The Energy and Angle Dependence of Response to Photons of the NRPB Thermoluminescence Dosemeter in Terms of the New ICRU Quantities

Abstract

Abstract The ICRU has introduced the quantities ambient dose equivalent and directional dose equivalent for environmental monitoring; and individual dose equivalent, penetrating, and individual dose equivalent, superficial, for individual monitoring. The quantities are for use as secondary quantities within the framework of the system of dose limitation recommended by ICRP, which includes limits for effective dose equivalent for stochastic effects and for organ dose equivalent for non-stochastic effects. Measurements have been made of the energy dependence of the photon response of the NRPB thermoluminescence dosemeter mounted on a cuboid phantom, and of the energy and angle dependence of response of the dosemeter mounted on a 30 cm diameter spherical phantom. The phantom material was MS20, an epoxy resin based material designed to simulate muscle and found to be an acceptably close approximation to ICRU 4-element tissue. Values of exposures at the position of the dosemeter in the absence of dosemeter and phantom were converted to ICRU operational quantities using published conversion coefficients. Measurements were made for 137Cs and 60Co gamma radiation, the ISO narrow series of filtered X radiation (9 qualities, 33, 48, 65, 83, 100, 118, 161, 205 and 248 keV) and the ISO fluorescence series lower energy, 17.4 keV.