radiation sources. Some of these parameters have beer orev ie irus investigated. principally for other than underwater-detonation conditions. In past calculations of Shipboard radiation attenuaticn, the n.ajor emphasis has been given to residual contamination on ships’ weather surfaces (Reterenc: 1!, with some work done for a ship enveloped in a radioactive volume? of air (Reference 2), assuming monoenergetic gamma radiation and uniform contamination in an idealized geometry. (Shielding calculations are in progress at NRDL, which for both residual contaminant and remote-source radiation take the entire radiation-energy spectrum into account and which eliminate much of the need for idealized geometries in the caSe of remote-source radiation. : Gamma radiation from Sources outside a ship has been investigated during various phases of the fallout environment from land-surface and water-surface megaton-range detonations during Operations Castle (Reference 3) and Redwing (Reference 4) and, to a very-limited ex- tent, during Operation Wigwam (Reference 5) for a deep-underwater detonation, using Liberty ships (YAG’s 39 and 40) as the test vehicles. * Oy Sasaro alee arth The experimental results from Operations Castle, Redwing, and Wigwam indicated that attenuation factors inside ships were dependent not only upon the geometries of the ships’ structures but also upon: (1) the geometries and relative magnitudes of the various radiation sources, which depend upon detonation conditions and also change with time: and (2) the gamma-energy Spectra, which are functions of time and weapon design. « n