On Wed, 20 Mar 2013 08:31:27 -0500, dpb wrote:

On 3/20/2013 12:02 AM, Martin Eastburn wrote:
Look at the atomic numbers - there is 72 for light bulbs and
9x, 1xx for the various depletion - meaning the half life is
reducing the radiation...
...

???

The half-life of 92U238 is ~4.5x10E9 _yrs_...(that's 4 billion w/ a B
years). One doesn't observe much change in specific radioactivity w/
time in a normal lifetime.

Cost aside, I don't think it's very easy to get ahold of. I didn't try
very hard, but I didn't see much on offer in macroscopic sizes.