The mountain test site collapsed following a fifth test blast last year, leading to the creation of a massive ‘chimney’, which could allow radioactive fallout to rise into the air from the blast zone beneath the mountain.
The previous five North Korean nuclear tests were carried out at the Punggye-ri nuclear test site under Mount Mantap in the north west of the country.
Following a nuclear test in September 2017, a 6.3 magnitude earthquake was recorded at the mountain according to the US Geological Survey’s findings.
A scientific team led by Wen Lianxing, a geologist at the University of Science and Technology in Hefei, said the most recent test last autumn tore a hole in the mountain, which then collapsed upon itself.
Mr Wen commented on the danger, saying: “It is necessary to continue monitoring possible leaks of radioactive materials caused by the collapse incident.”
Zhao Lianfeng, a scientist at the Chinese Academy of Sciences in Beijing, also concluded “the site was wrecked” beyond repair.
He commented on the results of the research, saying: “Different teams using different data have come up with similar conclusions.
“The only difference was in some technical details. This is the best guess that can be made by the world outside.”
The mountain does not currently appear to be leaking radioactive material, but the risk remains high.
Guo Qiuju, a Peking University professor, said: “So far we have not detected an abnormal increase of radioactivity levels.
“But we will continue to monitor the surrounding region with a large amount of highly sensitive equipment and analyse the data in state-of-the-art laboratories.”
Chinese scientists have also called on the North Korean government to allow them access to the mountain to evaluate the damage and secure the site.
Zhao Guodong, a government nuclear waste confinement specialist at the University of South China, said: “We can put a thick layer of soil on top of the collapsed site, fill the cracks with special cement, or remove the pollutants with chemical solution.
“There are many methods to deal with the problem. All they need to do is ask.”
North Korean leader Kim Jong-un however announced on Friday that he would freeze North Korea’s nuclear and long-range missile tests, and would shut down the nuclear test site.