A New High-Sensitivity Thermoluminescent Dosimeter for Short-Term Personnel Dosimetry

A new dosimeter is described which is capable of dose measurement down to sufficiently low levels for personnel to be monitored on a daily or hourly basis if required. However, unlike other low-level dosimeters previously in use the fading of the stored signal is small enough for this effect to be neglected in routine use. Applications of the new dosimeter include the assessment of doses received by visitors to a nuclear site before they have left the site boundary with very much greater accuracy and reliability than is possible using conventional condensor chambers (Q.F.E.'s). The new dosimeter consists of a dispersion of calcium sulphate: dysprosium thermoluminescent dosimetry phosphor in Teflon (PTFH). The resulting dosimeter can detect doses of less than 1 mrad and has acceptable fading of the stored signal at environmental temperatures. Data are presented on the precision of the dosimeter at various dose levels, the linearity of the response with dose, the fading of the stored signal as a function of time and temperature, and the sensitivity to natural and artificial light levels. An installation is described suitable for use by unskilled personnel which would permit monitoring of visitors to a nuclear site or a nuclear area. The main feature of the installation is the capability to immediately measure actual doses received down to meaningful levels for an exposure of only a few hours at low dose levels. (author)