3 ms·

Out of curiosity, how do irradiated plastics fail? Do they become brittle, soft, something else?

• azalemeth 5y ago
  The details are really, really complex, but either (a) they heat up from the absorbed dose (1 Gy is 1 kJ / kg) or (b) high gamma fluxes ionise CH bonds and cross link randomly, leading (typically) to brittle failure modes. Sometimes with heating you get spallation. The accelerator I most recently used has a large set of house-grade UPVC glass windows around the target stage to help thermally control it (it's variable temperature). It's after the beam dump and behind quite a lot of lead, but they've been there for a while. The glass is a weird shade of purple in a pretty gaussian pattern and the formerly bright-white UPVC is brown in places, purple in other places, and looks a bit like wood does when it's rotting and peeling off. If you hit it with a hammer I'm sure it would disintegrate. There are rad hard plastics but again it's all a function of "what radiation", "what energy", "how much" and "how long" and you end up doing monte carlo simulations pretty quickly.