Page:Operation Crossroads 1946.pdf/139

 Taking samples for laboratory analysis was unnecessary, since analysis of the filter samples taken while sandblasting portions of Laffey's hull showed no detectable plutonium. Using the ratio of plutonium to fission products to calculate the amount of plutonium present led to an estimate that a worker using a respirator would have to spend 100 million days of wet-sandblasting to inhale a dangerous amount of plutonium. From this came the conclusion that ships up to 100 times as contaminated as Laffey could be sandblasted without exposing shipyard personnel to a lung hazard. Filter samples collected during welding of contaminated saltwater lines also revealed no plutonium. Calculations using the plutonium-fission products ratio indicated an individual would need to weld for 1,000 days to accumulate a dangerous amount of plutonium in his body (Reference C.9.185, pp. 32 and 33). The findings of the laboratory assays appeared to show that nontarget ships of JTF 1 could be decontaminated and overhauled without radiological hazard to personnel, but, as discussed below, that work did not go forward immediately because of fears among the experts that hard-to-detect dangers were still present (Reference C.9.185, pp. 32 and 33).

The Question of Clearance Standards

About 20 September, the DSM left San Francisco for Washington, D.C., to present the findings from the decontamination experiments to higher authority. In Washington he prepared a directive setting forth the decontamination procedures established up to that point. Issued on 24 September as a joint BuShups-BuMed speedletter, it included authority and direction for decontamination of evaporators, heat-transfer apparatus (except condensers ), hulls beneath the waterline, and ships' boats of all contaminated ships scheduled to remain in the active fleet. Members of each ship's crew were to clean the evaporators and heat-transfer apparatus as soon as practical. Hulls were to be cleaned below the waterline using standard wet sandblasting were to be kept wet until dumped at sea. Monitors were desirable but not essential for this work. Saltwater lines could be cut and welded without hazard, but sections removed were to be dumped at sea. All zinc plates used to retard electrolytic action were to be removed from main and auxiliary condensers and discarded at sea. Different rules were being developed to cover ships scheduled for disposal or deactivation (Reference C.9.187, pp. 16 and 19).

The DSM's directive was greeted with great enthusiasm by all commands concerned. The message from CJTF 1 on 9 September had led to fears that a great and indeterminant hazard to personnel was present. Now the hazard had been found to be minimal if the indicated safety precautions were taken. The methods to remove contamination were not too complicated, and regular maintenance could proceed more or less on schedule. BuShips representatives taking part in the work at San Francisco visited the 11th, 13th, and 14th Naval Districts at San Diego, Seattle, and Pearl Harbor, respectively, to brief shipyard management

134