Damages of extreme doses to nuclear spent fuel
This microscopic scan of a pellet of nuclear fuel was taken after it had spent between 3 and 4 years inside a reactor. The exposure has already caused significant damage, as the cracks clearly show. These structural weaknesses are among the main factors which limit the amount of energy that can be extracted from these pellets. It must be remembered, however, that the damage made was caused by the tens of billions of joules per kilogram (also known as grays) that fission reactions produce in the uranium pellets. These are extreme levels of exposure.
CEA