I'm pretty sure the "nuclear" kit is going to be a UV penetrant, rather than visible. Since it fluoresces under blacklight, much smaller traces are detectable, making UV penetrant quite a bit more sensitive. It's more expensive in several respects, though. First being the cost of the materials. Second, of course, is a powerful enough blacklight... A good 50W longwave will set you back $400 or so, and replacement bulbs for ours were $116 last time we bought. Third is the time and material to black out all light from your test area, if your piece is too big to move to a dark room.
On a side note, don't EVER blacklight anything in the company rest room... You do NOT want to see what glows in there...
I should add, I don't use UV penetrants at this time (we have the blacklight for oxygen-clean checks), as the visible is more than sufficient for what I'm testing.