Effect of contamination of large-volume monitor inner surfaces on measuring volume gamma activity of water

Quantitative assessment is presented of the error in measuring the gross volume gamma activity of water, the error being due to the contamination of structural elements of the measuring instrument. In photon motion in water, all three basic photon interactions with matter occur (the photoelectric effect, the Compton effect and electron-positron pair production). The measured water samples were poured in a spherical sampling vessel with a detector in the centre. An analysis of the results shows that in low level counting, contamination is the factor limiting the determinable values of activity. (J.C.)