DOE-HDBK-1019/1-93
NUCLEAR CROSS SECTIONS AND NEUTRON FLUX
Reactor Theory (Neutron Characteristics)
NP-02
Page 12
Rev. 0
Example 2:
An alloy is composed of 95% aluminum and 5% silicon (by weight). The density of the
alloy is 2.66 g/cm . Properties of aluminum and silicon are shown below.
3
Element
Gram Atomic Weight
)
)
a (barns)
s (barns)
Aluminum
26.9815
0.23
1.49
Silicon
28.0855
0.16
2.20
1.
Calculate the atom densities for the aluminum and silicon.
2.
Determine the absorption and scattering macroscopic cross sections for thermal
neutrons.
3.
Calculate the mean free paths for absorption and scattering.
Solution:
Step 1:
The density of the aluminum will be 95% of the total density. Using
Equation (2-1) yields the atom densities.
