iL
a
1
4
ty
1955
0.5
a
oa
putl
a
OcTORER
|
tp
BEST, EXPONENTIAL
GOO0, POWER
POOR, LOGARITHMIC
POOR, LINEAR
1
bE
ag td
(not all data shown}
(1}
{2}
(3)
(4)
pial
I-129 ACTIVITY PER GRAM OF SURFACE SOIL, pCi g°!
3
oO
QUALITY OF FIT
po
200
e
4
JULY
1956
ik
JULY
1957
i
400
600
BOO
1000
TIME POST DETONATION, days
F200
Figure 3. Curve fit of archival soil results.
1.5 days was taken from Table 3 of Crocker's report (Cr65). Individual nuclide
activities were calculated by Crocker's methods and the original input data used
by him (Cr63).
The values for the hypothetical ratio of nuclide activity rela-
tive to total fission product activity are tabulated in Table 7, columm E.
6. The Ratio of Nuclide Activity to Total Activity for Bikini Ash.
Bikini ash was the name given by the Japanese for actual fallout from BRAVO
(1s56). Estimates of Bikini ash activity per unit mass of soil were calculated
from results for activity per unit area given in Table 13 of this report. Table
13 was devised by normalizing Bikini ash measurements to external exposure-rate
measurements. Using the nuclide composition of Bikini ash, a fallout decay exponent specific for BRAVO fallout was developed (see Section IID.1l.e) and was
-1.4. Values for individual nuclide and total activity were developed for the
surfaces of Rongelap, Utirik and Sifo Islands for different points in time.
Bikini ash activity per unit mass of soil estimates were tabulated in Table 7,
colum C. The times are 1.5 days post detonation at Utirik and 0.5 days post
detonation at Rongelap.
To estimate specific activity from areal activity, approximately
65,000 g/m of soil were assumed to be present in the top 5 cm (2 in.) of soil.
This value comes from a conversion factor of 6000 g/ft? proposed by the survey
team which visited Rongelap on March 8, 1954 (0C68).
A bulk soil-humus density
of 1.3 g/cm? in the top 5 cm (2 in.) of soil could be assumed to estimate a similar conversion factor.
-15-