IAEA TLD based audits for radiation protection calibrations at Secondary Standard Dosimetry Laboratories. International Atomic Energy Agency.

The IAEA has developed a TLD system with the aim of checking 137Cs radiation protection calibrations provided by the Secondary Standard Dosimetry Laboratories (SSDLs). The SSDLs are supplied with TLDs and they are asked to irradiate them at 5 mGy air kerma. The dosemeters are evaluated by the IAEA. The routine service was established in 1999. The service is organised in two runs per year. Each run involves 15 laboratories. The results of two pilot studies (1997-1998) and audits (1999-2000) are presented. They show that about 30% of the results are outside the acceptance limit of +/-3.5%. This limit has been set up as an acceptable deviation and is based on the value of the relative standard uncertainty of the TL measurements, evaluated at 1.8%. Participants with results outside the acceptance limit were approached with the aim to resolve discrepancies.