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| China-Japan-Koreas |
| North Korea Muffs It Again, Yield About 4Kt |
| 2009-05-27 |
| According to early reports, Monday's North Korea event certainly seems like a deliberate explosion in the right place. However, it was too small to be a successful Hiroshima-class crude explosive device, by a factor of three or four. The reported estimates of Richter magnitude spread from 4.5-5, and the standard conversions to explosive yield suggest a yield of 2-6 kiloton-equivalents of TNT. Most of the latest Richter magnitude estimates have come in the low half of the 4.5-5 range, so it seems likely that the yield was 4 kilotons or smaller. That's a lot of energy, much larger than the 2006 North Korean test, but it still falls far short of an expected 12-20 kiloton yield of a crude Hiroshima-style device. For comparison's sake, the first nuclear tests of all other nations that are self-announced members of the nuclear club had larger yields than this latest North Korean test. Because the expected Hiroshima-style explosion didn't occur, there are four options as to what did happen during the test: *the device failed to detonate properly; *the device was a higher-tech device designed for smaller yield with less fissile matter (e.g., missile warheads or briefcase bombs); *the North Koreans faked a nuclear explosion with conventional explosives; *or the North Koreans detonated a larger device in a large cavity to muffle its yield. The first option is the most likely case given what is publicly known about North Korean diplomacy and technology. It's important to realize that nuclear tests in the past 15 years have primarily been demonstrations of power and national will, rather than driven by engineering. The two different kinds of simple bombs are uranium 235-based and plutonium-based. The United States used one bomb of each type on Japan in the closing months of World War II, with roughly similar explosive yields. The technology for a uranium 235 bomb is so simple, relatively speaking, that such a device need not be tested. To wit, the United States dropped the uranium 235 Hiroshima bomb without testing its design in a controlled detonation. Conversely, building a plutonium-based bomb represents a technical challenge because the critical mass can blow apart in a split second before the detonation reaches max efficiency. Once U.S. weapon designers confirmed the trickier detonation scheme of a plutonium device in the famous Trinity Test in 1945, confidence in the simpler uranium 235 detonation design seemed justified. The technology for making the raw material for each device differs. Uranium 235 must be separated from the heavier isotope uranium 238 to make a bomb, so a country that buys or builds high-tech centrifuges is investing in those types of bombs. The term "enriched uranium" refers to uranium metal with an increase of the 235 isotope that's sufficient to allow an explosive chain reaction to occur. (Complete separation of the two isotopes is neither feasible nor necessary to create a weapon.) Plutonium comes from nuclear reactor waste, many stockpiles of which North Korea possesses. In other words, North Korea is attempting to make the trickier of the two devices. When arms control experts estimate North Korea to have a nuclear stockpile of 6-8 weapons, they are converting the likely amount of reactor waste that the country has produced into plutonium bombs of the World War II-era design. When the device is built correctly (the earliest technology used a sphere with precisely timed explosions to press an array of small plutonium masses into one critical mass), the yield is 10-20 kilotons. It's unlikely that North Korea has skipped this step and gone on to more sophisticated designs that involve other elements (for instance, tritium) to generate a smaller yield from a smaller plutonium mass. China didn't. Its tests grew in size and sophistication in the 1980s and 1990s until Beijing induced seismic events that registered higher than 6 on the Richter scale. Then they stopped. Thus, I would rule out option number two. Option number three also seems unlikely. The 2006 test was never proven to be fake, and more largely, there's no reason for Pyonyang to fake a test if it could at least attempt a real nuclear detonation. Nor has any world leader ever publicly called out North Korea for executing a failed or fake test in 2006; such a response probably would have pushed Pyongyang to attempt a second test much more quickly. It's the same reason why the United States and Europe--despite seismic data to the contrary--didn't call India's thermonuclear bluff in 1998; they wanted to reduce tensions, not raise them. The last option--detonation in a cavity--makes no sense at all. The common assumption behind the Comprehensive Test Ban Treaty is that countries would attempt to evade detection. But in the twenty-first century, what good is a