large inconsistency indicated for the crater lip measurements could have been cuased in
part by a cave~-in of crater walls caused by postshotrain:
3.5.2 Lagoon and Reef Areas. The plan to establish a calibration of buoy~mounted
sticky pans by comparing dose rates measured on the large barges to counting rates of
nearby buoy-mounted sticky pans had to be abandoned when large numbers of the buoys were
lost. Instead, land measurements were used to establish a calibration that was assumed to
apply everywhere in the fallout area.
At 16 land stations where H+1 hour dose rates were obtained, sticky-pan fallout collectors were recovered and counted. A composite sticky-pan decay curve (Figure 3.7)
was obtained from four of these and from three buoy-mounted sticky pans. All pan counting
rates were normalized to H+3 hours by use of this composite decay curve.
The ratio of H+3 hours count rate to H+1 hour dose rate was found for each of the 16
land stations; the mean ratio was determined from the graph shown in Figure 3.8. The
mean ratio was used to determine full-field dose-rate.estimates for lagoon and reef stations.
It was also determined from this curve that +50 percent is the probable error for a dose
rate inferred by a single, land sticky-pan reading. Table 3.2 lists counting and doserates.
3.5.3 H+1 Hour Dose Rates for Complete Array. In Figure 3.9, the H+1 hour dose
rates inferred from sticky-pan collectors and from RAMSand monitor readings on the
barges are listed for all stations in the lagoon and on the reef. Also shown are intensity
contours for the entire array, which represent the best estimate of the H+1 hour values.
The zero intensity contour was positioned on the basis of cloud trajectory calculations
and measured cloud dimensions.
Consistent dose-rate histories were obtained on the YCV barge (S-6) by continuously recording RAMS and by monitors equipped with survey meters. The position of the 1-r/hr
contour on the small barge (P-5) is well established from survey data. On both of these
barges, readings taken at the center were about the same as readings taken near the edge,
indicating uniform deposition of fallout.
Reliable land readings established a hot-line direction on land, which is consistent with
cloud trajectory, cloud height, and wind data. The land hot line is directed toward the
small barge, showing that contamination came primarily from the 0~ to 500-foot altitude
range. Hot lines for contamination that fell from higher altitudes up to 2,700 feet passed
to the north of the small barge with the 2,700-foot hot line falling on the YCV barge. Data
from the 10 buoy collectors (S through M on lines 5 and 6), which covered the important
region between these two barges, allow some confidence in the estimated contour lines,
especially in the 1-r/hr contour.
3.6: CLOUD SHINE
The RAMS instrumentation that was located on the YCV barge recorded gammaradia-
tion “shine” from the passing cloud.
Peak dose rates of 125 and 165 r/hr were recorded
by two detectors that were set to cover the 1- to 1,000-r/hr range. Dose rate versus time
is shown for these recorders in Figure 3.10. Peak dose rate was observed at slightly less
than H+ 2.5 minutes.
Calculations of the cloud trajectory, using measured nonuniform rise rate and measured
winds, show that the center of the puff passed almost directly over the barge at about 2.4
minutes after zero time. In Figure 3.11, the plan position of that portion of the cloud
41