang’s missile capability. It is a crucial topic, considering the Trump Administration pulled out of its obligations under the Iran Nuclear Deal, in part, because Iran continued developing and testing missile technology.

Under the 2015 agreement, known as the Joint Comprehensive Plan of Action, Iran removed the core of its Arak heavy water nuclear reactor and filled it with cement in exchange for sanctions relief. Yet the Trump Administration tore up the deal last year, citing Tehran’s continued missile testing even though it wasn’t explicitly part of the deal. “We can’t repeat the mistakes of the past,” Hanham said.

Under Kim, the country relentlessly pursued it toward its military goal of being able to unleash a nuclear strike on the U.S. and its allies. North Korea is now believed to have a dozen or more nuclear warheads and an arsenal of several hundred short- and medium-range ballistic missiles capable of hitting South Korea, Japan, along with U.S. military bases and territories in the region. Pyongyang also has developed long-range missiles that can range every major city in the continental United States.

North Korean state-run media says the nation now has a standardized nuclear weapon design with warheads small enough to be affixed atop ballistic missiles. The nation has not yet demonstrated a fully functional reentry vehicle, which carries the warhead atop the ICBM, capable of surviving the searing heat, pressure and vibration of falling from space back to Earth. Nor has it shown an ability to hit a target with precision, but it has demonstrated enough advancement to be treated as a full-fledged nuclear weapons state.

North Korea’s string of 23 missile launches in 2017 posed serious national security concerns for the U.S., including two ICBM launches that climbed to new heights in outer space — several times higher than the International Space Station. The two launches only went a short distance but if their astronomical trajectories were flattened out, the missiles would be capable of hitting nearly all of the United States. Meanwhile, North Korea continued to develop medium-range ballistic missiles that are driven on a mobile launcher into a remote area, blasted off, and delivered to their targets. The weapons are considered deeply destabilizing to Asian allies because of their capability to launch a devastating strike without early warning.

North Korea does appear to have halted its overt testing efforts, which may be a result of Trump’s “maximum pressure” campaign, or, some a reflection that Pyongyang has learned what it needed to learn from its missile tests last year and is secretly working on another aspect of the program.

After decades of defying international pressure to hold off on additional weapons development, North Korea did not test in 2018 and has yet to test-launch a missile in 2019.

With reporting by Feliz Solomon in Hanoi

Write to W.J. Hennigan at william.hennigan@time.com.

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