What Nuclear material is used in nuclear power plant?

Answer 1

The reactor is usually initially fueled with uranium (for water moderated reactors this is enriched to 3% uranium-235, but other designs may be enriched more or less than that). A few reactors (e.g. reactors in France) are initially fueled with plutonium or a mixture of both uranium and plutonium.

After a reactor has operated for a period of time significant levels of transuranic elements have built up in the reactor core, these will also fission and the reactor uses them also as fuel (but unless it is a fast breeder reactor it neither produces nor burns these transuranic fuels very efficiently.

Note: a fast breeder reactor contains no moderator to slow neutrons and therefor if fueled with uranium usually requires it to be enriched to 93.5% uranium-235, commonly referred to as weapons grade uranium). The advantage of a fast breeder is that it efficiently converts the normally unusable uranium-238 to plutonium and other transuranics. The plutonium it produces would have far too much plutonium-240 and plutonium-241 in it (due to long fuel burn cycles) for use in weapons and could be used to fuel nuclear reactors of other types. It is also able to efficiently burn all the transuranics it produces, meaning the waste it produces would contain little more than the fission products which all have short halflives; therefor this waste would only have to be stored a few hundred years (not the tens of thousands of years that the wastes of current reactors must be stored, because they still contain unburned plutonium and other transuranics).