Repeat Steps 4, 5, and 6 as later dose rate measurements at that location become available.
Step 7.
Repeat Steps 1 through 7 for each location of interest within the overlapping fallout patterns.
Step 8.
EXAMPLE PROBLEM. At a location where fallout has been received from two detonations, dose rate
measurements were made at intervals as shown on Figure 6-8 on page 6-20. The time of the second
burst is at 0800 hours.
Time
Dose rate cGyph
0900
360
1100
165
1300
108
1500
80
0200
30
1200
17.5
After receipt of the measurement made at 1100 hours, predict the dose rate at that location at 2000 hours
on the following day (36 hours after burst). After receipt of each succeeding dose rate measurement,
update this prediction.
Solution: Sufficient data are not available to separate the two contributors, but enough is known to use
the extrapolation method.
Plot on log-log graph paper the 0900 and 1100 dose rate measurements against time after
Step 1.
second burst.
Draw a straight line through these points and extrapolate the line past H + 36 hours.
Step 2.
As a first approximation, determine a dose rate of 28.0 cGyph for 2000 hours on the day
Step 3.
following the burst (R36) directly from the graph. Figure 6-8.
Upon receipt of the 1300 measurement, plot this reading on the graph.
Step 4.
Draw a new straight line through the 1100 and 1300 points and extrapolate the line past H +
Step 5.
36 hours.
As a second approximation, determine a dose rate of 20.5 cGyph for H + 36 hours directly
Step 6.
from the second extrapolation.
CM2308
6-18
Previous Page
