0800-1200, 1330-1700, and 1800-2000 hours. This amounts to 40 percent of the day (9%
hours) topside and 60 percent (14% hours) below.
shielding provided by the ship's structure.
While below, the crew was offered
In References 3, 4, 5, and 6, it is estimated
that ship-shielding factors vary from approximately 0.06 to 0.15, depending on the
main deck thickness. A time-averaged shielding factor is computed as 0.4 + 0.6 x shipshielding factor, where the 0.4 and 0.6 represent the fraction of the day spent above
and below the deck, respectively.
approximately 0.44 to 0.49.
The time-averaged shielding factors vary from
An average value of 0.46 (corresponding to a ship-
shielding factor of 0.1) is used in this analysis and variations are treated as an
uncertainty in Section 4
A similar argument is used to obtain a time-averaged
shielding factor of 0.8 for the land-based personnel. This assumes that 60 percent of
the day is spent outside and 40 percent inside. While inside, personnel are afforded a
protection factorof 2, i.e., a shielding factor of 0.5.
In addition to being exposed to a fraction of the topside (fallout) radiation
environment, crew members, while below, were exposed to radiation from the ship's
hull and saltwater systems that became contaminated while in the radioactive waters
of Bikini Lagoon.
day,
they
Since the typical crew was below for an estimated 14% hours per
received
60
percent of
the
integrated
intensity below due
to
ship
contamination.
3.2
CALCULATED PERSONNEL FILM BADGE DOSES
Film badge doses are calculated by applying the actual exposure conditions to
the free-field integrated intensity and converting this to a film badge dose. Conditions of exposure include shielding as well as duration of exposure.
When fallout was
significant, actual periods topside (outside) and below (inside) are used, such as for the
APACHE on 1 March when crew routines were altered due to BRAVO fallout.
When
fallout was relatively minor and duty routines were not significantly altered, film
badge doses are calculated by applying the appropriate time-averaged shielding factor
to the free-field integrated intensity and again converting to a film badge dose. The
conversion factor has been determined to be 0.7 rem/R (Reference 7). The following
sections describe the dose calculations for both island-based and shipboard personnel.
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