North
Korea’s nuclear test site has collapsed ... and that may be why Kim
Jong-un suspended tests
The mountain’s
collapse after a fifth blast last fall has led to the creation of a
massive ‘chimney’ that could leak radioactive fallout into the
air, researchers have found
SCMP,
25
April, 2018
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.
“It
is necessary to continue monitoring possible leaks of radioactive
materials caused by the collapse incident,” Wen’s team said in
the statement.
The
findings will be published on the website of the peer-reviewed
journal, Geophysical Research Letters, likely next month.
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.
Wen
concluded that the mountain had collapsed after analysing data
collected from nearly 2,000 seismic stations.
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.
Another
research team led by Liu Junqing at the Jilin Earthquake Agency with
the China Earthquake Administration in Changchun reached similar
conclusions to the Wen team.
The
“rock collapse … was for the first time documented in North
Korea’s test site,” Liu’s team wrote in a paper published last
month in Geophysical Research Letters.
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, they said.
North Korea nuclear test site has signs of ‘Tired Mountain Syndrome’ after five blasts
Zhao
Lianfeng, a researcher with the Institute of Earth Science at the
Chinese Academy of Sciences in Beijing, said the two studies
supported a consensus among scientists that “the site was wrecked”
beyond repair.
“Their
findings are in agreement to our observations,” he said.
“Different
teams using different data have come up with similar conclusions,”
Zhao said. “The only difference was in some technical details. This
is the best guess that can be made by the world outside.”
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.
US
reveals how its forces would secure North Korea’s nuclear sites
Although
the purpose of Lee’s visit was not disclosed, two days later
Pyongyang announced it would no longer conduct land-based nuclear
tests.
Kim
Jong-un announced the suspension of nuclear testing last week. Photo:
EPA
Hu
Xingdou, a Beijing-based scholar who follows North Korea’s nuclear
programme, said it was highly likely that Pyongyang had received a
stark warning from Beijing.
Are North Korean quakes signs of instability at nuclear test site?
“The
test was not only destabilising the site but increasing the risk of
eruption of the Changbai Mountain,” a large, active volcano at
China-Korean border, said Hu, who asked that his university
affiliation not be disclosed for this article because of the topic’s
sensitivity.
The
mountain’s collapse has likely dealt a huge blow to North Korea’s
nuclear programme, Hu said.
Hit
by crippling international economic sanctions over its nuclear
ambitions, the country might lack sufficient resources to soon resume
testing at a new site, he said.
“But
there are other sites suitable for testing,” Hu said. “They must
be closely monitored.”
Guo
Qiuju, a Peking University professor who has belonged to a panel that
has advised the Chinese government on emergency responses to
radioactive hazards, said that if fallout escaped through cracks, it
could be carried by wind over the Chinese border.
“So
far we have not detected an abnormal increase of radioactivity
levels,” Guo said. “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.”
Zhao
Guodong, a government nuclear waste confinement specialist at the
University of South China, said that the North Korean government
should allow scientists from China and other countries to enter the
test site and evaluate the damage.
Was
North Korea to blame for radiation spike in north China city?
“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,” he said.
“There
are many methods to deal with the problem. All they need [to do] is
ask.”
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