ESTIMA” 7 OF RADIATION DOSE TO THYROIDS OF THE RONGELAP
CHILDREN FOLLOWING THE BRAVO EVENT
Ralph A. James
Lawrence Radiation Laboratory, 'niversity of California
Livermore, Calitornia
,;
December 16, 1964
ABSTRAC’
An estimate is made of the radiation dose to the thyroids of Rongelap
children following the Bravo event of March 1,
1954.
The available experi-
mental data are used to estimate the dose under two alternate assumptions of
mode of intake:
(a) all of the intake was by inhalation, and
intake was by oral ingestion.
(b) all of the
It is concluded that the most probable dose to
the thyroid of a 3- to 4-year-old girl is in the range 700 to 1400 rad.
GENERAL INFORMATION
The cloud arrival time is given! as H+4to6 hours.
The duration of
the cloud passage is less well known, but probably lies in the range of 8 to
16 hours.
In all calculations we will assume that cloud passage was in the
interval H +6 to H + 18.
The residents of Rongelap were evacuated at H +51 hours.
Reliable
dose-rate measurements were not obtained at that time, but the gamma dose
rate 3 feet above the ground was measured as 375 mR/hour 7 days after the
‘detonation,
Assuming pi? decay, the H + 24 hour dose rate was then about
3.8 R/hour.
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 R.
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
>
— !
cm
FT
?
cloud but only from fallout,