I think they already tried.
Remember the container ship flap? Where alpha radiation was detected?
And where after a great deal of searching and strange activity the source was supposedly "trace elements in a consignment of tiles"?
You mean like make tiles with plutonium added to the mix, ship it to wherever your destination is, grind up the tiles, and chemically extract/concentrate the plutonium? This would actually be relatively trivial to do...
Speaking of ships, What happened to those three ships supposedley circling in the Indian Ocean? Does anyone know what happened to those?