Chapter 5 | CONCLUSIONS and RECOMMENDATIONS 5.1 CONCLUSIONS The gamma radiation field over fallout-contaminated ocean was successfully surveyed by aerial detectors after Shots Zuni, Navajo, and Tewa. No fallout was found in the sea following Shots Cherokee and Mohawk. Contamination on the aircraft determined the minimum detectable dose rate over the sea. Airborne radioactive material was encountered by the survey aircraft on D+1 day after Shot Flathead. These isodose plots therefore were limited to the relatively hot close~in fallout area. 5.1.1 Altitude Absorption. The field measurements of gamma dose rate at various altitudes over contaminated land and water areas agree with the relationships developed by theoretical calculations. A 500-kev average gamma-emission energy was assumed, and this is substantiated by the ratio of readings of an energy-dependent detector compared to the readings of an energyindependent detector. 5.1.2 Fallout Distribution. A land-equivalent isodose plot may be inferred from the surveys ever the sea. For example, a fallout density of 0.36 megacurie/naut mi’, on a land surface, will result in 1 r/hr at 3 feet from the surface. The same fallout density in the sea, after mixing, will result in 0.88 mr/hr at 3 feet from the surface (Section 1.3.4). However, the location of the isodose contours must be corrected to the location of the ocean surface at the time of fallout. The repeat surveys on subsequent days after the shot indicate the distortion of the contours, and the direction and magnitude of the ocean currents at the surface. The 0.1 r/hr gamma dose rate at Parry Island 24 hours after Shot Tewa agreed with its location between the 0.025 and 0.25 r/hr land-equivalent isodose contours determined from the aerial survey over the sea. The land-equivalent conversion is based on uniform mixing of the fallout in the sea to a depth of 60 meters. Samples of sea water from various depths provided the data on which this esti- mate was based. While only a few stations could be sampled, the reproducibility of the areas enclosed by the isodose contours from aerial surveys on succeeding days indicate that the mix- ing becomes stabilized for a reasonable number of days after a shot. 5.1.3 Material-Balance Estimates. The conversion from fission-product contamination density to gamma dose rate could not be conclusively validated from the data available. However, estimates were made based on the calculated factors. The measuremen Ss, show no detectable fallout from the air burst, Shot Cherokee. The two water-surface shots, Flathead and Navajo, deposited of their fission-product yield as fallout in the local area percent, respectively, Shot Zuni was fired on a land site, and its fallout accounted ior of its fissionproduct yield. It is possible that the soil picked up in the fireball provides relatively heavy particles which, on condensation, fall to the surface faster than the products resulting from a water shot. The fallout from Shot Tewa, fired on a reef site, was approximately 30 percent of the total yield. DOE ARCHIVES 60 SECRET