RADIOACTIVITY VS. HEIGHT IN NUCLEAR CLOUDS
637
the bomb in a 1000-ft-thick layer. The volume sampled is determined
from the altitude, the air temperature, the aircraft speed, the sampling
time, and the sampling-tank and filter-paper characteristics.® The aver-
age dose rate is determined from the readings taken in the cockpit at
l-min intervals during the sampling period. From Eq. 2 the gamma
megacuries in the sample can be calculated. If it is assumed that 1 kt
of fission (1.4 x 107° fissions) is equivalent to 550 gamma megacuries
at 1 hr, the following conversion factor can be used: 1 Mc (H+ 1) =
2.64 x 10° fissions. Table 1 gives the pertinent data and the fissions
Table 1—COMPARISON OF CALCULATED AND ANALYZED
FISSIONS PER SAMPLE
Mission
Altitude,
ft
Sample
volume,
cu ft
A
43,000
1.06 x 108
C
45,000
1.10 x 10°
B
48,000
Average
dose rate,
mr/hr atH+1
1.11 x 10
190
270
560
Fissions
Calculated
fissions
per sample
per sample
(radiochemical
analyses)
1.9 x 1914
3.3 x 1014
5.6 x 1014
5.8 x 1014
2.3 x 1044
4.9 x 1014
per sample as calculated from dose-rate readings and as determined
from radiochemical analyses of the samples.
The agreement between the calculated values and the results of
the sample analyses is remarkably good, considering the uncertainties
due to the possibility of shine from other portions of the cloud, air-
craft shielding, and aircraft contamination. The calculated values for
the samples from missions A and B are low by about a factor of 2,
possibly because of the effect of the blank space previously mentioned.
The calculated value for the sample from mission C is in almost perfect agreement with the result of the sample analysis. Mission C is the
one depicted in Fig. 4 and for which there was reason to suspect a shine
contribution to the dose rates which may have compensated for the
blank-space effect.
Additional experimental data are needed to evaluate all the factors
involved, but the results indicate that the method employed on these
missions is a practical and promising way to obtain the distribution of
activity in a nuclear cloud.
REDWING IN-CLOUD DOSE-RATE DATA
The doses and dose rates at various altitudes in several nuclear
clouds (all but one from surface bursts) were investigated by aircraft
penetrations? during Operation Redwing in 1956. Some of these pene-
trations were complete traverses through the cloud. Since thealtitude,