7)
Station B-30.
Compared to the nearly logarithmic decrease in
.oncentratitons between these stations, the concentrations of
at a rate of 3.5 times faster than the
Pu
137 Cs decrease
23942405. concentrations measured.
239+240
distribution of similarly increasing
239+240
The
Pu/ 137 ~'Cs ratios to the northwest
of the Zuni Crater ranqe from 5.76 to around 30-40 and indicate the second distribution observed.
These data show that relative to the distributions of 23942405, 24h am,
and
155 Eu, the regions of high 1376 concentrations are restricted
in geo-
graphical area.
Such localized regions of high
137 Cs concentrations were
also noted by Nelson and Noshkin (1972) in the surface sediments of Eniwetok
Atoll lagoon.
Because 13766 has volatile radioactive precursors, its initial
distribution might be expected to be significantly different from the refractory radionuclides Pu, Am and Eu.
5.1-6
Bismuth-207 and Cobalt-60
The areal distribution of the concentrations observed for
the induced radionuclides
between that for
tribution of
238
2074 and 606, (Figs. 16 and 17) is intermediate
Pu and that for
2394240,
u.
The similarity of the dis-
207 Bi and 60 “Cot 0 239+240 Pu is that decreasing concentrations in
lagoon sediments appear to radiate from high concentrations at Stations B-2
or B-20; the ratios
239+240 pu/"'Co
across the central lagoon.
207
Bi to that found for
238
and
23942405 1/278; are almost constant
The similarity of the distribution of
60
~Co and
Pu is that the highest measured concentrations of
these three radionuclides occur in crater sediments and show Jarge and systematic variations at different locations in Bravo Crater.
Bismuth-~207 is an induced radionuclide produced by reactions such as
2065), (d,n) 20755
Struction material.
The lead was present probably as a device or harge conSince the major source of 2078, to the lagoon environment