Calibration of non-discriminating scintillating instruments for sensitivities to naturally occurring gamma radiation emitting radionuclides at environmental concentrations

A method of calibrating non-discriminating gamma radiation detectors for environmental level measurements is described. It is based on a method used to calibrate field gamma spectrometers, and has several advantages over the more traditional point-source approach. Radiological measurements are taken on pads with known concentrations of potassium, uranium and thorium, and the sensitivities to these naturally occurring terrestrial sources of gamma radiation are determined. Measurements can then be converted into radionuclide concentration or exposure rates.