PART B - TOTAL DOSE PREDICTIONS
The dose rate of radiation does not directly determine whether or not
personnel become casualties.
Casualties are dependent on total dose
received. If the dose rate were constant, total dose would simply be the
product of dose rate and time in the contaminated area, just as in a road-
movement problem, rate x time = distance. But the dose rate is continually
diminishing because of decay; therefore, the calculation is a little more
complicated.
The actual dose received is always less than the product of
dose rate at time of entry and duration of stay.
1.
Total Dose Calculations.
The nomogram in Figure 5-2 on page 5-12 is used for predicting total dose to
be received while operating in a fallout radiation area resulting from a
single explosion. This nomogram relates total dose, dose rate referenced to
1 hour after the burst, stay time, and entry time.
The index scale is a
pivoting line that is used as an intermediate step between D, R1, Ts, and Te
The four values on this nomogram are defined as follows:
D
=
Total dose in cGy.
R1
=
Dose rate 1 hour after burst (H + 1).
When using this
nomogram, a dose rate referenced to 1 hour after the burst
(H + 1) must ALWAYS be used; NEVER use a dose rate taken at
any other time.
Ts
=
Stay time in hours.
Te
=
Entry time (hours after burst).
Any one of these values may be determined from the nomogram if the other
three values are known, as shown in examples on the next page.
2.
If the available dose rate was taken at a time other than H+1 hour, the
value of R1 may be found by using the Residual Radiation Decay (Fallout)
Nomogram, Figure 5-1, and the procedures for decay calculation in Part A.
In applying the given values, D and R1 are used together and Ts and Te are
used together. When working with the total dose nomogram, always start the
problem on the side of the nomogram for which two values are known. If D
and R1 are given, start with these two known values; if Ts and Te are given,
start with them. Never begin a problem by joining D or R1 with either of
the time values.
CM5206
5-10
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