Step 6. Zones I and II Downwind Distance Determination.
a. Using Figure 3-5, align a hairline from the yield
on the right-hand
scale to the value of the effective wind speed
on the left-hand
scale; at the intersection of the hairline with
the center scale,
read the value of the downwind distance of the
Zone of Immediate
Operational Concern (Zone I) for a surface burst.
Record this value
on line m of the worksheet.
b. If the Fission Yield/Total Yield (FY/TY) ratio is known, obtain the
FY/TY adjustment factor from Figure 3-6.
This information along
with the height of burst (HOB) is received from fire direction
personnel for friendly bursts. Lay a hairline from the total yield
on the left hand scale to the value of the FY/TY ratio on the right-
hand scale; at the intersection of the hairline with the center
scale, read the FY/TY adjustment factor. If the FY/TY ratio is not
known, assume the yield to be 100 percent fission and use an FY/TY
adjustment factor of 1.
Record the FY/TY adjustment factor on
line n of the worksheet.
c. If the height of burst is known (as in the case of a prestrike
friendly burst), obtain the height of burst adjustment factor for
yields equal to or less than 100 KT or for yields greater than 100
KT.
Lay a hairline from the yield on the left-hand scale to the
value of the height of burst on the center scale; at the
intersection of the hairline with the right-hand scale, read the
height of burst adjustment factor. If height of burst is not known,
assume a zero height of burst and use a height of burst adjustment
factor of 1. Record on line n of the worksheet.
d. Multiply the Zone I downwind distance for a surface burst, by both
the height of burst adjustment factor and the FY/TY adjustment
factor to obtain the adjusted downwind distance of Zone I for the
given conditions. Record this value on line o of the worksheet.
e. Double the distance found to obtain the adjusted downwind distance
of the Zone of Secondary Hazard (Zone II).
CM5206
3-12
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