A TUNNEL collapse at North Korea’s key nuclear testing site has sparked renewed fears of a major radiation leak and environmental disaster.
It is understood about 100 workers at the Punggye-ri nuclear site were killed in the collapse which took place around September 10 and followed Pyongyang’s sixth atomic test earlier that month, Japanese broadcaster TV Asahi reported.
A second collapse during a rescue operation meant it was possible the death toll could have exceeded 200, according to the broadcaster.
News of the two incidents is yet to be verified by North Korea and it is very unusual for the regime to acknowledge any major accident, especially anything involving its nuclear programme.
The September 3 test triggered landslides in the detonation area and beyond, according to satellite pictures taken the day after.
The reports follow warnings from experts and scientists who said future nuclear tests risked collapsing the mountain test site and triggering a radiation leak.
Just two days ago, the head of the Korea Meteorological Administration, Nam Jae-Cheol, told a parliamentary committee another test by the Democratic People’s Republic of Korea (DPRK) could lead to such an accident, South Korea’s Yonhap news agency reported.
“Based on our analysis of satellite imagery, we judge that there is a hollow space, which measures about 60 to 100 metres, at the bottom of Mount Mantap in the Punggye-ri site,” he said.
Mr Nam was asked if an earthquake would trigger a release of radioactive materials.
South Korea has detected several small earthquakes near the northeastern nuclear test site based at Mount Mantap which the North used for its sixth and most powerful test yet.
Experts warned the area was now too unstable to conduct further tests.
Lee Won-Jin, a Korea Meteorological Administration researcher, said an analysis of satellite photos indicated there were landslides around Punggye-ri after the September test.
He also said there might now be a hollow space inside Mount Mantap, the granite peak where the North’s test site is located, citing studies of past underground nuclear tests by the United States.
Me Lee said the North’s past six nuclear tests were not reported to have caused any radiation damage to neighbouring countries.
Chinese nuclear weapons researcher and chair of the China Nuclear Society, Wang Naiyan, also warned in September that such a collapse could spark a major environmental disaster.
He told the South China Morning Post: “We call it ‘taking the roof off’. If the mountain collapses and the hole is exposed, it will let out many bad things.
“A 100 kiloton bomb is a relatively large bomb. The North Korean government should stop the tests as they pose a huge threat not only to North Korea but to other countries, especially China.”
Dr Peter Layton, a visiting fellow at the Griffith Asia Institute at Griffith University, said the reports of the collapse could be entirely plausible and agreed it could cause a major disaster.
“I liked China Nuclear Society, Wang Naiyan’s comments about it being a much bigger bomb than the DPRK had tested before and so the results may have surprised them,” Dr Layton said.
“Bearing in mind the other tests have probably also destabilised the mountain. Secondly, he noted that the DPRK drills tunnels straight into the side of the mountain not down. This suggests the blasts are relatively shallow.”
“It suggests that another test is planned and they were making preparations for another hydrogen bomb test possibly larger than the last for more dramatic impact in the media,” he said.
“Does this suggest that the DPRK trying to expedite a test so as to conduct it while President Trump was in the region or better yet in South Korea?,” he said.
“I can think of some counter arguments — the President’s visit has been long announced, etc. So unless they were trying to unblock an already dug tunnel that the earlier test blocked, maybe? “But this then leads into maybes multiplied by maybes.”
Dr Layton said the radiation fears were real and would be felt for some time.
“I would think that would have a local impact only — some dozens of kilometres — as the dust settles,” he said.
“Then the rain will wash it into the ocean a bit like Fukushima. The radiated area will probably be dangerous for some decades.”
Research associate at California’s James Martin Centre for Nonproliferation Studies, Shea Cotton, said there had been speculation that some of North Korea’s nuclear scientists were killed in the accident which could slow down the program.
“Chances are the people who died were slave labourers forced to work in horrible conditions to advance the regime’s interests,” Mr Cotton said.
“And I also don’t think you could stop their program with a few of their scientists dying, I think it’s much too far along now.”
Warnings that Mount Mantap was under huge stress were raised in September following the nuclear test.
The Punggye-ri test site in the country’s northeast is carved deep into the side of Mount Mantap.
Geophysicists concluded the interior of the mountain may have collapsed in on a cavern created where the rock was vaporised by the blast of the hydrogen bomb.
Satellite imagery also showed the blast caused numerous landslides around the site, according to the Washington-based 38 North monitoring project.