It appears that a ship can be left hanging above a planet with minimal or no cost, as if it were simply 'parked'. This power is sufficeint to keep the Free Float system operational almost indefinitely. People tend to think there is no 'weight' in space, that's not strictly true. Weight is a product of gravity and mass. Without the gravity, the mass of an object is still there.
Objects retain the same mass, wherever they are.
The free float technology reduces mass and makes moving things easy. Free float technology could actually be vital to space travel - see the Faster than Light topic below. The source of the nuclear power is not the same as the radioacitve materials in use today. In one episode it is stated that the material comes from another planet where it is mined by robots. I conclude that the radiation from this source is 'safe' and does not break down in a way harmful to life.