https://media.ccc.de/v/36c3-10575-how_to_design_highly_relia... is a really interesting talk by some guys from CERN who have to design chips for use in particle accelerators and other physics experiments where they must survive unusually hostile radiation environments.
It's trickier than it seems because some forms of radiation can induce different kinds of radiation when they hit the dense shielding so you're kind of back to square one in that you still need a radiation resistant processor.
