Lesson 2/Learning Event 1
be normalized to H + 1. These two calculations can be combined into an overall correction factor
(OCRF). The OCRF is the product of the correlation factor (CF) and the normalizing factor (NF). The
calculation of this factor greatly reduces the work required to calculate the final data to be plotted.
Instead of multiplying each monitoring reading by the CF and then the NF, each reading is multiplied by
the OCRF only. The overall correction factor is calculated as OCRF = CF X NF.
The following is an example problem using the overall correction factor.
SITUATION: An NBC 4 (Nuclear) Report has been received from Company B which reported an
inside (shielded) ground dose-rate reading of cGy(rad)/hr and an outside (unshielded) ground dose-rate
reading of 20 cGy(rad)/hr. Both readings were taken within three minutes of each other. The nuclear
burst occurred at 0900 and the readings were taken at 1130.
The standard decay exponent (1.2) is being used. What is the overall correction factor?
SOLUTION: Step 1. Calculate CF.
Step 2. Determine NF from figure 6 on page 33.
Decay exponent = 1.2
Time after burst = 2 hours 30 minutes
NF = 3
Step 3. Calculate OCRF.
OCRF = CF X NF
All shielded ground dose-rate readings reported by Company B for this nuclear burst will be multiplied
by 12 to determine the unshielded ground dose rate at H + 1.
The NBCE, upon receipt of survey data, plots the location, time of reading, and normalized dose rates
contour lines by interpolating between the plotted dose rates. The plotter must use care and judgment in
plotting these contours and must visualize the probable general shape and direction of the pattern. In
addition, the plotter must carefully weigh dose-rate readings indicating possible hot spots. These will
appear as dose rates