Bokeh talks about the damage of X-Ray on film with a complete practical illustration: where, how many time, which film, and the actual images. Just an example of what can happen.
Personally I just avoid as much as I can traveling with film.
Arkadiusz Podniesinski, a Polish photographer, has a photoessay on Fukushima and the exclusion zone around the nuclear power plant disaster.
Petapixel has Daniel Lachman tell us how much you can over expose colour negative film:
“What I took away from this is that film basically can’t be overexposed, it can just be too dense for the scanner to be able to shoot through the negative. But the information will always be there.”
My quick take is that you can shoot it at +2 and it will be more tolerant to under exposure error.