‘ APPENDIX C RAD SAFE GAMMA SURVEY READINGS The following tables contain a fairly complete list of gamma residval radiation readings as obtained by the Task Group 7.1 Radiological Safety unit. These readings were primarily intended to be used as a guide for the Rad Safe Unit Commander to determine the conditions for access of personnel to contamimted areas during the field phase of the operation. The readings were subject to a multitude of variables, as was to be expected in field measurements of this type: readings were not always taken at the same location on or above the island; winds may have moved the debris around and concentrated it in "hot spots" and conversely, "cold spots"; rain may have leached some of the activity from the debris; and the AN/PDR-39 gamma survey meters which were used for the surveys were subject to both instrumental and operational errors. In the field, Rad Safe used a rough “rule of thumb" to convert the air readings taken from helicopters to ground readings which could be used as a guide for recovery and working parties in contaminated areas, The readings at 50 ft or higher above the ground were multiplied by 3 to estimate the corresponding ground readings, and readings taken at 25 ft were multiplied by 2 to estimate the corresponding ground read- ings. It must be borne in mind that these readings are subject to a variety of influences such as the energies of the redioactive nuclides in the contaminated area, which may vary with time after the shot, the size of the island and the radiation field from it, and the radiation field which may come from the water surrounding the island. As an example of the latter, note the 25 ft readings on Yoke, Zebra, Alfa, and Bravo on three days after Shot 2. The 25-ft readings are from 2.3 to 5 times higher than the land ground readings as a result of the contamination in the water around these islands. It should also be noted that secondary fallout occurred on the Oboe-Tare chain during the night following Shot 2. These data are used here with the permission of the Task Group 7.1 Radiological Safety Unit Commander and are included in this report be- cause they provide a background for understanding the results of the fallout and residual contamination projects. Where several readings were available from one island on the same day, an average of the readings was usually made, An asterisk by a reading denotes a reading made by Project 2.5b personnel at the Project 2.5b station on that ialand. vg