Nuclear test 'equivalent to 550 tons of TNT'

North Korea’s potential nuclear test was equivalent to 550 tons of TNT, a state-run South Korean geological institute said, which would be far smaller than the nuclear bombs dropped on Japan in the Second World War.

“It amounts to detonating 550 tons of trinitrotoluene, or TNT, at once,” said Park Chang-soo, a spokesman of the Korea Institute of Geoscience and Mineral Resources.