Four factor formula

The four-factor formula is used in nuclear engineering to determine the multiplication of a nuclear chain reaction in an infinite medium. The formula iscite book |last=Duderstadt |first=James |coauthors=Hamilton, Louis |title=Nuclear Reactor Analysis |year=1976 |publisher=John Wiley & Sons, Inc |isbn=0-471-22363-8 ]

$k\_\{infty\}\; =\; eta\; f\; p\; epsilon$

Multiplication

The multiplication factor, k, is defined as
$k\; =\; frac\{mbox\{number\; of\; neutrons\; in\; one\; generation\{mbox\{number\; of\; neutrons\; in\; preceding\; generation$

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.

In an infinite medium, neutrons cannot leak out of the system and the multiplication factor becomes the infinite multiplication factor, $k\; =\; k\_\{infty\}$, which is approximated by the four-factor formula.

ee also

* Critical mass
* Nuclear chain reaction
* Nuclear reactor

=References=