half-life or aire du nucléaire

Astoundingly, just a mere thirty kilometers outside of Paris, there is an abandoned nuclear testing grounds. Environmentalists have ventured, illegally, into this mothballed military facility and found few hot-spots, happily. Considering, however, the intensity and age of these experiments, one is nonetheless given pause to wonder whether Nature has not actually cleaned up the area but just managed to dilute it well enough to register as inconsequential. Or rather, has the dust and ash settled and is circulating over suburbia and the tourist haunts beyond?