1. A truly fissile "suitcase nuke" would use a few kilos of plutonium-239, which does have a shorter half-life than uranium, but still quite long (24,000 years), rather than tens of kilos of uranium-238. A "dirty bomb" would not be fissile, but even the isotopes likely to be used, eg cobalt-60, have half-lives measured in years to decades.

2. I'm assuming it's legit, but asking other questions.

3. I'm not a nuclear scientist by a long shot.

Confederate Yankee links to the raw seismograph data on CNN. The energy release profile is very suggestive, to my mind, of an implosion lens test sans nuclear fuel (which is a scarce and precious commodity in North Korea), followed by a massive conventional explosion after data collection completes on the lens test. The post-test conventional explosion could be an attempt at deception, or CYA, on the part of the North Korean nuclear engineers.

I'm not a bomb-tech, never pretended to be one, but something that is often overlooked in discussing "going critical" is that mass is only one part of the equation. Another part is geometry. Optimum critical geometry is, I believe, a perfect sphere. Also, decay isn't the only factor that degrades the efficiency of a weapon, as a larger mass will produce more spontaneous fissions, which in turn reduces the amount of fissible material available. The better one is able to quickly assymble a critical mass of material into a suitable geomotry, the less loss of material and the greater the yield. Obviously the "suitcase" nuke relies upon using the minimum of material and creating a critical assembly very rapidly, a very technical problem indeed. I find it highly unlikely that any nation's first efforts would be that sophisticated.

As for the spoof explosion theory, let's not forget the DPRK taught Saddam how to fool us if GWI into blowing up cardboard cutouts of Scuds. They are experts at cammoflage and deception. It is certainly a possibility.

The decay issue with a very small nuke is likely tritium, which in conjunction with hydrogen's other isotope, deuterium, is used to 'boost' the efficiency of a fission weapon. Essentially, the deuterium and tritium undergo fusion during the fission event, supplying additional fast neutrons to the reaction to maximize the amount of fissile fuel that gets 'burned' in the chain reaction. Any fission type device can have its nuclear yield doubled with a small amount of tritium and deuterium in the core. Tritium also has a very short half life (about 12.3 years), and I have read where the D-T charge in a boosted fission weapon must be replaced within five years of storage.

If you make a tunnel, and you pack it with 20,000 pounds of good old fashioned high explosives and no one is there who can independantly say what it is you put in the tunnel; then when it blows up how can anyone else tell exactly what it is?

Would a very large conventional explosion look any different to a richter scale than that of a nuclear explosion? Unless the "sniffers" pick something up soon, Im inclined to believe that North Korea hasnt done anything at all, except collapse a mountain tunnel in a very spetactular way.

I say this possible because in every case previous to this involving nuclear tests, it was the monitoring nations that spoke first, the nation that "did the deed" spoke last. In this case, the north koreans told us what they did, and weve been pouring over data since to prove it. that seems backward to me.

But why do this? Why fake a nuclear explosion? It would seem to me that this is a very interesting way for Korea to keep its word to the Chinese on not blowing up a nuclear bomb and to still being able to remain agressive to the west, keeping their anti-western bonafides.

A "dud" or "fizzle" nuclear test by North Korea would still give the U.S. and the West sufficient justification to accelerate the Proliferation Security Initiative aimed primarily at Iran and North Korea. It would also reaffirm a more active Japanese defense policy, and a tightening diplomatic cordon around China. All of this is bad news for China.

If the test was either a dud or a hoax, China has received a temporary reprieve from a looming harsh sentence. China will get one last chance to do something effective to either rein in or end Kim Jong-Il's leadership in North Korea, for China's own good. A Chinese invasion of North Korea, an "Operation North Korean Freedom," executed by the PLA would be one such possibility. Once it is certain that North Korea has nuclear weapons, this option will no longer exist for China. We will see if China takes advantage of this last opportunity, if it still exists.

Westhawk

Westhawk,

Do you think China has the expeditionary and logistics capabilities to mount such an invasion? They did cross the Yalu in the last Korean war, but everyone was much less sophisticated then; human wave attacks don't seem a good idea these days. And the North Koreans are fierce fighters.

There was a report some time ago that China had shifted the area of responsibility for one of its northwestern armies or corps such that the border with North Korea is now much more heavily patrolled. I don't think that was a temporary move.

As I understand it, plutonium does not decay in a suitcase nuke - the trigger does, which may be polonium or tritium or some such. Wikipedia says maintenance requirements mean suitcase nukes are only viable for a few months before requiring service. I have read that the technology required to make miniturized nukes is beyond the capability of just about anyone without a massive nuclear test program, such as only the US and Russia have conducted.

