No secondary fall-out was encountered within Bikini Atoll as a result of this detonation.
Intensities in the Ourukaen— Bokoaetokutoku-- Bokororyuru area tended to rise with increased flushing of contamination through the adjacent passages.
No significant fall-out was observed on land areas outside the Pacific Proving Grounds.
5WVANKEE
The survey on this date was conclusive enough to limit reentry and recovery to Enyu and
Airukiiji. Recontamination was extensive throughout the islands and lagoon (Fig. 4.12). Lagoon
contamination in this .rea approximated 500 mr/hr at 05/1047M, 22 mr/hr at 05/1700M, and
7 mr/hr at 06/0700M.
On shot day barges and boats in this vicinity were contaminated by fall-out with intensities
between 0.6 and 10 r/hr. Floating objects revealed readings of 1 to 3 r/hr, whereas submerged
equipment, i.e., buoys and anchors, revealed significant readings for the first time. It is estimated that the major portion of the floor of the lagoon was thoroughly contaminated by this
time.
Suspended sediment covered a circular area about 5 miles in diameter and moved to the
southwest or settled at the bottom for a period of four days. Tidal areas in the vicinity of the
southwest passages were retaining significant activity at this time.
Rainstorms shortly after YAWA¢E day were instrumentalin reducing radiationintensities
by a factor of 3 or 4. Radioactive material was being rapidly leached before chemical combination occurred.
No significant fall-out was noted outside the Pacific Proving Grounds.
4.3.6
~
NELTAR
This detonation in the Mike crater at Eniwetok caused limited contamination of the northern
islands (Fig. 4.13). An aerial survey indicated that radioactive contamination extended north of |
a line from Bogallua to Piiraai. Lagoon water was moderately contaminated in the vicinity of
the Bogallua-—Teiteiripucchi chain but was cleared within two days.
Background radiation levels on Parry Island started to increase at 1830M on WECTAR[oay.
Fall-out peaked at a radiation level of 1.9 mr/hr at 2100M.
Heavy rains in the forenoon of #f¢é7#[day delayed recoveries and materially increased
the rates of dissolution of intensity.
Nosignificant fall-out was reported on land areas outside the Pacific Proving Grounds.
4.4
CONTROL RESULTS
As a result of deliberations over a number of years by the National Committee on Radiation
Protection, certain principles have evolved which bear upon the general determination of what
is a permissible exposure of persons to radioactive materials. One of the considerations is the
degree to which radiation exposure may be integrated over a period of time without regard to
the rate at which such exposure has been acquired. The permissible limit for gamma exposure,
in general, presupposes a uniform rate, or at least one that is capable of being averaged over
a brief span of time. At the present time the geneticists tend to regard the genetic effects of
gamma radiation as related to total exposure, but there is beginning to be some question rela-
tive to the possible rate dependence of genetic effects. In general, somatic injury shows very
marked rate dependence,-and consequently the National Committee on Radiation Protection has
felt that there should be a definite reduction in total exposure when most of the exposure is ac-
quired at a high rate.
In such activities as the conduct of nuclear weaponstests, it is obvious that a uniform exposure rate cannot be the basis for the operation. A special case has therefore been madein
terms of the integration of the occupational permissible exposure rate over a reasonable period
37
me
waters were heavily contaminated with radioactive sediment and gave readings in excess of 1
r/hr at a 100-ft altitude in the vicinity of zero point onYANKEE 1 day. Enyu anchorage water