Examination of the long-term stability of radiation survey meters and electronic pocket dosemeters.

To describe the stability of radiation survey meters (RSMs) and electronic pocket dosemeters (EPDs), we examined 28 EPDs and 24 RSMs: 12 used NaI(Tl) scintillation RSMs and 12 used Geiger-Muller(GM) RSMs. We used simple methods for the relative calibration of the 24 RSMs and 28 EPDs. The RSM and EPD measurements were compared with a calibrated RSM and EPD (reference: traceable from the national standard of exposure) using a homemade measurement device to maintain the reproducibility of the measurements with reference radiation sources (i.e. 137Cs, 90Sr and 67Ga). The response of RSMs and EPDs, especially after prolonged use, should be checked periodically. In particular, GMRSMs that have been in use for many years have very low sensitivity and poor reproducibility. Our simple method for the relative calibration of RSMs and EPDs was shown to be effective for quality assurance purposes in checking RSMs and EPDs. We recommend regular checks and calibration for sustained performance of RSMs and EPDs.