BS EN ISO 9698:2019 pdf free

BS EN ISO 9698:2019 pdf free.Water quality一Tritium一Test method using liquid scintillation counting
The test portion is mixed with the scintillation cocktail in a counting vial to obtain a homogeneous medium. Electrons ( Beta particles) emitted by tritium transfer their energy to the scintillation medium.Molecules excited by this process return to their ground state by emitting photons that are detected by photodetectors[8].
The choice of the analytical procedure (either with or without distillation of the water sample prior to determination), depends on the aim of the measurement and the sample characteristicsl[19][20][21]. Direct measurement of a raw water sample using liquid scintillation counting[8] shall consider the potential presence of other beta emitter radionuclides. To avoid interference with these radionuclides when they are detected, the quantification of tritium is performed following the sample treatment by ditillation[22][23][24][25]. Annexes B, D and E describe three distillation procedures.
Liquid scintillation counter preferably with an automatic sample transfer. Operation at constant temperature is recommended following the manufacturer’s instructions. Depending on the limit of detection to be reached, a liquid scintillation counter with a low-level-configuration may be needed.The method specified in this document relates to the widely used liquid scintillation counters with vials that hold about 20 ml. When other vials are used with appropriate counters, the described method shall be adapted accordingly.
Different types of scintillation vials exist, manufactured using a range of materials. The most common are glass vials and polyethylene vials. Glass vials allow visual inspection of the scintillation medium,but have an inherent background, due to the presence of 40K. However, some organic solvents contained in scintillation cocktails diffuse through the polyethylene, accelerating the degradation of the mixture.
A monitoring program should be part of the laboratory quality system, in order to detect any potential cross contamination between samples with widely varying activity concentrations. The ambient air of the laboratory should be monitored for tritium, for example by measuring condensed humidity, free surface water from open vial, etc. or carrying out specific studies demonstrating the absence of risk of cross contamination.BS EN ISO 9698 pdf free download.