Results of Calculations of External Gamma
Radiation Exposure Rates from Fallout
and the Related Radionuclide Compositions
Operation Tumbler-Snapper, 1952
ABSTRACT
This report presents data on calculated gammaradiation exposure rates and
grounddeposition of related radionuclides resulting from Events that deposited detectable
radioactivity outside the Nevada Test Site complex.
INTRODUCTION
The Events which deposited detectable radioactivity outside the Nevada Test Site complex! are
listed in Table. 1.
RESULTS
Results of the calculations of relative external gamma radiation exposure rate and related
radionuclide ground deposition are given in the Appendices. These calculations are described in detail in
Ref. 2. The output of the calculation has 30 decay times, 10 from 1 to 21 h, 10 from to 300d, and 10 from 1
to 50 y. For each of these times and for zero time there are values of the external gammaradiation exposure
rate normalized to 1 mR/h, 1 m abovethe surface, 12 h after the event, the associated values of uCi/m? for
each radionuclide, and the total «Ci/m?.
The 793U, 73°U, 238U and 25%24°Pu data were omitted primarily to keep the output unclassified.
Futhermore,the natural uranium contentof the soil is about one million times that received from fallout and
at least half of the plutonium in Nevada and Utahsoils comes from worldwide fallout.?
Surface roughness effects are simulated by using Beck’s values* of (mR/h)/(uCi/m7?) for a relaxation length of 0.16 g/cm*. According to Beck, the concentration of fallout varies exponentially with soil
depth, Z, according to the relation C = C,ee. Hedefines relaxation length as 1/a.
TABLE 1.
Event |
Yield, date and placement of Events of Operation Tumbler-Snapper, 1952.
Yield (kt)
Date
Placement
Able
1
April 1
Air drop 793 ft
Baker
1
April 15
Air drop 1109 ft
Charlie
31
April 22
Air drop 3447 ft
Dog
19
May 1
Air drop 1040 ft
Easy
12
May 7
300 ft Tower
Fox
1
May 25
300 ft Tower
George
15
June 1
300 ft Tower
How
14
June 5
300 ft Tower
1