On 29 November 2007 the BBC reported that three conspirators were arrested in Slovakia for acquiring 500g of "highly enriched uranium" powder. It was said to be "enriched enough" to make a dirty bomb. This is yet another demonstration of the almost total popular ignorance of many scientific facts. The uranium was probably pure uranium enriched in the 235 isotope. They do not say how enriched, but 500g of even pure U235 would not be enough to make a bomb. That the sample was radioactive would have been difficult to determine (it was shown being held in the hand). If it were stored for a few million years, its activity might approach that of natural uranium, which is very feeble. If terrorists wanted to blow it up in a dirty bomb, they should be sure to tell someone, else their deed might go completely unnoticed. There would be no radioactivity, and the uranium would be quite insoluble, so would not leach into the water supply, where it wouldn't do much anyway. It is humorous that the world thinks that "enriching" uranium makes it more radioactive. Now if the terrorists could get enough together to go critical, they probably would not have time enough to do anything about it, and the radioactivity would make a rather small hot spot (there wouldn't be much, since the burnup would be very tiny, but enough to make them resemble boiled lobsters). Uranium is hardly radioactive at all, in fact. Enriched uranium is no more radioactive than depleted uranium. Uranium is quite dense (sp.gr. 19). A bare sphere of 8.3 cm radius of U235, weighing 44.8 kg, can go critical (see Am.J.Phys. 75, 1065-1072 (2007)).
This recalls the Italians who were trying to mass poison with potassium ferrocyanide, or the playgrounds contaminated by deadly silica.
Composed by J. B. Calvert
Created 30 November 2007
Last revised 3 December 2007