REACTIVITY
DOE-HDBK-1019/2-93 Reactor Theory (Nuclear Parameters)
Summary
The important information in this chapter is summarized below.
Reactivity Summary
The number of neutrons present in the core after a given number of generations is
calculated using Equation (3-4).
Nn No
keff
n
Reactivity is the fractional change in neutron population per generation.
Reactivity and keff are represented in Equation (3-5) and Equation (3-6),
respectively.
r
keff 1
keff
keff
1
1 r
The relationship between units of reactivity are listed below.
1%
D k
k
0.01
D k
k
1 pcm 0.00001
D k
k
A reactivity coefficient is the amount of change in reactivity per unit change in the
parameter. A reactivity defect is the total reactivity change caused by a change in
the parameter. The reactivity defect is the product of the reactivity coefficient and
the magnitude of the parameter change.
NP-03
Rev. 0
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