At 10:41 AM 9/11/03 -0700, Tim May wrote:

* depleted uranium (DU) is essentially pure U-238, with very low specific activity (decay rate); removal of the 2-3% of the higher specific activity U-235 lessens the overall decay rate of the original metal substantially.

Commericial airliners often contain tens of kilograms of DU as ballast. Ref: _Living with Radiation_, by Frame & Kolb. They often carry medical or other isotopes during civilian flights too. There are rules for distributing those containers so no one passenger gets too much extra dose. DU gives off plenty of alphas. (Thus you don't want to breathe DU dust, which will also heavy-metal your kidneys in the short term.) But they're stopped by anything, including aluminum foil-- lead pipe is overkill. The only way to detect shielded DU is gammas, to identify it you need gamma spectroscopy. The neutron analysis being done at some ports of entry only works on fissile materials. The Fatherland Security troops are publicly embaressed and showing their brown shirts. --- Of course Pierre Curie didn't die from radiation poisoning, he was hit by a horse drawn cart.