Environmental Factors Affecting Glass Rod Dosimetry

Abstract

Application of glass-rod dosimetry- is increasing in field radiation ecology studies. To qualify certain of these field uses, a study was made on the influence of temperature and sunlight on radiation response (fluorescence) of Toshiba low-Z rods. In a temperature range of 3.5 to 53.5°C, rods showed no change in response to beta radiation from ¹³⁷Cs solutions. The response to ¹³⁷Cs gamma rays, however, increased with increasing temperature. A linear expression describing this increase is Y = 4,32 – 0.014X, where Y is fluorometer units per rad, and × is temperature (°C). Predosed rods were found to fade (lose fluorescence) exponentially when exposed to sunlight for 30 hr, given in 6-hr increments at about 40 ft-c. Rods lost 37 to 46% of the dose during the first 6-hr exposure. Fading was also related to predose, as high-predosed (5515 fluorometer units) rods had a significantly greater (P < 0.01) percentage of fading than low-predosed (396 fluorometer units) rods. The effectiveness of several kinds of shields was studied, and nylon plastic shields painted black were found to prevent fading when tested by 24-day exposures on White Oak Lake bed.