Novel thermoluminescent dosemeter for the measurement of the eye lens operational dose equivalent in mixed neutron-gamma radiation fields

Abstract

Based on ICRP 118 (2012) recommendations, the Canadian Nuclear Safety Commission amended the Radiation Protection Regulations in their recent document “REGDOC-2.7.2, Dosimetry, Volume I: Ascertaining Occupational Dose”, reducing the equivalent dose limit for the eye lens of a nuclear energy worker from 150 mSv to 50 mSv in a one-year dosimetry period and to 100 mSv in a five-year dosimetry period, and adding the personal dose equivalent at 3mm soft-tissue depth, Hp(3), to the list of Radiation Protection quantities, as the representative operational quantity for the dose to the lens of the eye. The Hp(3) operational quantity is measured using a dosemeter covered by 3mm of tissue-equivalent material. To date, despite there being some attempts to calculate eye-lens conversion coefficients for neutrons and to evaluate the dose due to occupational exposure by Monte Carlo simulations, no operational eye-lens dosemeters for mixed neutron-gamma fields have been developed anywhere in the world. The objective of this research was to design and manufacture a novel thermoluminescent dosemeter to measure directly the Hp(3) in mixed neutron-gamma fields. A prototype was developed and its applicability to the concurrent measuring of the neutron and gamma operational eye lens dose equivalents in a mixed neutron-gamma field was demonstrated both experimentally and by Monte Carlo simulation with the GEANT4 toolkit.