four factor formula
Answers
The way in which neutrons are increased and absorbed can be described by a combination of factors in the 'four factor formula'
Neutrons are increased in two ways
Thermal fission factor h
Fast fission factor e
Neutrons are absorbed in two ways
Resonance escape probability p
Thermal utlisation factor f
h = the average number of neutrons produced per thermal neutron absorbed in the fuel.
e = the number of fission neutrons produced by fast neutrons before they are moderated. This will be largely in the 238U.
f = the fraction of thermal neutrons absorbed in the reactor that are absorbed in the fuel.
p = the fraction of neutrons that are in the course of thermalisation escape being captured by the resonance structure of 238U.
L = combined leakage factor L < 1
k¥ = hepf Þ
keff = hepfL