INTERLABORATORY BETA-SOURCE CALIBRATION USING TL AND OSL ON NATURAL QUARTZ

Laboratories using luminescence methods for dose reconstruction have t o make interlaboratory source calibrations-initially this will be a si ngle isotope beta or gamma source using one particular reference mater ial. The procedure requires not only the administration of exact doses to the material but also the uniform handling of the dosimetric mater ial and standardization of the procedures. An interlaboratory calibrat ion of an Sr-90 beta source was recently carried out by our five labor atories which are involved in a retrospective project. The reference m aterial was quartz but there were difficulties finding sufficient suit able quartz. Five different batches were obtained from the Merck compa ny and tested for sensitivity, linearity and stability of the 340 degr ees C peak, the 1992 batch was found to be the most appropriate. The i rradiations were performed at the Secondary Standard Dosimetry Laborat ory at GSF using a Go-60 source as well as the in situ measurements wi th an ionization chamber, calibrated to the primary standards of PTB B raunschweig. Irradiated and unirradiated quartz was distributed to the five laboratories and although different procedures were used for the rmoluminescence and optically stimulated luminescence, the source cali brations for the different laboratories agreed within +/-3% compared t o the previous calibrations of the laboratories.