~ 18 -
.
“the stratospheric reservoir will be completely deposited on the
earth's surface before any radioactive decay has occurred.
More~-
over, it will be assmed that the geographical distribution in the
future will follow approximately the same distribution as has been
true of the deposition of stratospheric debris in the past.
This
will tend to introduce an error on the side of safety since it
would be expected that future fallout would be more uniform than
in the past.
Future Estimate of Sr-90 in Man
As noted earlier, it will be assumed that essentially all
of the 2.4 megacuries of Sr-90 stored in the stratosphere in
mid-1956 will be deposited on earth's surface.
occurred by about 1970.
This will have
It will be further assumed that
stratospheric fallout in the future will be distributed in
approximately the same pattern as the past.
This discussion of future levels of Sr-90 in man will be
based on data for the North Midwestern and Northeastern United
States, where fallout is as high as in any region of the world
for which data are available.
The fellout levels in mid-1956
renged from 19 to 33 millicuries per square mile, the average
being 25 no/ni®,
Of this, about 6 me/mi” is the result of
tropospheric fallout from tests prior to mid~1956.
The
stratospheric fallout of the past may thus be estimated as
19 millicuries per square mile.
This was the level which
existed when the world-wide deposition of Sr-90 was ebout
l megacurie.
When the 2.4 megacuries now in the stratosphere
has deposited, the deposition in Northern United States may
DOE ARCHIVES