ISO 8769:2020 pdf download – Measurement of radioactivity — Alpha-, beta- and photon emitting radionuclides — Reference measurement standard specifications for the calibration of surface contamination monitors.
3.3 saturation layer thickness <of a source constructed of a homogeneous radioactive material> thickness of the medium equal to the maximum range of the specified particulate radiation 3.4 instrument efficiency ratio between the instrument net reading (counts per second after background subtraction) and the surface emission rate of the reference measurement standard (particles emitted per second) in a specified geometry relative to a standard Note 1 to entry: The instrument efficiency depends on the energy of the radiation emitted by the standard, the area of the standard, and the area of the detector entrance window. 3.5 self-absorption <of a source> absorption of radiation which occurs within the material of the source itself 3.6 uncertainty standard uncertainty (k = 1) unless otherwise stated Note 1 to entry: The treatment of uncertainties is in accordance with the ISO/IEC Guide 98-3 [8] to the expression of uncertainty in measurement. 3.7 uniformity <of a surface in respect of a given property> indication of the lack of variation of that property over the surface
National metrology institutes shall, at their discretion, provide the means whereby Class 1 reference measurement standards of a specified range of radionuclides may be certified by them. For those countries which are signatories to the Mutual Recognition Arrangement (MRA) [9] , a certificate of calibration from another participating institute in a second country is recognized as valid in the first country for the quantities, ranges, and measurement uncertainties specified in Appendix C of Reference [9]. The activity and surface emission rate of Class 1 reference measurement standards shall be measured, using, for example, a windowless gas-flow proportional detector, or by using an instrument that has been calibrated using standards that have been measured absolutely. Calibration procedures for activity determination are discussed for example, in References [10], [11], [12] and [13]. Organizations with a requirement to type test and to calibrate instruments to be used for monitoring radioactive surface contamination need to have access to suitable Class 1 or Class 2 reference measurement standards. The purpose of a working measurement standard is to check the calibration of surface contamination monitors in the field; they are not to be confused with check sources, which are only intended to verify that a monitor is operating.