Neutron Life Cycle Summary

Reactor Theory (Nuclear Parameters) DOE-HDBK-1019/2-93 NEUTRON LIFE CYCLE Neutron Life Cycle Summary The infinite multiplication factor, k � , is the ratio of the neutrons produced by fission in one generation to the number of neutrons lost through absorption in the preceding generation. The effective multiplication factor, k_eff, is the ratio of the number of neutrons produced by fission in one generation to the number of neutrons lost through absorption and leakage in the preceding generation. Critical is the condition where the neutron chain reaction is self-sustaining and the neutron population is neither increasing nor decreasing. Subcritical is the condition in which the neutron population is decreasing each generation. Supercritical is the condition in which the neutron population is increasing each generation. The six factor formula is stated as k_eff = _f p _t f h. Each of the six factors is defined below. number of fast neutrons produced by all fissions number of fast neutrons produced by thermal fissions f number of fast neutrons that do not leak from reactor number of fast neutrons produced by all fissions p number of neutrons that reach thermal energy number of fast neutrons that start to slow down t number of thermal neutrons that do not leak from reactor number of neutrons that reach thermal energies f number of thermal neutrons absorbed in the fuel number of thermal neutrons absorbed in all reactor materials h number of fast neutrons produced by thermal fission number of thermal neutrons absorbed in the fuel Rev. 0 NP-03 Page 15