Explanation of why NK changed its tune

SCMP:

North Korea’s mountain nuclear test site has collapsed, putting China and other nearby nations at unprecedented risk of radioactive exposure, two separate groups of Chinese scientists studying the issue have confirmed. The collapse after five nuclear blasts may be why North Korean leader Kim Jong-un declared on Friday that he would freeze the hermit state’s nuclear and missile tests and shut down the site, one researcher said.

The last five of Pyongyang’s six nuclear tests have all been carried out under Mount Mantap at the Punggye-ri nuclear test site in North Korea’s northwest. One group of researchers found that the most recent blast tore open a hole in the mountain, which then collapsed upon itself. A second group concluded that the breakdown created a “chimney” that could allow radioactive fallout from the blast zone below to rise into the air.

A research team led by Wen Lianxing, a geologist with the University of Science and Technology of China in Hefei, concluded that the collapse occurred following the detonation last autumn of North Korea’s most powerful thermal nuclear warhead in a tunnel about 700 metres (2,296 feet) below the mountain’s peak. The test turned the mountain into fragile fragments, the researchers found.

The mountain’s collapse, and the prospect of radioactive exposure in the aftermath, confirms a series of exclusive reports by the South China Morning Post on China’s fears that Pyongyang’s latest nuclear test had caused a fallout leak. Radioactive dust could escape through holes or cracks in the damaged mountain, the scientists said.

North Korea saw the mountain as an ideal location for underground nuclear experiments because of its elevation – it stood more than 2,100 metres (6,888 feet) above sea level – and its terrain of thick, gentle slopes that seemed capable of resisting structural damage.

The mountain’s surface had shown no visible damage after four underground nuclear tests before 2017. But the 100-kilotonne bomb that went off on September 3 vaporised surrounding rocks with unprecedented heat and opened a space that was up to 200 metres (656 feet) in diameter, according to a statement posted on the Wen team’s website on Monday.

As shock waves tore through and loosened more rocks, a large section of the mountain’s ridge, less than half a kilometre (0.3 mile) from the peak, slipped down into the empty pocket created by the blast, leaving a scar visible in satellite images. Three small earthquakes that hit nearby regions in the wake of the collapse added credence to his conclusion, suggesting the test site had lost its geological stability. The breakdown not only took off part of the mountain’s summit but also created a “chimney” that could allow fallout to rise from the blast centre into the air

Speculation grew that North Korea’s site was in trouble when Lee Doh-sik, the top North Korean geologist, visited Zhao’s institute about two weeks after the test and met privately with senior Chinese government geologists. Although the purpose of Lee’s visit was not disclosed, two days later Pyongyang announced it would no longer conduct land-based nuclear tests.

Also: Radiation levels in a Chinese city nearly 2,000km from a North Korean nuclear test site spiked following Pyongyang’s latest and most powerful nuclear weapons test in September, according to Chinese scientists.

WSJ: “North Korea’s Kim Jong Un and South Korean Leader to Pursue Peace Deal, Denuclearization.” There’s a guy in the US who would appear to have very good luck.

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