nuclear weapon if it can't be used to openly check adversaries? Plus, a country doesn't even need a military useful device to do so. With cable news, the ability to detonate something fissionable does the trick--at least in a political sense. So my guess is that North Korea tried and failed to get a simple plutonium bomb to detonate correctly. Make no mistake--an inefficient nuclear weapon is nothing to dismiss. Even at the low end of its estimated yield (2 kilotons), the May 25 test released as much or more explosive energy than the largest conventional-explosive air raids during World War II. But one should be mindful of the technical challenges North Korea still faces in carrying out the threats implied by its deliberate pairing of its explosive test with test missile launches. |
| Posted by:Anonymoose |
| #15 The author is engaged in wishful thinking. This is 2009. Computers are far more powerful, simulation techniques are advanced. We understand far more about the compression of Plutonium and Uranium. Further, Korea doesn't have to reinvent the wheel. China has already provided implosion weapon designs, with detailed instructions on fabrication. These are missile deliverable warheads, not primitive 1945 technology. The NKoreans have at least this base level (the updated early Chinese missile warhead) to work with. They are interested in deliverable weapons. That 4kt yield is enought to ignite the secondary of a thermonuclear weapon and 2kg means it is quite physically small. |
| Posted by: john frum 2009-05-27 13:15 |
| #14 "there's no reason for Pyonyang to fake a test if it could at least attempt a real nuclear detonation." I'm going to line up with those saying this test was faked. PU has huge commercial value. NK needs the money. Why blow up your PU when you can sell it for a king's ransom? Assuming that you get the same saber-rattling effect from a faked detonation there is no reason for a real one. The more interesting news today is that NK has repudiated the 1953 Armistice. |
| Posted by: Iblis 2009-05-27 12:29 |
| #13 Not just an ICBM... a heavy ICBM - MX class The Japanese are also quite versed in ICF (shock driven fusion). Their nukes will not only work first time, they will be advanced |
| Posted by: john frum 2009-05-27 11:12 |
| #12 The Japanese have a solid-fuel satellite launcher that could easily be "weaponized" into an ICBM. They also have 63 nuclear power plants and a spent fuel reprocessing facility. I don't know if they have any nukes anywhere, but I bet they could build a few in a hurry if they thought they needed to. Bet they'd work on the first try, too. |
| Posted by: Mike 2009-05-27 10:59 |
| #11 Before the 2006 test, the North Koreans told the Chinese they were aiming at a 4 kt yield. Later they told them they used 2 kg Plutonium for the pit. |
| Posted by: john frum 2009-05-27 10:38 |
| #10 1) A Pu mass must be compressed symmetrically and quickly or else most of the mass is blown apart before detonating (partial detonation, the classic "fizzle"). As Uloluns points out, this is technologically tricky and it doesn't surprise me that the Norks couldn't get it quite right. 2) Even a fizzle would be a potent weapon given that it would create a large amount of dispersed Pu which would cause mass panic in addition to the explosive effects noted by OldSpook. 3) In response to Mike, the point of conducting these tests is to saber-rattle, gain concessions, and for internal purposes. Their goal isn't necessarily to build an arsenal. They can realize results just by playing "big man with the bomb", so why not? |
| Posted by: Spot 2009-05-27 08:44 |
| #9 ...I still vote for option three. Why? 1. It CAN be done. In the mid-80s there was an aboveground conventional shot in Nevada (name escapes me) that piled up a kiloton or so of fertizer soaked in diesel fuel to create small scale nuclear effects. There's a great description of it in Edward Zuckerman's The Day After World War III - IIRC, the shot was also used to calibrate seismographs. Also keep in mind: they may not have food, they may not have medical care, but the one thing the Norks got in spades is HE. It would have been easy to round up 4KT worth. 2. If it is indeed a nuclear shot - and he is not producing enough material for a useful-size arsenal - why is he popping them off like this? It's like a couple years ago when Pakistan popped off like three in a row - that was an appreciable fraction of their arsenal, and I know the Norks don't have anywhere near as many. And the question also comes up - if the Paks helped them out, how come they can't get a functioning shot above a certain yield? Two apparent fizzles in a row (to us, anyways) means either a lot of Nork Nuke guys are in for the chop, or that's the best they can do...and I'm just not buying that. Mike |
| Posted by: Mike Kozlowski 2009-05-27 08:09 |
| #8 North Korea has precipitated the heretofore impossible - the rearmament of Japan. Great job, Kimster. |
