Uranium and/or Plutonium fuel
Nuclear reactors.
No substitute for nuclear power reactors especially if there is no available fossil fuel.
Uranium is a radioactive element used to fuel nuclear reactors. It is a nuclear fuel.
Uranium is not a fossil fuel; uranium is used as nuclear fuel for nuclear power reactors.
Well, as nuclear reactors are nuclear reactors, nuclear reactors are not used inside nuclear reactors.
It is Uranium
Typically, Uranium-235 is used as fuel in nuclear reactors.
Uranium is used as nuclear fuel in nuclear power reactors.
To make fuel rods for nuclear reactors
Uranium
Not as fuel, but it can be used in breeder reactors as breeding material to make fissile Uranium-233.
We usually find that uranium is used as fuel in nuclear reactors (though some use plutonium).