A SMALL nuclear explosion, barely a fifteenth the size of the bomb that levelled Hiroshima, has shaken the world鈥檚 uneasy nuclear balance. On Monday North Korea announced it had successfully triggered a nuclear device deep in a coal mine in the north of the country. A second test was considered possible as 快猫短视频 went to press.
The thought that maverick North Korean leader Kim Jong-il now has nuclear weapons to use or sell may herald the collapse of the already shaky global non-proliferation regime by prompting neighbouring South Korea and Japan to join the nuclear club. Yet ironically North Korea鈥檚 act proves how well the 1996 Comprehensive Test Ban Treaty is working. 鈥淭hat test was really well detected,鈥� says Paul Richards of Columbia University in New York, who helped develop the CTCB鈥檚 seismic monitoring network.
The network was not expected to reliably pick up explosions of less that 1 kiloton. Yet the waveform of the signal showed it couldn鈥檛 be an earthquake, says Richards. He and other experts contacted by 快猫短视频 agree the device was small. It may even have been only half a kiloton 鈥� the same explosive power as the terrorist bomb in Oklahoma City in 1995. The Hiroshima bomb was 15 kilotons.
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The seismic network even shows Kim was not trying to bluff the world with a big conventional explosion. US experiments in the 1990s showed how difficult it is to mimic a nuclear blast with chemical explosives, plus 鈥渁 satellite should have seen trains delivering the hundreds of tonnes of explosive鈥�, concludes Richards.
A gust of released radionuclides at monitoring stations could clinch the matter, though their absence might only mean the test was small and deep enough to be contained. Site inspections, of the kind called for by the CTBT, would verify the nature of the explosion but the treaty has yet to be ratified by a handful of nuclear countries 鈥� including the US, which has said it will not do so.
Less clear is whether the blast was the product of a small bomb or a larger one that fizzled out. If large it would cast doubt on North Korea鈥檚 real nuclear expertise. Small bombs are harder to make, as the chain reaction has to be very precisely induced when the amount of fissile material is limited. To overcome this technical hurdle, says Friedrich Steinh盲useler of the University of Salzburg, Austria, the North Koreans would need the right tools, such as laser-guided lathes which are capable of shaping deflectors that can accurately concentrate neutrons. There is no reason to assume this is not the case, says Steinh盲useler, or that the size of the blast was not deliberate. 鈥淲hen you have only a little material you save it. The political signal is independent of the yield.鈥�
鈥淭hat North Korea now has nuclear weapons to use or sell may herald the collapse of global nuclear non-proliferation鈥�
The political signal has been heard loud and clear. 鈥淭his reported nuclear test threatens the nuclear non-proliferation regime,鈥� warns Mohamed ElBaradei, head of the International Atomic Energy Agency. 鈥淲e will be entering a new, dangerous nuclear age,鈥� Japanese prime minister Shinzo Abe agreed on Monday.
That, of course, will depend on what North Korea can do with its bomb. Experts agree that it is probably too heavy to fit onto any North Korean missile. But a small device could be detonated remotely in a shipping container, say, wreaking havoc in a port, and in the world order. One measure now before the UN Security Council would impose mandatory inspections on all ships leaving North Korea.
