Our teacher is currently teaching nuclear physics and I am confused on the process of calculating the energy released in a fission reaction. An example given in class is as follows:
Uranium-235 + 1n ---> Krypton-92 + Barium-141 + 3n
I understand that nuclear binding energy is the amount of energy needed to free all the nucleons in the nucleus, and the method taught to us is to take the binding energy of the krypton and barium nuclei and subtract the binding energy of the uranium nucleus to find the energy released.
My question is, why is the energy needed to free the 2 new free neutrons not also subtracted because they were previously bound in the uranium nucleus (at about 7.59 MeV)?