Michelle*s_Farm
12-15-2009, 06:09 AM
Iranians outed by uranium deuteride? - December 14, 2009
The Times (of London) has a big spread today, which reportedly outs the Iranian nuclear programme. Documents from "an Asian intelligence source" show that, in 2007, the Iranians were preparing experiments with uranium deuteride in order to develop a neutron "initiator" for a nuclear bomb. That would be four years after they claimed to have stopped their bomb programme.
Nuclear weapons are all about getting enough uranium into a small enough space to trigger a boom. The simplest nuclear bomb is a "gun type" device, in which a critical mass is assembled by firing a uranium plug into a doughnut-shaped ring at high speed (or visa vice versa). When the plug and doughnut are united, the bomb goes critical and explodes.
It works alright, but compression is better. Modern bombs use explosives to compress a sphere of Uranium-235 or (better still) Plutonium-239 until it reaches a critical density. Helping in the process is an "initiator" at the bomb's core, which sends out a burst of perfectly timed neutrons that trigger the explosion.
And that's where uranium deuteride comes in. The Iranian documents appear to call for a research programme into using uranium deuteride as a neutron initiator. The Institute for Science and International Security (ISIS) has a little graph explaining how this works:
This type of initiator works by the high explosives compressing the nuclear core and the initiator, producing a spurt of neutrons as a result of fusion in D-D [deuterium-deuterium] reactions. The neutrons flood the core of weapon-grade uranium and initiate the chain reaction. It does not boost the yield.
Initiators are important because if they don't work, your bomb might not either. The most widely described design uses combination of beryllium and polonium. Basically helium atoms (alpha particles) from the decay of the polonium trigger a big neutron flux in the beryllium. The US and others use more sophisticated initiators that slam tritium into a deuterated target, initiating fusion and, in the process, creating a precise pulse of neutrons.
UD3 is kind of an unusual material for an initiator. Where would Iran have gotten an idea? Hmm… Well as Jeffrey Lewis at Arms Control Wonk points out, it might have been everybody's favourite nuclear smuggler AQ Khan. This photo, from the cover of Khan's own book, show's a pretty bomb design. And what did Khan have as the initiator? Why it's "Uran-Deuteride"!
ACW has a great discussion about how the Chinese fooled around with UD3 in the 1980s, and ISIS has posted the original documents from the Times story here. For my own offering of uranium deuteride trivia, I'll point out that the US apparently tested a bomb made entirely of the stuff back in 1953. The test was part of the Upshot-Knothole series, although it didn't have anything to do with initiators, so far as I can tell.
Posted by Geoff Brumfiel on December 14, 2009
Source One (http://blogs.nature.com/news/thegreatbeyond/2009/12/iranians_outted_by_uranium_deu.html)(comment on Times piece)
Source Two (http://www.timesonline.co.uk/tol/news/world/middle_east/article6955351.ece) (original Times piece)
The Times (of London) has a big spread today, which reportedly outs the Iranian nuclear programme. Documents from "an Asian intelligence source" show that, in 2007, the Iranians were preparing experiments with uranium deuteride in order to develop a neutron "initiator" for a nuclear bomb. That would be four years after they claimed to have stopped their bomb programme.
Nuclear weapons are all about getting enough uranium into a small enough space to trigger a boom. The simplest nuclear bomb is a "gun type" device, in which a critical mass is assembled by firing a uranium plug into a doughnut-shaped ring at high speed (or visa vice versa). When the plug and doughnut are united, the bomb goes critical and explodes.
It works alright, but compression is better. Modern bombs use explosives to compress a sphere of Uranium-235 or (better still) Plutonium-239 until it reaches a critical density. Helping in the process is an "initiator" at the bomb's core, which sends out a burst of perfectly timed neutrons that trigger the explosion.
And that's where uranium deuteride comes in. The Iranian documents appear to call for a research programme into using uranium deuteride as a neutron initiator. The Institute for Science and International Security (ISIS) has a little graph explaining how this works:
This type of initiator works by the high explosives compressing the nuclear core and the initiator, producing a spurt of neutrons as a result of fusion in D-D [deuterium-deuterium] reactions. The neutrons flood the core of weapon-grade uranium and initiate the chain reaction. It does not boost the yield.
Initiators are important because if they don't work, your bomb might not either. The most widely described design uses combination of beryllium and polonium. Basically helium atoms (alpha particles) from the decay of the polonium trigger a big neutron flux in the beryllium. The US and others use more sophisticated initiators that slam tritium into a deuterated target, initiating fusion and, in the process, creating a precise pulse of neutrons.
UD3 is kind of an unusual material for an initiator. Where would Iran have gotten an idea? Hmm… Well as Jeffrey Lewis at Arms Control Wonk points out, it might have been everybody's favourite nuclear smuggler AQ Khan. This photo, from the cover of Khan's own book, show's a pretty bomb design. And what did Khan have as the initiator? Why it's "Uran-Deuteride"!
ACW has a great discussion about how the Chinese fooled around with UD3 in the 1980s, and ISIS has posted the original documents from the Times story here. For my own offering of uranium deuteride trivia, I'll point out that the US apparently tested a bomb made entirely of the stuff back in 1953. The test was part of the Upshot-Knothole series, although it didn't have anything to do with initiators, so far as I can tell.
Posted by Geoff Brumfiel on December 14, 2009
Source One (http://blogs.nature.com/news/thegreatbeyond/2009/12/iranians_outted_by_uranium_deu.html)(comment on Times piece)
Source Two (http://www.timesonline.co.uk/tol/news/world/middle_east/article6955351.ece) (original Times piece)