Reactor Theory (Nuclear Parameters)DOE-HDBK-1019/2-93NEUTRON LIFE CYCLEThe final factor numerically describes the production of fission neutrons resulting from thermalneutrons being absorbed in the fuel. This factor is called the reproduction factor (h). The valuefor the reproduction factor can be determined as shown below.h number of fast neutrons produced by thermal fissionnumber of thermal neutrons absorbed in the fuel10004952.02The number of fission neutrons that exist at the end of the life cycle which are available to starta new generation and cycle is represented by the quantity No fp tf h.In the example illustrated in Figure 1, keff is equal to one. Therefore, 1000 neutrons areavailable to start the next generation.Example:10,000 neutrons exist at the beginning of a generation. The values for each factor of thesix factor formula are listed below. Calculate the number of neutrons that exist at thepoints in the neutron life cycle listed below.1)Number of neutrons that exist after fast fission.2)Number of neutrons that start to slow down in the reactor.3)Number of neutrons that reach thermal energies.4)Number of thermal neutrons that are absorbed in the reactor.5)Number of thermal neutrons absorbed in the fuel.6)Number of neutrons produced from thermal fission.= 1.031f= 0.889f = 0.751p = 0.803t= 0.905h= 2.012Solution:1)N = No= 10,3102)N = Nof= 9,1663)N = Nofp = 7,3604)N = Nofp t= 6,6615)N = Nofp tf = 5,0026)N = Nofp tf h = 10,065 Rev. 0NP-03Page 13
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