Establishing a Secondary Standards Dosimetry Laboratory

Abstract

The role of an SSDL is to provide its users with a link to the international measurement system through its calibration services. In addition to traceable calibrations, SSDLs disseminate information, experience and expertise in metrology, dosimetry and calibration procedures. Some SSDLs also provide dosimetry audit services to check the implementation of dosimetry procedures in hospitals and/or personnel dosimetry programmes. The difference between a PSDL and an SSDL lies in the way each determines the reference quantity used for calibration purposes. An SSDL uses a reference secondary standard instrument together with calibration coefficients that are provided by a PSDL. A PSDL, having a primary measurement standard for a given dosimetry quantity, establishes the quantity based on fundamental physical principles and can determine this without reference to any other instrument that measures the same quantity. Establishment of primary dosimetry standards is not covered in this publication. However, regardless of the difference in the determination of the reference values, the facility, equipment and calibration procedures of PSDLs and SSDLs are similar, and the guidelines given in this publication could also be applied in PSDLs. The definitions of primary and secondary standards are clear, but the naming of the laboratory is not always as straightforward. Some laboratories might hold both primary and secondary standards and some countries use different names for their SSDLs (e.g. accredited dosimetry calibration laboratories in the United States of America). However, the term SSDL has been used throughout this publication.