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Iran’s Thin Man Gun-type, Plutonium, Nuclear Dirty-Bomb

By Mark Langfan
Arutz Sheva 
25 December, 2012

The gun-type plutonium bomb mechanism is a small, cylindrical, and very physically robust technology; the manners of delivery of such a nuclear device are infinite. Guess who has the technology.

Mark Langfan

On December 5th, 2012, the Wall Street Journal (WSJ) published an article entitled “From Bushehr to the Bomb.” The blockbuster WSJ article reported that Iran had removed, from its supposedly “proliferation-proof” Russian-built Bushehr Reactor in the Northern Persian Gulf, up to “220 pounds of weapons-grade plutonium.”  

And, the WSJ article further relates that “experts tell us that the rapid extraction of weapons-useable plutonium from spent rods is a straightforward process that can be performed in a fairly small (and easily secreted) space.” And, “as many as 24 Nagasaki-type bombs could be produced with 220 pounds of plutonium.”
However, the real, immediate danger of the 220 pounds of weapons-grade plutonium in Iran’s hands is not that they would build a technologically-complicated “Nagasaki” “Fat Man” implosion nuclear bomb, but that they could build a technological-no-brainer “Thin Man” gun-type nuclear “dirty” bomb.
Given Iran’s unexpected and unmonitored Bushehr plutonium diversion, and Assad’s imminent fall, it is vital that the public and the decision-makers clearly understand the difference between the two types of plutonium nuclear bombs.
Firstly, a gun-type plutonium nuclear bomb is not only feasible, it’s an established fact. The United States Department of Defense Defense Treaty Inspection Readiness Program currently states on its website:
“It is impossible to achieve a large nuclear explosion by using plutonium in a gun-type device. Nonetheless, a plutonium gun-type bomb could release as much energy as a few tons of TNT, which could conceivably cause many casualties. Moreover, this kind of bomb would release large amounts of plutonium and other radioactive materials, thereby making it a potent radiation dispersal device, or "dirty bomb."”

