ESR scientists are monitoring the Pacific for airborne radioactivity resulting from yesterday's underground nuclear test in North Korea.

Wim Nijhof from the Institute of Environmental Science and Research said the explosion detected yesterday was believed to be stronger than North Korea's previous tests in 2006 and 2009.

"There is not expected to be any threat to New Zealanders from any release as the amount of any radioactivity detected will be low, given that the test was carried out underground."

A range of data is collected and analysed to identify a nuclear test, Dr Nijhof said. Radioactivity monitoring involves measuring radioactivity in particles and gases collected from the atmosphere.


Airborne radionuclides from the 2006 North Korean event were picked up on the monitoring system in Canada several days after the explosion was detected.

The monitoring is done for the Comprehensive Nuclear-Test-Ban Treaty Organisation, which has 80 sites around the world. ESR is contracted to monitor six of those sites, at Kaitaia, Chatham Island, Rarotonga, Fiji, Kiribati and Mauritania.

An agreement from late last year between Australia and New Zealand now sees scientists on both sides of the Tasman working together to boost detection of any explosions in contravention of the Comprehensive Nuclear Test Ban Treaty.