Page:Operation Crossroads 1946.pdf/115

 DECONTAMINATION OF HEAVILY CONTAMINATED TARGET VESSELS AT BIKINI

Decreasing lagoon radioactivity by 27 and 28 July allowed the Director of Ship Material (DSM) aboard USS Reclaimer (ARS-42) to survey other target ships from a distance of 50 to 100 feet (15 to 30 meters). Of the 92 target vessels, only 10 ships in the target array and 20 landing craft beached on Bikini islands had readings less than 0.1 R/24 hours by 2000 on 3 August (Reference C.11.19). Since "the nature and extent of contamination of the targets was completely unexpected, no plans had been prepared for organized decontamination measures" (Reference C.9.185, p. 4). As a result, the Technical Director and the DSM could not complete their programs in a timely way unless a means could be found to decontaminate the target vessels.

Washdown of Target Ships

After conferring with members of the Radiological Safety Section, the DSM took the lead in trying to remove contamination from the target vessels with materials and equipment immediately available to the task force at Bikini. First, task force firefighting equipment was used. Use of firefighting equipment is shown in Figure 34 as USS Achomawi (ATF-148) uses its forward monitor to wash down USS New York (BB-34).

Firefighting vessels of Task Unit (TU) 1.2.7, the Salvage Unit, twice attempted to wash down the heavily contaminated USS Hughes (DD-410) with saltwater on 27 July. The first effort produced a 50 percent reduction in radiation levels, but the second did not lower the radiation level. Next, foamite, a foam-like preparation used for smothering fires, was tried. Foamite was plentiful and was hoped to have a detergent action on the contamination adhering to Hughes. Fireboats sprayed Hughes with foamite and then with saltwater. Figure 35 shows the beached Hughes whitened by the foamite as two Salvage Unit ships stand by.

The reduction in radioactivity led to a decision to use foamite and saltwater until a better method was devised. The foamite and saltwater method, however, could be used only after waiting for the lagoon water to become virtually free of contamination. Radioactivity from the lagoon would itself contaminate both target and firefighting ships. Moreover, because the foamite and saltwater method was not totally effective, a search for better methods continued (Reference C.9.185, pp. 5 and 6).

Early Experiments in Decontamination

At a meeting on 27 July, attended by the DSM and members of the Radiological Safety Section, the radiological safety (radsafe) group was directed to study the decontamination problem. It selected pieces of contaminated equipment and blasted them with ground corncobs, coconut shells, barley, rice, ground coffee, rice hulls, and sand. Sandblasting worked best, but it was not suitable for general decontamination of the more than 60 contaminated vessels of the target fleet (Reference C.9.185, pp. 6 and 7).

Observation had revealed that most radioactivity stemmed from radioactive material collecting on painted or rusty surfaces, or on exposed organic materials, such as canvas, life rafts, manila lines, swabs, brooms, wood decks,

110