a. This nomogram contains four lines of two scales each, which denotes time after burst (in hours)

denotes time after burst (in hours) for the standard rate *n *= 1.2 of decay. The *R*1 scale at the right of the

time scales shows dose rates at H + 1; the *R*t 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.

b. In working with nomograms, care should be taken to be as 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 5-2 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. 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. The use of the nomogram is demonstrated by the following:

EXAMPLE: If a dose rate reading taken at H + 3 was 40 cGyph, what was the H + 1 dose rate?

SOLUTION: The hairline is placed at the 3-hour mark on the index line *n *= 1.2 and held in position with

a pin or sharp pencil. The hairline is then rotated until one end crosses the 40-cGyph point on the *R*t

scale. The point where the hairline crosses the *R*1 scale indicates the H + 1 reading, H + 1 = 151 cGyph

(Figure 5-2).