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1. PRELIMINARYREMARKS? At the planning conference st Kwajalein am 20 April
it was agreed that radiation levels at Utirik ulght allow en early return of
the natives. Accordingly, it was dectded to make @ field study of food and
water &s.well as an external radiation survey based on the pattern employed
at Rongelap.
2. METHOOS: SSxcternal gemma dese rates were measured with AN/PDR-39 and
MX-5 survey instruments. These instruments gave readings in good agreement
with each cther, Average readings integreted over the exposure tims closety
checked dosimeter readings.
3. RATESDOSE : Prior te this survey, no standard positions were
established om this island. A dfandard position was established on April 23
at 1100 hears. The reading at this point sad three feet above the ground wa
3.0 or/ar. Am average reading in the vegetated area of the island was 2.8 or/k
The readings about the buildings where gravel is prevalent averaged about 2.2
ar/hr. This data with the aeasurements made on & and 1) March fit a decay
formulas Dpz2cecl.42 p/day (t in days after 1 March)
An integration
fi
This formile indicates that a level of 0.3 r/week would be reached in 75
to 80 days after 1 March, 15-20 May).
doaage fran 1 June 1954 to 2 Jun 1955 gives a 3.4 Yr exposure. This can be
-
compared with ths 3.9 © external gamma per year level established by the
atomic Energy Cammiseion es 4 limit for offeeite populations.
external gama dodage over the year beginning
June could be
not signifiecntly, higher if the decay rate leveled off to the conventioa]
t°1.2
.
rate,
4.
OFCONTAMI ON: ‘The contamination ws fair
distributed over the ialand. The Aighest reading cut of doors
reduction in readings indoors, and this reduction we substantially larger,
& percent in a large building like the church, as compared with 4 small
tuilding like a typical
» Grewal areas (2.2 ar/hr) gave lower
readings than the grassy areas (2.8 ur/hr).
The sleeping mats showed gars readings (1.0 - 1.2 ar/hr) about half
the levels citdcore(2.2 - 2.4 ar/hr) bat deta plas gam levels were
scpewhat bigeer (3.5 mx/tr) tinn the outdoor gamma readings. Contamination
of the thatched roofs was noted.
It was neceemry to place the instrument
Close to (dese than 3} feet) and perpendicular to theroof surface to
consistently detect this effect with gama measurements, The MI-5 picked
wp this increase in contamination more consistently when detecting doth
beta
gum.
w - {03