Reactor Theory (Nuclear Parameters) DOE-HDBK-1019/2-93 NEUTRON LIFE CYCLE The final factor numerically describes the production of fission neutrons resulting from thermal neutrons being absorbed in the fuel.  This factor is called the reproduction factor (h).  The value for the reproduction factor can be determined as shown below. h   number  of  fast  neutrons  produced  by  thermal  fission number  of  thermal  neutrons  absorbed  in  the  fuel         1000 495 2.02 The number of fission neutrons that exist at the end of the life cycle which are available to start a new generation and cycle is represented by the quantity N_o     f p _t f h. In  the  example  illustrated  in  Figure  1,  k_eff  is  equal  to  one.    Therefore,  1000  neutrons  are available to start the next generation. Example: 10,000 neutrons exist at the beginning of a generation.  The values for each factor of the six factor formula are listed below.   Calculate the number of neutrons  that exist at the points 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. = 1.031 f = 0.889 f = 0.751 p = 0.803 t = 0.905 h = 2.012 Solution: 1) N = N_o = 10,310 2) N = N_o f = 9,166 3) N = N_o f p   = 7,360 4) N = N_o f p _t = 6,661 5) N = N_o f p _t f = 5,002 6) N = N_o f p _t f h = 10,065 Rev. 0 NP-03 Page 13