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measurements taken at the side of the detector tank
were considered. For 8 90 deg, the experiments
indicate that the ng into the side and that
into the rear of th or tank are approximately
equal. If it is ass hat this is nearly true for
angles between 45 and 90 deg, the air scattering
into the rear can be estimated from the measure-
ments at the side. When the air-scattered neutron
flux estimated in this manner is a
calculated direct beam flux, the dash
Fig. 12.6 is obtained. The fair agreement between
the dashed curve he measured curve indicates
that the simple used to calculate the angle
of distribution of the leakoge neutrons from the
shield surface may be adequate for divided-shield
Figure 12.7 represents an attempt to compare the
measurements o ft scattering into the side of
the detector tank he air scattering indicated
by single-scatter lations. The ordinate in
Fig. 12.7 is the ratio of the flux at the side surface
of the detector tank for a given beam direction 8 to
the flux at the re the detector tank obtained
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GEOMETRY FOR SINGLE-SCATTER CALCULATION FOR e= o
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0.40
PERIOD ENDING DECEMBER 70,1954
when the beam is pointed directly towcirds the
detector tank, that is, for 8 = 0 deg. He,nce, the
ordinate is a measure of the fraction of the beam
scattered into the sides of the detector tank. The
abscissa is the beam direction 8. The points indicated
by the experiments for 8 = 30 and 90 cfeg were
obtained by extrapolation of the fluxes measured
in the water to give the extrapolated surface values.
The measured relaxation lengths were used in the
extrapolation; no relaxation length measurements
were made for 8 = 0 deg, and therefore this procedure
could not be used for this angle. The only
single-scatter calculation presently available is for
8 = 0 deg, and it is based on the assumption of a
2~- isotropic detector, that is, an isotropic detector
with one hemisphere shielded. This calculation
gives a value of 0.048 for 8 = 0 deg, which is to be
compared with the values indicated by the experi-
ments of 0.063 for 8 = 30 deg and 0.048 for 8 = 90
deg. As the beam is rotated from 30 to 0 dleg, it is
nearly cut in half insofar as scattering into the one
side of the detector tank is concerned, md this
should result in a decrease of the scattering into
the one side of the detector tank. The scattered
flux measurements taken within the water show
this to be the case. The point calculated by
single-scatter theory for 8 = 0 deg appears ‘to agree
with the points obtained from the experirnent for
8 = 30 and 8 = 90 deg. However, it should be
cautioned that the fair agreement indicated in the
figure could be fortuitous. In the comparisbon, the
assumption is involved that the thermal flux re-
sulting from a given fast-neutron current into the
side of the detector tank is the same for air-scattered
INTERPRETATION OF AIR AND GROUND
SCATTERING AT THE
TOWER SHIELDING FACILITY
itude for two diff
J. Van Hoomissen”
n of reactor-detector
as Indicated by Measurements and by a Single- I5On loan to Tower Shielding Facility frorrl Boeing
Scatter Calculation. Airplane Company.
147
c