The period during which personnel

remain

within

a

particular

area

of

contamination or radiation hazard.

A radiation dose, determined by the command prior to a survey, at which

personnel must turn back to avoid exceeding the operation exposure guidance.

A radiation dose rate, determined by the command prior to a survey, at which

personnel will turn back to avoid undue exposure hazard.

The decrease in the radiation dose rate from a single explosion can be

calculated by the use of a nomogram. The Residual Radiation Decay (Fallout)

Nomogram, Figure 5-1 on page 5-9, allows the user to find the dose rate at

any time if a dose rate at a known time after the burst is available.

This nomogram contains 4 lines of 2 scales each, which denote time after

burst (in hours) for nonstandard decay exponents as indicated above each

scale, and 1 line (the index scale) which denotes time after burst (in

hours) for the **standard rate (n = 1.2) of decay. ** The R1 scale, at the right

of the time scales, shows dose rates at H + 1; Rt scale, at the left of the

time scales, shows dose rates at times other than H + 1. The outside left

and right lines are reference lines to be used in aligning the hairline.

Use of the decay nomogram, involving **standard decay, (1.2), **is shown in the

examples below.

consistent as possible when joining values with the hairline. Be sure that

the hairline intersects the vertical line and the interpolated value (tick

mark) as closely as possible.

Dose-rate values smaller or greater than

those shown on the nomogram in Figure 5-1 may be reported. In the case of

smaller values, multiply the dose rate by 10, proceed with the calculation,

and divide the resulting dose rate by 10, see Example Problem 4.

In the

case of greater values, divide the dose rate by 10; proceed with the

calculation, and multiply the resulting dose rate by 10.

When using this

process, NEVER multiply or divide a number from the time scale; multiply or

divide, as appropriate, using only the dose rate values, see Example Problem

5.

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