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Discussion of the Piolesicel Facinr,
As longer periods of time are
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involved in the delivery of a given radiation dose, lesser biological effects may be expected.
Frau the tine of fallout until the
time of evacuation prokebly wili be a matter of hours, which has teen
dose factor is 1/1.
From tne time evacuation could be accomplished
to time of return probably would be a matter of several days, so the
biological factor has been estimated at 3/4.
From 15 days after
:
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fallout until one year Jeter is essentially ae duration of one year,
so the biological factor kes been estinated ct 2/3,
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considered essentially an izstanieneovs dose, i.e., the blologica:
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It will be noted
there is no calculation after one rear, because it is expected under
actual conditicns of radiological cecsay and weathering that protabiy
no significant dose will be delivered after a year's time in populated
areas around the Mevada Test Site.
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It is recognizcd thet the precise cuantities sugsested for the
biological factor cannot ts supported by conclusive evidence.
Itis
reasonable to expect that ine delivery cf » given radiaticn dese over
& period of many days will heve less biologicel effectiveness than an
instantaneous one (neglecting genetic effects) and thet the extension
of the period to essentially one yeer should yield a still lower tiolesical factor.
One piece of supportive evidence is the work of Strandgvist*
where X-ray doses to the skin were fractionated into daily amounts, end ©
the biological effects compared to a one-treatment dose.
A log-log
plot of total doses versus days after initial treatment yielded straight
lines.
For example, the curve for skin necrosis indicated a ratio of
3000/6700 roentgens for a one-treatment
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ally
frec-
*Sievert, Rolf M. "The Tolerance Dose and the Prevention of Injuries
Caused by Ionizing Radiations". Eritish Journal of Radiology, Vol. M,
No, 236, Aug. 1947.
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