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Investigation of Pre and Post Irradiation Fading of the TLD100 Thermoluminescence Dosimetry for Photon Beams

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R Faghihi

s sina1 , M Sadeghi2 , R Faghihi1,2*, S Sarshogh 2(1) Radiation Research Center, Shiraz University, Shiraz, Iran (2) Nuclear Engineering department, Shiraz university, Shiraz, Iran


SU-E-T-222 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:The pre-irradiation and post-irradiation fading of the Thermoluminescense dosimeter signals were investigated in this study.
Methods:Two groups of TLD chips with pre-determined ECC values were used in this study. The two groups were divided into 6 series, each composing of 5 TLD chips.The first group was used for pre-irradiation fading. 5 TLDs were exposed to a known amount of radiation from Cs-137 source, and were read out the next day. After seven days, the other 5 TLDs were exposed to the same amount of radiation and were read out after a day. The other series of 5 TLDs were also exposed after 7,19,28, 59, and 90 days, and were read out a day after irradiation. The loss in TLD signal were obtained for all the above cases.
The second group, was used for post-irradiation fading. All the TLDs of this group were exposed to a known amount of radiation from Cs-137 source. The 6 series composed of 5 TLDs were read out after 1,7,19,28,59, and 90 days.
The above-mentioned procedures for obtaining pre-irradiation, and post-irradiation fading were performed for three storage temperatures (25°C, 4°C, and -18°C).
Results: According to the results obtained in this study, in case of pre-irradiation fading study, the signal losses after 90 days are 12%, 24%, and 17% for 25°C, 4°C, and -18°C respectively. In case of post-irradiation fading study, the sensitivity losses after 90 days are 25%, 216%, and 20% for 25°C, 4°C, and -18°C respectively.
Conclusion: The results indicate that the optimized time between exposing and reading out, and also the optimized time between annealing and exposing is 1 day.The reduction of Storage temperature will reduce the post-irradiation fading, While temperature reduction does not have any effect on pre-irradiation fading.

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