Reactor Theory (Nuclear Parameters)DOE-HDBK-1019/2-93NEUTRON LIFE CYCLENeutron Life Cycle SummaryThe infinite multiplication factor, k, is the ratio of the neutrons produced by fissionin one generation to the number of neutrons lost through absorption in the precedinggeneration.The effective multiplication factor, keff, is the ratio of the number of neutronsproduced by fission in one generation to the number of neutrons lost throughabsorption and leakage in the preceding generation.Critical is the condition where the neutron chain reaction is self-sustaining and theneutron population is neither increasing nor decreasing.Subcritical is the condition in which the neutron population is decreasing eachgeneration.Supercritical is the condition in which the neutron population is increasing eachgeneration.The six factor formula is stated as keff = fp tf h. Each of the six factors isdefined below.number of fast neutrons produced by all fissionsnumber of fast neutrons produced by thermal fissionsf number of fast neutrons that do not leak from reactornumber of fast neutrons produced by all fissionsp number of neutrons that reach thermal energynumber of fast neutrons that start to slow downt number of thermal neutrons that do not leak from reactornumber of neutrons that reach thermal energiesf number of thermal neutrons absorbed in the fuelnumber of thermal neutrons absorbed in all reactor materialsh number of fast neutrons produced by thermal fissionnumber of thermal neutrons absorbed in the fuelRev. 0NP-03Page 15
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