I just want to say that there are ideas out there other than the one I just described. The National Research Council, along with the small company Mevex, for example, has proposed using moly-100 targets from which you can remove a neutron and make moly-99. There's another proposal by Advanced Applied Physics Solutions, which is a spinoff of TRIUMF, to add a neutron to moly-98 to make moly-99. You can put moly-98, which is the natural molybdenum, inside a reactor--this is done around the world now--but then you need to purify it. They're working on purifying it after it's been irradiated.
There are a number of ideas out there.