Neutrons passing through steel would occasionally collide with a cobalt-59 nucleus, producing easily detectable cobalt-60 if trigger experiments were carried out in the steel chamber at Parchin. (From a Wikimedia Commons illustration of the 1911 Rutherford experiment where alpha particles were sent through a thin gold foil.)
Both Marcy, here, and b, over at Moon of Alabama, have roundly criticized the cartoon released on Sunday by AP’s George Jahn purporting to depict a chamber at Iran’s Parchin site where various groups accuse Iran of carrying out work aimed at an explosive trigger device for a nuclear weapon. David Albright, working through his Institute for Science and International Security, has been near the forefront in most of these accusations, with one of his accusations coming out in December of 2009 (pdf). As described in his 2009 piece, Albright accuses Iran of attempting to replicate A.Q. Khan’s uranium deuteride (UD3) initiator for a bomb, which “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 reactions. The neutrons flood the core of weapon-grade uranium and initiate the chain reaction.”
Prior to the release of the cartoon, Albright had claimed on May 8 that he had detected activity aimed at “cleansing” the Parchin site. I debunked that claim the next day, by pointing out that all traces of radioactivity cannot be washed away and that Albright’s claims would mean that the waste water carrying the radioactivity was allowed to drain freely onto the grounds surrounding the building, where the radioactivity could be found without much effort. Albright repeats those claims in Jahn’s article accompanying the cartoon, and he brings in another expert to support his claims that residue from testing a trigger device could be scrubbed:
A cleanup “could involve grinding down the surfaces inside the building, collecting the dust and then washing the area thoroughly,” said David Albright, whose Institute for Science and International Security in Washington looks for signs of nuclear proliferation. “This could be followed with new building materials and paint.
“It could also involve removing any dirt around the building thought to contain contaminants,” Albright said in a statement emailed to selected recipients. “These types of activities could be effective in defeating environmental sampling.”
Fitzpatrick, the other nuclear nonproliferation expert, also said a cleanup could be effective.
“In the past, the IAEA has been able to catch out Iran by going to a building that Iran tried to clean and they still found traces of uranium,” he said. “And Iran learned from that and they learned that ‘boy you have to scrub everything really clean; get down into the drains and grind away any possible residue.”
Earlier in the article, Fitzpatrick (who is Mark Fitzpatrick, director of the Non-Proliferation and Disarmament Program of the International Institute for Strategic Studies) mentions that Iran is specifically accused of using uranium in the explosives research. Also, the article claims that the equipment associated with the chamber includes “a neutron detection system outside the explosion chamber to measure neutron emissions”.
Albright and Fitzpatrick completely overlook a very important basic aspect of the nuclear physics involved here. If they really are going to claim that uranium is being used and that bursts of neutrons capable of initiating a nuclear reaction are the goal of the experiments, then the neutrons originating from the uranium and from the neutron bursts would result in neutron activation of the steel container itself. Continue reading