As the body of North Korea's "dear leader" Kim Jong-il lies in state at his palace in Pyongyang, his youngest son Kim Jong-un takes control of the country's nuclear weapons program. Despite being named Kim's successor in 2009, Kim Jong-un remains a bit of a mystery to the West. One unanswered question: How much power does the younger Kim wield over the country's military?

To better understand what the succession of power in North Korea means for its nuclear program, Scientific American spoke with Frank von Hippel, a professor at Princeton University's Woodrow Wilson School of Public and International Affairs and co-founder of the school's Program on Science and Global Security. Von Hippel, a former assistant director for national security in the White House Office of Science and Technology during the Clinton administration, discusses new evidence of North Korea's nuclear capabilities, the possibility of U.S.-orchestrated regime change, and the amount of plutonium needed to ruin your day.

[An edited transcript of the interview follows.]

How has the nuclear threat out of North Korea changed with the death of Kim Jong-il?
I don't think you would see a nuclear weapon used out of the blue by North Korea. Still, it's hard to tell. There have been incidents in the past few years leading up to Kim's death that have provoked South Korea in particular. Any transition is a time of some instability and that instability might lead to crazy things happening.

What impact will the succession of Kim Jong-un have on the direction the country takes?
There's been a lot of talk for a long time about the North Korean regime collapsing. But the Chinese don't want North Korea to collapse because they are concerned about South Korea absorbing North Korea and then, in effect, the U.S. military having a position on the Chinese border. They see North Korea as a buffer state. But North Korea's direction really depends on their [Korea's own] military and whether they will support the succession of Kim's son.

There have been incidents in the past couple of years—the sinking of the South Korean destroyer and the shelling of an island contested between the two counties—attributed to Kim Jong-un as a way of showing that he's not scared of South Korea and that he's leadership material.*

There's no indication that Kim Jong-un has the background or education (except for a fairly short period of time in Switzerland) to be the one to open up North Korea and bring them in from the cold the way [Mikhail] Gorbachev did for the Soviet Union in the late 1980s. And there's also a question of whether the military would let him do that even if he wanted to. At this point, he's probably not an absolute leader. He's a leader only as long as long as he leads in the direction that the military wants to be led.

In your January 2010 Scientific American article "Time to Ban Production of Nuclear Weapons Material" you write that India, Pakistan and North Korea are increasing their weapon stockpiles. How do we know about the current state of North Korea's nuclear weapons capabilities?
A year ago, Siegfried Hecker [co-director of the Center for International Security and Cooperation [CISAC] at Stanford's Freeman Spogli Institute for International Studies] returned from North Korea with some CISAC colleagues. During their stay in North Korea, they were shown a uranium-enrichment facility. They had expected to see an outdated facility based on equipment and designs that were at least 60 years old. Instead, they were surprised by the small, ultramodern, industrial-scale enrichment facility with 2,000 centrifuges. This is comparable to what Iran has. No one has questioned Sig Hecker's findings.

*Shortly after Kim Jong-un was named Kim Jong-il's successor, North Korea conducted a nuclear test large enough to cause a magnitude 4.7 seismic event in that country. Then in March 2010 a North Korean torpedo sank a South Korean navy ship, killing 46 sailors. Months later, North Korea fired about 200 artillery shells at Yeonpyeong, a South Korean island near a disputed maritime border, killing four people. Most recently, South Korea has accused the North of test firing a short-range missile shortly before the announcement of Kim Jong-il's death.

How does North Korea's nuclear program compare with that of Iran?
The difference between Iran and North Korea is that North Korea is out of the box—they've acquired the means to make weapons and exited the Non-Proliferation Treaty.** Most people think it's harder to get a country back in the box once they've left. Iran has lived up to the letter of the Non-Proliferation Treaty in terms of allowing the International Atomic Energy Agency (IAEA) to inspect what they're doing. Iran declares that its program is for energy purposes, not for weapons. But they've also been moving closer and closer to a posture where they could break out quickly and produce the highly enriched uranium used to make weapons. There's a lot of concern about this. Actually there's a lot of anxiety about both of them, and there's a concern with regard to North Korea that South Korea and perhaps even Japan might get so worried that they [also will] feel they need nuclear weapons.

With North Korea, we're trying to get them to see that they would be better off cashing in their status as a nuclear weapons state. Still, it's debatable how hard we've been trying. I don't think we've given them a convincing offer to do this.

What would be a convincing offer?
We are still technically in a state of war with North Korea since there was no peace treaty after the Korean War. North Korea worries about the U.S. interfering in the regime change there. They cite Libya as an example of a country that gave up its nuclear program and this year was vulnerable to bombing by NATO. North Korea would need some kind of assurance that if they got rid of their nuclear weapons we would leave their regime change up to them and not interfere. It's hard to make a convincing guarantee of this because it's such a repulsive regime, but that's really what they want.

