The much ballyhooed "North Korean nuclear test" is apparently the subject of some confusion about it's actual nature.
Here is a report from Yahoo:
http://news.yahoo.com/...
WASHINGTON - An air sampling taken after North Korea's claimed nuclear test detected radioactive debris consistent with an atomic explosion, Bush administration and congressional officials said Friday night. They said no final determination had been made about the nature of last weekend's mystery-shrouded blast.
"The betting is that this was an attempt at a nuclear test that failed," a senior administration official said. "We don't think they were trying to fake a nuclear test, but it may have been a nuclear fizzle." The officials who described the results spoke on condition of anonymity because of the sensitive nature of the information...
...The contradictory readings reinforced uncertainty about the size and success of Monday's underground explosion, which North Korea has trumpeted as a nuclear test. Data from seismic sensors have already indicated the explosion was smaller than expected.
The Chinese and Japanese governments have done their own air sampling and found no trace of radioactive material, officials from both countries said Friday. A Japanese government official said his country sampled air over the Sea of Japan, as well as rainfall and ground-level air on Japanese territory and found nothing...
For various reasons, many people assume that nuclear weapons are easy to make and use. Not too many days go by in our pixilated and easily distracted media that we don't hear speculation about "nuclear terrorism," even though - some sixty years after the invention of the nuclear reactor - not one such event has ever been experienced.
Moreover, we know of many nation states that actively sought nuclear weapons - some with large resources at their disposal - and failed to come even close. It is known that Algeria, Brazil and Argentina (yes, Brazil and Argentina), Iraq (before the first Bush war, and some other countries had nuclear weapons programs and failed to produce actual weapons. Apartheid era South Africa working closely with Israel assembled such weapons, but after the accession of the world statesman Nelson Mandela to the South African Presidency, South Africa disassembled their few weapons and disclosed their program. Israel is widely thought to possess nuclear weapons, but like South Africa, never tested them. Nations that possess and have tested nuclear weapons are the United States, Russia, Great Britain, France, China, India and Pakistan.
This week it was announced that North Korea had tested a "nuclear weapon," but did they?
How are nuclear tests verified and compared with chemical explosions? It turns out that nuclear materials can be detected with great sensitivity, quite literally on the level of individual atoms. In fact many of the atoms in the periodic table with atomic numbers over 100, the "Transfermium" elements have existed in laboratories on a scale of just a few atoms.
When a nuclear fission reaction takes placed, the fissioned atom, usually an atom of uranium or plutonium, splits into a variety of atoms. Many of these atoms are themselves metals, like Ruthenium, Zirconium and Cerium that do not travel far from an underground test site. However underground nuclear tests - like above ground tests - can and always do release some elements that are gases or simply volatile elements. Typical gases that are released include some radioactive isotopes of the element xenon - xenon-133 and xenon-135, the element Krypton - Krypton-85 as well as isotopes of iodine, including Iodine-131. Because these isotopes occur in nature only in very tiny (but detectable) equilibrium amounts - they are formed by nuclear reactions in the upper atmosphere caused by particles streaming from the sun and from deep space - variations in their concentration represent a signature of a nuclear weapons test. Indeed, a great deal can be recognized by these signatures, whether nuclear fuel is being reprocessed, what the isotopic concentration of the fuel in question is, how long it has been irradiated in a nuclear reactor, whether a successful nuclear test has been conducted, what the yield of the bomb was, as well as what type of bomb it was, a plutonium bomb, a uranium bomb or a hydrogen bomb.
Although the media would like to represent that ordinary nuclear fuel is suitable for bomb making, and that the world faces a vast terrorist threat from spent nuclear fuel, the actual situation is somewhat more complex. If a uranium bomb is manufactured one must do some very elaborate separations - often involving thousands of steps. This is the matter of concern in the Iranian situation that is being played up to justify a possible war with Iran. However it is also to make a nuclear weapon with plutonium manufactured in a nuclear reactor. However, in general the kind of plutonium found in reactors used in power generation is not ideal for weapons purposes.
