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Summary |
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 No f
p t f h.
In the example illustrated in Figure 1, keff 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 = No
= 10,310
2)
N = No
f
= 9,166
3)
N = No
f
p = 7,360
4)
N = No
f
p t = 6,661
5)
N = No
f
p t f = 5,002
6)
N = No
f
p t f h = 10,065
Rev. 0
NP-03
Page 13
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