Fuel temperature coefficient of reactivity


Fuel temperature coefficient of reactivity is the change in reactivity of the nuclear fuel per degree change in the fuel temperature. The coefficient quantifies the amount of neutrons that the nuclear fuel (such as uranium-238) absorbs from the fission process as the fuel temperature increases. It is a measure of the stability of the reactor operations. This coefficient is also known as the Doppler coefficient due to the contribution of doppler broadening, which is the dominant effect in thermal systems.

Contributing effects

Doppler Broadening

Doppler shifts resulting from motion of atoms within the fuel cause doppler broadening, which results in a broader neutron spectrum and consequently increased neutron capture

Thermal Expansion

Thermal expansion of the fuel at higher temperatures results in a lower density which reduces the likelihood of a neutron interacting with the fuel

See also


  • USNRC Glossary