HPS N13.37:2014

This standard is applicable to passive environmental dosimetry systems used to monitor areas surrounding radiological facilities to assess potential facility-related radiation doses and to verify compliance with public dose limits. Such environmental dosimetry systems include dosimeters which accumulate radiation dose and any readout device required to process the dosimeters. Passive dosimeters include thermoluminescence dosimeters (TLDs), optically stimulated luminescence (OSL) dosimeters, and direct ion-storage dosimeters, which are deployed at field locations around a facility and exchanged periodically (e.g., quarterly). Dosimeters could be processed at the facility or off-site.
Sections 1 through 4 of this standard cover the overview, definitions, general considerations and a summary of requirements and recommendations. Sections 5 and 6 describe laboratory type tests to determine the fundamental performance characteristics of a specified dosimetry system design and establish criteria that will enable a level of bias and precision in field measurements suitable for quantifying the radiological impact of facility operations on members of the public and the surrounding environment. Section 7 of this standard provides implementation performance objectives, requirements, and recommendations for field measurements using a dosimetry system that has satisfied the performance criteria in Section 5 and 6.
Establishing conformance with this standard requires fully documenting the system design. The system design is defined to include the dosimeters, readout equipment and other processing hardware as well as the equipment configuration, operating/processing procedures, and dose calculation methods used for type testing. All of these play a significant role in determining system performance.1 If a specific documented system design has been tested and shown to meet the performance criteria in Sections 5 and 6, then the test results are applicable to any processor implementing the same system design.
It is important to note that the type tests in Sections 5 and 6 are not intended as tests of a particular processor but rather as tests of a specific system design. Some manufacturers may offer turn-key systems (hardware and software) and recommended operating procedures that have been optimized for environmental monitoring. Others offer systems with flexibility in configuration and operation that allow the processor to design a system tailored to their needs. It is ultimately the processor who determines the final system design that is implemented and which is the subject of the type tests in this standard. 2 It is recognized that the end user must sometimes take certain actions that alter the system design that has been tested (e.g., additional dosimeter packaging or field mounting hardware). When this is the case, the end user shall document that those changes have not altered the basic performance characteristics that were determined in the type tests.
Purpose
This standard provides performance test methods and criteria for system design and implementation of environmental radiation dosimetry systems used to measure external photon radiation.
1 For example, with TLD and OSL systems, depending on the particular detector material used, the preirradiation anneal treatment and readout protocols (e.g., time-temperature profile for TLD, or optical stimulation wavelength, power, and duration for OSL) can significantly impact the sensitivity, reproducibility, and minimum quantifiable dose for a system, as well as the fading characteristics of the system. The dose calculation algorithms used can significantly influence the angular and energy dependence of dose results. Because routine dose calculation methods are called for in many of the type tests, details of those methods shall be included in the documentation of the system design that is tested.
2 The distinctions between manufacturer and processor and processor and end user are not always clear. In some cases, the manufacturer and processor may be one and the same, or have a close working relationship. In other cases (e.g., 'in-house' dosimetry programs) the processor and end user may be one and the same, or have a close working relationship. The term 'processor' is used generically here to refer to the laboratory in which dosimeters are prepared and processed (i.e., readout and results reported to end user).