Instrumentation and Methods
A)
Ion Chamber Measurements
All environmental exposure rate measurements were obtained using a Reuter
Stokes environmental radiation monitor model RSS-111.
The instrument is
designed to measure environmental radiation as low as 100 wRad/year.
The
RSS-111 consists of a spherical high pressure ion chamber filled to 25 atmospheres of argon.
Incident radiation produces ion pairs within the active
volume of the chamber which result in a current flow.
The current flow is
measured by an electrometer and is directly related to the free air exposure
rate (1).
The active volume of the stainless steel ionization chamber is known to
+01%.
The current produced inthe chamber is a function of incident radiation
from an external field, cosmic ray-response and contamination found in the
Stainless steel.
The equation relating instrument response to energy of the
incident radiation is:
Rj = Kj Ij + Ra + Ke Ic
where
Rj = current produced in the chamber by the incident
gamma field
Kj = proportionality constant stating the variability of
instrument response to the energy of the incident
gamma field
Ij = intensity of the gamma field in »R/hr
Ry = current produced by activity in the stainless steel
Ke = proportionality constant for cosmic rays
Ic = intensity of cosmic rays