APPENDIX 2 # UCRKL 12273
Estimate of Radiation Dose to Thyroids of
the Rongelap Children Following the Bravo Event
Ralph A. James
Lawrence Radiation Laboratory,
Livermore,
University of California
California
December 16, 1964
General Information
The cloud arrival time is given‘)? as H + 4 to 6 hours.
The duration
of the cioud passage is less well known but probably lies in the range of
8 - 16 hours.
In all calculations we will assume that cloud passage was in
the interval H + 6 to H + 18.
The residents of Rongelap yere evacuated at H +51 hours,
Reliable
dose rate measurements were not obtained at thar time but the gamma dose
rate 3 feet above the ground,was measured as 375 mr/hr seven days after
the detonation.
~3.8 rad/hr.
Assuming t
~°"
decay the H + 24 hour dose rate was then
The sources of exposure to the thyroid which must be considered are:
(1)
Whole body gamma dose.
(2)
Internal deposition of iodine isotopes.
Whole Body Gamma Dose
The whole body dose was estimated?) to be 175 rad.
The exact method of
making this estimate is not given, so an independent estimate is made below.
In particular, it appears that this estimate does not include the dose from
the cloud but only from fallout.
If we assume a linear buildup of. fallout from H + 6 to H + 18,
phe?
decay during this interval and use the reading of 375 mr/hr at seven days,
the estimated dose from fallout during cloud passage is 47 rad.
The dose
from the fallout from H + 18 to evacuation at H + 51 is 114 rad.
Experience
from Sedan indicates that the dose from the cloud,
itself,
equal to the dose from fallout during cloud passage.
is then 47 +47 + 114 = 208 rad.
is approximately
The total estimated dose
Within the error of the measurements and the accuracy of the assumptions,
this estimate, which does not contain any correction for the small effege of
.
We
time indoors, does not differ significantly from the value of 175 rad
will, therefore, take the average whole body gamma dose as 175 + 25 rad.