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RADIATION STANDARDS, INCLUDING FALLOUT

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INDUSTRIAL EXPOSURE EXPERIENCE

Although the employment of workers by industry engaged in the handling of
large sources of radiation has expanded rapidly during the past 20 years, the
present work force of some 200,000 (7) is still very smali in comparison with
that of the major industries. Nevertheless, a substantial experience record
has been accumulated which attests to the exemplary success of the operators
in minimizing radiation exposure through prudent engineering design and strict
control. Quantitative assessment of the performance of the larger atomic energy
sites is practical in four broad areas, viz:

(1) The magnitude of the exposure from external sources received by

employees during the normal course of their work assignments.
(2) The small burden of radioactive materials which may be deposited
in the bodies of the workers.
(3) The magnitude of the exposure received by persons who live in the
vicinity of the plant.
(4) The frequency and severity of accidents which result from loss of
control,
The first three classes of exposure can be compared with pertinent limits,
and the accident experience can be followed as a trend.
Compilations of exposure records for recent years (table I) indicate that
the vast majority of workers employed by AEC contractors receive a radiation
dose of less than 1 rem per year. Only in very few cases (about 1 worker in
10,000} has the NCRP short-term control limit of 3 rems in 18 weeks been exceeded and invariably this has resulted from some sort of an accident rather
than imprudent work assignments.
We were unable to make a comprehensive survey of the radiation experience
of the whole of industry. While our information from industrial users is incomplete, in replies from representative major users covering about 30,000
people, the average annual radiation exposure in 1960 and 1961 was about 0.3
rem per person.
There is a widely used formula for the control of accumulated dose for an
individual over the years, which is written (10)
MPD—5 (N—i8) rems

where MPD = maximum permissible accumulated dose, and

NV is a number equal to the present age of the individual in years; (the
formula begins to apply after age 18, the employment of minors below this age
being avoided).
Among the group replying to our survey, including ourselves, only two eases
showing accumulated doses exceeding the formula values appeared. Including
all the radiation accident cases known to us, the total is less than 15; if our
resources had been complete, the total would probably remain below 30. It
is important to reiterate that many of these do not represent real injury to
the recipients and some will be self-correcting as the respective values of
N increase. To the best of our knowledge these cases are principally due to
single large accidental exposures. We were not able to uneover any specific
case in which an employee was in excess of this limit due to radiation received
chronically in the course of his work.
There is very little public data available on the radiation control experience
of the small users. Examination of the most recent data on licensee experience
reported by the Atomic Energy Commission for about a 144-year period ending
November 30, 1961, gives some indication of the degree of control experienced
by the small user. In this 17-month period during which about 10,000 licenses
were in force, the great majority of the 40 radiation incidents reported were
minor in nature. None of the incidents reported resulted in a serious level of
radiation exposure.
Nationwide experience on internal deposition of radionuclides in industrial
workers is not readily available in published reports but in our limited survey,
there was a nearly complete absence of significant deposition cases. In our
own experience at Hanford in 6,600 man-years of direct werk with one of the
most dangerous elements, plutonium, only three employees have acquired body
burdens of plutonium which approximate or exceed the present applicable standards. The quantities involved are not expected to produce clinically observable
symptoms and none have appeared? Additionally, in about 75,000 man-years
8 There is growing evidence that the present standard for plutonium, which is based on
analogy with radium depositions, may have a yery considerable safety margin.

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