North Korea’s Punggye-ri nuclear test complex is an ideal place to conduct underground atomic detonations due to its geological features and isolated location, South Korean observers said.

Observers in the military and government said Pyongyang selected the region and started constructing the site likely over two decades ago, although the certain date is not known. From the 1990s onward, the South Korean and U.S. intelligence agencies have been closely observing the site. The site was used by the communist country to detonate its first and second nuclear tests in 2006 and 2009, with Seoul predicting a third test can take place at anytime if the North’s leadership decides to take such a step.

The North said late last month that it will build up its capability to deter aggression right after the U.N. Security Council passed a resolution condemning the Dec. 12 launching of a long range rocket. The international community viewed the launch as a cover to test the country’s ballistic missile technology.

Local geologists said the region located in North Hamgyeong Province, Kilju County has extensive granite bedrock formations that can help prevent radioactive materials from leaking to the surface following an atomic detonation.

In addition, the site is located in the remote Hamgyeong Mountain Range in the northeastern part of the country, and surrounded by high peaks such as the 2,205-meter-high Mt. Mantap and Mt. Hakmu. The mountain range has the largest number of high peaks on the Korean Peninsula and forms one of the natural barriers of North Korea’s Kaema Plateau.

North Korean watchers said that Pyongyang probably dug “L-shaped” tunnels for the two previous tests with the aims of preventing radiation leaks, although precautions taken ahead of the first detonation may have not prevented radioactive materials from escaping into the outside environment.

The first test conducted in the eastern shaft may have used a straight horizontal tunnel connected to the vertical shaft that leads to the surface. This construction may have been inadequate to deal with the tremendous pressure and shock blast of a nuclear explosion.

The second test carried out on the western shaft, on the other hand, may have used a spiral shaped horizontal shaft reinforced with barriers to contain the contamination, while the new southern tunnel probably has similar features. Satellite images showed for some time that the isolationist country had completed work on a new shaft located south of the 2006 and 2009 test areas, while TV footage that was released by South Korea’s military earlier in the day showed the inside of a test tunnel with spiraling features and some 9-10 barriers captured in September 2010. The footage taken by the (North) Korean Central TV Broadcasting Station is probably of the latest tunnel.

Related to various features of the Punggye-ri test site, the Institute for Science and International Studies (ISIS) said in a report that the location of the instrumentation bunker, which can collect data from the test, is generally very similar to the Ras Koh complex used by Pakistan for its 1998 nuclear test. The ISIS is a Washington, D.C.-based non-profit think tank dedicated to informing the public about international security issues.

Intelligence also showed that while the eastern shaft used in the first test has been sealed off, there has been considerable activity in the new southern shaft and the western tunnel used for the second test almost four years ago.

“Such activity can be seen as a sign that these shafts will be used for the next detonation test,” a government insider, who did not want to identified, said.

He said that Seoul thinks that the western shaft may be used in the upcoming test, but policymakers have said that if the North decides to really test its weapons ability, both tunnels may be utilized.

The North’s powerful National Defense Committee issued a warning on Jan. 24 that it will conduct a “high level” test to show its nuclear deterrence capability.

Meanwhile, Seoul has consistently warned the North that detonating another tunnel is the wrong move and will only worsen the situation.

“At this juncture, the right step for the North would be to listen to the international community and desist from another test,” said Unification Ministry spokesman Kim Hyung-suk. 

(Yonhap News)