North Korea's explosive show of force also a revelation for experts trying to track just how much nuclear firepower the country has. Pyongyang appears to have massively ramped up its nuclear capabilities. Experts suggesting its now on course to have enough radioactive material to make 20 nuclear bombs by the end of the year.
Reuters Raju Gopalakrishnan explains why there's confidence in that number.>> The amount of nuclear material that North Korea has to make nuclear bombs has always been an estimate. But what has happened recently is that these estimates have been proved because of its ability to have conducted two nuclear tests this year, after only three in the previous decade.
And talk that they might be considering a sixth nuclear test.>> Experts have long tracked the country's stockpile of plutonium, using satellite images to monitor reactors. But there's another key ingredient, enriched uranium. But with strict sanctions squeezing trade, where is it coming from? The answer? It looks to be homemade.
>> North Korea has abundant supplies of natural uranium. What it did not have in the past were the technical know-how, how to enrich this. Now, we do know, that in 1999, Pakistan gave North Korea two dozen centrifuges and some technical know-how. Siegfried Hecker, who is a former director of the US Los Alamos National Laboratory visited Pyongyang in 2010 and he was told at that time that they had 2,000 centrifuges.
Taking those projections forward, Hecker has now said that they can make about 135 kilograms of enriched uranium each year. One hundred thirty-five kilograms, that's almost 300 pounds, is enough to produce six bombs a year. Meaning that what Pyongyang has today is basically a self-sufficient nuclear program.