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et
Vol 66
Tapce II:
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AprproxrmatTB ARZAS ENCOMPASSED BY
gHE EFFECTIVE Briococical Isopose Lines SHOWN IN
Tie Map (Fic. 1).
Msodose Liue
(r)
&
109
< 409
*,
A erearin tr He Bere ie Pte roe op Smepene *
Approxiniate
Arees Excompessed
(square miles)
:
25 ,CO0
12,509
5,099
doses may be extrapolated linearly to any
other dose rate at time of failout. For exainple, if fallout begins three hours aiter
detonation and the dose rate at that time is
10 r per hour, about 67 r (effective biological dose) will be accumulated provided
personnel continues to live normally in the
contaminated area.
10 _
0.15 67
e
we
ate
0
as?
SIATLTS eee
Fig. 1.
Idealized fallout diagram, based on high-
yield nuclear detonation of March +, 1954.
Isocdose
lines represent efiective biological doses (roentgens).
continued occupancy of these areas with
no special protective measures. These
percentages would, of course, rise within
the encompassed areas.
The 50-r effec-
tive biological isodose line has no unique
significance but suggests the magnitude of
Itis frankly recognized that in any single dose which might call for emeryency meascurve, such as that shown in Graph 3, there ures against radiation exposures even in the
ere inherent a number of uncertainties face of other possible hazards. Tabie II
.that are open to discussion. Criteria shows the approximate areas encompassed
_ based ondeliberate analyses of the relevant by the three isodose lines. For areas
data, however, may be more valid than where the fallout oceurs a few hours or
those determined under the duress of an more following detozation, many days or
emergency situation. Such a simplified weeks will be required to accuinulate the
graph might provide radiological monitors major portion of effective biological doses,
with a quick, even if rough, estimate of the so that spot decisions involving additional
potential hazards and thusassist in making hazards might not be necessary.
decisions as to possible evacuation, etc.
FALLOUT PATTERN FROM
HIGH-YIELD WEAPONS
From Graph 5 and data from other
sources (10, 11), an idealized diagram of
effective biological doses for fallout from the
March }, 1954, surface detonation at the
e
ihe,
Pacific Proving Ground has been prepared
(Fig. 1). It is to be emphasized that (a)
different yields of weapons, different wind
Structures, and different kinds of land surface, would result in different patterns, and
that (b) this ts the amount of fallout from a
single high-yield weapon.
The two innermost isodose lines shown
were selected to suggest regions where (a)
a significant percentage of personnel might
‘be expected to die (400 r) and (6) a few
per cent to becomeill (100 r), assuming
PROTECTIVE MEASURES
The idealized fallout diagram is based
on the assumption that people continue to
live normally in an area and that they do
nothing
special
to
protect
themselves.
Actually many measures can be taken to
reduce the gamma radiation dose.
These
may be classified under four headings:
1. Evacuation. 2. Useofshielding. 3.
Decontamination of the environs. 4. Al-
lowing for lapses of time before entry into
a contaminated area. These measures
will be discussed onlybriefly.
Whererelatively small numbers of people
are involved, evacuation could be an easy
solution. For large communities, maior
factors of danger and/or hardship must
be considered. Each situation may be
unique, and independent decisions must be