If that's one of the 10-20 mCi numbers, I'd advise thinking twice. You're looking at a 432y halflife, medium-E alpha-emitter (60keV photons). The loss of one would be a major pain. The Co57 wands that are widely available are usually no more than 100 uCi, with a 270d halflife. And, they're relativley cheap, even at a replacement rate of 1/y. chris alston