Exposure To Personnel
All Crossroads operations were designed to keep personnel from being exposed to more than 0.1 roentgen (R) per day. At the time, this was considered to be an amount of radiation that could be tolerated for long periods without any harmful effects on health. Since there was no special clothing or radiation shielding available, the protection plan relied on managing who went where, when, and for how long.
Radioactively "hot" areas were predicted in advance, and then checked with Geiger counters, sometimes by remote control, to see if they were safe. The level of measured gamma radiation determined how long personnel could operate in them without exceeding the allowable daily dose.
Instant gamma readings were taken by radiation safety specialists, but film-badge dosimeters, which could be read at the end of the day, were issued to all personnel believed to be at the greatest radiological risk. Anyone whose badge showed more than 0.1 R / day exposure was removed for one or more days from areas and activities of possible exposure. The maximum accumulated exposure recorded was 3.72 R, received by a radiation safety specialist.
A percentage of each group working in less contaminated areas was badged. Eventually, 18,875 film-badge dosimeters were issued to about 15% of the total work force. On the basis of this sampling, a theoretical total exposure was calculated for each person who did not have a personal badge. As expected, exposures for target ship crews that reboarded their ships after Baker were higher than those for support ship crews. However, the hulls of support ships that entered the lagoon after Baker became so hot that sleeping quarters were moved toward the center of each ship.
Of the total mass of radioactive particles scattered by each explosion, 85% was unfissioned plutonium which produces alpha radiation not detected by film badges or Geiger counters. There was no method of detecting plutonium in a timely fashion, and participants were not monitored for ingestion of it.
A summary of film badge readings (in roentgens) for July and August, when the largest number of personnel was involved, is listed below:
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