Sines
WT-1121
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SHIELDING STUDIES.
Operation THAPOT.
John R. Hendrickson, Elmer H. Engquist, Robert Marmiroli,
Paul E. Grant, and Samel S. Holland, August 1956.
SECRET-RESTRICTED DATA
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Nuclear-shielding studies were carried out on a variety of
surface and underground structures, shelters, field fortifications,
foxholes, vehicles, and vehicle trenches,
Total gamma dose was obtained
using the Evans Signal Laboratory - National Bureau of Standards film
packet in a standard holder. Two types of chemical dosimeters were also
used:
the Chemical Corps Fl and the University of Texas laboratory model.
Total neutron dose was obtained using gold, sulfur,
detectors.
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EST AVAILABLE COPY
and fission threshold
In most instances, gamma-ray and neutron measurements were made
at more than one height above a shelter floor and at entranceways as well
as the interiors of many shelters, in order to determine interior dose
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contours.
Tre average attermation factors for armored vehicles against
Initial gacoma radiation were determined to be 0.1, 0.6, and 0.7 for the
M48 tank, the TOT self-propelled gun, and the AIV-M59 personnel carrier,
respectively.
Greater protection was afforded when the T97 and M59 were
oriented rear-on to the burst. The average attenuation factors for the
same vehicles against residual gamma radiation were 0.2, 0.4, and 0.6,
respectively.
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Gacoma-~shielding data were determined on 38 field fortifications
d neutron data on 29 field fortifications.
The covered bunker type of
fortification, with 12 to 25-ft line-of-sight earth cover, afforded
greater protection.
for this structure.
The gamma attenuation factors were 10-3 to ?x10~-3
The neutron-attenuation factors were 107? for fast
neutrons (above 2.5 Mev) and 10-4 for slow neutrons (below l ev).
remaining Tield fortifications offered less protection.
attenuation factors varied from 10°?
The gamma~
The
to 1073, and the thermal-neutron
attenuaticn factors varied from 10-4 to 107-.
wa
Tne studies showed that for devices where a high neutron to
gamma ratio exists,
such as thin high-explosive tactical weapons, a
neutron exposure results inside shelters, emplacements, etc., when only
line-of-sizht shielding is present, due to scattering of thermal neutrons.
In underground shelters and field fortifications where sufficient line-of-
sight thiczness of shielding material is present to shield out all the
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direct rays from a conventional air-burst atomic weapon, the main hazard
is from air-scattered neutrons and gamma rays, which proper and adequate
baffling cf? entranceways reduces to a minimun.