How are nuclear materials (reactancts and products) handled in nuclear power plants? Thanks!?

Answer 1

Very carefully. Reactants are held by control rods that regulate how much fissionable material is available. The products are stored in containment tanks and eventually shipped off to remote locations where they can radioactively decay for millenia.

Answer 2

Nuclear material in commercial power plants is contained in the form of pellets or fuel plates. At the end of the life of the reactor core, the spent material is removed from the core and allowed to give up "decay heat" (low-level heat generated by fission products) in a storage pond. Control rods in a reactor core can be reused a certain number of times before they too have to be replaced.
It is possible to reprocess uranium-235 in spent fuel. A spent core still contains about 65% of its initial loading of usable U-235. But although reprocessing plants are common in Europe, none currently exist in North America.