vided at least as much protection as implied by the broad estimate for
Army field clothing to the effect that
"... the average field issue
clothing will stop approximately one-half of the incident beta radia-
tion from fall-out material".
It has long been a moot question whether within an intense
fall-out field the beta burn problem could be the factor limiting the
period of exposure of personnel.
CASTLE provided an unexcelled oppor-
tunity to observe such a situation.
Personnel receiving whole body
gemma doses of about 200 roentgens suffered no burns under the clothing
except where the radioactive material was carried by perspiration or
body motion under a collar or cuff.
Over unclothed areas of skin, how-
ever, burns were sufficiently severe to reduce the efficiency of personnel more than would be predicted from the exposure to the concomi-
tent gemma component.
Thus, from CASTLE data has come the fairly de-
fensible statement that for well clothed personnel in a fall-out field,
gamma measurements alone will suffice to determine the radiological
effects to be expected and the permissible time of entry into, or
period of exposure within, such an area.
The Beta Hazard.
The term “beta burn” as used here is damage
to the skin by ionizing radiation.
The radiations primarily effective
for this phenomenon are beta particles and low energy gamma rays.
Thus,
the term "beta burn", as generally used is a misnomer to the extent of
the contribution by the low energy gamma or x-rays.
Skin burns occur when the quantity of radiation absorbed by the
living layers of skin exceeds a certain critical level.
The flux of
radiation necessary to cause a given degree of skin damage depends upon
the energy and kind of radiation arriving in the critical area.
The
thickness of the outer protective layer of dead tissues, plus the
attenuating effect of clothing, determines the radiation dose delivered
to the living tissues.
.
a
The energy of gamma radiation is frequently referred to in
terms of half-value thicknesses while that of the beta radiation is in
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