WASHINGTON -- While there are plenty of recent satellite images of North Korea’s nuclear testing grounds to pore over, extrapolating just exactly what the reclusive nation has planned for its next underground blast is a challenging task.
Among the questions surrounding the anticipated trial are: when will it happen, exactly where, how many devices will be involved and what type of fissile fuel will be involved?
The reclusive regime closely guards all aspects of its nuclear weapons program, making it difficult for interested observers to obtain precise information about the widely anticipated event.
David Albright, who heads the Institute for Science and International Security in Washington, has been analyzing photographs taken as recently as Jan. 28 by commercial space imagery company DigitalGlobe of the North’s Punggye-ri site.
“We can’t tell if the test is imminent or not,” Albright said in a Monday interview, summarizing the results of his most recent assessment with ISIS image analyst Robert Avagyan. “North Korea likes to hide what it does. Who knows what their schedule is. I would guess it could be from today to a couple of weeks.”
At the nuclear trial site in the country’s northeast, activity has been detected at the “west portal” used in the 2009 nuclear blast and the more recently excavated “south portal” that is viewed as the likeliest location for the anticipated blast -- assuming the North uses only one tunnel -- given placement of nearby facilities thought to house sensitive monitoring instruments.
The existence of two tunnels that have apparently both been primed for a nuclear test has government officials and independent experts wondering if North Korea intends to detonate multiple devices or if it is all an elaborate feint.
"There is a chance that the southern tunnel is a decoy, but we aren't ruling out that the regime will conduct nuclear tests simultaneously at both tunnels," an anonymous South Korean military source told the Chosun Ilbo newspaper earlier this week.
Albright sees “no evidence to suggest one [tunnel] is a decoy,” though he added that “people are free to speculate” on what they want.
North Korea has a history of attempting to confuse international observers with its weapon tests. One day prior to the country’s December firing of a long-range rocket, satellite images seemed to show the three-stage Unha 3 rocket had been removed from its launchpad. This led some foreign analysts to conjecture that there was a problem with the rocket and that the space launch would be delayed. It turned out that, however, that the North had apparently thrown a camouflage net over the rocket, possibly with the aim of catching observers off guard with its launch, which was widely seen as another test of ballistic missile technology.
“Security appears particularly strict around the west portal, potentially indicating that the test device is or will be housed there until emplacement into the south tunnel,” prominent U.S. nuclear weapons expert Siegfried Hecker wrote in a lengthy analysis published Monday in Foreign Policy.
“We think it’s unlikely they’d use the west portal but then we decided we don’t have enough evidence to say ‘no it can’t be used,’” Albright said in describing his research with Avagyan.
A likely sign that a nuclear blast is about to take place would be the evacuation of personnel and vehicles from Punggye-ri. Another indicator would be workers plugging the entrance to the testing tunnel or tunnels with a sealant mixture -- possibly one made of sand and cement, according to Albright. “That barrier will take some number of hours to dry.”
Being able to catch that happening will not necessarily be easy.
For analysts relying on the images captured by orbiting satellites, important objects, such as the entrance to a test tunnel, can be difficult to clearly discern depending on the time of day when the photograph was taken and whether it was in the shade, Albright said.
Pyongyang has warned that the coming test will be of a “higher level” than its previous two trials in 2006 and 2009. Guessing exactly what “higher level” portends has led nuclear specialists to throw out a number of possibilities, including that the event could involve a thermonuclear, or hydrogen, bomb -- a much more advanced technology than atomic weapons powered by fission.
Nonproliferation analyst Jeffrey Lewis explored this possibility in an Arms Control Wonk blog post last week. While issue experts generally do not believe North Korea’s nuclear weapons development is yet sophisticated enough to produce a thermonuclear explosion, Lewis said “we should at least consider the possibility that … the North Koreans may burn a fusion fuel like Lithium 6.”
He further noted that China detonated a thermonuclear device in its third nuclear trial.
Albright said he does not believe the North has yet acquired the capability to develop hydrogen bombs: “I doubt if they could detonate an H-bomb and it’s very unclear that they could detonate a boosted-fission weapon,” which is less advanced than a thermonuclear bomb.
Many nuclear analysts believe that the higher level test cited by Pyongyang indicates that more than one detonation is to take place, that the North for the very first time will test a device powered by highly enriched uranium, or both.
The Stalinist regime could even carry out multiple detonations using both plutonium-fueled and HEU-fueled devices, according to Hecker. “One more plutonium test provides valuable information on the yield-to-weight ratio, critical for miniaturized designs. An HEU test allows them to move to a possibly expanded future arsenal.”
North Korea could be interested in saving itself some political condemnation by carrying out multiple detonations in one test. Such blasts are "more challenging to conduct, but they have the huge advantage of not incurring additional political cost -- in other words, they can get two for the price of one," Hecker said.
"They may test a composite [device] of plutonium at the core and weapon-grade uranium wrapped around it to get a greater explosive yield than they could get from either one," speculated Albright.
The ISIS president said there are greater benefits for the North -- if it does intend to carry out multiple denotations -- in housing both explosions in the same portal as it is easier to set up the sophisticated scientific equipment that will be collecting data from the tests in a single tunnel complex. “It’s just easier to instrument it in one.”
A key goal, according to many experts, of the coming test is likely to be the demonstration of some capability to miniaturize nuclear weapons so they can be fitted to a long-range ballistic missile.