There have been no new radioactive isotopes released from North Korea’s underground nuclear test, South Korean experts said Thursday. Finding isotopes can help determine what type of nuclear device was used, but a well-contained test could yield no isotopes. North Korea claimed Tuesday to have carried out an underground nuclear test, and seismic activity trigged by the test has been detected by several nations. The United Nations Security Council has condemned the test, and Australia blocked a visit by North Korea diplomats over it.
