Evaluation of Uncertainty Measurement of Radionuclides Minimum Detectable Activity in Large Plastic Scinllators

This work is devoted to the evaluation of the measurement uncertainty of minimum detectable activity (MDA) for
¹³⁷
Cs on its gamma radiation with large plastic scintillators (PS) used in the portal monitors (PM). The influence of scintillators volume and irradiation geometry on the MDA evaluation of the measurement uncertainty was studied. It is shown that the estimated expanded MDA measurement uncertainty interval on
¹³⁷
Cs is 21-23 per cent. The absolute value of the MDA measurement uncertainty when changing geometry of irradiation increases 10 times. Change in the volumes of the examined PS causes a change of MDA measurement uncertainty within 10 per cent.