Had the network of sensors picked up radionuclides from the North Korean explosion two weeks ago? Seismologists here today say they are comfortable that explosion was a nuclear test, but detecting radionuclide evidence in the form of radioactive gas is the "smoking gun". And the big news here is that they have not found that signal. What's more, scientists don't really seem to know why. One delegate, an expert on radionuclide detection from Sweden, told the conference how well the network performed after North Korea's nuclear test in 2006. Twelve days after that event the network picked up just a few hundreds of atoms of the noble gas Xenon 133 in Canada. He confessed to being "surprised" that this time round, so far, there has been nothing. Read more
On the morning of 25 May, when North Korea announced that it had tested a second nuclear device, supporting evidence was already available in the form of waves picked up by seismic stations around the world within minutes. But piecing together what the blast means in terms of the nation's nuclear capacity will take a lot longer.
Officials in South Korea said they had detected a tremor consistent with those caused by an underground nuclear explosion. The country's Yonhap news agency reported that the North had test-fired three short-range missiles from a base on the east coast immediately after the nuclear test. The underground atomic explosion, at 9.54am local time (0154 BST), created an earthquake measuring magnitude 4.5 in Kilju county in the country's north-east, reports said.
North Korea says it has staged a "successful" underground nuclear test, prompting international condemnation. The state says it was more powerful than the previous one in October 2006. A number of external agencies have confirmed a powerful explosion took place, suspected to be associated with a nuclear test. Read more