North Korea plans to use long-range missile technology to launch a satellite later this month despite international condemnation. There are also troubling signs that the isolated country is preparing for a third nuclear test. In a new Q&A, James Acton explains the significance of the mid-April satellite launch, the technological reasons North Korea would want to test another nuclear device, and what to watch for if it does.

How significant are North Korea's plans to launch a satellite in April?

Relations between North Korea and the United States are rapidly deteriorating again. On February 29, the two sides appeared to have made a diplomatic breakthrough when Pyongyang agreed to suspend nuclear and long-range missile tests as well as its enrichment program in return for 240,000 metric tons of food aid from the United States.

Just over two weeks later, however, North Korea announced its intention to launch a satellite sometime between April 12 and 16. Given the technical similarities between space launch vehicles and ballistic missiles, the United States, many regional states led by South Korea and Japan, and—very significantly—Russia have said they would consider the launch a violation of UN Security Council resolutions prohibiting North Korea from engaging in ballistic missile activities, as well as the February 29 agreement. By contrast, China’s foreign minister, Yang Jiechi, said he is “troubled by the developments,” but Beijing stopped short of condemning the launch or asserting it would be illegal and instead urged negotiations.

The North Korean rocket is due to be launched almost due south. Apart from overflying some isolated South Korean islands, it is set to travel above nothing other than the ocean until it passes over the Philippines about 3,000 kilometers south of its launch point. Both Japan and South Korea, however, have mobilized missile defense assets with the warning to destroy the rocket should it threaten them. 

While it is unlikely that either South Korea or Japan will actually attempt to destroy the North Korean rocket, it is certain the launch will be met by a wave of denunciation. There is growing concern that Pyongyang will use the formal renunciation of the so-called Leap Day Deal by the United States as an excuse to conduct a third nuclear test.

Has Pyongyang indicated it intends to conduct a nuclear test?

Indirectly. A Japanese newspaper with close links to the North Korean government, Choson Sinbo, carried an article last week stating that “North Korea’s commitment to a temporary moratorium on nuclear tests...can be cancelled.”

In a reference to North Korea’s last nuclear test on May 25, 2009, which was preceded by a widely criticized satellite-launch-cum-missile-test on April 5, the article went on to say that if the United States fails to deliver food aid, Washington would be “turning the clock back to post-April 2009.” This story has been widely interpreted as a signal from Pyongyang that it will retaliate to international condemnation of its satellite launch with a nuclear test.

Is there any evidence of technical preparation for a nuclear test?

Yes. Over the last two years, there have been sporadic media reports of activity, including tunnel digging, in the area where North Korea’s first two tests were conducted. This weekend, an anonymous South Korean official stated that satellite images show the existence of a large pile of earth near the entrance to one of these tunnels. This is evidence that preparations are fairly advanced as the earth could be used to seal a tunnel after the emplacement of a nuclear test device.

If North Korea does conduct another nuclear test, what should we look for?

Analysts will be looking at two things in particular: the size of the explosion—its yield—and the fissile material—highly enriched uranium or plutonium—from which the device is made.

Is it true that North Korea's previous nuclear tests had quite low yields? Is that why Pyongyang wants to conduct another test?

North Korea conducted two previous nuclear tests, on October 9, 2006 and May 25, 2009. Recent analysis suggests that the first explosion had a yield of about 900 tons (the amount of TNT required to make an equivalently large conventional explosion) and the second had a yield of about 4,600 tons. By way of comparison, the first U.S. test, called Trinity and conducted in New Mexico on July 16, 1945, had a yield of about 21,000 tons.

Given the small size of both North Korean tests, most analysts have concluded that they performed significantly less well than intended. Accordingly, a third explosion may be intended to test an improved, higher yield design.

That said, a minority of experts have argued that North Korea may have intended to produce lower yield devices. Surprisingly perhaps, such devices are more difficult to manufacture than the simple design used in the Trinity test, but could be lighter and hence easier to carry by missile. If this speculation is correct, then North Korea’s nuclear program may be more advanced than generally believed.

What is the significance of the fissile material from which the device is made?

Radioactive emissions from North Korea’s first nuclear test in 2006 indicated the device was made from plutonium. North Korea’s plutonium stockpile is only sufficient to produce a handful of weapons and, given the dilapidated state of its plutonium-production infrastructure, producing more would be slow-going and very noticeable. Consequently there was reason to hope that North Korea’s arsenal would remain very small.

In November 2010, however, North Korea revealed the existence of a sophisticated uranium enrichment effort that appears to be capable of producing highly enriched uranium in significant quantities and, as a result, of significantly expanding North Korea’s arsenal. Many analysts, therefore, anticipate that a third test would be a highly enriched uranium device.

There is no guarantee, however, that the radioactive emissions from a third North Korean test would be detectable. Without such emissions it is impossible to identify the material from which the device is made. Indeed, North Korea’s second test in 2009 did not produce measurable radioactive emissions and it is not known whether it was made of plutonium or highly enriched uranium.

If a third nuclear test takes place without producing radioactive emissions, how will we know it has occurred?

Even if there are no radioactive emissions, it will still be possible to detect the shock waves that propagate through the earth after a large explosion. Seismic monitoring is a reliable means of detecting nuclear tests and estimating their yields. The earth is covered in seismic sensors, including those that are part of the International Monitoring System for the Comprehensive Nuclear-Test-Ban Treaty (an agreement to ban all nuclear tests that has yet to enter into force because a number of countries, including the United States and North Korea, haven’t ratified it). This sensor array, along with many others, detected both previous North Korean nuclear tests and provided sufficient data to allow analysts to estimate the yields with reasonable accuracy.

Apart from possibly increasing the yield of its devices and trying out highly enriched uranium, are there any other technical reasons North Korea would want to conduct a third nuclear test?

Yes. Given North Korea’s aggressive ballistic missile development program, it is likely that Pyongyang’s goal is to develop a warhead that is small and light enough to be mounted on a missile since this would enhance its ability to threaten South Korea, Japan, and eventually the United States.

Testing would be helpful to North Korea in miniaturizing its warheads if it has not done so already (and many analysts believe it has not). If radioactive emissions are present, they may give clues about the design—and hence the size—of the device. However, it is unlikely that the U.S. intelligence community, which will certainly try to detect such emissions, will comment on them, beyond confirming their existence as it did in 2006.

Are there political reasons why North Korea might want to conduct another nuclear test?

Almost certainly. While it is very difficult to interpret Pyongyang’s decisionmaking, it seems highly likely that the timing of the probable test is dictated primarily by political considerations. The test may be intended to bolster the domestic authority of North Korea’s new leader, Kim Jong Un, who took over following the death of his father, Kim Jong Il, in December last year. Moreover, 2012 is the one hundredth anniversary of the birth of Kim Il Sung, the nation’s founder, and the year in which his son, Kim Jong Il, declared that North Korea would become a “strong and prosperous” nation.