greater than 4. (If most of the debris were produced in a brief period, e.g., a few weeks, short
period irregularities in precipitation might increase irregularity in fallout distribution.) Since
the area of North Temperate Zone is 5.3 x 10’mi*, average deposition per KT detonation would
be about G0")
0.7 12x
10-8 KT/mi?.
2. Surface burst:
Much of the debris from surface shots falls out within 12-24 hours.
may be estimated (PE—factor of 1.5).
A value of 70%
The fraction of debris which does not fall out in 24 hours
is considered, in the absence of better information, to behave like airburst debris.
B. Dose:
1. External gammaradiation:
Assume:
(1) 1 KT/mi? at 1 day gives external gamma dose rate of 625 rads/day at 3 feet above
an infinite plane.
(2) Humans, through shielding of houses, etc., receive 30% of infinite plane dose
(PE=factor of 2).
(3) Unshielded infinity dose subsequent to fallout at t days after detonation—
(2.5) (625 t-°4) (PE—factor of 2). An arbitrary change has been made from prediction
of t-1* decay law to allow for weathering; i.e., a t-'* decay curve is assumed.
The infinity dose (whole body) received subsequent to a fallout of 1 KT fission debris/mi?
at various days after detonation is shown in Table 5.
2. Debris ingested through soil-plant chain:
a. Sr-90 (calculations for infant or child):
Assume:
(1) Half of Sr-90 fallout remains in soil in available form until decays or is taken up
by plant (PE=factor of 1.5).
(2) Available Ca/ft? to depth of 6” (plow depth) —8me/100 gms (PE—factor of 2).
(3) 70%of plant Ca and Sr uptakeis from top 6” of soil (PE=factor of 1.4).
(4)
(Sr/Ca) plant _
_
(Sr/Ca) soil =0.5 (PE=—factor of 1.4)
(Sr/Ca) skeleton _
(5) ~(Sr/Ca)
food =0.5 (PE=—factor of 1.5)
etc.
(6) 70% of Ca intake is in milk (PE=factor of 1.4).
Less outside U.S. Remainderin plants.
Depends on age, dietary habits,
(7)
(Sr/Ca) milk
=0.15 (PE=factor of 1.3)
(Sr/Ca) cow feed
(8) Skeletal Ca—15% of skeletal weight (PE—factorof 1.2).
(9) Average Sr—90 dose in skeleton is only 0.6 of value it would have if full skeleton
of young adult were constituted within 1 year after fallout (PE—factor of 1.3).
(This re-
duction in dose is brought about through dilution of current deposition in the previously
formed skeleton of a rapidly growing adolescent, or through radiological and environmental
attrition of activity before it is deposited in an individual who was an infant at the time
of fallout. For adults, dose would be less.)
The infinity dose received for a fallout of 1 KT/mi? is shown in Table 5.
Penni
17
TOS ARCHIVES