nuclear waste 
noun [mass noun]
Radioactive waste material, for example from the use or reprocessing of nuclear fuel.She has no objection to the process as such of discharging nuclear waste; obviously nuclear waste has to be dealt with....
- Scientists are examining Humber estuary mud in the hope it could hold the key to the safe disposal of radioactive nuclear waste.
- An internal report written by a manager at the Sellafield nuclear waste reprocessing plant was leaked this week.