North Korea’s Nuclear Testing: How Big Was The Bomb?


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Bomb Blast Radius: Image courtesy of Fastfission

North Korea is in the news again, after exploding a nuclear bomb – with two more tests projected this year plus a potential rocket launch, as well. We do not know the exact composition of the material for the warhead at this time.

The first successful testing of a nuclear warhead in North Korea was in 2006, while the second was in 2009; both enriched plutonium. The third, February, 2013, could be plutonium, uranium or both.

So, what could the bomb composition be, and how big was it?

Testing a Warhead – How Large Was the NK Bomb?

Why don’t we know exactly how big the bomb was that North Korea tested? Yields of nuclear explosions are very hard to calculate; the margins of error can be very large. To determine precise measurements are difficult but usually are calculated based upon certain factors, including blast size, blast brightness, siesmic factors, and the shock wave it produces.

The latest North Korean test could only be detected through seismic activity that many nations measured, since the test was conducted underground.  From the location of the seismic event, and the magnitude, the USGS and others indicated that a nuclear blast, ‘clear explosion like characteristics’, occurred. The estimated size of the blast ranged from 7 kilotons to 10 kilotons.

North Korea’s first and second nuclear warheads were comprised of 93% Pu-239, originating from  nuclear reactors and enriched in a processing plant. After closing down the reactors, plutonium was difficult to produce. However, North Korea has natural uranium, a ready source of bomb material, and the capability for enrichment. It makes sense that the new warhead might be enriched uranium, 85-90% U-235 or a combination of both U-235 and Pu-239. To find out the composition of the warhead, from the recent North Korean test, Japan and U.S. have sent aircraft to sample the air around the test site and determine the decay products, thus determining the composition of the original material.

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