Monte-Carlo Evaluations for Response of the Gamma-ray Spectrometer with Various Locations on Calibration Pads

During a radiation emergency, especially due to accidental releases of radionuclides or weapon fallout, it is of prime importance to quickly determine the ground contamination and resulting exposure in planning and taking the necessary measures and controls if required. Up to now, many methods have been developed for the purpose of doing this and aerial gamma spectrometry can be regarded as a very effective method for a rapid survey of large areas which might be possibly contaminated. Figure 1 shows the airborne gamma-ray spectrometer introduced from Sweden for the purpose of constructing the radiological survey system using aircraft (i.e. fixed-wing or helicopter) in South Korea. A large NaI detector, which has a dimension of 4'x4'x16' and is frequently used for high efficiency measurements of low level of gamma emitting radioactivity, is employed in the spectrometer. This paper describes Monte-Carlo investigations for response of the airborne gamma-ray spectrometer with various locations on transportable concrete pads