TR DB Set Part lla - Radiological Safety’ 1. Discussion A temporary washdown system consisting of hoses and special no7zles comected to the fire main system, like that used in IVY, was ‘dustalled by a =uShins representative on all mamed ships engaged in CASTLE, with the exception of the USS TaiaXONI. The TAWAXONI reported to CTG 7.3 for the overation with a washdown system already installed by the ship's force frem standard ship's fire fighting equipment (noses, nozzles end applicators), ané this system was found quite satisfactory and was used throughout the cperation as necessary. The theory behind a waskdown system is that radioactive particles landing on a dry deck will tend te settle in pores, cracks and fissures, while nearly all of the same particles falling on a wet deck with weter flowing. over it will ve carried over the side. This theory is well borne out by the results of the ships in CASTLE, including the experiment with two YAGa, only ene of which carried a weaidow system. The washdowm systems reduced contamination of weather surfaces to a small fraction.of what it was on surfaces not protected by a washdewn systen. It wes found late in the operation that. largs areas of the sea's surface are ‘eimificantly radioactive after a "bargo"™ shot. (Although there is no positive evidence on the subject, there is reason to belleve that this effect is also present on "land" shots though probably to a mich smaller degree). These areas may extend for several hundred miles downwind trom the ahot site.and versist for several days. 7iffusion and settling seemedto be Slow, decreased 3.) tt? mo ~-