"such that the border with North Korea is now much more heavily patrolled. I don't think that was a temporary move."

This is probably to prevent a greater influx of refugees (a big problem now, likely to get much worse in case of a NK war/collapse), I doubt China intends to fight the NK; it would be a very hard fight with ne prospect of gaining anything.

I'm not a weapons tech but I am a nuke tech. All the reports I've seen of the purported Russian 'suitcase nukes' describe the device as taking up two very large 'suitcases' and weighing over a 100 kilos. Sub-critical devices are much harder to make than a Nagasaki type plutonium device. And that is hard enough to make.

The most likely scenarios are this: one-- the device fizzled and failed to go supercritical. Probably due to the failure to get a symmetric blast front on the collapse charge.

Two—nothing happened and the Koreans had a tunnel packed with explosives so they could disguise the failure by firing the conventional material. This seems likely after the missile test fiasco and loss of face.

Nuke explosions give off a very distinct double peak optical/gamma signature. But I don’t know if that is reflected on the seismographic signature. The peaks are milliseconds apart. One was spotted in the sea south of South Africa and is suspected to have been a possible Israeli or South African test. That was back in the Carter administration and was of course ignored.

http://nuclearweaponarchive.org/Safrica/Vela.html

Miniturized or suitcase nukes may be beyond the capabilities of countries other then those with a massive nuke test program..BUT, If Ledbed was'nt lying and the North Koreans and Iranians got their hands on one, could'nt their scientists backengineer them to build new ones or perhaps just replace the deteriorated triggers????Perhaps unemployed and hungery Soviet nuke techs came with the bombs??

China does not need to do much to utterly collapse North Korean militry capability. A simple turn off the oil supply will ensure that nothing in North Korea moves. Since they are the only supplier of fuel, how much stockpile do you think DPRK has?

They won't do that of course, that will trigger the worst case scenerio as far as China's concern (total collapse of DPRK, and massive refugee to China).

Like China would care about "massive refugees"...

"Do you think China has the expeditionary and logistics capabilities to mount such an invasion?" A PLA invasion of North Korea certainly would not be a trivial exercise. However, as BigFire notes, a very effective preparatory step would be a fuel cutoff, especially if done during the winter. One should never assume a military task will be easy. But a totally immobile and logistically zeroed-out North Korean army would not seem very effective, especially when it would be forced to defend a 360-degree perimeter.

Speaking of logistics, the fear of North Korean refugees flooding over the Chinese border seems exaggerated. How far can starving North Korean peasants walk in winter, carrying their own "logistics" on their backs, and getting no resupply along the way?

If things ever got to that point, a PLA invasion of North Korea would be viewed as an act of mercy.

Westhawk

If China took the big step of invading North Korea why do you think they would stop at the DMZ and not take both Koreas? That would work in China's favor to isolate Taiwan even more and make Japan the only viable buffer in the Pacific. China hasn't lost face, she has a very big face and the PRNK is only a festering sore more a worry to the West than to China. The Dear Leader's nuke folly can never be used without the total destruction of that little country.

The one thing the Dear Leader wants is International recognition; he does not want to become a peaceful, prosperous leader of an Asian Luxemburg, unnoticed on the World stage.

Would the size of the blast have anything to do with the need to fit a primitive device on a delivery vehicle?

In other words, If you need to put a primitive device on a small platform, don't you end up with a primitive device with a small blast?

Just a question that seems reasonable, I am no expert.

Those *atomic canon* were monsters so heavy they sank into the ground if they ran off paved roads, and on muddy ground they sank up to their axels, which required huge cranes to get them upright again. The Army had two in Europe. I guarded one at Vogelweh Depot, west of Kaiserslautern, in 1953, on a bitter cold night, temp below zero. It was covered with ice. There were very few roads the Army could drive them on since they couldn't navigate sharp turns.

Been out of town for a few...and I confess the conspiracy theory "no nuke" test idea hadn't occurred to me. Why get in such big trouble for no nuke ?

Japanese jets looking for signs of a nuclear test ? Quick...call the Science Patrol ! Where's Ultra Man ?

In the early 50's (hardly a period of "sophisticated" nuke design) the US produced stuff small enough to be fired from the M65 "atomic cannon".

My dad worked for 30+ years at the Watervliet arsenal where all the tubes for these guns were made. There is still one on display just inside Broadway (main gate by the Bennet Lab) entrance off to the right as you drive in. It's visible from I-787.