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 crew was berthed. The decontamination report (Reference C.2.54) written by Prinz Eugen's commanding officer on 13 August appears to indicate a definite concern for radsafe matters.

The officer in charge of target ship monitors complained that work on the target ships had increased to the point where his men could not adequately protect the decontamination crews. As an example, he described the situation on USS Salt Lake City (CA-25), where from 3 to 7 August four of six monitors received exposures in excess of 0.1 R/24 hours, along with twenty other personnel of the ship's working teams (Reference C.0.11). On 10 August, the Medico-Legal Board recommended that work cease on Salt Lake City until 20 September, and the board's chairman in a minority report called for the ratio of monitors to decontamination personnel be increased from one to sixteen to one to ten and for all personnel working on target ships to be badged (References C.0.8 and C.0.21).

Discovery of Plutonium Contamination

Into this situation a new element was introduced (Reference C.9.185, p. 13): "On 9 August, The Director of Ship Materiel requested the Radiological Safety Officer and the Commander Target Group to visit ships on which ship's forces were employing the detailed decontamination procedures. During that inspection, samples of materials were obtained from areas of the wardroom of PRINZ EUGEN for which geiger counter readings showed radiation intensities sufficiently low to permit extended personnel exposure (8 hours) without danger of injury. An analysis of the samples revealed the presence of alpha emitters which were not detectable with monitoring instruments in use at Bikini. Further investigation showed probable widespread presence of the alpha emitter (plutonium) in the target area even in spaces not obviously contaminated."

It is unfortunate that this discovery, which so markedly affected subsequent CROSSROADS operations, is so poorly reported in the surviving documents. The only direct reference is the quotation above from the DSM report. It is not mentioned in the portion of the Technical Director's Report devoted to nuclear radiation (Reference C.9.209, Enclosure J), and although allusions to the existence of plutonium contamination and reports of laboratory determinations of the presence of plutonium can be found in the voluminous collection of papers of the Radsafe Section Chief, these do not appear to directly relate to Prinz Eugen.

The Chief of the Radsafe Section and his staff probably did not directly detect alpha emitters on Prinz Eugen. Instead, indirect evidence convinced them the hazard existed.

The difficulty of directly measuring alpha emissions with the field instruments of 1946 has been discussed earlier. The Radsafe Chief in a speech in 1947 said that beta activity was measured and then a ratio used to calculate alpha activity (Reference C.12.4, p. 23). Direct determination of alpha

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