If you have access to a gamma spec system (and the parts are small enough), you can try counting them directly. You'll need to calibrate a geometry that minimizes to the extent practical the problem of the size and shape of the item. Or you can get one of the fancy in-situ counting systems. Sometimes we do this with small parts. If you have a point calibration source, you could try calibrating with the source at some known distance from the detector, then when counting, place the object at that distance. It will get you a fair estimate. In some materials (Al for example) you'll often have a lot of positron emitters that you can't ID and therefore can't estimate activity for because all you'll get is a big 511 peak. But if you know what nuclides are present, you can estimate their activity by the count rate in that peak. But it sounded like you were looking for a way to calculate the induced activity rather than measure it. I'll pass your post along to our resident expert on that. But often, because of the assumptions you have to make when calculating this, the direct measurement method is probably just as good or better.
--
Keith Welch
Thomas Jefferson National Accelerator Facility
Newport News VA
welch@jlab.org
Ph: (757)269-7212
FAX:(757)269-5048
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html