BS EN ISO 10704:2019 pdf download – Water quality – Gross alpha and gross beta activity – Test method using thin source deposit 4 Principle The gross alpha and gross beta activity of the deposit is measured by counting in an alpha- and beta-particle detector or counting system previously calibrated against alpha- and beta-emitting standards. In order to obtain a thin and homogeneous deposit directly on a planchet, the sample can be progressively evaporated to dryness at a temperature below about 85 °C. Alternatively, for the gross alpha determination, radionuclides can be concentrated via a co-precipitation, the filtered co- precipitate deposited on the planchet being measured [8] . When suspended matter is present, filtration through 0,45 µm filter media is required and the gross alpha and gross beta activity can also be determined for the material retained on the filter. 5 Chemical reagents and equipment 5.1 Reagents 5.1.1 General All reagents shall be of recognized analytical grade and shall not contain any detectable alpha and beta activity, except for radioactive standards solutions. 5.1.2 Standard solutions 5.1.2.1 Alpha standard. The choice of alpha standard depends on the knowledge of the type of radioactive contaminant likely to be present in the waters being tested. In general, this leads to a choice between naturally occurring and man-made alpha emitters. Commonly used standards of artificial alpha-emitting radionuclides employed for this purpose are 241 Am solutions and 239 Pu solutions. When 239 Pu is used, the presence of 241 Pu as an impurity shall be taken into account as it leads to growth of 241 Am in prepared standard solutions of sources. When 241 Am is used, take into account the interferences of its x and γ emission. NOTE A uranium compound of certified natural or known isotopic composition has one arguable advantage, in that its specific activity can be calculated from established physical constants and isotopic abundance date which are independent of the calibration procedures of a particular organization. However, a uranium compound of known isotopic composition is difficult to obtain. Furthermore, since the energies of the alpha emissions from uranium isotopes are less than those from the artificial transuranic nuclides, the use of a uranium standard tends to give a high result for transuranic elements. 5.1.2.2 Beta standard. The choice of beta standard depends on knowledge of the type of radioactive contaminant likely to be present in the waters being tested. 5.1.3 Wetting...
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