Personal monitor glass badge: theoretical dosemeter response calculated with the Monte Carlo transport code MCNPX

Personal dosimetry at the Paul Scherrer Institute

The Paul Scherrer Institute (PSI) is the largest research institute for natural and engineering sciences in Switzerland. PSI develops, builds and operates complex large research facilities. Every year, >2400 scientists from Switzerland and around the world come to PSI to use the facilities and to carry out experiments. Many areas at PSI are radiation protection areas. Depending on the radiation protection area, the work carried out and the time the users spend in these areas, they have to carry a personal dosemeter. PSI runs an individual monitoring service in compliance with the Swiss legislation on radiological protection and approved by the Swiss Federal Nuclear Safety Inspectorate. The service provides about 35 000 dosemeters per year for the internal and external customers consisting of whole-body dosemeters for photons and neutrons as well as extremity dosemeters. This paper gives an overview on the employed personal dosimetry techniques by the individual monitoring service of PSI, the number of distributed dosemeters for internal and external customers and statistics about the measured doses at PSI over 30 years.

RPL Neutron Dosimetry in n-γ Fields in Comparison with Polymer Detectors Type CR-39

Previously we characterized radiophotoluminescent (RPL) detectors for measuring both fast and thermal neutrons for personal monitoring. The linear response and angular dependence, which satisfies the ISO 21909 standard makes their application possible in neutron dosimetry. The polymer CR-39 track detectors remain one of the most used dosimeters where neutron radiations are to be measured, but the visualization process is time consuming. The difference between results obtained by RPL and CR-39 has been discussed mainly for fast neutrons. The present study has also looked at thermal neutron dosimetry, where we found few results in the literature for CR-39. Our measurements demonstrate that RPL detectors can be advantageously incorporated into a dosimeter to measure thermal neutrons.

DEVELOPMENT OF THE NEW GLASS BADGE

The glass dosemeter, which is a component of the glass badge (GB), is used on the basis of radiophotoluminescence phenomenon. Chiyoda Technol Corporation has been providing it for personal monitoring services since the year 2000. Through the experience acquired over 15 y, Chiyoda Technol Corporation has developed the New GB, which was brought into service in Japan for radiation monitoring in January 2014. The New GB was developed with the aim of improving radiation measurement methods, streamlining the provision of GB monitoring services and realising a user-friendly dosemeter. As the result, in this study, the measurable energy range covered for beta rays was expanded to include those emitted from ¹⁴⁷Pm, the directional dependency was improved, a film was designed to remove secondary electrons arising from interactions between incident photons and the metallic filters, and the arrangement of the metallic filters was optimised.

Calculated angular responses of an RPL dosemeter to photon and beta radiation

The calculated dose equivalent response as a function of the angle has been examined for the radiophotoluminescent (RPL) glass dosemeter that was exposed to narrow series X-ray, N-60, N-80, N-100, N-150, N-200, N-250, N-300, photon sources ((60)Co and (137)Cs) and beta-ray emitter ((90)Sr/(90)Y) while mounted on an ISO water slab phantom. The angular dose equivalent responses H(p)(10) and H(p)(0.07) were calculated using the Monte Carlo MCNPX code. The RPL dosemeter and the phantom were rotated in the horizontal and vertical planes from a variety of angles of interest. The results were compared with the experimental data. Good agreement was found between the measured and calculated values of the relative dose equivalent angular responses of the RPL dosemeter.