The pellets are homogeneous. The reprocessing of fuel involves melting or dissolving them and chemically separating out the waste products, with the remaining unused fuel going back into new pellets.
The waste products are spread throughout the fuel pellets evenly, so the pellets have to be deconstructed to remove them.
The waste products are spread throughout the fuel pellets evenly, so the pellets have to be deconstructed to remove them.