Some early and some experimental reactors used sodium as the primary coolant.
Sodium is used as a coolant in kalpakkam nuclear power plant for Prototype Fast Breeder Reactor.
liquid sodium or water
Not a nuclear reactor!
Water (H2), or heavy water (D2O). Sometimes, liquid sodium is used.
This is used in the nuclear reactor that is known as Boiling Water Reactor (BWR) in which heat produced by the nuclear fission in the nuclear fuel allows the light water reactor coolant to boil. Then, the nuclear reactor moisture separator is used to increase the dryness of the produced steam before it goes to the reactor steam turbines.
Never a nuclear reactor is used in airplanes. However, it is used in submarines.
Boron is used inside a nuclear reactor inside a control rod which is used to 'soak' up the neutrons inside the nuclear reactor, a control rod can be used to control the rate of fission inside a nuclear reactor.
Sodium is an element and therefore in the strictest sense can not be made. However, in theory it could be made in a nuclear reactor.
The pressurised water reactor (PWR)
fuel
A Nuclear Reactor.
Most often, light water (H2O) is used as a moderator in a nuclear reactor. Sometimes, heavy water (D2O), or graphite is used.