Iran’s nuclear warhead design survives new international deal reached in Geneva

Despite Tehran’s protestations that it has no intention of ever creating a nuclear weapon, they have been developing a warhead for some 15 years.

By EDWIN BLACK
Interior of Bushehr nuclear plant 370 (photo credit: REUTERS/Stringer Iran)
Interior of Bushehr nuclear plant 370
(photo credit: REUTERS/Stringer Iran)
While the world’s leaders are still coming to grips with the enrichment aspect of the Obama administration’s new deal in Geneva to curtail Iran’s nuclear weapons program, no one has noticed that Iran’s warhead and delivery program remains untouched.
Despite Tehran’s protestations that it has no intention of ever creating a nuclear weapon, Iran, in fact, has been developing a warhead for some 15 years. That design is now near perfect.
Compare Iran’s nuclear weapons program to the use of gunpowder. One stuffs gunpowder into a bullet, loads it into a rifle, and then finds a marksman who can hit the target. Iran has nearly mastered all those steps – but in nuclear terms. Four technological achievements are key to completing Tehran’s nuclear weapon: 1) accretion of enough nuclear materials, highly enriched to weapons grade – that is, about 90 percent; 2) machining that material into metal to create a spheroid warhead small enough to fit into a missile nosecone, where it will be detonated; 3) developing a trigger mechanism to initiate the atomic explosion at the precise moment of missile reentry; and, of course, 4) obtaining a reliable rocket delivery system to carry such a weapon.
Start with the nuclear material. Experts estimate that a single bomb would require approximately 25 kilograms of highly enriched uranium, or HEU, that has been boosted to concentrations of at least 90 percent. Much of Iran’s nuclear enrichment remains at 3.5% and 20% levels. But the numbers are deceiving. Enriching uranium to 3.5% is 75% of the distance needed to reach weapons grade. Once Iran has reached 20%, it has gone 90% of the distance.
Today, Iran possesses enough nuclear material for a fast breakout that would finish the job in about six weeks, creating enough material for five or 10 bombs. The current international deal leaves large stockpiles of 3.5% material and the centrifugal ability to quickly enhance to the next level of 20%, which again, is 90% of the distance needed.
Second, that HEU must then be metalized and shaped into a dense spheroid compact enough to fit into a missile nosecone. Iran has mastered the nuclear metallurgy, testing the process by using other high-density metals, such as tungsten. Tungsten objects have been detonated in a special underground chamber to measure its analogous explosive character.
Third, the spheroid must be detonated. Iran’s warhead design employs a R265 shock generator hemisphere drilled with 5mm boreholes filled with the volatile explosive PETN. When triggered with precision, the PETN array can cause a massive synchronized implosion. This will fire an internal exploding bridgewire that will, in turn, actuate an embedded neutron initiator to finally detonate the atomic reaction – and the mushroom cloud. This sequence of devices has already been assembled and tested by Iran. It possesses more than 500 exploding bridgewires on hand, adding more each day.
Fourth, the warhead must be delivered. The Shahab-3 missile nosecone is large enough to accommodate the warhead. The outer radius of the R265 shock generator- wrapped warhead is 550mm, less than the estimated payload chamber diameter of about 600mm. Most of all, the Iranian military has selected the Shahab-3 not only because it possesses a range of 1,200 kilometers but because on re-entry, it can be detonated in an airburst some 600 meters off the ground. The height of 600 meters was used in the Nagasaki explosion. Such a bomb cannot be crashed into the ground. If the nuclear reaction is to ignite, it must be detonated while still airborne. Iran has a small fleet of Shahab-3 missiles.
Hence, Iran’s metronomic accretion of enriched nuclear material is not just an ambiguous physics undertaking.
It is part and parcel of a nuclear attack plan that the international community must be determined to address. Any real deal to halt Iran’s nuclear weapon program must confront not only the easily replenishable gunpowder but also the bullets and rifles that have already been painstakingly assembled to stage the crime of the century.
The writer is the author of the award-winning IBM and the Holocaust and the recently released book Financing the Flames: How Tax-Exempt and Public Money Fuel a Culture of Confrontation and Terror in Israel.