Monday, April 06, 2009

The nuclear sculptor

This week's Nature journal features an interview with James Acord, reputedly the only private individual in the world with a license to possess and handle radioactive materials. James even has his license number tattooed on the back of his neck (Washington State Radioactive Materials License # WN-10407-1).

(Presumably, the need for a license is a matter of degree, given that our own bodies contain radioactive potassium-40, and given that the walls of most buildings contain the radioactive isotopes from the natural uranium-238 and thorium-232 decay chains).

Acord creates sculptures out of radioactive materials, but his latest project seems to be more a means of creating plutonium-239 in the garden shed. He explains in Nature that he has taken the americium-241 from a smoke detector, and coupled it to an emerald stone. Americium-241 is a source of alpha particles, and when alpha particles collide with the beryllium in the stone (emerald is a variety of the mineral beryl Be3Al2(SiO3)6), it produces neutrons. Acord has therefore basically produced a conventional americium-beryllium neutron source from home-made materials.

Acord then moderates the neutrons with a hydrogenous material, which could easily have been water or plastic, but which Acord has ingeniously chosen to be a 6cm slice of beeswax. The moderated neutrons then impinge upon the glazing to be found on certain ceramics from the 1940s. The glazing contains a form of uranium-oxide, and a certain fraction of the uranium-238 nuclei will absorb the moderated neutrons, and thereby transform to uranium-239. The latter will then undergo beta decay to neptunium-239, which in turn will beta decay to plutonium-239.

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