a. This nomogram contains four lines of two scales each, which denotes time after burst (in hours)
for nonstandard decay exponents as indicated above each scale and one 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; the 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.
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 Rt
scale. The point where the hairline crosses the R1 scale indicates the H + 1 reading, H + 1 = 151 cGyph
(Figure 5-2).
5-5
CM23066
Previous Page
