wathV (FLATHEAD) DP Project 2.10 =~ Verification of Washdown Effectiveness as a Shipboard Radiological Countermeasure - M, M, Biggers ' Objectives Operation of YAG's and LST to be stationed in fallout area RadSafe support for NRDL Projects Washdown evaluation Procedure and Results - Ship Operations The project ships, YAG=39, YAG-40, and LST-61l, successfully completed their mission on the FLATHEAD) shot. Precise information in ships position and other operational information has been given Project 2.63 for inclusion in their reports, YAG- " erations YAG=39 encountered fallout at 1030 of D-day (12 Jume). At 1100, when the gamma radiation intensity had increased by 2 mr/hr, the ship was closed and washdown activated. The radiation level peaked at 1800, Deday, with an intensity of 140 - 150 mr/hr. on the unwashed deck forward, and 10 = 14 mr/hr on the unwashed deck aft, was 8.4 mr/hr. Peak intensity on the bridge Fallout apparently stopped at the same time it peaked (1800). Washdown was secured at 1950, the ship partially opened at 2115 and complet- ely opened at 2400. YAG-LO Operations: YAG-40 encountered fallout (i.e. a 2 mr/hr increase in gamma radiation intensity) at about 1415 on D-day, Watch was transferred to the bridge and the ship closed except for several hatches, When the radiation intensity reached 20 to 30 mr/hr at 1600, the engine room hatch was closed and the washdown system was activated, COPIED DOE bate RO - 39 - Peak intensity occurred at about aU