Reassessment of radiation doses using TL dosemeters - a fresh look

Thermoluminescent (TL) CaSO4:Dy - teflon dosemeters are currently in use for country wide monitoring of external X, β and γ radiations, over 2x10-4 - 10 Gy. Using a TL readout cycle of 60 s at T max of 280 degC empties out charge carriers from the main dosimetric peak (220 degC). Exposure of the readout dosemeters to the visible spectral region repopulates 120 degC and 220 degC TL peaks, giving rise to photo transferred thermoluminescence (PTTL). PTTL response of the dosemeters, observed to be proportional to the initial radiation exposure, is a useful tool for assessment of the initial radiation doses. Results obtained using 254 nm, 310 nm, 365 nm and high pressure mercury lamp are presented. PTTL output using 365nm photons is around 11 - 15 % of the first TL signal. Reproducibility of the PTTL based reassessed doses is 10-12 % (σ). (author)