A nuclear reactor is rated for producing electrical energy but not all of the heat released in the core can be converted into useful output. Assume the reactor fuel is 235U in which each fission releases on the average 200MeV of energy.
(i) Define the term “energy per fission” and state its typical numerical value for 235U. Express your answer both in MeV and in joules. (Use 1eV=1.6×10−19J.)
(ii) Show that the number of fission events N required to deliver a net electrical energy output Eout is given by N=ηEfEout, where η is the overall efficiency of the power-conversion system and Ef is the energy released per fission.
(iii) If the efficiency of the plant increases from 25% to 50%, by what factor will the required number of fissions for the same electrical output change? Explain the physical reason for this change without performing a detailed numerical calculation.