that the radioactive constituents can comprise as much as 0.01 per cent of the total fallout. Hence, most of the properties of the contaminant except the radiation characteristics will be essentially determined by the inactive elements, Therefore, emphasis wes placed on determining the states of the inactive constituents and the states of a few impor~ tant gamma emitting elements, 1.1.4 Proof Testing Atomic Warfare Countermeasures for Ships There has been extensive laboratory and field scale development work on atomic warfare (AW) countermeasures for ships.2/ Project 6.4 tested the washdown system at CASTLE and corducted decontamination operations on the ships used in the operation. Since the contamination found from certain of the shots of CASTLE differed from either real or simulated contaminants previously studied, detailed knowledge of the properties of the contaminant was needed for interpreting these results. Information on the rate of radioactive decay, gross gamma energy spectrum, and the ratio of beta to gamma rediation was furnished by Project 2.68.