Performance evaluation of vertical feed fully automated TLD badge reader using 0.8 and 0.4 mm teflon embedded CaSO4:Dy dosimeters

The personnel monitoring of more than 80,000 radiation workers in India is at present carried out by semi-automated TLD badge Reader systems (TLDBR-7B) developed by Radiation Safety Systems Division, Bhabha Atomic Research Centre. More than 60 such reader systems are in use in all the personnel monitoring centers in the country. Radiation Safety Systems Division also developed the fully automated TLD badge reader based on a new TLD badge having built-in machine readable ID code (in the form of 16x3 hole pattern). This automated reader is designed with minimum of changes in the electronics and mechanical hardware in the semiautomatic version (TLDBR-7B) so that such semi-automatic readers can be easily upgraded to the fully automated versions by using the new TLD badge with ID code. The reader was capable of reading 50 TLD cards in 90 minutes. Based on the feedback from the users, a new model of frilly automated TLD badge Reader (model VEFFA-10) is designed which is an improved version of the previously reported fully Automated TLD badge reader. This VEFFA-10 PC based Reader incorporates vertical loading of TLD bards having machine readable ID code. In this new reader, a vertical rack, which can hold 100 such cards, is mounted from the right side of the reader system. The TLD card falls into the channel by gravity from where it is taken to the reading position by rack and pinion method. After the readout, the TLD card is dropped in a eject tray. The reader employs hot N2 gas heating method and the gas flow is controlled by a specially designed digital gas flow meter on the front panel of the reader system. The system design is very compact and simple and card stuck up problem is totally eliminated in the reader system. The reader has a number of self-diagnostic features to ensure a high degree of reliability. This paper reports the performance evaluation of the Reader using 0.4 mm thick Teflon embedded CaSO4:Dy TLD cards instead of 0.8 mm cards