Nuclear scientist and CISAC co-director Siegfried Hecker and Frank Pabian, recent CISAC visiting scholar and senior geospatial information analyst at the Los Alamos National Laboratory, have published a study in the Bulletin of the Atomic Scientists which takes a hard look at North Korea’s Punggye-ri nuclear test site. Using open-source technology, they believe they now have the best calculations for the epicenters of the two nuclear tests conducted by Pyongyang in 2006 and 2009 – and conclude the North is capable of carrying out a third within weeks. Whether Pyongyang is willing to pay the political costs of another test remains open to debate.

Hecker answers questions about the current state of nuclear affairs in North Korea:

Following the failed launch of a satellite by North Korea in April, a third nuclear test appeared imminent. Yet more than three months have passed and there has been no test. Why?

We make the case in the article that Pyongyang has much to gain technically and militarily from another test, but the political costs may be too high. That was also the case in 2006 and 2009, but Kim Jong Il decided to pay the price, which turned out not to be that great in the end because China did not want to destabilize the regime despite its displeasure with the tests. Now we have a young new leader, Kim Jong Un, and a more assertive China trying to guide the regime toward market reforms. So the equation has changed.

Does that mean Kim Jong Un may take a less confrontational stance on the nuclear issue?

It’s too early to tell, but the country is clearly under new management. Photos of the young leader on rides in Pyongyang’s version of Disneyland and photos with his new wife in modern dress – and both of them mingling with the ordinary public – is a far cry from his father’s style. 

You believe that you have done the most accurate job to date in locating the epicenters of the two North Korean nuclear tests and that leads you to the best estimate of what the explosion yields were. Yet there are still significant variations in yields between your analysis and the official U.S. government estimate released by the Director of National Intelligence. Why?

We have done the most precise analysis of locating the epicenters by combining results from seismic signals and Google Earth 3D maps of the test area. Taking our understanding of standard nuclear test practices, we were able to determine accurate depth-of-burial for the nuclear devices. We then took these new results and refined the calculations of Los Alamos National Laboratory researchers, who use a model in which yield depends on depth-of-burial. However, researchers at the Lawrence Livermore National Laboratory use a model that does not depend on depth-of-burial within the range in question. Their model predicts a yield close to 2 kilotons, as expressed by the DNI. Our new analysis, based on the Los Alamos technique, suggests a yield between 4 to 7 kilotons. The jury is still out as to which of the models is more accurate, but we believe we have the best estimate of the location of the epicenters to date.

What have recent satellite images shown around the Punggye-ri nuclear testing site?

Right after the missile launch, satellite imagery showed significant new activity at what has been identified as a likely third nuclear testing tunnel, which is why we believe it's important to re-examine North Korea's past nuclear tests to learn what we can about its future test capabilities.

North Korean leader Kim Jong Un prepares to take a ride with other high-level officials during the opening ceremony of the Rungna People's Pleasure Ground in Pyongyang on July 25, 2012. Photo credit: Reuters/KCNA

Why are you so concerned about another nuclear test?

I believe that North Korea has the bomb, but not much of a nuclear arsenal. With its limited testing success to date, Pyongyang likely does not have confidence to field a miniaturized nuclear weapon on one of its missiles. If it can’t mount a nuclear weapon on a missile, its bombs are more like a terrorist’s threat – that is, they would have to be delivered by van, boat or plane. North Korea needs more nuclear tests to demonstrate they can build a miniaturized warhead. 

Does that mean if they test they may attack the United States or its allies with nuclear-tipped missiles?

I don’t believe another test would lead to that – but it greatly increases the threat that North Korea poses to all of us. That’s exactly what Pyongyang is trying to convey when they say they will strengthen their deterrent. The deterrent is meant to warn the U.S. and putting warheads on missiles makes their deterrent more credible.

Do they have missiles that can reach the United States?

No – the failed missile launch showed they still have a long way to go in improving their rocket technology. In addition, for a space launch the payload (satellite) needs to reach orbit, whereas for a missile attack the payload (nuclear warhead) also has to survive the enormous temperatures and stresses of re-entry. We have no indication that they have developed and tested the required re-entry vehicles to do so.

In the Bulletin article you speculate the North may simultaneous test a plutonium bomb and one fueled by highly enriched uranium (HEU). What brings you to that conclusion?

Plutonium production has ceased in the North, so they only have enough for four to eight bombs. When they showed Stanford Professor John Lewis, Bob Carlin and me their new centrifuge facility during our Nov. 2010 visit, they served notice that they can produce HEU if they so choose. So from a technical standpoint, a plutonium test gives them one more important data point for plutonium bombs and an HEU test opens up another line of possible bombs.

Why not just do two separate tests instead of complicating the containment challenges?

North Korea has to pay a political price for each test. Beijing may be getting very impatient with Pyongyang. If North Korea conducts two simultaneously, they would only have to pay the price for one test, not for two. That may be enough incentive to do multiple tests simultaneously. They can’t do five like the Pakistanis, because each test depletes their meager supply of fissile materials.

Have other countries conducted multiple nuclear bomb tests before?

Yes, the United States has tested multiple nuclear devices simultaneously; so has Russia. But, as we describe in the article, the most interesting case is Pakistan. In response to the Indian tests (which were also multiple tests) in 1998, Pakistan not only tested five nuclear devices simultaneously, but also publicized this widely. There were other similarities between what North Korea advertised about its 2009 test and the Pakistani testing information, which albeit circumstantial, leads us to suspect that the North Koreans may have learned a lot from the Pakistani testing experience.

What should Washington be doing to make sure that a third test does not take place?

Work with Beijing to make sure the political price for North Korea conducting another test is too high for the new regime to bear.

How were you able to gather and present the information in your study using open-source material? How does this work fit into the broader context of open-source nonproliferation work being done today by researchers and bloggers?

This is a great example of how the new information technology tools like Google Earth and social media are revolutionizing the intelligence world. Even for a country as reclusive as North Korea, there is an enormous amount of information available for a great number of socially networked analysts around the world. Some of the information comes from satellite imagery, some from what the state puts out in propaganda and some from Track II visits such as those made by my Stanford University colleagues and me.