Comparison of laboratory and in situ evaluation of environmental TL dosimeters

The passive environmental gamma-radiation dosimetry is mainly based on TL (thermoluminescent) dosimetry. This method offers considerable advantages due to its high precision, low cost, wide range, etc.. At the same time its application involves uncertainty caused by the dose collected during the transport from the point of annealing to the place of exposure and back to the place of evaluation. Should an accident occur read-out is delayed due to the need to transport to a laboratory equipped with a TLD reader. A portable reader capable of reading out the TL dosimeter at the place of exposure (in situ TLD reader) eliminates the disadvantages mentioned above. A microprocessor based portable TLD reader was developed by us for monitoring environmental gamma-radiation doses. Using a portable reader for in situ evaluation there are several disadvantages as well. The method requires the transport of the reader instead of dosimeters. The portable reader should be battery operated with low power consumption. Due to this requirement the temperature stabilization of the reader requests different solution as in laboratory type devices. Comparison of recently developed in situ and traditional laboratory evaluation methods of environmental TL dosimeters is given in recent paper. The comparison was made in the same conditions. The most characteristic - for environmental monitoring - numerical TL data (dose range, reproducibility, fading, self dose etc.) are given for manufactured by us CaSO4:Dy bulbs (portable reader) and very advantageous, high sensitive Al2O3:C dosimeters (laboratory evaluation). (author)