BS ISO 7503-2:2016 pdf free

BS ISO 7503-2:2016 pdf free.Measurement of radioactivity一Measurement and evaluation of surface contamination
Indirect evaluation of surface contamination is more generally applicable when the surfaces are not readily accessible because of difficult location or configuration, where interfering radiation fields adversely affect contamination monitors or when methods of direct measurement with standard instrumentation are not available [e.g. tritium]. Also, the indirect method cannot assess fixed contamination, and, due to the uncertainty associated to the wiping efficiency, application of this method results in conservative estimations.
Due to the inherent shortcomings of both the direct measurement and the indirect evaluation of surface contamination, in many cases, the use of both methods in tandem ensures results which best meet the aims of the evaluation.
Tritium and its compounds are special case. As a nuclide of hydrogen, tritium has great mobility and may penetrate into a surface [e.g. along grain or crystal boundaries) to a depth that makes the indirect evaluation of the tritium surface contamination very difficult. This holds also for other mobile radionuclides.
In many cases, tritium contamination is present in the form of contaminated water, which can evaporate,making the tritium airborne. Because of the ability of tritium (as HT, T2or HTO) to diffuse and substitute hydrogen against tritium in hydrogen containing compounds, tritium contaminations are found on and in the surface. Therefore, special care shall be taken when evaluating tritium surface contamination.
The total surface contamination cannot be accurately evaluated in any cases. Indirect measurements performed by dry or wet wipe tests generally provide only a “best guess” of the removable surface contamination at the time of collection. Because of diffusion (e.g. as HTO) into the surface, absorbed tritium contamination tends to replace the removable surface contamination that was partially or totally removed by a decontamination process or by wet wipe tests. Therefore, a radiological hazard from volatile tritium may still remain. BS ISO 7503-2 pdf download.