Closing North Korea’s nuclear program poses many challenges

SEOUL, South Korea—An unknown number of nuclear warheads. Stockpiles of weapons-grade plutonium and highly enriched uranium. ICBMs. Weapons factories—and the scientists who work at them.

The list of what it would take for the “complete denuclearization” of North Korea is long.

It wouldn’t be hard to hide at least some of the warheads and radioactive materials in the country’s vast complex of underground facilities.

A look at the many pieces of a secrecy-clouded bomb program that has rattled the region for decades:

THE WARHEADS

The size of North Korea’s nuclear arsenal is a mystery, with estimates ranging from 10 bombs to as many as 60 to 70.

How sophisticated they are is also unclear. It’s one thing to conduct a nuclear test—North Korea has carried out six underground explosions since 2006, including what it says were two hydrogen bomb tests.

It’s another thing to make the warheads small enough to be carried by a long-range missile that can strike the U.S. mainland.

Kim said last November that his country had mastered that technology, and many foreign experts and governments believe North Korea is at least getting there.

THE INGREDIENTS

Nuclear bombs can be made from plutonium or highly enriched uranium, and North Korea has both.

A 2016 South Korean government report says that North Korea is believed to have produced 110 pounds of weaponized plutonium, enough for six to 10 bombs.

North Korea shut down the plutonium-producing factory at its main nuclear complex in Nyongbyon in 2007 as part a disarmament-for-aid deal, but the accord later fell apart, and satellite imagery indicates the North has resumed extracting plutonium in recent years.

THE MISSILES

The United States would want North Korea to include any intercontinental ballistic missiles in its disarmament steps as they are the delivery vehicles for nuclear weapons targeting the U.S. mainland.

Last year, North Korea test-launched three ICBMs that it says are all nuclear-capable. Experts say, though, that North Korea has yet to demonstrate the technology needed to protect its bombs from the severe heat and pressure that a longrange missile is subjected to on returning to the Earth’s atmosphere.

Lee Choon Geun, a missile expert from South Korea’s Science and Technology Policy Institute, says he believes that North Korea has “several but less than 10 ICBMs.”