Mass balance estimate of the energy released per fission in a reactor

The total energy released per fission in a reactor is equal to the difference in mass between the reacting particles (neutron and fissile nucleus) and end products (stable or long-lived fission products, neutron capture products, etc.) The major components in this mass balance are known with a very small uncertainty and are tabulated in UCRL-16964.; ; To obtain the energy per fission appearing as heat in a reactor, estimates are required for the energy carried away by neutrinos, the β decay energy of long-lived fission products and the binding energy of (v-1) neutrons captured in fuel, fission products, control rods or equivalent, moderator, structural materials and shielding. Loss of energy by γ-rays and neutrons leaking through the shielding is assumed to be negligible. The calculations have been done for thermal neutron fission of U²³³, U²³⁵, Pu²³⁹, and Pu²⁴¹ and fast fission of the Th²³² and U²³⁸. The calculated 'MeV per fission' appearing in a CANDU-type reactor are: Th²³², 196.2±.1; U²³³, 199.0±.1; U²³⁵, 201.7±0.6; U²³⁸, 208.5±1.1; Pu²³⁹, 210.7±1.2; Pu²⁴¹, 213.8±1.0. (author)