for natural uranium before these estimates of device-related uranium
can be accepted as accurate.
Four profile samples from A Site are currently available for study.
.
235
238
239-240
Figs. 5,
6, 7, and 8 are plots of the
U,
U, and
Pu
results from the 10 levels (2.5-cm increments) from each profile (the
data from two other profiles of A Site are not yet available).
Figs. 5 and 6 show the decrease with depth in atom percent 2354
235
and concentration of
U (ug/g dry soil), respectively.
The device
used in the safety shot at A Site was largely 2351, and the decrease
in concentration with increasing distance from GZ is reflected in
Figs. 5 and 6.
Concerning stake 3 in stratum 1 (210 feet from GZ),
the atom percent averages 0.720 over the 10 depths and plots as a
horizontal line in Fig.
of natura
5.
As noted above,
1 *35y is 0.72, the 7° U
since the atom percent
concentrations for this profile
(plotted in Fig. 6) have been used to approximate the inventory of
238
U for this profile
natural
U (Table 3).
The concentrations for
were used in a similar manner.
Fig.
7 is a plot of
tions in these same profile samples.
238
U concentra-
The slightly elevated concentra-
tions in the first 2.5 cm of soil for those three profiles nearest
ground zero suggest a relatively small percentage increase of 238y to
the surface soil from the device.
This contrasts with the rather
235 U concentrations in surface soil for
large percentage increase in
profiles near ground zero (Fig.
profile data for 239-240, u.
6).
Fig. 8 gives the available
Most of the plutonium appears to be in
the top 2.5 cm, with perhaps a gradual decline with depth below 5 cm.
The plutonium present here could have come in part from the safetyshot device at B Site which is some 1,600 feet or so away.
in Figs.
5 and 8 were fit by eye.
In Fig.
6,
The lines
the data for two
profiles were fit by the sum of two exponential terms (parameter
estimates statistically significant at 9 = 0.05 or less).
CONCENTRATIONS IN DIFFERENT SOIL FRACTIONS
Analysis of plutonium and americium concentrations in ball-mill,
mesh, and >100 mesh soil fractions was approached by asking, and
attempting to answer, the following three questions:
131
<100