PART B: COMPUTE THE TIME OF ENTRY
USING THE ABC-M1A1 RADIAC CALCULATOR
The ABC-M1A1 RADIAC Calculator of the M28A1 Nuclear Calculator Set can be used to determine
the time of entry into a fallout area when the rate of decay is standard (n = 1.2). Just as with the
nomogram to determine the time of entry using the calculator, you must know the total outside dose,
dose rate, and the time of stay. These values are determined the same as was discussed in Part A, when
using the nomogram. To determine the time of entry using the calculator, you must set the known data
on the calculator. The dose rate is located on the outer disc and aligned with the H + 1 hour mark on the
intermediate disc. Locate the total outside dose on the outer disc and note this position in relation to the
guide band on the intermediate disc. Follow this guide band through the intermediate disc and visualize
the relative position where the guide band meets the inner disc. Rotate the inner disc until the stay time
fits between the relative position on the guide band and the time of entry mark. The time on the inner
disc at the time of entry mark represents the time after burst that personnel may enter the fallout area.
As an example, with the following data follow the procedures as shown in Figure 3-2. Total dose is 100
cGy, H + 1 dose rate is 150 cGyph, and the time of stay is 2 hours.