ORNL-2106 - the Molten Salt Energy Technologies Web Site

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in. long, 18’4, in. wide, and 2% in, thick. The
beryllium layer immediately below it was 34% in.
long and 245/,, in. wide.
The top layer and the corners of the,second
beryllium layer were subsequently removed, and
the resulting reflector was 8% in. thick. The
new top layer was 18’) in. wide and 34% in.
1 6.
long, A second longitudinal traverse was then
made. The results are shown in Fig. 4.4.4, in
which the.top lobe is plotted to a scale one-half
that used to plot the end lobe.
Two series of lateral traverses were also made
at the side of the reactor at several distances
from the mid-plane. For reflector thicknesses of
118 and 8% in. the outer slab dimensions for
each side reflector thickness were the same as
those given above. The latitudinal variations of
the fast-neutron leakage for the two reflector
thicknesses are shown in Figs. 4.4.5 and 4.4.6.
The curves show a slight asymmetry about the
center of the reactor, which is attributed to the
reflection of neutrons by the aluminum and steel
structure on which the critical assembly rests.
The area under each curve of Figs. 4.4.5 and
4.4.6 is proportional to the counting rate observed
at the corresponding distance from the mid-plane
in the longitudinal traverses made at the top of
the reactor. By integrating the results of the two
longitudinal traverses over the distance from the
mid-plane, it was possible to determine that the
removal of the 2% in. layer of beryllium from the
top of the reactor increased the fast-neutron leak-
age there by a factor of 3.7.
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PERIOD ENDfNG JUNE IO, 1956
shmc
ORNL-LR-DWG 44421
MEASURED WITH 2- in.- DIA
HORNYAK BUTTON
TOP BERYLLIUM LAYER:
48% x 34314 in.
THE MTA AT THE TOP
- OF THE REACTOR ARE
PLOTTED TO A SCALE
ONE-HALF THAT USE0
FOR PLOT OF THE EN0
Fig. 4.4.4. Polar Distribution of Fast-Neutron
Leakage at Surface of 8kin.ofhick Reflector of
Compact-Core Reflector-Moderated-Reactor Critical
Assembly.
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