Feasibility of CaSO₄:Tm thermoluminescent dosimeter for environmental radiation monitoring

Error factors which should be considered in precise environmental dosimetry by CaSO₄: Tm TLD are investigated. It was found that errors originated from TLD materials themselves are small. (1) Fading during 1 month refered to the value 2 days after exposure is negligiblly small (<1%), and the temperature dependency of fading in the range of -5°∼40℃ is also negligible. (2) Light fading appearing in dosimeters with case which were left under sunshine during 1 month is within 0.8%. (3) Sensitivity change is not appreciable even after 3,000 cycles of exposure-reading-annealing procedure. Errors attributable to sensitivity difference and to reading reproducibility are somewhat appreciable, however, by using a group of elements (6 elements in 1 group) and by making reference exposure and calibration at each measurement the total error can be decreased below 3%. It is concluded that CaSO₄:Tm TLD is applicable to the measurement of environmental dose with a precision of 1% in the standard deviation. (auth.)