~ 23 It should be noted that this estimate includes a number
of essumptions which are deliberately conservative.
No
allowance has been made for the radioactive decay which will take
place before the Sr-90 descends from the stratosphere to the
earth.
This may diminish the enount of available Sr-90 by
about 25%.
The assumption that all the Sr-90 in milk
originated by root uptake is another conservative assumption.
It has been estimated that 30% of the Sr-90 in milk in 1956
originated by direct foliar deposition.
fnother conservative
assumption is that the Sr-90 remains in the root zone of the
vegetation.
It is likely that over a period of meny years an
appreciable fraction will leach below the root zone.
The combined effect of these and other safety factors is
appreciable.
It is probeble that the maximum human burden fron
detonations which occurred up to/1986 will be somewhat lower
then 15 ppe/g Ca.
It is likely that 15 ppec/g Ca over-
estimates the true value by a factor of at least 2 and possibly eas
much as 5.
Assuming 15 ppe Sr-90/gn Ca to be the maximum value to be
attained, one can calculete thet this amount of Sr-90 will
deliver a dose of 1.4 rads to the skeleton over a life time
of 70 years.
This compares with a normal skeletal irradiation
of 7 to 30 reds resulting from potassium 40, carbon 14, cosmic
rays, terrestrial gamma rediation and radium.
The maximum
foreseeable value of 15 ppe Sr-90/g Ce is thus ecuivalent to
4-5 to 18% of the dose frm natural sources of skeletal
irradiation.
‘DOE ARCHIVES