The six-factor formula is used in nuclear engineering to determine the multiplication of a nuclear chain reaction in a non-infinite medium. The formula is[1]
Symbol | Name | Meaning | Formula | Typical Thermal Reactor Value |
---|---|---|---|---|
Reproduction Factor (Eta) | The number of fission neutrons produced per absorption in the fuel. | 1.65 | ||
The thermal utilization factor | Probability that a neutron that gets absorbed does so in the fuel material. | 0.71 | ||
The resonance escape probability | Fraction of fission neutrons that manage to slow down from fission to thermal energies without being absorbed. | 0.87 | ||
The fast fission factor (Epsilon) |
|
1.02 | ||
The fast non-leakage probability | The probability that a fast neutron will not leak out of the system. | 0.97 | ||
The thermal non-leakage probability | The probability that a thermal neutron will not leak out of the system. | 0.99 |
The symbols are defined as [2]:
The multiplication factor, k, is defined as (see Nuclear chain reaction):
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.