DIN ISO 7503-3:2017-12

In most cases it is not possible to identify or distinguish the different radionuclides involved in surface contamination, and the assessment of such contamination can then only be done on a qualitative basis. Instead of using measuring instruments calibrated for specific nuclides, it is necessary to use instruments that are generally suitable for such purposes. However, there may be cases, such as contaminated nuclear fuel shipping casks, where the single radionuclide or radionuclide mixture that caused the surface contamination can be clearly determined. It may then be necessary to make a determination of surface contamination that goes beyond a purely qualitative assessment of fixed or non-fixed contamination. In addition, a comparison shall be made between a measured surface contamination activity per unit area and the surface contamination guide values or limits, as specified in national regulations or international agreements. The surface contamination guide values are radionuclide-specific and therefore require complex calibrations of the measuring instruments that are specific to the radionuclide in question. The quality of the calibration shall ensure that no underestimated readings are obtained that falsely suggest compliance with the given surface contamination guideline or limit values. The determination of a surface contamination caused by a mixture of radionuclides with known radionuclide constituents (that is, with a known radionuclide vector) necessitates the use of appropriate calibration factors. This Part 3 of ISO 7503 addresses these instrument calibration requirements. It focuses on the detailed development of a nuclide-specific calibration methodology, taking into account the overall correction that is absolutely necessary. The Annexes in this Part 3 describe calibration procedures that are simplified but provide conservative values in terms of radiation protection requirements. This part of ISO 7503 also refers to the following: - calibration laboratories or institutions dealing with radionuclides with complex emission characteristics or radionuclides for which no reference calibration sources are available; - institutions confronted with the task to evaluate surface contaminations consisting of a radionuclide mixture; - institutions/authorities controlling nuclear material transports or material/equipment clearance according to national legislation guideline values or international convention limits. The responsible committee is DKE/GUK 967.2 "Aktivitätsmessgeräte für den Strahlenschutz" ("Radiation protection instrumentation") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.