Uncertainties in dosemeter intercomparison techniques.

Abstract

The results of 180 intercomparisons of field dosemeters with an NPL secondary-standard exposure meter (type 2560, with a type 2561 chamber) have been analyzed in order to study variations in readings when ionization chambers are interchanged during the comparison process. It is suggested that the percentage standard error of the mean of the combined series of chamber intercomparisons be used to set a target uncertainty (0.3%), action level (0.5%) and limit of acceptability (1.0%). The target uncertainty is consistent with IAEA estimates of uncertainty for this part of the calibration chain. It is shown that if the calibration procedure is repeated, the percentage difference between the geometric means calculated from each calibration (i.e. a single interchange of chambers) may be as high as +/- 1%. This reinforces the need for at least one repetition of the intercomparison procedure.