Instrumentation and Methods A) Lon Chamber Measurements All environmental exposure rate measurements were obtained using a Reuter Stokes environmental radiation monitor model RSS-lLI1L. The instrument is designed to measure environmental radiacion as low as 100 .Rad/year. The RSS-LLL consists of a spherical high sressure ion chamber filled to 25 atmospheres of argon. Incident radiation sroduces ion pairs within the active volume of the chamber which result in a current flow. The currene flow is measured by an electrometer and is directly related to the free air exposure race (1). The active volume of the stainless steel ionization chamber is known to +025. The current produced inthe chamber is a function of incident radiation from an external field, cosmic tay-resvonse and contamination found in the stainless steel. The equation relating instrument response to energy of the incident radiarcion is: Rj] = Kj Ij} + Ra + Ke Ic where Rj * current produced in the chamber by the incident gamma field Kj = proportionality constant stacing the variability of instrument response to the energy of the incident gamma field Ij = intensity of the gamma field in -R/hr Ra = current produced by activity in the stainless steel Ke = proportionality constant Ic = intensity or cosmic rays for cosmic rays