radioactive debris associate? What out and mixing of fallout deposited Owing to the incompleteness CROSSROADS, essentially nothing was is the rate and extent of <ettling on the water surface? of the data taken at Shot Baker, known prior to CASTLE concerning the mechanism of formation of wet contamination from this type of burst, The relative contributions of base surge and fallout were uncertain; the roles of condensation, evaporation and mixing with sea water in the production of either base surge or fallout were unknown. Particle size and individual particle studies undertaken at JANGLE and IVY have ylelded considerable information on the mechanism of formaticn, dispersion and reactions of dry contaminants from these operations .2292%442/ 1.1.2 Assessment of Radiological Situations Extensive laboratory contamination-decontamination programs have been undertaken to solve presumed field radiological problems but in many cases lack of fullescale test data has made it impossible to define them cleacly. For exarple, before CASTLE it had not been determined whether an interns] contamination hazard would be produced on ships by radioactive aerosols from an underwater detonation, because the nature of such aerosols was unknown; the relative contribution of gamma radiation from fallout in the water with that on contaminated ships could not be calculated because the rate of settling or mixing of the contaminant in the water was unknown. Insoluble perticies will cettle depend- ing on size and density while dissolved (ionic) contaminants will mix; colloidal material, if present, will mix and settle slowly. The assess- ment of such radiological situations and the development of countermensures require a knowledge of many physical and chemical properties of tho contaminant. Linited data exist with regard to the contaminants which may be produced by surface and underground detonations because of the atypical nature of the soils at IVY and JANGLE. No direct information has been obtained on the nature of contaminants from underwater detonations. For this reason, there is special interest in surface water shots which should produce a contaminant most similar in nature to that from an underwater detonation. 1.1.3 Specifications of Simulants for Radio ca it, t If meaningful laboratory contamination-decontamination results are to be obtained, it is essential that the artificial contaminants used must simulate real ones in chemical and radiochemical composition and in important chemical and physical characteristics. In the past, the radiochemical composition of artificial contaminants 14/has been based upon yields of various radicelements from slow fission of 0235, It ia important to know the extent of difference in fission yields for nuclear processes other than slow fission and whether induced activities contribute appreciably to the contamination. Finally, it is necessary to evaluate the relative contribution ¢ esch radiocelement to contamination fielde on the tasis of its yield and the number and energy of the gamma rays emitted by the various radionuclides of that element, 16