nuclear physics Nuclear physics is the field of physics that studies atomic nuclei and their constituents and interactions, in addition to the study of other forms of nuclear matter. Nuclear physics should not be confused with atomic physics, which studies t ...

, resonance escape probability

p

is the probability that a neutron will slow down from fission energy to thermal energies without being captured by a nuclear resonance. A

resonance absorption Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscill ...

of a neutron in a nucleus does not produce

nuclear fission Nuclear fission is a reaction in which the nucleus of an atom splits into two or more smaller nuclei. The fission process often produces gamma photons, and releases a very large amount of energy even by the energetic standards of radio ...

. The probability of resonance absorption is called the ''resonance factor''

\psi

, and the sum of the two factors is

p + \psi = 1

. Generally, the higher the neutron energy, the lower the probability of absorption, but for some energies, called ''resonance energies'', the resonance factor is very high. These energies depend on the properties of heavy nuclei. Resonance escape probability is highly determined by the heterogeneous geometry of a reactor, because fast neutrons resulting from fission can leave the fuel and slow to thermal energies in a moderator, skipping over resonance energies before reentering the fuel. Resonance escape probability appears in the

four factor formula The four-factor formula, also known as Fermi's four factor formula is used in nuclear engineering to determine the multiplication of a nuclear chain reaction in an infinite medium. The symbols are defined as: *\nu, \nu_f and \nu_t are the averag ...

and the six factor formula. To compute it,

neutron transport Neutron transport (also known as neutronics) is the study of the motions and interactions of neutrons with materials. Nuclear scientists and engineers often need to know where neutrons are in an apparatus, what direction they are going, and how qu ...

theory is used.

References

Literature

* Nuclear technology Radioactivity {{Nuclear-stub