Determination of quality parameters from statistical analysis of routine TLD dosimetry data

Abstract

Following the as low as reasonably achievable (ALARA) practice, there is a need to measure very low doses, of the same order of magnitude as the natural background, and the limits of detection of the dosimetry systems. The different contributions of the background signals to the total zero dose reading of thermoluminescence dosemeter (TLD) cards were analysed by using the common basic definitions of statistical indicators: the critical level (L(C)), the detection limit (L(D)) and the determination limit (L(Q)). These key statistical parameters for the system operated at NRC-Negev were quantified, based on the history of readings of the calibration cards in use. The electronic noise seems to play a minor role, but the reading of the Teflon coating (without the presence of a TLD crystal) gave a significant contribution.

Analysis of the personal doses lower than the reporting level

“…Even if it is known and expected (German et al, 2006), this study proves that part of the TL signal of the personal dosemeters is due to the natural background radiation. This can affect the evaluation of the low doses in the individual monitoring of the occupationally exposed workers.…”