Page:Operation Crossroads 1946.pdf/123

 It seems more reasonable to assume that the phrase "not obviously contaminated" refers to more obvious criteria such as visible deposit of coral sand or presence of blast damage. What had actually been discovered was radioactivity in places that, because they were below decks or closed, were not expected to be contaminated. This probably was announced in an undated memorandum from the "Pill Counting Lab" (presumably the laboratory on USS Haven (AH-12) set up to analyze Program VII activation samples) to the Radsafe Advisor. The subject was "Dust Samples Taken in Crew Spaces on Prinz Eugen 9 August 1946." The memo states that B counts (the typewriter perhaps lacked Greek characters and this refers to beta counts) on four dust samples taken from certain given crew spaces were made and the results were from 0.00005 and 0.68 mc (perhaps micro-curies) per gram of dust. This memo further states that the background radiation measured in these spaces by an X-263 meter was 0.10 R/24 hours (Reference C.11.31).

This discovery, along with the assumption of the presence of plutonium wherever there was any radioactive material, led to the inference that plutonium had been discovered. This assumption was perhaps reinforced by the New York data that showed that plutonium was actually present in paint on the lookout platform. That information became available the same day as the CJTF 1 conference.

This interpretation of the events is strengthened by a telegram sent by the Radsafe Section Chief to the United States on 13 August and probably intended for the Oak Ridge Laboratory of the Manhattan Engineer District (Reference C.11.29). "UPON USING RATIONAL [sic] ALPHA BETAS FURNISHED BY YOU FIND INNER COMPARTMENTS ALL TARGET SHIPS HIGHLY CONTAMINATED BY ALPHAS." The reference to the ratio provided may refer to the results of analysis of ABLE or BAKER cloud samples done at Oak Ridge and made available at some time before 9 August.

In the light of what the surviving records show to be the actual knowledge of the degree of plutonium contamination, the decision to halt all further decontamination work appears to have been prudent and conservative. As the Medico-Legal Board recorded at their 13 August meeting at 1300 (Reference C.0.9.a): For safe guidance of the Operations from this time onwards, we need to know:


 * a. The number of alpha particles per second per square centimeter


 * b. The alpha tolerance for different types of surfaces.

Furthermore, special clothing and intensive training would have been required if major work on the target ships was to continue. According to a radsafe official (Reference C.11.4, p. 2):

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