Additionally, the United Nations recently translated a book entitled
 "Nuclear Weapon Design" as follows:
“Such an assembly [plutonium gun-type] designed by terrorists using reactor-grade plutonium would have an expected yield of a few times the fizzle yield, amounting to 1 kiloton or more and having catastrophic consequences. A mere fizzle yield would still be a very damaging explosion, with effects of blast, heat, and prompt radiation extending out to a radius of at least one-third of a mile.”
How did this type of nuclear weapon come about? Is it new?
During the Manhattan Project in the early 1940’s, the nuclear scientists focused on two elements as suitable for nuclear bombs: uranium and plutonium. Each has advantages and disadvantages.
Uranium was hard to enrich in quantities necessary to build a bomb. But, the actual nuclear bomb technology was a simple linear gun-type mechanism, code-named “Little Boy,” where a uranium “bullet” was fired down a cylindrical “gun barrel” into a uranium slug, and “bang.”
Hiroshima,was a 16 kiloton TNT-equivalent explosion. (This means 16 thousand tons of a conventional TNT explosion.) US scientists were so confident in the "Little Boy" gun-type design that they, unbelievably, didn’t even test the uranium bomb before the US dropped it on Hiroshima.
On the other hand, plutonium (Pu) was very easy to make in large quantities. But, early on, the Manhattan Project scientists concluded that given plutonium’s particular nuclear properties of “pre-detonation,” they couldn’t use plutonium in the uranium analog cylindrical, simple gun-type bomb which they code-named “Thin Man” (named after the Dashiell Hammett detective character whose dog was named Asta).
Consequently, the nuclear scientists were forced to devise a totally different new bomb structure with a fantastically complicated and “fat” spherical shaped necklace of explosives, code-named “Fat Man” (named after another Hammett “Maltese Falcon” character played by Sidney Greenstreet, who was literally "fat."). The spherically placed explosives had to explode simultaneously - perfectly - and implode the plutonium core inwards, and then, “bang.” Nagasaki,was a 21 kiloton TNT explosion. US scientists weren’t so sure of the Fat Man design, so they first tested it at Alamogordo, New Mexico, code-named “Trinity." 
Plutonium’s particular nuclear property of “pre-detonation”, requiring a special Fat Man device to effectively explode the plutonium to a high-yield of TNT, is the key to how the Thin Man gun-type plutonium device is a modern-day nuclear “dirty bomb.”
Nuclear-reactor plutonium, like that of Bushehr, is generally composed of two isotopes Pu-239 and Pu-240 where Pu-240 has one more neutron in its nucleus than Pu-239. Pu-240 is a touch more unstable than its cousin Pu-239 isotope, and chain-reacts faster than Pu-239. So, when plutonium containing both Pu-240 and Pu-239 isotopes is exploded in a gun-type device, the pace of the Pu-240 nuclear reaction is faster than the Pu-239 reaction, and literally “pre-detonates” and explodes out the Pu-239 atoms away from each other before the Pu-239 can properly chain-react.
Consequently, you get a low-yield compared to a TNT explosion, and a wide dispersion of the highly radioactive and deadly Pu-239 atoms, and other nuclear fission residue. The plutonium gun-type reaction is called a “fizzle” when there is only a small Pu-240 nuclear reaction with a very highly radioactive Pu-239 fallout dispersion. Unfortunately, Pu-239, while extremely radioactively poisonous, is very elementally stable, and has a half-life of 24,100 years.
With the “help” of the nuclear power industry, nuclear proliferation efforts have mostly focused on uranium proliferation. This approach was based on the dubious theory that since you “need” an extremely complex spherical technology to build a “high yield” bomb out of plutonium, “one need only worry about uranium bombs.” The nuclear proliferation-minders seem to have generally ignored the catastrophic possibility of a desperate, rogue nation building a gun-type plutonium device which could be used in numerous, monstrously evil ways.
With the Russian-built Iranian Bushehr nuclear reactor, Putin thought he was smarter than Joseph Stalin, who from August 1939 to June 1941 (as part of the economic protocol to the 23 August 1939 Hitler/Stalin “Non-aggression” Pact) sold Hitler the crude oil fuel he needed for his Nazi war machine. I.G. Farben then refined the crude to power the Nazi tanks and planes that then proceeded to annihilate the Soviet Union in June 1941 with Stalin’s “crude” oil (having earlier obliterated London).
Like Stalin, Putin originally didn't realize that by supplying nuclear fuel to Bushehr, he would be arming Iran with 24 plutonium dirty "fizzler" nukes that could make Hitler's Barbarossa look like a game of tiddlywinks.
Putin asked his Russian scientists (who were used to building 160 kilo-ton hydrogen fusion nuclear bombs, and who would have been shot dead by Putin's buddies pushing the Iranian nuke deal), if Bushehr plutonium reactor-grade plutonium was dangerous. Well, compared to a 160 kiloton hydrogen fusion bomb, a one kiloton plutonium gun-type device isn't really a big deal.
Anyway, Putin forgot to ask those same scientists whether Iran, with readily available off-the-shelf technology, could build a crude gun-type bomb, using only 8-kilograms of Bushehr reactor-grade plutonium, that was capable of achieving a one-kiloton nuclear "fizzle" event which could irradiate Moscow for 62,642.6 years. (Pause.)
How do you translate "Oy gevalt" into Russian? Putin will go down in history as making Stalin look like a genius. That is, if there's a 'history' after Iran "fizzles" Moscow.
Given that the gun-type plutonium bomb mechanism is a small, cylindrical, and very physically robust technology, the manners of delivery of such a nuclear device are infinite.
Imagine use against a US aircraft carrier battle group massing in battle formation in the Arabian Sea - via an Iranian kamikaze mini-submarine with about a minimum of 1/3 mile to a full mile guaranteed kill radius (Think, nuclear-sea-mine US carrier group killer!).
Or, a secreted weapon could be loaded onto a cargo ship, and the device could be exploded in New York harbor close to the new World Trade Center.
Or perhaps, an Iranian-supplied Chechen Black Widow armed with one of these 1-kiloton weapons could light up the Kremlin brighter than Chernobyl.
It is also important to draw the difference between a gun-type plutonium nuclear “dirty” bomb, and the technologically trivial conventional radiological “dirty” bomb.
In the plutonium gun-type bomb, there is an actual small nuclear Pu-240 fission event that disperses both the radioactive Pu-239, and the radioactive nuclear fission residue of the highly fissile Pu-240 (Note: highly radioactive fission residue is the components left after the Pu-240 nucleus has broken up in a nuclear event).
In a conventional “dirty” bomb, conventional explosives, packed with radiological materials. explode, dispersing the radiological materials without any fissile product residue because there is no actual “nuclear” fission event.
The bottom line is that with Syrian President Assad on a fast trajectory to political “implosion,” Iran has become desperate to acquire “gun-type” nuclear capability as fast as possible.
Diverting the Bushehr plutonium to build 24 small easily transportable, widely dispersed, hidden, gun-type plutonium nuclear “dirty” bombs may be Iran’s shortest, surest, and ugliest ticket to Nuclear Bomb capability, and the actualization of their belief in the re-emergence of the 12th and final Imam, Muhammad al-Mahdi.
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Mark Langfan writes articles on Middle East Security. He has created an original educational 3d Topographic Map System of Israel to facilitate clear understanding of the dangers facing Israel and its water supply. It has been studied by US lawmakers and can be seen at