Page:Operation Crossroads 1946.pdf/54

 Multifilm badges, called casualty badges, were used to record high-range exposures. They were placed aboard a small number of ships and aircraft that might enter areas of high radiation. Casualty badges were also placed aboard target ships as part of the scientific program to determine exposure from the detonations.

Radiological Safety Instruments

CROSSROADS requirements for radsafe instruments turned out to be far greater than had been expected when planning for the operation began. No comprehensive program existed for development and manufacture of rugged instruments for use under field conditions: thus, the head of the Radsafe Section had to make do with what the Manhattan Engineer District could provide from its inventory and what the Victoreen Instrument Company could manufacture quickly (Reference C.11.1; Reference C.0.12, p. 18).

Each monitor unit or monitor-advisor was equipped with a Geiger-Mueller counter (X-263 Survey Meter) and an ionization meter (Model 247 Survey Meter), as well as other equipment, depending on the nature of the mission (Reference B.0.1, pp. E-II-2 through E-II-8).

The X-263 measured beta and gamma radiation from about 0.001 R/24 hours to about 0.4 R/24 hours (References B.0.10 and C.0.13). This range made the meter too sensitive for some radiation fields encountered during CROSSROADS (Reference A.2, pp. 7 and 8). The X-263 proved too delicate to function consistently under field conditions (Reference C.0.14, p. 3). Three hundred twenty of these instruments were available 2 days before BAKER (Reference C.0.12, p. 9). Every monitor tried to have three or four of them to assure that at least one would be working when he reached his post (Reference C.0.15, p. 3).

The 263 G.M. Set, an older version of the same instrument, also was used at Bikini, but information is lacking on the number available. Experienced monitors preferred it whenever accurate and reliable data were required (Reference C.0.12, p. 18).

The 247 Survey Meter measured gamma radiation only. Its range was from 0.5 to 200 R/24 hours, and it was often used for measuring intensities beyond the range of the X-263. It was rugged, spray resistant, and held its calibration well (Reference A.2, pp. 7 and 8; Reference C.0.12, p. 23). Twenty of these were available for monitoring after the BAKER detonation (Reference C.0.14, p. 3).

Pocket dosimeters were designed to measure cumulative gamma dose up to about 0.3 R. About 160 were issued for the BAKER test. They were relatively rugged and easy to repair. Apparently they were often issued to divers (Reference C.0.12, pp. 27 and 28).

Several other instruments were available to the monitors, although in numbers smaller than the X-263, the 247, and the pocket dosimeter. The L&W survey meter measured between 0.001 and 25 R/24 hours. Twelve were in service following BAKER. They were used mostly by boarding parties and by special groups, such as the target monitor group. The head of the monitor group wrote

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