A core has fuel and moderator temperature coefficients and
PHYSICS · Multi-part · Fermi University Physics · Nuclear Physics · Electronics, Instrumentation & Communication · Signals, systems, control and digital signal processing
Energy from Physics, Ch Running a reactor: kinetics, heat removal, feedback, burn-up and the fuel cycle
Problem
A core has fuel and moderator temperature coefficients αF=−3×10−5K−1 and αM=−1×10−5K−1. Following a rod withdrawal of ρ0=8×10−4, the moderator is found to heat by only 0.4ΔTF once the power has settled, because the coolant flow carries much of its heat away.
((a)) Predict the fuel temperature rise ΔTF at which the combined feedback cancels this step.
((b)) Separately, plutonium-239 is compared as a fuel in two spectra: thermal (η=2.11) and fast (η=2.7). If conversion and control losses take 0.15 neutrons per absorption in fuel over and above the chain-continuation and conversion neutrons, decide in which spectrum, if either, this fuel could breed.