Well, also they want some sort of economic assistance because they're in such terrible shape. South Korea and China have tried to set up factories in certain areas, but they haven't worked out. I'm critical of the U.S. for not doing a better job on its end. The first [George H. W.] Bush administration was ambivalent toward North Korea, thinking we should pressure them until they collapse. Clinton thought they were close to a deal but then they were out of office. Neither the [George W.] Bush or the Obama administrations have done much in terms of negotiations with North Korea.

** In 1985 North Korea agreed to the Non-Proliferation of Nuclear Weapons Treaty (NPT), which requires non-nuclear weapon states to give up the development and acquisition of nuclear weapons, but refused to sign an obligatory safeguards agreement with the IAEA. In 1994, the same year Kim Jong-il assumed power, North Korea agreed to freeze its plutonium weapons program in exchange for aid from the U.S., an agreement that collapsed in 2002. In August 2003 China, Japan, the two Koreas, Russia, and the U.S. launched another major diplomatic effort known as the Six-Party Talks. A few years later North Korea pledged to abandon all nuclear weapons and existing nuclear programs and return to the NPT. But the talks broke down in 2009 following North Korea's nuclear missile test that year. (The country conducted its first nuclear test in October 2006.)

How did North Korea's nuclear program begin?
North Korea began its nuclear program using a graphite-moderated reactor and a reprocessing plant in which they separated the plutonium from irradiated natural uranium. It's been said that the design for North Korea's reactor was copied from a design the British used to make plutonium weapons. The British later added the ability to produce electricity from these reactors. North Korea did this, too, although because their reactor is small it generated a relatively small amount of electricity, presumably supplied to a village adjacent to the Yongbyon reactor site.***

Where did the North Koreans get the designs, expertise and equipment needed to build their reactor?
The U.S. and the U.K. made their reactor designs public information as part of the Atoms for Peace conferences. [These conferences were launched following a December 1953 speech by President Dwight D. Eisenhower to promote nuclear energy worldwide. The Atoms for Peace program led to the declassification of hundreds of nuclear studies and reports.] Of course, building a reactor requires an effort to master certain technologies and to make, for example, very pure graphite so it won't absorb neutrons. For that North Korea sent quite a few people to the Soviet Union to be trained. The North Koreans saw nuclear as a path to energy and military independence.

How does North Korea's nuclear weapons arsenal compare with the world's other nuclear powers?
We're talking about enough plutonium to make 10 weapons or less. So not very much—but enough to ruin your day. The U.S. and Russia have thousands while other nuclear countries like the U.K., France, China, India, Pakistan and Israel have weapons numbering in the low hundreds.

Based on what we know about North Korea's nuclear arsenal, what is the extent of the damage it could inflict?
Their arsenal is a deterrent. They have the potential to blow a Hiroshima-sized hole in a city in South Korea or Japan, or several holes maybe. The question of whether they have designed these warheads so they can be carried by the missiles they have is unanswered. But I think nobody would bet against it. They've also been working on missiles that could reach the U.S., although without having a successful test to prove this.

What has been the rest of the world's reaction to North Korea's attempts to build a nuclear arsenal?
In response to Western concerns about the reactor, which had been discovered by surveillance satellites in the 1980s, Russia successfully pressed North Korea to sign the Non-Proliferation Treaty, which it did in 1985. They were then expected to set up a system whereby the IAEA [International Atomic Energy Agency] could inspect North Korean nuclear facilities, although they really didn't want the IAEA to look at evidence of their activities relating to past plutonium production. It got to be a cat-and-mouse game with inspectors.

Concerns over North Korea's nuclear program built up over a period of nine years until 1994, when the U.S. considered bombing the site. That was when Jimmy Carter parachuted—not literally, of course—into Pyongyang and reached an agreement with Kim Jong-il's father, Kim Il-sung, to freeze their atomic program. As part of the Agreed Framework, North Korea said it would freeze operation and construction of nuclear reactors, which were suspected of being part of a covert nuclear weapons program. In exchange they were supposed to get two light-water nuclear power reactors that couldn't be used to make weapons. In the meantime, we were also supposed to send them heavy fuel oil to compensate for the energy they weren't getting from the reactors they had shut down.

The U.S. claims that in October 2002 North Korea admitted to having a uranium-enrichment program that could be used to make nuclear weapons. North Korea denied having said it has such a program, but the damage was done. How did the Agreed Framework fall apart?
We stopped sending the heavy fuel oil. Meanwhile the schedule for completing the new reactors had slipped [from 2003 to 2008]. North Korea kicked out the IAEA inspectors and started reprocessing the irradiated fuel that had been in the reactor when it had shut down. They were able to capture something like 30 kilograms or so of additional plutonium for a few more bombs, perhaps 10 kilograms of which they used for their nuclear tests in 2006 and 2009. Subsequently, North Korea irradiated more uranium in the Yongbyon reactor and produced 20 to 25 kilograms more plutonium.

*** In the mid-1960s Kim Il-sung built the Yongbyon Nuclear Scientific Research Center 90 kilometers north of Pyongyang with help from engineers trained in the Soviet Union. By 1985 U.S. intelligence reports indicated North Korea had built a fully functioning nuclear reactor.