There has been for many years former French servicemen (or their family) complaining about health issues allegedly due to radiation exposure. Like always in this type of situation, it's difficult to determine if the cancer (or any other disease) you've been diagnosed with is due to your being exposed to nuclear radiations 30+ years ago or if you would have gotten it anyway.
As mentioned by Joseph, the safety conditions were quite bad during the first tests held in the Algerian Sahara in the early 60s (a bit like the US tests done in the 40s/50s in Bikini or Nevada). The French authorities have recently admitted that and accepted to grant some form of compensation to the (still living) victims. On the other hand, the official position is that everything was safe in French Polynesia (Mururoa / Fangataufa) nuclear testing facilities. You can believe that... or not, but I too have friends who spend some time over there in the early 80s and they're still alive.