S = 1800 mR-day?-3 for destroyers, 1570 mR-day9-3 for all other ships, 2240 mR-day®-3 for PGMs(patrolcraft). C = 11.0 day! for all ships. The exterior hull gammaintensity (Ip) is then used to determine the averageinterior ship intensity. This analysis, as described in detail in Reference 4, results in an apportionmentfactor F,, which relates average interior intensities (1;) to exterior hull gamma intensities (Ij,) by the relation: I, = F,Iy - Therefore, the interior intensity at any time t after the detonationis given by: I(t) = F,St!-3 [1-exp (-CS!Dy ()}] . The saturation levels and apportionmentfactors (from Reference 4) are given below for the pertinent CASTLEship types. - Ship Type S (mR-day®-3) Fa ATF, ARS, ARSD 1570 0.39 DM 1800 0.39 LST 1570 0.33 Patrol Craft 2240 0.67 It was also observed at Operation CROSSROADS that steaming in clean water reduced the accumulated contamination by about half duringthefirst day after departing the lagoon,butthat subsequent steaming had a much smaller effect. In the model, it is assumed that both hull and piping intensities were reduced to half their departure values during the first day after departure from the lagoon, and that subsequent decay while out of the lagoon followed the r}-3 decayrate. Some elaboration of the steaming factor concept is required for application to CASTLE, where multiple lagoon departures and shots were involved. The first 50 percent achieved of 13