Evaluation of Bicron NE MCP DXT-RAD Passive Extremity Dosemeter

Abstract

Passive extremity dosemeters currently used in dosimetry communities worldwide have shortcomings. In general, an extremity dosemeter has too thick a detector element, and the dosemeter response is highly energy dependent for beta rays with energies ranging from 200 keV to 2 MeV. It often does not have dosemeter identification, causing problems in the chain of custody. It is often read manually, rendering reading/packing operations very labour intensive. As a result of collaboration between AECL and BICRON ✦ NE, a new extremity dosemeter, incorporating a highly sensitive LiF:Mg,Cu,P TLD and tentatively code named MCP DXT-RAD, was developed. It has been evaluated for radiological performance against an ISO draft standard for extremity dosemeters in twelve categories: homogeneity, detection threshold, beta ray energy response, beta angular response, photon energy response, photon angular response, reproducibility, stability under various climatic conditions, linearity, residue, self irradiation, and effect of light exposure. Test results, as detailed in this paper, show that this extremity dosemeter meets the ISO draft standards requirement in all categories except residue. Its 2nd reading residue (7%) is much higher than other TLD materials (0.2%). However, it was found that an annealing in the oven at 240°C for 10 min prior to the 2nd reading reduces the residue to 0.4%, comparable to that of other TLD materials. The greatest advantage of this dosemeter is that it can measure beta skin dose accurately over a wide range of beta energies.