On ISO 21909–1:2015 and the metrological performance of the Landauer Neutrak-T dosemeter

Abstract

Personal dosimetry for ionizing radiation is a regulated activity in Europe. More particularly, in France Individual Monitoring Services (IMS) are required to be accredited against ISO/IEC Standard 17025 (ISO 17025:2017) for the personal dose equivalent measurements they perform. In the field of external personal dosimetry for ionizing radiations, there are no standardized methods for routine measurements of participants' personal dose equivalent. Instead, the standards focus on defining protocols and associated acceptable performance limits for testing the measurement process. ISO Standard 21909 is the one related to passive neutron dosimetry systems. This standard has been completely revised and its newest version was published in 2015. The two versions of the standard differ in terms of methodology and performance limits. At the time when the new version was written its effects on system compliance were unknown. Landauer provides individual monitoring services for ionizing radiation dosimetry worldwide. The service for neutrons is based on an internally developed dosemeter called Neutrak® which has two versions: Neutrak-J for fast neutrons and Neutrak-T for fast and thermal. The study described here focuses on the neutron dosimetry system as implemented at the Paris office. This system has been tested by the UK National Physical Laboratory (NPL) against ISO 21909–1:2015. The NPL is one of the few calibration laboratories able to cover the extensive series of tests required by the standard. The purpose of this paper is twofold. Firstly, it aims to present the differences between ISO 21909:2005 and ISO 21909–1:2015 for non-linearity, reproducibility, energy-angle dependency and fading. This illustrates the challenges arising from ISO 21909–1:2015 and should prove useful to other IMSs since, to the authors’ knowledge, the work described herein is the first of its kind. The second aim is to document the results of the type test of the LANDAUER neutron dose measurement process based on the Neutrak-T dosemeter.