A North Korea mountain above the country’s nuclear bomb test site is at risk of collapsing and leaking radiation across the region, China has warned.
Pyongyang staged its sixth nuclear trial at its Punggye-ri base on Sunday, in an underground blast estimated to be up to ten times more powerful than the device dropped on Hiroshima.
US monitors measured a powerful 6.3-magnitude earthquake near the North’s main testing site, felt in parts of China and Russia, with an aftershock possibly caused by a rock cave-in.
Experts in China now fear that a mountain – believed to be above the underground chambers where North Korea has staged all of its tests – is under threat of collapse.
Wang Naiyan, a former chairman of the China Nuclear Society and a researcher on China’s own nuclear weapons programme, said he feared just one more test could ‘take the mountain’s roof off’ sparking a toxic radiation drift across the region.
‘We call it “taking the roof off”. If the mountain collapses and the hole is exposed, it will let out many bad things,’ he said, according to the South China Morning Post.
He said North Korea had a lack of suitable places for nuclear tests and that the length of time the mountain continued to stand would depend on where exactly the blasts take place.
If they were put in ‘difficult and expensive’ vertical tunnels, it would do less damage, he said.
But it is easier to make horizontal tunnels, increasing the risk of the mountain collapsing, Wang added.
According to the South’s Yonhap news agency, Seoul’s National Intelligence Service said it was the fifth blast the North had conducted in the same No 2 tunnel at the Punggye-ri test site, and it was ‘likely to have collapsed’.
But it said the North had already completed construction of a third tunnel, so that it could carry out another test at any time it chose, and work was underway on a fourth.
The North hailed the test as ‘a perfect success’.
Despite fears of a possible radioactive leak after the apparent collapse, Japanese and Chinese scientists said they had detected no radiation in the atmosphere.
Sunday’s test had registered with international seismic agencies as a man-made earthquake near a test site. Japanese and South Korean officials said the tremor was about 10 times more powerful than the one picked up after North Korea’s previous nuclear test a year ago.
China’s National Nuclear Safety Administration said data from radiation monitoring stations near the North Korean border showed no impact on ‘China’s environment or populace’.
Both China and Japan said on Monday they had not yet detected any atmospheric radiation from North Korea’s nuclear test, amid fears of a leak from a ‘cave in’ during the underground blast.
Japan’s top government spokesman Yoshihide Suga told reporters there was ‘nothing special detected from monitoring posts across the country’, nor from air samples taken by the Air Self-Defense Force after Sunday’s blast.
China’s environment ministry said Monday that radiation levels near its Korean border were also normal.
‘Results of monitoring make clear that this North Korean nuclear test as of now has produced no effect on our nation’s environment or the public,’ the ministry wrote on its official website.
Japanese defence minister Itsunori Onodera said Sunday that Tokyo had deployed ‘sniffer’ planes capable of detecting radioactive particles.