Construction of the ABC-M1A1 RADIAC Calculator.
The ABC-M1A1 RADIAC Calculator consists of three movable plastic discs joined in the center by a
metal rivet. The large (outer) disc is approximately 4 inches in diameter. See Figure 2-3. The front of
the calculator contains the circular scales required to complete nuclear calculations.
The outer disc is scaled from 0.1 through 10,000. These numbers represent dose rate in cGyph or
outside dose in cGy dependent on the calculation being made.
The intermediate disc is graduated around the outer edge in time after burst from 5 minutes to 30 weeks.
The inner portion of this disc contains white, black, and red guide bands. The red guide bands are
represented in Figure 2-3 by the shaded/dotted area. There is a time of entry index line shown on this
The inner disc is graduated in time increments representing time of entry-time of exit, ranging from 5
minutes through infinity (shown as oo). The hours and weeks portion of this disc, which appears as a
shaded area in Figure 2-3, is yellow on the actual calculator.
On the back of the calculator are printed instructions on the use of the calculator. Following the
instructions, seven commonly used transmission factors are printed on the calculator. See Figure 2-4.
Set known data on the ABC-M1Al RADIAC Calculator.
To work nuclear calculations on the ABC-M1A1 RADIAC Calculator, you must first set any known
data on the appropriate disc of the calculator. In order to determine the total outside dose of radiation
which may be received by unprotected personnel, the time of entry, time of stay, and dose rate must be
known. The dose rate is located on the outer disc and aligned with the H+1 mark on the intermediate
disc. Locate the time of entry on the inner disc and align this mark with the time of entry mark on the
intermediate disc. The exit time mark is located on the inner disc by adding the time of stay to the time
Example: The time of entry is H + 2 and time of stay is 2 hours, therefore the time of exit is H + 4
hours. Total dose is then determined by following the relative position of the exit time on the
intermediate disc guide band to the same relative position on the outer disc (Figures 2-5 and 2-6).