ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPORT
Measurements of neutron flux have been made in
a vertical direction along a radius by using indium
foils with and without cadmium covers. The foils
are 10-mil aluminum-indium alloy, t6 in. in diameter,
having an effective indium thickness of 3 x
lo-' in., and the cadmium covers are 20 mils thick.
The results of these measurements are given in
Fig. 4.2. The values of the indium-cadmium fraction3
and the indium activation produced by neutrons
having energies less than the cadmium cut-off are
also plotted. A relative power, or fission-rate,
JThe cadmium fraction by definition is the ratio of the
difference between the bare and cadmium-covered acti-
vations to the bare activation.
45
40
35
30
-
0
+
5 25
z
L. 0
.- +
D
0 - 20
>
t
2
0 4
15
40
5,
0
0 2 4 6
distribution was made through the core along the
radius that was used for the indium flux measure-
ments by observing the activity of the fission
fragments retained in aluminum foils placed in
contact with uranium. Similar data, presented in
Fig. 4.3, were obtainedwith the uranium and alumi-
num enclosed in cadmium covers. The average
uranium-cadmium fraction for the core is 0.33. The
fission rates were measured on opposite sides of
three uranium foils near the reflector, and the
results are plotted. In each case
-
the rate was
higher on the side toward the beryllium.
Measurements will be made of the reactivity
coefficients, as functions of the radius, of a few
ORNL-LR-DWG 3017
0
8 io 12 14 16 20 22
RADIAL DISTANCE FROM CENTER OF CORE (in)
Fig. 4.2. Radial Neutron Distribution at Mid-Plane of First Reflector-Moderated Reactor Critical
Assembly.
46
io
08
06
z
2
4
cr LL
5
04 2
a
u
02