North Korea announced on April 2 that it would restart its nuclear facilities, including its 5-megawatt-electric (5-MWe) nuclear reactor in Yongbyon, north of the capital, which had been disabled and mothballed since an agreement in October 2007.

Pronouncements from Pyongyang during the past few weeks have been ominous, including threatening the United States and South Korea with pre-emptive nuclear attacks. On April 2, 2013, a spokesman for North Korea’s General Department of Atomic Energy told the Korean Central News Agency that at the March 2013 plenary meeting of the Central Committee of the Workers' Party of Korea: “A new strategic line was laid down on simultaneously pushing forward economic construction and the building of nuclear armed forces.”

The pronouncement continued: “The field of atomic energy is faced with heavy tasks for making a positive contribution to solving the acute shortage of electricity by developing the self-reliant nuclear power industry and for bolstering up the nuclear armed force both in quality and quantity until the world is denuclearized.”

We ask Stanford Professor Siegfried S. Hecker – former CISAC co-director and now a senior fellow at CISAC and the Freeman Spogli Institute – to weigh in. Hecker has been invited seven times to North Korea and he made international headlines when he returned from his last trip in November 2010 and announced the isolated North Asia nation had built a modern uranium enrichment facility.

Q: How concerned should we be about North Korea’s announcement that it will restart all its nuclear facilities? Does this fundamentally change the threat imposed by Pyongyang?

Hecker: It does not immediately change the threat, but it really complicates the long-term picture. This announcement indicates that North Korea’s nuclear arsenal is severely limited by a lack of fissile materials, plutonium or highly enriched uranium (HEU) to fuel its bombs. Despite its recent threats, North Korea does not yet have much of a nuclear arsenal because it lacks fissile materials and has limited nuclear testing experience. In the long term, it’s important to keep it that way; otherwise North Korea will pose a much more serious threat. So, it is important that they don’t produce more fissile materials and don’t conduct more nuclear tests. The Kim Jong Un regime has already threatened to conduct more tests and with this announcement they are telling the world that they are going to make more bomb fuel. I should add that they also need more bomb fuel to conduct more nuclear tests.

Q: What do you make of the previous threats to launch an all-out nuclear war against the United States and South Korea? Does North Korea have the technical means to do so?

Hecker: I don’t believe North Korea has the capacity to attack the United States with nuclear weapons mounted on missiles, and won’t for many years. Its ability to target and strike South Korea is also very limited. And even if Pyongyang had the technical means, why would the regime want to launch a nuclear attack when it fully knows that any use of nuclear weapons would result in a devastating military response and would spell the end of the regime?  Nevertheless, this is an uneasy situation with a potential for miscalculations from a young and untested leader.  

Hecker spoke about North Korea with Christiane Amanpour on CNN, April 2, 2013. 

Q: The Kim Jong Un regime has reiterated and apparently put into law that North Korea will not give up its nuclear arsenal. Does the current announcement really make things that much worse?

Hecker: I have previously stated that North Korea has the bomb, but not yet much of an arsenal. It has been clear for some time that North Korea will not give up its nuclear weapons, so what we should have focused on is to make sure things don’t get worse. I have stated it as the three No’s: no more bombs, no better bombs and no export. We don’t know much about North Korea’s nuclear exports, but that potential is a serious concern. Pyongyang took a step toward better bombs with its successful Feb. 12 nuclear test, although it still has little test experience. The current announcement demonstrates that they will now redouble efforts to get more bombs by increasing their capacity to make plutonium and HEU. It won’t happen quickly because these are time-consuming efforts – but it bodes ill for the future.

Q: Let’s look at the technical issues of the latest announcement. What do you think Pyongyang means by “readjusting and restarting all the nuclear facilities in Yongbyon? 

Hecker: The restarting is easy to decipher: They plan to take the 5-MWe gas-graphite plutonium production reactor out of mothballs and bring the plutonium reprocessing facility back into operation. The “readjusting” comment is less clear. It may mean that they will reconfigure the uranium enrichment facility they showed to John Lewis, Bob Carlin and me in 2010 from making low enriched uranium (LEU at 3 to 5 percent for reactor fuel) to making highly enriched uranium (HEU at 90 percent for bomb fuel). 

Q: What did you learn about the 5-MWe reactor during your November 2010 visit to Yongbyon? Will they really be able to restart it?

Hecker: Lewis, Carlin and I were shown the beginning of the construction of the small experimental light-water reactor. The containment structure was just going up. I pointed to the 5-MWe reactor right next door and asked the chief engineer of the reactor, "What about the 5-MWe gas-graphite reactor?" He replied: “We have it in standby mode.” I told him that people in the West claim it is beyond hope to restart. He chuckled and said, "Yes, I know, that's what they also said in 2003, and they were wrong then as well." The reactor had been mothballed since 1994 as part of the Agreed Framework. The North Koreans restarted it in 2003 without much of a problem and ran two more campaigns to make plutonium.

