My answer may be not very informed.
Originally Posted by Andre Noble
I read that UV-C will damage almost any avaible plastic or composite material. (Or to say it the other way around, nobody produces plastics resistent to UV-C as this radiation is not present at earths surface except when it is produced artificially. I guess some specialised plastics are produced for space missions.) An effective method to protect them is to wrap it in aluminium foil. So I'm pretty shure UV-C will not penetrate your freezer.
I don't see any overlapping between Gamma and UV in that diagram. I see Gamma from 10^-15 to 10^-10 and UV above 10^-10 at about 10^-5.
Howewer the text suggest water, concrete and lead to block Gamma. Put your freezer with film in the pool and you're set.
I also intended to radiate some of my lenses wiht UV-C. As precaution and also for killing existing fungus.
May I ask you for how long have you used UV-C on your lenses and if you could observe plastics going brittle or elsehow damaged?