EXAMPLE PROBLEM 2. If the available dose rate was taken at a time other than H + 1 hour, the R1

value can be found by using the residual radiation decay (induced) nomogram as described in Example

Problem 1 for Soil Type II or when soil type is not known. For Soil Type I, III, or IV, these procedures

should be modified as follows:

Align the hairline with the time after burst tickmark on the proper soil type scale and equal values of the

left and right reference lines; pivot the hairline about the point of intersection with the index scale to the

proper Rt reading on the Rt scale; read the H + 1 dose rate at the point of intersection with the R1 scale.

Given:

Rt = 50 cGyph at H + 7 hours when the soil composition approximates Soil Type III.

Find:

R1

Answer: 300 cGyph

Solution: Align the hairline with the 7 hour tickmark on the Soil Type III scale and equal values of the

left and right reference lines. Pivot the hairline about its point of intersection with the index scale to the

50 cGyph point on the R1 scale. Read the dose rate as 300 cGyph at the point of intersection with the Rt

scale, (Figure 6-14).