Q: Is there any indication that they actually have an HEU bomb?

Hecker: We really don’t know. To the best of our knowledge, the first two nuclear tests in 2006 and 2009 used plutonium for the bomb fuel. We do not know what was used in the most recent test on Feb. 12. It could have been either HEU or plutonium. It would not surprise me if they have been pursuing both paths to the bomb; that’s what the United States did during the Manhattan Project.

Q: Will we know when they restart the reactor?

Hecker: Yes, using satellite imagery we should be able to see the steam plume from the cooling tower as soon as they rebuild and restart it.

Q: Didn’t North Korea also have a 50-MWe reactor under construction? What happened to that?

Hecker: As part of the Agreed Framework in 1994, North Korea agreed to freeze the operation of the 5-MWe reactor and the construction of its bigger cousins, a 50-MWe reactor in Yongbyon and a 200-MWe reactor in Taecheon. We saw the 50-MWe reactor in 2004 and were told that they were evaluating what it would take to get it restarted. During later visits we were told and saw for ourselves that it was not salvageable. We were told the same was true for the Taecheon reactor. The North Koreans had been willing to trade these two gas-graphite reactors for the KEDO light-water reactors that the United States, South Korea and Japan had agreed to build at Sinpo. However, the deal fell apart when the Agreed Framework was terminated in 2003.

Q: What would it take to restart the 5-MWe reactor? And how much plutonium could it make?

Hecker: The reactor has been in standby since July 2007. In June 2008, as a good-will gesture to Washington (and a reputed fee of $2.5 million from the U.S., according to North Korean officials), Pyongyang blew up the cooling tower. In addition, based on our previous visits, we concluded that they also needed to do additional work to prepare the fresh 8,000 fuel rods required to restart the reactor. If they restart the reactor, which I estimate will take them at least six months, they can produce about 6 kilograms of plutonium (roughly one bomb’s worth) per year. What they may do is to run the reactor for two to four years, withdraw the spent fuel, let it cool for six months to a year, and then reprocess the fuel to extract the plutonium. In other words, from the time they restart the reactor, it would take roughly three to four years before they could harvest another 12 kilograms of plutonium. The bottom line is that this is a slow process.

Q: How difficult would it be for North Korea to adjust its centrifuge facility to make HEU? And, if they did, how much HEU can they make?

Hecker: Not very difficult. It just requires reconfiguration of the various centrifuge cascades and adjusting operational procedures. That could be done very rapidly. They most likely had everything prepared in case they ever wanted to make this move. If they reconfigure, then based on our estimates, they could make roughly 40 kilograms of HEU annually in that facility – enough for one or two HEU bombs a year.

Q: How big is North Korea’s plutonium stockpile?

Hecker: After our 2010 visit, I estimated that they had 24 to 42 kilograms of plutonium, roughly enough for four to eight bombs. If the 2013 nuclear test used plutonium, then they may have 5 or 6 kilograms less now. Because they have so little plutonium, I believed that they might have turned to uranium enrichment to develop the HEU path to the bomb as an alternative.

Q: Could you explain what you see as North Korea's capabilities in regard to putting nuclear warheads on short-, medium-, and long-range missiles?

North Korea has conducted only three nuclear tests. The 2006 test was partially successful; the 2009 and 2013 tests likely were fully successful. With so few tests, the North Korean ability to miniaturize nuclear warheads to fit on its missiles is severely limited. After the first two tests, I did not believe North Korea had sufficient test experience to miniaturize a nuclear warhead to fit on any of its missiles. I believed the nuclear devices tested were likely primitive -- on the order of the Nagasaki device, which weighed roughly 5,000 kilograms. Official North Korea news outlets implied they were more advanced, and some Western analysts agreed. I stated that they needed additional nuclear tests to miniaturize.

Q: After the test in February, Pyongyang announced that it had successfully tested a smaller and lighter nuclear device. North Korean news media also specifically stated that this was unlike the first two, confirming that the earlier tests involved primitive devices. The Kim Jong Un regime followed the claim of having smaller and lighter warheads with threats of launching nuclear-tipped missiles against the United States and South Korea.

My colleague, CISAC Affiliate Nick Hansen, and I do not believe that the North Koreans have the capability to miniaturize a warhead to fit on a long-range missile that can reach the United States because the weight and size limits are prohibitive for them. They have insufficient nuclear test experience. Although last December they were able to launch a satellite into space, it is much more difficult to develop a warhead, fit it into a reentry body, and have it survive the enormous mechanical and thermal stresses of reentry on its way to a target. In April 2012, Pyongyang paraded a road-mobile long-range missile we call the KN-08. It may have been designed to reach as far as Alaska and the US West Coast, but to our knowledge it has never been test fired. There is some evidence that the first-stage engine may have been tested last year and early this year at the Sohae (Tongchang) launch site on North Korea's West Coast. North Korea would need a lot more missile tests as well as more nuclear tests to present a serious long-range threat.