Radiation Protection Dosimetry 34:99-102 (1990)
© 1990 Oxford University Press
Uniformity and Stability of LiF Sensitivity - A Review of Fourteen Years' Monitoring Experience
The Personnel Dosimetry Services of the Bureau of Radiation and Medical Devices have utilised an increasingly large pool of thermoluminescence dosimetry (TLD) plaques since 1976. Between 1975 and 1981, the volume increased from 60,000 to 180,000 to implement a change from films to TLDs. As of 1989, 317,000 plaques are in service. Most, but not all, of the thick and thin LiF-100 chips contained on each dosemeter plaque have been individually calibrated. Because the TLDs have been obtained over a period of fourteen years, it is possible to quantify the variation of response sensitivities for each batch purchased. A continued increase in sensitivity has been noted. Furthermore, because detailed records of use have been maintained, it is also possible to quantify information relating the purchased batch sensitivities to other parameters such as cumulative exposure, time of use, and number of readings. Some selected examples are given. Of most interest is the variation of sensitivity factors for individual LiF crystals in relation to the above parameters. Results for periods of one to fourteen years are presented.