While the world’s diplomats are discussing the best way to deal with an increasingly hostile North Korea, the scientific community has begun asking whether or not yesterday’s bomb test was in fact nuclear.

According to New Scientist, reports on the size of the detonation vary wildly, with the Korea Earthquake Research Centre in South Korea saying “there was a 3.58-magnitude tremor from North Korea’s North Hamgyong province – the equivalent of 0.8 kilotonnes of TNT explosives.”

By comparison, Russian reports put the blast size at five to 15 kilotonnes (Hiroshima was 12.500 kilotonnes), a more likely figure for the successful test of a nuclear device. But as nuclear physicist James Acton told New Scientist, “The Russian figure is not a difference of 10% or 20% (in the yield). It’s huge. We should wait to see if that Russian statement is confirmed.”

The New Scientist report continued:

Going for a 15-kilotonne yield was “the natural size” for a country trying to test a nuclear weapon, (Acton) adds. Paradoxically, it is easier to make and test a Hiroshima-sized arm of this size rather than to make a smaller one, which requires mastery of important miniaturisation techniques.

If it turns out to be less than a kilotonne, it could look very much like a “fizzle” – a bomb that failed to detonate properly and achieve a full chain reaction.

The view that the test was a “fizzle” is also gaining strength. The UN’s Comprehensive Nuclear-Test-Ban Treaty Organisation (CBTO) reported a seismic event of 4.0 on the Richter scale, corresponding with South Korean reports of 3.58-3.70.

But as Jeffrey Lewis, Executive Director of the Managing the Atom Project at the Belfer Center for Science and International Affairs, points out:

Even at 4.2, the test was probably a dud … 3.58-3.7 gives you a couple hundred tons (not kilotons) … The same equation, given the US estimate of 4.2, yields around a kiloton. A plutonium device should produce a yield in the range of the 20 kilotons, like the one (the US) dropped on Nagasaki. No one has ever dudded their first test of a simple fission device. North Korean nuclear scientists are now officially the worst ever.

Reports today of a second nuclear test have not been confirmed, despite Japan reporting another tremor.

Peter Fray

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