Uncertainty evaluation of fluorescent nuclear track detectors (FNTDs) for neutron dose measurements

Abstract

Fluorescent nuclear track detectors (FNTDs) developed by Landauer Inc. are used as passive dosimeters for neutron dose measurements. Commercial FNTD readers are operated in a track counting mode for low dose neutrons (up to 50 mSv). In order to evaluate the ability of the reader to detect recoil proton tracks, the relationship between track densities of FNTDs and etch pit densities of CR-39 plastic nuclear track detectors (PNTDs) for 241Am-Be neutrons was compared. The relationship was linear in the range of the measured doses from 0.63 mSv to 13.30 mSv. The correlation indicates that both neutron dosimeters similarly detect the recoil proton tracks. The low limit of detection (LLD) using the reader was 1.44 tracks/mm2. In this measurement, the uncertainty of track counting was also evaluated. The relationship between track counts and coefficients of variation (CVs) agreed well with the Poisson distribution. According to the theoretical estimation and the LLD, more than 11.11 counts per 2.08 mm2 are needed to obtain CVs below 30%. In addition, decreasing the CV value was demonstrated by expanding the scan area. Therefore, there is a possibility to improve the measurement accuracy for the LLD with a wider scan area.