EVENT
AND
DESCRIPTION OF
a. The estimated durations of fallout which
jewuli from the aiove extrapelation of inital
fallout rate for Group | and [IP appear ton
I ce ae me alr
long to have occurred at the clistances of
these people from the shot island, since the
wind velocity in the area was high enough
to move the cloud over the islands ina
considerably shorter time, as little as onehalf of the above indicated time.
b. The accounts of the visibibty of the fallouts,
although conflicting, do not indicate such
late cessation.
c.
Doses calculated on a long fallout constant
rate of increase hypothesis ate lower than
those due to a short fallout, since a short
fallout quickly deposits a large amaqunt of
activity. For both a 16 hour and & hour
faliout assumption, a dose value was esti-
mated.
The ranges are then as follows:
Table 1.2
Location
Rongelap (Group |)
Ailinginae (Group [ID
Rongenk (Group TED
Vtink (Group PV)
Dee IN
Fattoor Time
tar
Sur
120
Toe
i2r
Mar
200 5
“2 r
16 r
lar
On Rongerik (Group TTP) a set of film badge
readings were obtamed which constitute the
only direct evidence of total dose. Several
badges worn both outdoors and imside lightly
constructed
buildings on
the island read
about 50 to 65 nr. and one badge which remained outdoors over the 28 5 hour period
read 98 ro
Another group of badges, kept
Indoors inside a steel refrigerator. resd 38 r
These dose values represent a variety of
conditions, but. considermg the shielding
and attenuation factors. are consistent with
-
é
EXPOSED GSOUPR
d. For Uturrk etalt Conc TY nts a imdpent
time of about 12 hours of lean i consemtent
with the later dose rates observed. provided
the fallout actually began ea late an was
estimated from wind and distance factors
eA long fallout probably would not be un-
formly heavy throughout. the first: portion
being the most intense and the balance de-
creasing with time. The total phenomenon
would thus tend toward the effect of a
shorter fallout. This is supported by monitor date from other nuclear events, where
initially heavy fallout is reported to produce
a peak of air-borne radioactivity soon after
arrival, with the airborne activity level then
decreasing. The latter pert of the fallout:
though still detectable as dust, may then
produce only a small fraction of the total
dose from material on the ground, Hence
the total dose mav be estimated fairly accurately by assuming a conatant fallout to
have been complete ino a much shorter
“effective” time.
The dose values given in ‘Table 1.1, based on
films badge, meter and monitor data, are consistent with a constant fallout: hypothesis of
about [2 haurs effective time.” One exception
istuade: the dose values for Crroup PL are about
vo percent of the 12 hour fallout value, averaged
for 2Sand Ob hour exposures. This was felt
to express most accurately the average wir dose
received by personnel who spent roughly half
their time inside structures where the dose rate
was hater found to be roughly half that) out.
doors.
On the other shins such shielding: was
not available,
Figure i.3.
cUustrates the cumulation of
radiation dose asa function of time after detonation, “Phe dose rate cared continuously.
The nuager portion of redintion was received at
the higher dose rate prevailing in the early porHionof the exposure period. By the time that
"Tossa Eo bers ae tuatis resatts om values Whe hh are
the assumption that the dose outside during
the firms 28 5 hours after the begining of
Poacher than theese of Vatie Pdota ote dor. Table 21
the fallout corresponded to about 2 hours
Wiese vaaidabele
of constant fallout
boston
thee
vaplepe=
cqade tgtaatesd
Foeertarrty
wreceter Phere Chas bi fPerete ee
Yeefese ail
spe trim
ctielay
be tll the amfecctisa tions ys
owt be re teegtios fond