North Korea said on Wednesday it had carried out a “successful” miniaturised hydrogen bomb test — a shock announcement that, if confirmed, would massively raise the stakes in the hermit state’s bid to strengthen its nuclear arsenal.
The announcement triggered swift international condemnation but also scepticism, with experts suggesting the apparent yield was far too low for a thermonuclear device.
“The republic’s first hydrogen bomb test has been successfully performed at 10:00 am,” North Korean state television announced.
“We have now joined the rank of advanced nuclear states,” it said, adding that the test was of a miniaturised device.
The television showed North Korean leader Kim Jong-Un’s signed order — dated December 15 — to go ahead with the test, with a handwritten exhortation to begin 2016 with the “thrilling sound of the first hydrogen bomb explosion”.
South Korean President Park Geun-Hye condemned what she described as a “grave provocation” and called for a strong international response as the UN Security Council planned to hold an emergency meeting later Wednesday.
The North’s main ally China voiced its strong opposition, while the White House said it was still studying the precise nature of the test and vowed to “respond appropriately”.
A hydrogen, or thermonuclear, bomb uses fusion in a chain reaction that results in a far more powerful explosion than the fission blast generated by uranium or plutonium alone.
Last month Kim suggested Pyongyang had already developed such a device.
That claim was questioned by international experts at the time and there was continued scepticism over Wednesday’s test announcement, which took the international community by surprise.
“The seismic data that’s been received indicates that the explosion is probably significantly below what one would expect from an H-bomb test,” said Australian nuclear policy and arms control specialist Crispin Rovere.
The test, which came just two days before Kim Jong-Un’s birthday, was initially detected as a 5.1-magnitude tremor at the North’s main Punggye-ri nuclear test site in the northeast of the country.
The weapons yield was initially estimated at between six and nine kilotons — similar to the North’s last nuclear test in 2013. The first US hydrogen bomb test in 1952 had a yield of 10 megatons.
Bruce Bennett, a senior defence analyst with the Rand Corporation, said if it was an H-bomb that was tested, then the detonation clearly failed — at least the fusion stage.
“If it were a real H-bomb, the Richter scale reading should have been about a hundred times more powerful,” Bennett told AFP.