The value is known as the effective delayed neutron fraction, and it describes the fractional contribution of delayed neutrons to the fission rate of the system and is quantified as the ratio of the total number of fissions caused by delayed neutrons to the total number of fissions in a system. This number is slightly different than the delayed neutron fraction , which is the fraction of neutrons in the system that are delayed, because delayed neutrons are generally born at lower energies, and thus are easier to thermalize, meaning they are more likely to cause a fission than a prompt neutron. This weighting effect is given in the derivation of .
The value is known as the effective delayed neutron fraction, and it describes the fractional contribution of delayed neutrons to the fission rate of the sy,stem and is quantified as the ratio of the total number of fissions caused by delayed neutrons to the total number of fissions in a system. This number is slightly different than the delayed neutron fraction , which is the fraction of neutrons in the system that are delayed, because delayed neutrons are generally born at lower energies, and thus are easier to thermalize meaning they are more likely to cause a fission than a prompt neutron. This weighting effect is given in the derivation of .