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A COMPARISON BETWEEN SPRING 1959 FALLOUT AND STRATOSPHERIC AIR CONTENT
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Articles: Yursyamall 1960
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In a note by R. J. List in an earlier report (HASL77, pages 39+h3),-tt-—
was noted that rainfall at Westwood, N. J. and Pittsburgh, Pennsylvania after
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about January 1959 contained Sr-90 which was highly dominated by debris which
dated from the Soviet tests in October 1958.
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by
Le Machta and N. Muirayama® Thay | Arghives/Comms.onGEM
Taken literally, over 75% of
the Sr-90 could be attributed to the date of October 18, 1958.
A similar and more extensive analysis is made of the fission products
collected by Project Ash Can in the stratosphere since November 1958.
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In this
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case, several short lived isotopes were used to determine an apparent "age"
and a fraction of October 18th Sr-90 (Soviet debris).
sented in Table 1.
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These results are pre-
The ratios of radioactivity at formation and the half-lives
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of the radioisotopes were taken from (1) and are the same as were employed by
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Table 1 shows that the origin of the bulk of the stratospheric Sr-90 after
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List for the fallout calculations.
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November 1958 is more likely Hardtack or earlier than the October 1958 Soviet
test series.
Further, it shows that (except for the Ce-1¥4/Sr-90 results which
will be discussed below), much less than 75% of the Sr-90 was attributable to
October 1958.
We shall first discuss some of the possible sources of error in comparing
the apparent age and fraction of Sr-90 from October 1958 in fallout and stratospheric samples.
We will then describe a meteorological interpretation result-
ing from this difference.
The computation of apparent age from a pair of fission product radio-~
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isotopes is subject to several sources of potential error.
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First, fractionation of the isotopes is known to take place.
Thus, the
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assumed thermonuclear fission yield ratio for Cs-137/Sr-90 is usually exceeded
by a significant factor in the stratospheric samples.
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This departure from the
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ratio might also be due to erroneous estimates of fission yield of either
radioisotope or due to differing efficiency of collection by the fallout or
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stratospheric sampling procedures.
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Japan Meteorological Agency assigned to the U. S. Weather Bureau,
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