| Posted by: Kofi Flomotch5556 2009-05-27 07:01 |
| #7 Detonation is executed by a system similar to an array of Ignition Coils, as in a motor vehicle. It requires a high degree of synchronicity. Pentagon analysts are likely assigning primitive status to NK nanotechnology. Similarly, Pakistan's nuke tests produced poor results for controlled applications. One has to wonder if these devices would even survive a missile launch. As to the questioning of quid pro quo in the financing, there has been speculation that the Saudis received nukes from Pakistan, in exchange for financing both the espionage and development that led to their program. The Iranians must be getting some payback from the NKs. NK hardline status will collapse when they are totally isolated. That won't happen if Obama continues appeasing the Ayatollahs. |
| Posted by: Uloluns Scourge of the Bunions1692 2009-05-27 05:32 |
| #6 Gee, I wonder what this means: Reuters: Russia taking preventative measures including military ones after N.Korea nuclear test - Interfax quotes security source Reuters: The measures -- which did not include troop movements -- were needed in case a nuclear war broke out on the Korean peninsula. |
| Posted by: crosspatch 2009-05-27 04:03 |
| #5 It isn't nuclear that I am worried about. North Korea would not hesitate to use chemical or biological warfare. They aren't worried about "world condemnation" as their government is already pretty much the dregs of humanity. What do they have to lose? They are starving anyway. Methamphetamine does dangerous things to the mind and we have a nation led by a cabal of tweakers holding nuclear weapons and who knows what else. These people are dangerous. There is no point in talking to them. The only answer is to render North Korea "safe". |
| Posted by: crosspatch 2009-05-27 04:01 |
| #4 See also RIAN > IN AN EXTREME SITUATION, NORTH KOREA MAY SELL ITS [new] NUCLEAR CAPABILITY TO AL QAEDA [Radical Islamist Milit groups]; + EXPERT: NORTH KOREAN NUCLEAR TEST CONFIRMS IRAN IS STILL A THREAT TO ISRAEL. |
| Posted by: JosephMendiola 2009-05-27 02:01 |
| #3 What's worse - what do you think Obama would do (or fail to do) if Kimmie-boy did pop one off over Seoul or Tokyo? What do you think the UN Security Council would do? Send yet another strongly worded letter? Hold a fucking conference in some 5-star hotel in some exotic location? More Six-minus-one party talks? Remember the Democrats and Obama have absolutely no problem selling our allies down the river without a raft. Just as South Vietnam. |
| Posted by: CrazyFool 2009-05-27 01:11 |
| #2 Even 2KT airburst over Seoul (or worse, Tokyo) would do immense damage, human and economic. The equations below provide approximate scaling laws for relating the destructive radius of each effect with yield: r_thermal = Y^0.41 * constant_th r_blast = Y^0.33 * constant_bl r_radiation = Y^0.19 * constant_rad If Y is in multiples (or fractions) of 2.5 kt, then the result is in km (and all the constants equal one). This is based on thermal radiation just sufficient to cause 3rd degree burns (8 calories/cm^2); a 4.6 psi blast overpressure (equivalent to force exerted by a CAT5 hurricane max winds) and a 500 rem radiation dose. As a general guide, in the range yielded by these equations: The thermal effects will cause multiple fires and over 25% body area 3rd degree burns The bast effect overpressure of 5psi cause city areas to be completely destroyed (most buildings collapse, with massive loss of life) The radiation effect of 400-600 rem has a mortality that rises steeply in this range, from around 50% at 450 rems to 90% at 600 (unless heroic medical intervention takes place), and generally will cause large changes in organs, blood; When death occurs, it is usually 2-12 weeks after exposure and results from infection and hemorrhage. Recovery can take in excess of 1 year. This yields: 1.5km for the 3rd degree burns and thermal damage 1.4km for the blast overpressure of 4.6psi 1.2km for the 500rem of radiation It doesn't seem like a "large" radius, but you need to consider the densities of Tokyo or Seoul, much higher than a typical spread-out US (especially western US) city. Plot this against populations of city centers in Seoul or Tokyop and you are looking at massive fatalities, and even more damage and casualties. This does not include EMP effects, which would likely shut down medical equipment, radios, firefighting equipment (electronic ignition = dead firetruck/ambulance)etc, which will cause further casualties due to inability to perform rescue operations. This also does not count any casualties from fires/conflagration/firestorms that may form. Folks, even small nukes are nothing to be trifled with. |
| Posted by: OldSpook 2009-05-27 00:48 |
| #1 Wouldn't the two types of bombs produce different signature radiation and fission isotope products? |
| Posted by: Richard of Oregon 2009-05-27 00:22 |