ACA just posted an analysis from Richard L. Garwin and Frank N. von Hippel on the DPRK nuclear test.
It contains some evidence that I don’t think has been made public before. Here’s an example:
…it is not surprising that a range of yields has been reported. One authoritative estimate from Terry Wallace, a seismologist at Los Alamos National Laboratory, based on an unclassified analysis of open data, estimates a yield between 0.5 and 2 kilotons, with 90 percent confidence that the yield is less than 1 kiloton.[7] A second authority, Lynn R. Sykes of Columbia University estimates a yield of 0.4 kilotons, with 68 percent confidence that the yield is between 0.2 and 0.7 kilotons and a 95 percent probability that the yield is less than 1 kiloton.[8]
I also liked this observation:
One notable byproduct of the test is that it has demonstrated that university and other independent seismic detection systems, as well as those of governments and the International Monitoring System of the Vienna-based Comprehensive Test Ban Treaty Organization very effectively detect underground explosions in the sub-kiloton range.
But read the whole thing…I can’ t do it justice. And I need time to help Jeffrey pick out a third vacation home, now that our fear-mongering has pushed revenues through the roof.
Jeffrey Adds: “Perhaps North Korea’s weapon designers tried to go directly to a weapon in the 500-1000 kilogram class that could reach South Korea on a Scud missile…” Sounds familiar, eh?
Arrigo | October 20, 2006
It would probably help if you didn’t slap that gold replica of Fat Man on your front lawn, wouldn’t it?
On a more relevant note: I am still puzzled as to why the possibility of a decoupling cavern has been totally ignored.
Is there something “obvious” I am missing (except brains possibly)?
CKR | October 20, 2006
Some of the early reports were that the test was conducted in abandoned mines, which would have a network of tunnels and shafts that I would expect could serve to decouple the blast.
Also, I’ve read reports that the seismologists don’t even have much information about the geology of the site, which is essential for analyzing the seismic information.
On the other hand, they could probably do several modeling runs with different geologies and see how much they differed.
But so far, there’s not enough in the open literature on either seismics or radionuclides for us to do more than speculate.
It doesn’t sound like Garwin and van Hippel have any more than we have.
yale | October 20, 2006
It is good to see Garwin and von Hippel emphasize a point that seems to be ignored in the discussion of the NK device:
”… even a 1 kiloton explosive would still be a terrifying weapon. Recall that the 1995 Oklahoma City explosion involved only a few tons of ANFO. A 1 kiloton (1,000 ton TNT equivalent) bomb could kill people in an area of about one square mile and would partially destroy a much larger area. Most of these deaths would be from fire or from the prompt nuclear radiation.”
Calling what was likely a “fizzle”, a “dud” or a “failure” is a major error, leading to underestimating what a terrible thing has occurred.
A fizzle is simply a detonation of lower yield than designed. It does not mean a dud. Wrong words leads to wrong thinking.
The 1/2 kiloton NK fizzle would kill with immediate radiation over a 2 square kilometer area.
The area in the red ring in this image of Manhattan is the >500 REM lethal zone. The yellow arrows show the World Trade Center for scale purposes:
Steve | October 20, 2006
As previous poster correctly notes, a “fizzle” yield is most definitely not a “dud.” But if the device was designed to yield, say, 10-20 kt and only produced 200 tons, or even only 1 kt, that could still be considered a “failure” of the test.
yale | October 20, 2006
I would agree with Steve, that it would be considered a “failure” in the sense of not meeting design goals of, say, 4 kiloton yield.
But in the sense of a “failure” to detonate a fully effective, massively destructive atomic weapon, that “failure” would be a misleading description.
Robot Economist | October 21, 2006
yale does have a point – even a “fizzle” from an implosion device can still yield an economy of explosive power (and spread Pu particles everywhere).
If the North Koreans can only produce a fizzle through testing, what does that say about their ability to field a credible nuclear weapon? Chances are a fizzle under test conditions will yield nothing when traveling at a few hundred kph on the tip of a Scud.
yale | October 23, 2006
Robot Economist mentions one of the long-term effects of a “fizzle” detonation. It does “spread Pu particles everywhere”.
If the NK device carried 5 kilograms of plutonium, and it were detonated in the atmosphere, it would disperse somewhere around 4,970 grams of plutonium.
Interestingly, if it went to the full yield of 4 kilotons, rather than 1/2 kiloton, it would still disperse some 4,770 grams of Pu into the biosphere.
That fizzle came within 200 grams of Pu fissioning (only a few 10s of billionths of a second) from going full-tilt-boogie.
sunbin | October 23, 2006
the difference isa) 4970 grams of relatively stable radioactive Pu, plus little atomic soup (Cs/etc)b) 4770 grams + 200 more grams of highly radioactive element soup. a lot more detrimental.
and a successful blast means a lot more than 200grams of element soup.
yale | October 23, 2006
They are all successful blasts, just with different yields.
1/2 kiloton blast releases roughly 30-40 grams of fission products, 4 kilotons release roughly 200 grams of fission products, and a WW2 size blast about 1,000 grams.
Altho the fission products cause acute contamination, (some lasting for 100+ years), the Pu is a hazard for many multiples of its ~30K year halflife.
The ideal target for a small atomic weapon is a “civilian” atomic plant.
Each reactor (there may be 1 to maybe 8 reactors at a site) contains fallout equivalent to detonating 1,000 hiroshima-sized bombs.
Upwind of a city, industrial area, or agriculteral zone, the civilian power plant makes an excellent high leverage target for a terror weapon.
sunbin | October 24, 2006
a couple point to consider1) 4970g of Pu blast apart is no different from the same mount of dirty bomb blast by 20kg of TNT in the middle of the sky?
2) could the ‘fizzle’ (less than intended blast) be caused by purity problem of the Pu?