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Chapter 4
betucen 6 and 650. Considering the leck of uniformity of the surfaces involved and tho
widely differing circumsiances in which the aircraft became ocntaminated, this variation
ig not surpriging.
The probfem is to evaluate these measured ratios and to determine the importance
that must be attached to them. Ratios less than ten muy be regarded as unimportant,
since the skin-toleran.c dose is probably at least ten times groater than the t lerance
for wtule-hody radiation. Under these conditions, the whole-body radiation dose would
be the fimiting factor, and the contact hazard would not hamper the activities of personnel
in an operational situation. Obviously, the higher ratloa are the once that must be given
_ considerat.en.
From the limited experimental] data shown in Table 3.6, {t can be seen
that the actsal ratio of the contact dose to the whcle-body exposure is approximately two
for those personnel who wear gloves. Even though this ia true, it fe instructive to carry
out a further theoretical analysis of the problem.
The highest contac:-dose rate measured during the entire study was 3,500 rep/hr. The
ratio betwaen this dose rate and the T1B reading was 650. This dose rate was measured
by means off 2 film tightly taped to an impingement siriace.
In order for = human being
tee
8
mk
cas be expressed in terms of the intensity indicated by some standard survey ‘natrument
such as the T1B.
The ratio between the total contact dose rate and the T1B reading was found to vary
as RO a oe ct oe NtAae tne nme >
The object of this study was to evaluate the contact hazard that existe for personnel who
must come in contact with aircraft contaminated by {Mlght through nuclear clouds. In
_ achioving this goal, the apparent beta-gamma ratio of fisaion-fruyn:ent contamination
waa measured.
Moeasurcarént of the actua! beta-gamma ratic was not attempted. The actual ratio
would be extremely difficult to determine and would have some theorotical value, but
Uttle practical use. The requirement is for a meana of determining a working ratio that
ONE EL
DISCUSSION
SECRET
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28
.
Ag analysis of probable operationa) situations tends to minimize the algnifican:e of
the highest ratios and focus attention on the intermodiate values. Personnel who perform
work on an aircraft do not grasp any one part (especially impingement surfaces) fo- long
periods df time. Instead, the grip is changed conatantly from one point to another. with
the resait that the exposure becomes nearly uniform and the het spots of high activity are
eliminated. This was shown by the uniform blackening of the films that were placed on
the hands of the men who handled the survey film. If one considers the average dose
rate over the entire film lo be representative of the actual situation, the mean ratio of
the total dose rate to Tid reading becomes 55 for impingement 6urfaces and 20 for sliding
lam ooh.
ratios ia opnjunction with a survey of the aircraft with a T1B.
deta gy
nificant uncertainty, the contact radiation hazard can be evaluated by the uge of these
RTT Teayerew TN TE
contact with the surface for an extended period. The mean ratios between the maximum
contact dome rate and the T1B readings were found to be 110 for impingement surfaces
and 49 for aliding surfaces. When an area of several square centimeters ia considered,
teese meex values can be halved. For practical purposes, and without introducing a sig-
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to sustain @ beta burn, the bare surface of the skin would have to be held in equally close