This is because when plutonium is formed in a nuclear reactor, it results from the capture of the most common isotope of uranium found on earth, uranium-238, which is commonly known as "depleted uranium."
In a commercial nuclear reactor not designed for weapons production, the fuel stays in the reactor for a period of one or two years. Initially the uranium-238 in the reactor captures a single neutron and undergoes two nuclear decays to form neptunium-239 and finally plutonium-239. (This process takes a few days.) Like uranium-235, plutonium-239 is fissionable and splits in a neutron flux. In fact a considerable portion, as much as 30 to 40 percent, of the power provided in a nuclear reactor actually comes from the fission of such plutonium. However not all of the plutonium under these conditions fissions. Sometimes, a plutonium-239 atom simply absorbs a neutron without fissioning, forming an atom of plutonium-240. So while all of the plutonium that first forms in a reactor is plutonium-239, after a few months of power operation - as the concentration of plutonium increases - the initially pure plutonium-239 is contaminated with a significant amount of plutonium-240.
Weapons designers don't like to have plutonium-240 in their bombs. The reason is that plutonium-240 releases neutrons spontaneously. For technical reasons, weapons designers like to control the rate of neutrons released, and the timing of the release. A nuclear weapon during the period of an explosion gets very hot and much of the trick of weapons design is to control the rate of formation of a "critical mass" so that as much of the plutonium or uranium can be fissioned before the boiling of the metals from which the critical mass has formed. Critical mass depends on density, and when the metal boils it forms a gas that is no longer critical. Plutonium-240, limits the possibility of doing this because the release of neutrons can cause the metal to heat too quickly and boil before the critical mass has enough time to fission all of the material.
To prevent the formation of plutonium-240, it is necessary to remove plutonium from a nuclear reactor after only a relatively short period of irradiation. This necessarily means that the concentration of plutonium in the fuel is relatively low. One needs to process lots of fuel with short irradiation times, adding a great deal of expense. Moreover, one can not ordinarily accomplish this with any kind of reactor. Although one could in theory use a reactor of the CANDU type, which allows continuous fueling, most nations that have produced nuclear weapons based on plutonium have used a reactor of the Chernobyl type, a graphite moderated reactor. (Only one such reactor was ever connected to the power grid in the United States, the "N-reactor" in Washington State - its primary mission was to make plutonium for weapons and the power was considered a "side product.")
During the Clinton administration the energy secretary, Hazel O'Leary announced that the United States had conducted a nuclear test in the 1960's using so called "reactor grade" plutonium - plutonium having a significant fraction of the isotope plutonium-240, plutonium typical of that made in commercial power nuclear reactors. The bomb, according to Ms. O'Leary worked; however its yield was low. We do not know all of the technical details, but it appears that it was very difficult to assemble the bomb, and the high radiation meant that it would not be very stable for long periods of time - it would degrade quickly. The weapons designers were very concerned that it would go critical before expected. This would not ordinarily result in a nuclear explosion, but would result in a momentary small flash of radiation in the immediate area, a flash that could easily be contained in a small room.
But - with great difficulty - using the premier weapons laboratory in the world at that time, the bomb was built and successfully tested.
North Korea, however, is a primitive backward country ruled by a Xenophobic dictator. One cannot imagine that the technical base in that country is world class.
I would not be surprised to learn that the North Korean test was a failure - because making nuclear weapons is not as easy as people are likely to believe. We know from released information that the Koreans were reprocessing nuclear fuel to get their plutonium. This again we can tell from the isotopic signatures of the gases I described earlier. We also know that the North Koreans are poor, and probably could afford only a limited amount of nuclear fuel. The temptation to push the envelope on the idea isotopic content must have been considerable - since to get enough plutonium requires lots of fuel. (Remember the low concentrations.)
I suspect that the North Korean test was a failure and that the difficulty stemmed from the quality of the plutonium they were able to produce.
We know of course that Dick Cheney's claim about the Niger uranium was not only a lie, but was - if you know how nuclear technology actually works - on its face ridiculous. It is not easy to make nuclear weapons, not in North Korea, not in Saddam era Iraq, and not in Iran.
Knowing this will make it more difficult to manipulate you.