after the burst. Any reading that is not recorded 1 hour (H + 1) after a burst is commonly referred to as
an Rt reading. In order to perform radiological calculations and make decisions on the nuclear
battlefield, all readings must be represented using the same reference time. If this is not done, the
radioactive elements will decay and a true representation of the hazard, past and present, cannot be made
For instance, a monitor reports a dose rate of 100 cGyph 5 hours after the burst. The decay rate was
determined to be standard decay (n = 1.2). What was the dose rate at monitor A's location at H + 1?
This can be determined mathematically by the use of nomograms, (Figures S-2 through S-39 in the
b. Mathematical Method for Determination of n.
The formula for the mathematical determination of the decay exponent is found by solving the Kaufman
equation for n, decay rate of fallout.
Symbols used in the above equation are:
n = decay rate of fallout
R1 = dose rate (cGyph) measured at time, T1
(a peak dose rate or later)
R2 = dose rate (cGyph) measured at time, T2
(the last dose rate available)
T1 = the time (H + _____ hours after burst) that
dose rate R1 was measured
T2 = the time (H + _____ hours after burst) that
dose rate R2 was measured
In the equation, the time and dose rate of the earlier reading is represented by T1 and R1 and the time
and dose rate of the later reading is represented by T2 and R2.