The six-factor formula is used in nuclear engineering to determine the multiplication of a nuclear chain reaction in a non-infinite medium.
Symbol | Name | Meaning | Formula | Typical thermal reactor value |
---|---|---|---|---|
Thermal fission factor (eta) | neutrons produced from fission/absorption in fuel isotope | 1.65 | ||
Thermal utilization factor | neutrons absorbed by the fuel isotope/neutrons absorbed anywhere | 0.71 | ||
Resonance escape probability | fission neutrons slowed to thermal energies without absorption/total fission neutrons | 0.87 | ||
Fast fission factor (epsilon) | total number of fission neutrons/number of fission neutrons from just thermal fissions | 1.02 | ||
Fast non-leakage probability | number of fast neutrons that do not leak from reactor/number of fast neutrons produced by all fissions | 0.97 | ||
Thermal non-leakage probability | number of thermal neutrons that do not leak from reactor/number of thermal neutrons produced by all fissions | 0.99 |
The symbols are defined as:[2]
The multiplication factor, k, is defined as (see nuclear chain reaction):
- k = number of neutrons in one generation/number of neutrons in preceding generation
- If k is greater than 1, the chain reaction is supercritical, and the neutron population will grow exponentially.
- If k is less than 1, the chain reaction is subcritical, and the neutron population will exponentially decay.
- If k = 1, the chain reaction is critical and the neutron population will remain constant.
- ^ Duderstadt, James; Hamilton, Louis (1976). Nuclear Reactor Analysis. John Wiley & Sons, Inc. ISBN 0-471-22363-8.
- ^ Adams, Marvin L. (2009). Introduction to Nuclear Reactor Theory. Texas A&M University.