Use of the decay nomogram is shown in the following example problems.
EXAMPLE PROBLEMS. In working with nomograms, care should be taken to be as consistent as
possible when joining values with the hairline. Be sure the hairline intersects the vertical line and the
interpolated value, tickmark, as closely as possible. The following problems are concerned with
technique only and do not consider the impact that these high dose rates might have on operations in the
EXAMPLE PROBLEM 1. Given: Rt = 150cGyph at H + 3 hours
Answer: 190 cGyph
Solution: Since the soil type (composition) is not known, calculations will be performed on the Soil
Type II (index) Scale. Align the hairline with the 3 hour tickmark on the Soil Type II (index) Scale and
the 150 cGyph point on the Rt scale. Read the dose rate as 190 cGyph at the point of intersection with
the R1 scale (Figure 6-13).