The UN's nuclear watchdog has asked Iran to explain evidence suggesting that Iranian scientists have experimented with an advanced nuclear warhead design, the Guardian has learned.
The very existence of the technology, known as a "two-point implosion" device, is officially secret in both the US and Britain, but according to previously unpublished documentation in a dossier compiled by the International Atomic Energy Agency (IAEA), Iranian scientists may have tested high-explosive components of the design. The development was today described by nuclear experts as "breathtaking" and has added urgency to the effort to find a diplomatic solution to the Iranian nuclear crisis.
The sophisticated technology, once mastered, allows for the production of smaller and simpler warheads than older models. It reduces the diameter of a warhead and makes it easier to put a nuclear warhead on a missile.
Documentation referring to experiments testing a two-point detonation design are part of the evidence of nuclear weaponisation gathered by the IAEA and presented to Iran for its response.
In fact, the described design is similar to that of six- or eight- inch diameter nuclear artillery shells dating to the 1950's and 60's, and is the likely design for so-called suitcase nuclear weapons.
In this type of design, an egg-shaped block of fissile material (isotopes of Uranium or Plutonium are most likely) is encased in a cylinder of high explosive, and at opposite ends of the cylinder there are detonators and explosion wave shapers. On triggering the detonators, blast waves compress the egg of fissile material into a ball, which is supercritical and undergoes a rapid chain reaction, triggering an explosion.
As Carey Sublette (source for the above description - cf Diagram here) also notes:
It is impossible to verify at the time of this writing whether nuclear devices sized to fit in side a suitcase were actually manufactured by the former Soviet Union, as alleged by Alexander Lebed in September 1997. It is certainly possibel to assess the technicial plausibility of such a claim and to provide a analysis of the likely characteristics of the weapons Lebed described.
A suitcase bomb with dimensions of 60 x 40 x 20 centimeters [2 ft x 18 inches x 8 inches] is by any standard a very compact nuclear weapon. Information is lacking on compact Soviet weapons, but a fair amount of information is available on compact US designs which provides a good basis for comparison.
The smallest possible bomb-like object would be a single critical mass of plutonium (or U-233) at maximum density under normal conditions. An unreflected spherical alpha-phase critical mass of Pu-239 weighs 10.5 kg and is 10.1 cm across.A single critical mass cannot cause an explosion however since it does not cause fission multiplication, somewhat more than a critical mass is required for that. But it does not take much more than a single critical mass to cause significant explosions. As little an excess as 10% (1.1 critical masses) can produce explosions of 10-20 tons . . . . A mere 1.2 critical masses can produce explosive yield of 100 tons, and 1.35 critical masses can reach 250 tons. At this point a nation with sophisticated weapons technology can employ fusion boosting to raise the yield well into the kiloton range without requiring additional fissile material . . . .
It is reported that designs least as small as 105 mm (4.1 inches) are possible. A hypothetical 105 mm system developed for use in an artillery shell would be about 50 cm (20 inches) long and weigh around 20 kg.
Compact nuclear artillery shells (208 mm and under) are based on a design approach called linear implosion. The linear implosion concept is that an elongated (football shaped) lower density subcritical mass of material can be compressed and deformed into a critical higher density spherical configuration by embedding it in a cylinder of explosives which are initiated at each end. As the detonation progresses from each direction towards the middle, the fissile mass is squeezed into a supercritical shape. The Swift device is known to have been a linear implosion design.
It is quite likely, that should the suitcase bombs described by Lebed actually exist, that they would use this technology. It is clear that any of the 155 mm artillery shells, if shortened by omitting the non-essential conical ogive and fuze would fit diagonally in the package that Lebed describes, and the Swift device would fit easily. If the yield is as much as 10 kilotons, then the device would have to be fusion boosted.
A somewhat more sophisticated variation would extend the linear implosion concept to cylindrical implosion, in this case an oblate (squashed) spheroid, roughly discus-shaped, of plutonium would be embedded in a cylinder of high explosive which is initiated simultaneously around its perimeter. The cylindrically converging detonation would compress and deform the fissile mass into a sphere, that could be wider than the original thickness of the system. This type of design would make the flattest possible bomb design, perhaps as little as 5 cm. The only obvious application for such a device would be briefcase bomb, and would require a special development effort to create it.
In short, we have reason to infer that:
1 --> the Iranian weapons programme has a feasible, small warhead design,
2 --> it has tested the most important part of the weapon, the implosion system (most of the design effort on the Manhattan programme bombs went into gettinghe implosion system to work)
3 --> Such small, relatively low yield weapons are well suited to the known ballistic missiles that Iran has developed
4 --> They are also well adapted to possible suicide nuclear tterrorism using so-called suitcase nuclear bombs.
In short, the world just took a big step closer to nuclear war in the Middle East; and therefore, to an Israeli pre-emptive strike.
Should either of these eventualities happen (or even just come close), the resulting instabilities could easily shoot the price of oil back up to unprecedented levels, maybe -- as a raw guess -- spiking to twice or more as high as the previous high of just less than US$ 150/barrel for crude oil.
In short, we have to get ourselves ready for a whole new level of possible instabilities. And, we need to pray for the peace of Jerusalem. END