Proof testing of atomic weapons ship countermeasures

The proof test of existing and proposed radiological countermeasures for naval ships and aircraft not in flight is presented in detail. In this part of Operation Castle, two test vessels, one equipped with a complete washdown system and the other not, were guided by remote control along relatively close courses through the fallout regions of four nuclear detonations. Operation of washdown during fallout, until approximately 10 hr after detonation, achieved a reduction in dose rate of 90 to 96% and a reduction in accumulated dose of 87 to 94% at exposed locations. Subsequent washing for 2 hr only increased these reductions to 93 to 97% for dose rate and 89 to 95% for accumulated dose. The accumulated dose at exposed locations was as much as 300 r at 10 hr after detonation. The transit dose (dose from fallout prior to deposition) was estimated to have minor significance on a nonwashdown ship.