Someone argues: "The prompt neutron generation time is only
PHYSICS · Subjective · Fermi University Physics · Nuclear Physics · Fission, fusion and nuclear energy · Fission, fusion and nuclear energy
Energy from Physics, Ch Running a reactor: kinetics, heat removal, feedback, burn-up and the fuel cycle
Problem
Someone argues: "The prompt neutron generation time is only Λ=2×10−5s, so a reactor's neutron population responds to any change within microseconds. This means control rods, which move mechanically over seconds, are actually keeping pace with the prompt neutrons perfectly well: the reactor's response to a rod movement is prompt, and the delayed neutrons emitted seconds after fission are essentially irrelevant to how fast the reactor can be controlled." Find the error in this reasoning, using the one-group inhour relation ρ=Λ/Tp+β/(1+λTp) with β=0.0065, λ=0.0767s−1 and a representative rod-withdrawal step of ρ=0.001.