multiplying the unshielded dose rate by a NF. The NF is the ratio of the ground dose rate at a reference

time (*R*1) to the ground dose rate at any other known time (*R*2) after the completion of fallout in the area

of interest, or

1

Each method is described in the following paragraphs:

a. Mathematical method. The equation below is used to determine the NF to convert an *R*2 dose

rate to a reference time *R*1 dose rate.

The equation 1 2*n *is used in determining the NF by the mathematical method.

Thus, since *NF *

, and since

n , it follows that *NF * n .

(1) To determine a reference time of H + 1, *T*1n 1 and *NF * 2*n *.

EXAMPLE: A nuclear burst occurred at 1030. At 1400, a reading was taken. What NF would be used to

normalize the reading to H + 1 if the decay exponent *n *was 1.2?

3.51.2 4.496

SOLUTION: *NF *

4.50

1

1

(2) To determine a reference time of H + 48, *T*1 48 and NF

.

EXAMPLE: A dose rate of 16 cGyph measured at H + 50 in a fallout area where the decay exponent *n*

was 0.6. What NF would be used to normalize the reading to a reference time of H + 48?

50 0.6

10.45

SOLUTION: *NF *

1.02

480.6

10.20

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