wunean Curry Ll march 1953 distribute this activity both to the cist and west. Under previlling _wind conditions for the Castle conoupt, the grast aajority of Lagoca contamination should be contained in the northern half of tha lagoon. Chango in wind eonditiona can cause small amounts of north ind scutt. diffusion as wns exemplified during Operation Ivy. During this operation, the lageon was samplod for radiocctivity at the surface and thirty fet below the surface on a dcily basis. Station a was loestod at the ligoon side of tha deep entrance, station B was located at the Lagoon’ side of the wide passage, station C was located on tne lagoon side of Rigili Island, station D was 4s lagoon location three miles northeast of Rigili Island, station EB was a sid- lagoon location half way between Rigili and Runit Island, station F was @ lagoon location three alles weet of Runit Island, station G was & lagoon location two ailes south of the detonation, and station H was an anchorage loeation at the Rendova buoy. Sxamination of the Sampling resilts indicestes that the southern portion of the lagoon remins relatively frees of contamination, the southwest passags tands to remove contaxination from the western seator, and tho bulk of residual contamination tends to remain in the northesasturn sector of tha lagoon. 6. Contaminstion Ships that are reqaired to re-entcr the Bikini Lagoon or northern seator of iniwetok Lagoon following tha surface detonations will become radioactiviy contaminated. This dows not mean that personnal «board the vessels will be subjectod to serious health hasards, but rather that wator evapors.tors, water distribution lines, ind microorganisas adhering to the bottoa of the ship will tand to concuntrate the radio active sirtieles of tho ligoon to 1 degree that extensive decontasinstion procedurse may be nucussitatod st the campl.tion of tho oper-tion. During Operation Crossrosds, the roontry of the non-targst vossele to tha contnminatad lagoon was fallowed oy 1 period in which mdic- Active mtcrials tanded to sdhore to tae outar enell below the wet or line. The conditions here were ideal for lon-exmhange and although tne water iteelf showed 4n intonsity of radioactivity 1% or cesr thc sur faeo of only. about 10 millircontgms per day (far bolow any tolurance Lieit) the active mttor wns sbecorbded so afficiantly fran thu l:goon waters that within a period of thre. diys several of the non-target vessels began to show readings of greatcr thin 100 miliircentgens per day of gaum radiation inside the hull in the vicinity of the witurline. In addition, salt wator lines and salt wot.r systems continuously eireulating water in fire mins, condensers and evnpor-tors, Sugin to show increasing gemma mdistion readings on exterior surfaces to the cxtent that curtain sroas adjscent to thesa systums ware in axcass of tolerance, E¢