News@Nature has another fabulous North Korea science update:

What more have we learned about last week's North Korean test?

Scientists have been able to confirm that it was indeed a nuclear weapon. US intelligence is reporting that the explosive force of the bomb was less than a kiloton of TNT, and used plutonium as opposed to uranium.

How do we know all that?

The first clues came from seismic data immediately after the blast. A sharp pulse of seismic waves meant it was a man-made explosion and the size suggested it was too big to be a conventional weapon but too small to be a successful nuclear test - more likely a 'fizzle'...

Satellites trained on the site caught additional details, such as signs of activity around the test site (including, apparently, a volleyball game going on at the dorms nearby).

But the critical information came in the days following the blast, when Japan and the United States dispatched reconnaissance aircraft to the edge of North Korean airspace. Those planes scooped up huge volumes of air looking for radioactive traces. US officials say they detected some "radioactive debris" from the blast.

Definitely read the whole thing.

It would appear that my initial skepticism that North Korea did not detonate a nuclear bomb was unjustified. My bad. You see what happens when you listen to CNN.

However, given the small yield, I think my statement that something went wrong or that they haven't perfected the process is still valid. Unfortunately, it looks like the North Koreans may be attempting another test to rectify this failing.

UPDATE:...or not. The Korea Times is reporting that the Chinese were told that North Korea plans to conduct no more nuclear tests:

North Korean leader Kim Jong-il told a ranking Chinese envoy that his country has no plan to conduct additional nuclear tests, the Yonhap News Agency reported on Friday (Oct. 20).

Quoting an unnamed diplomatic source in Beijing, Yonhap said Kim made the promise in his meeting with Chinese State Councilor Tang Jiaxuan, who visited Pyongyang as Chinese President Hu Jintao's special envoy earlier this week.

"Kim was known to have clarified his stance that there will be no additional nuclear test," the South Korean news agency quoted the source as saying.

It said that if Kim's position is confirmed to be true, it will raise hopes for the resumption of the six-party talks on Pyongyang's nuclear program and defuse the tension escalated by North Korea's detonation of a nuclear bomb on Oct. 9.

The question is why did they cave? Glenn Reynolds wonders:

Is it because diplomacy worked? (Yay, Condi!) Or is it because his scientists told him there was no chance of a pulling off a successful test any time soon?

Daniel Drezner says economic pressure from the Chinese.

To be totally I honest, I doubt it was diplomacy just because it has never really worked with the North Koreans. It might technical issues -- what I said early would certainly support that -- or it might be economic pressure.