Performance of silver metaphosphate glass as dosimeter at elevated temperatures

The effect of temperature on silver-activated metaphosphate glass, used as a personnel monitoring dosimeter in the range 20 mR to 104 R using the property of radiophotoluminescence (RPL) and as an integrating device for high level dosimetry using the measurement of the optical absorbance changes due to the color centers produced in the glass, has been investigated. Any heat-treatment given to the glass dosimeter before the actual irradiation is observed to have a negligible effect on the dosimeter response, provided sufficient time is allowed to bring the glass down to room temperature (220C). This is true for RPL as well as for absorbance studies. Increase of temperature during irradiation seems to enhance the RPL as well as absorbance up to certain temperatures. Enhancement is maximum (approximately equal to 25%) around 2200C for RPL, whereas it is maximum at 1400C for absorbance. The RPL and absorbance behaviour following post-irradiation heat treatment are shown graphically indicating that a build-up in RPL can be accelerated by heat treatment at elevated temperatures (22 to 2500C). It is shown that the percentage build-up and fading with respect to time at all the temperatures is independent of the gamma exposure in the range 10 to 100 R. The observations show a reduction of only approximately equal to 1.5% in absorbance at 315 nm if 5 min heat-treatment at 1000C is given after normal room temperature irradiation. The present observations that the glasses can be used even at elevated temperatures make it a very useful dosimetric system. (U.K.)