Final answer:
Spent nuclear reactor fuel is typically stored in specially designed pools of water or dry storage containers.
Step-by-step explanation:
Spent nuclear reactor fuel, known as high-level radioactive waste, is typically stored in specially designed pools of water or dry storage containers.
The spent fuel assemblies are initially stored in pools of water, which acts as a radiation shield and cools the fuel.
Alternatively, reactor operators can choose to store older spent fuel in dry storage facilities using special outdoor concrete or steel containers with air cooling.