SCATTERED GAMMA RADIATION MEASUREMENTS FROM A Co$sup 60$ CONTAMINATED FIELD

A 90 deg sector of a circle of 604-foot radius was contamirated with cobalt-60 point sources to an approximate level of 1.72 millicuries per square foot, as a means of simulating an area approaching an infinite contaminated field. Radiation measurements were made in an open hole with a PDR-27A radiac instrument and Dupont 553 film to determine the percentage of the total radiation which is due to scattered radiation (skyshine). It was found to be approximately 10 plus or minus 4 percent. These measurements were made at selected points from approximately 36 inches above to 25 inches below ground level. Data were obtained in a miniatare basement to determine the attenuation of the skyshine by various thicknesses of concrete on the roof. Additional data were obtained to determine the energy of the scattered radiation as a function of the angle above the plane, using a total absorption gamma spectrometer. The unshielded effective energy for dose considerations ranged from 0.90 to 0.12 Mev for elevation angles from 10 to 80 deg above the plane. All the instrunnentation was placed in the vicinity of the apex of the radiation field. (auth)