Fuel Reprocessing
Question:
how can we enrich the spent fuel (used U-235)? Can we combine the
fission products again like in nuclear fussion? But I think this
method will used up the energy produced during nuclear fission.
Answer:
The uranium 238 which makes up the majority of the fuel absorbs
neutrons during the reactor operation and decays to an isotope of
plutonium which may be made to undergo fission similar to uranium
235. Reprocessing the spent fuel involves chemical separation of
the plutonium to be used as fuel in another reactor. There is no
possibility of reassembling the fission fragments into the
original uranium nucleus because of the energy considerations you
mentioned.