RADIOACTIVITY IN THE SOUTHERN STRATOSPHERE
411
Table lL—SUMMARY OF 1961 AND 1962 ATMOSPHERIC TESTS
Detonation
Inclusive dates
Mean date
Fission
Latitude
for series
yield, Mt
52°N, 7o°N
Oct. 15, i961
17
U.S.S.R.
Sept. 1—Nov. 4, 1961
U.S.S.R.
Oct. 30 (~55 Mp)
75°N
Oct. 15, 1961
8
United States
July 9, 1962*
17°N
July 1, 1962
i
U.S.S.R.
U.S.S.R.
Aug. 5—Nov. 17, 1962
Dec. 18—Dec. 24, 1962
Oct. 15, 1962
Dec. 20, 1962
60
U.S.S.R.
United States
United States
Oct. 23 (~25 Mt)
Apr. 25—July 11, 1962
Oct. 2—Nov. 4, 1962
75°N
2°N
L7°N
92°N, 7o°N
52°N, 75°N
=
>
Oct. 15, 1962
*Starfish Prime detonation at 400 km.
The 1961 U.S.S.R. test series has been subdivided into three components since data obtained at 31°N in 1962 suggests that each of these
components may have followed significantly different distribution pat-
terns. The altitude profiles for long-lived *°Sr concentrations, ®Zr (65day half-life)/**Sr, and *4Mn (310-day half-life)/*"Sr activity ratios are
shown in Fig. 1 for February 1962 at31°N. Manganese-54 is a neutron-
activation product rather than a fission product, and one may reasonably presume, therefore, that it was produced in largest quantities in
the 55-Mt thermonuclear detonation of Oct. 30, 1961, in which the high-
est neutron flux was produced. These data show that (1) a considerable
fraction of new debris, indicated from high values for the ™Zr/*"Sr
ratio, was present at 60,000, 90,000, and 105,000 ft but only traces at
70,000 and 80,000 ft; (2) the largest quantity of new debris was at 60,000
ft where both *zr/™Sr and total Sr were the greatest; (3) the new
debris at 60,000 and 105,000 ft was low in “Mn, whereas that at 90,000
ft contained relatively large amounts of “Mn. The following hypotheses
may be made to explain these observations: (1)debris from all the 1961
U.S.S.R. tests except the 25- and 55-Mt thermonuclear events stabilized
below 70,000 ft; (2) fresh debris at 90,000 ft was due primarily to the
55-Mt device for which the activity ratio of “Mn/*°Sr at formation was
about 100, a value determined from the observed Mn and a calculation
for the new Sr based on the observed ™Zr and the expected ™Zr/*"Sr
formation ratio; (3) fresh debris above 100,000 ft came from a shot
other than the 55-Mt detonation (either from the 25-Mt shot or from
one or more unannounced high-altitude detonations). If the 25-Mt device accounted for this new material, a large fraction of the debris
from this shot may have been present above the maximum sampling
altitude of 105,000 ft.
Neutron-activation products other than "Mn, such as »Fe and
124Sb, were also found in the stratosphere after the 1961 U.S.S.R. test
series.’ Additional quantities of these radionuclides, as well as ™y,
were produced in the 1962 atmospheric tests,4 Their use as tracers for