Hmmm.. pitchblende isn`t a very good thing to have around in all honesty, it can contain many different radioactice isotopes and be responsible for Radon gas buildups in homes. it maybe worth getting it checked out by the environmental health agency, they set up a few simple tests (usualy little peices of film in sealed units around your home to detect radiation) and will also take a few samples of what you suspect is pitchblende.
as for your plants, that`s a tough question, edibles would certainly need to be free of any soil before eating (good practice anyway!
you may find that your germination percentage is a little lower than should be due to ionising radiation effecting the DNAs aleales (chromosomes). the plants themselves however will not become inherantly radioacative by simple exposure
get it checked out though, if you`re right, and do nothing about it, it could be cause for concern!