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 on the decontamination procedures (Reference C.9.185, p. 36). Meanwhile, a vigorous program of decontamination experiments went on at the San Francisco Naval Shipyard in an effort to develop better methods.

However, considerable uncertainty persisted about whether the 0.1 R/24 hours standard, as measured with a Geiger counter or similar device, could be used for determining when a vessel required decontamination and when it could be considered safe and given clearance. No reliable instrument was available for determining the presence of absence of alpha contamination in the field. Analyses of the samples taken from Laffey, Whiting, Henrico, and Mount McKinley had provided an approximate ratio of plutonium to fission products, but no radsafe expert of recognized reputation was ready to declare that a Geiger of reading of 0.1 R/24 hours or less assured protection from the total alpha hazard, that is, from plutonium or any other alpha emitters (Reference C.9.185, p. 41).

Consequently, BuShips called a conference in San Francisco on 1 October to grapple with the problem. The decision was made to study contamination of USS Rockbridge (APA-228). At that time it was considered the most heavily contaminated ship to arrive in the area, and it was of a size and type judged suitable for a detailed study of wide implications. The hope was not only to improve the accuracy of the plutonium ratio, but particularly to determine the total amount of plutonium on the ship. The figure could then be used as the basis for the needed standards. Numerous samples were taken from the ship and sent to the University of California for analysis, but the University's facilities for radiochemical analysis were sufficiently limited that weeks passed before the results were available (Reference C.9.185, pp. 41, 45 and 46).

While awaiting the results of the work on Rockbridge, BuShips in Washington, D.C., on 10 October proposed a set of contamination limits. After discussions between naval and civilian radsafe experts on the west coast and BuShips and BuMed in Washington, the final clearance standard for all ships was set at 0.001 R/24 hours (gamma) from shielded sources and 0.005 R/24 hours (combined beta and gamma) from exposed surfaces, subject to change if required by new information. These limits required decontamination of almost all nontarget ships that spent more than one day in the Bikini Lagoon after BAKER (Reference C.9.185, p. 49). Twelve ships were found to be within radiological limits. These ships were associated with CROSSROADS, but either had never entered Bikini after Baker or had been in the lagoon following BAKER for 1 to 3 days. They were USS Charles P. Cecil (DD-835), USS Limestone (IX-158), USS LST-871, USS LST-989, USS Albemarle (AV-5), USS Panamint (AGC-13), USS Appalachian (AGC-7), USS Blue Ridge (AGC-2), USS Furse (DD-882), USS Turner (DD-834), USS Shangri-La (CV-38), and USS Bountiful (AH-9).

Decontamination work on a large scale apparently started after 14 October, when BuShips authorized crews of all nontarget ships, including those scheduled for disposal and deactivation, immediately to go forward with acid cleaning of evaporators and of firefighting, flushing, cooling, and drainage systems. At least 55 nontarget ships that had arrived at one of the west coast naval districts were involved. CINCPAC and ComWestSeaFron were to see that work was done. The final clearance limits recently agreed upon by BuShips and other interested parties were used, however, only as a temporary standard for

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