the [959 curve back to October 1958.
Points falling in between are then resolved algebraically into two values
(black dots in Fig. 1) that coincide
with the extended curve.
Calculated contributions to total Sr*
fallout from Soviet testing in the fall
of {958, from Operation Hardtack,
and from earlier series are listed in
Table 2. Since the W™ levels fell beJow the detection limits of the collection system used (/0), it is not possible to trace Hardtack activities in samples taken after July 1959. An additional difficulty for this period is the
possibility that there was fallout from
U.S. high-altitude devices detonated
during the summer of 1958; this has
been inferred by Gustafson (/) and
others from the detection of Rh™ in
air and ground measurements. However, it is clear that, prior to July, rates
of fallout from the Soviet series were
as much as ten times as high as rates
of fallout from Hardtack, and that the
Soviet series delivered a total of at
least four times more Sr” to the New
York City area.
Air Activity Concentrations
The rough proportionality that exists
between fallout level and amount of
rainfall permits the use of the specific
activity of rainfall as a relative index
of concentrations of activity in air.
Thus, with knowledge of the sources
of debris and monthly precipitation
totals, it is theoretically possible to
follow the fluctuations in air levels that
resulted in the Sr® depositions listed in
Table 2.
With the additional assump-
tion that the atmospheric dispersion of
Table 2. Sources of Srfallout in New York
City during 1958 and 1959.
Sr*® activity level (me /mé2)
Sampling
month
oo
Operation
Apr. 1959 Flardtack
Soviet,
ggg
May 1988
3.44
0.006
July 1958
Aug. 1958
Sep. 1958
1.28
0.358
0.378
0.224
0.198
0.197
Ocr. 1958
Nov, 1958
0.596
0.450
0.227
0.320
0.347
0.420
Dec. 1958
Jan. 1959
0.119
0.179
0.525
0.474
0.479
Feb. 1959
Mar. 1959
Apr. 1989
0.512
0.707
0.492
1.30
3.74
3.67
May 1959
June 1989
July 1959
0.313
0.260
0.104
1.21
2.17
0.416
June 1958
1.23
Table 3. Integrated gamma-radiation doses delivered by principal gamma-emitting pairs in fallout in
New York City during 1958 and 1959. The JO-year dose from the estimated total Ru-e*-Rhies
deposition during 1958 ts given in parentheses.
30-year gamma dose (millirads)
Sampling
quarter
Cs'3t-gagia?
Zr*s-Nbes
Jan.-Mar. 1958
3.21
4.10
Apr.-June [958
Jul.-Sept. 1958
Oct.-Dec. 1958
4.316
2.93
3.23
4.42
2.08
7.39
Apr.-June [959
July-Sept. 1959
Oct.-Dec. 1959
7.87
(.22
0.967
2.05
0.0925
0.0
Jan.-Mar. 1959
7.20
6.24
Celts piss
0.108
(LET)
1.20
0.203
0.0862
0.166
0.284
1.24
0.178
0.125
0.217
0.0230
0.0113
1.10
Total 30-year dose
30.8
26.4
3.91
Total 70-year dose
47.6
26.4
391
1.10
Total infinity dose
56.7
26.4
3.91
1.10
other fission products is not radically
different from that of Sr”, the build-up
and depletion of concentrations of total
Hardtack and Soviet debris in the air
over New York City during 1958 and
1959 may be traced. Moreover, it is
not unreasonable to expect material
from possible future polar and equatorial detonations, carried out under
tack curve suggests a decline in tropo-
spheric activities after 90 days, followed
by the defayed arrival of stratospheric
debris after 150 days. As a result of
the difference in timing, there was appreciably more shorter-lived material
in the fission fragments deposited from
the Soviet series.
the same conditions, to arrive in simi-
lar fashion.
Figure 2 compares the fractions of
total fission-product yields from Hardtack and total yields from the Soviet
October 1958 series found in unit
monthly rainfall volumes in New York
City after May 1958. The vaiues are
derived from the Sr” data in Table 2;
an average Sr® yield of 4.0 atoms per
100 fissions for the two series was used
(19). Total TNT megaton equivalents
for the two events are taken from the
reports of Libby (8) and Martell (6).
A mean production date of 18 October
1958 for the Soviet series is calculated
from the Sr”/Sr” ratios illustrated in
Fig. 1. Rainfall volumes are taken
from monthly weather summaries distributed by the United States Department of Commerce (20).
The curves show that both series
produced significant levels of specific
activity and, by inference, significant
concentrations of activity in air in New
York City as early as 30 days and as
late as a year after their mean detona-
tion dates. Although it is not possible
0.039
Rul Rhies
to follow the long-term effects, it appears that the major contributions from
the Soviet series occurred over a span
of about 150 days, while the dissipation of concentrations from Hardtack
required about 250 days. In addition,
the Soviet activity build-up was higher
by roughly a factor of 10 and occurred
about 100 days sooner relative to the
date of production than did the Hardtack build-up. The break in the Hard-
55
Gamma Dose
From theoretical gamma- to beta-
fission-product ratios (/5), the total
deposition of fallout in New York City
during 1958 and 1959 is estimated to
have produced from one-half to onethird as many gamma photons as beta
particles. Calculated contributions of
cumulative levels of representative
photon-emitting pairs to total infiniteplane gamma dose rates from fallout
are illustrated in Fig. 3. All values are
corrected for monthly decay. The Ru
levels for January and February and
for June through December 1959 were
obtained from the Cemeasurements
by extrapolating the decrease observed
in the Ce'“/Ru™ ratio during March,
April, and May. The estimate is believed to be fairly consistent with actual ruthenium levels, since the slope
of the decrease agrees with that theoretically calculated from the decay
constants of the two nuclides. The estimate for gross 1958 ruthenium deposition is obtained by assuming a Ru™/
Ce™ activity production ratio of 0.71
(79) and a mean production date of
30 June 1958, as in the approximation
for total beta activity.
Although the dose rates shown for
the shorter-lived photon-emitting systems are sustained through only a few
half-lives of the parent activity, significant integral doses are produced.
Table 3 lists the genetically important
30-year gamma doses calculated for