SESSION IIIB DISCUSSION
693
transport processes in the higher atmosphere, pointing out differences
between the more disturbed northern-hemisphere flow patterns and the
more zonal southern ones, The second group was concerned with an
attempt to explain seasonal changes in radioactive fallout, especially
the rather conspicuous spring maximum, etc. The third group concentrated on various aspects of dry transport processes of radioactive debris. The fourth group, dealt with the rather complex wet
transport processes and washout phenomena,
One area that was covered in this session concerns the chemistry
and origin of some of the radioactive tracers that are carried about
in the atmosphere. One question has already been asked about beryllium and other nonfission products, and I wonder if this question has
been answered in full. Is there someone in the audience who might
be able to contribute something to this ?
SALTER: There was a question earlier on the origin of several
nonfission products. The answer at that time was specifically in re-
lation to 'Be. I think it would be helpful to summarize these radio-
nuclides and their origins as far as we can tell from the data from
high-altitude sampling.
From the 1961 U.S.S.R. series, “Mn, *Fe, Co, Co, 4Sb, and
2047] have been observed. The major fractions of these neutronactivation products were mostlikely formed in the high-yield (55- and/
or 25-Mt) shots of the series. Dr. Kuroda pointed out that '*Sb levels
appeared in his tropospheric air and precipitation samples. On looking
back over our high-altitude data, I concur with his suggestion that an
excess of '*5Sb over that expected from fission was producedin a high-
yield device and that the ratio of excess '*Sb to Sr in the device was
about 10 to 1.
In addition to the data for “Mn/*Sr that I showed yesterday for
31°N in February 1962, we have some data from samples collected
at 70,000 ft in the summer of 1962 in which almostall the debris
appears to have originated in the high-yield 1961 U.S.S.R. tests. In
these samples the “Mn/Sr ratio, corrected for decay to October
1961, is about 100 to 1, and the excess '°Sb/"Sr ratio is about 10 to 1.
From all the 1962 U. S. and U.S.S.R. atmospheric tests taken as
a group, we have observed 88y and additional quantities of “Min and
24Sph, Iron-55 and other neutron-activation products probably were
produced also in some of these detonations. Unfortunately, the relatively high frequency of testing after April 1962 limits our ability
to assign the specific production of radionuclides to a given device
except for the }4Sb, which appears to have been formed predominantly
in the December 1962 U.S.S.R. series.
Cadmium-109 (470-day half-life) was produced in the 1962 Starfish
detonation by neutron activation of cadmium that was added to the