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 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. 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 or surfactant agents Vinyl acetate.
5.1.4 Volatile organic solvents Ethyl alcohol.
5.1.5 Water Water, complying with the requirements of ISO 3696, grade 3.
5.1.6? Specific? reagents? for? alpha-emitting? radionuclides? co-precipitation Ammonium hydroxide solution, c(NH 4 OH) = 6 mol/l. Nitric acid, concentrated, c(HNO 3 ) = 15,8 mol/l. Sulfuric acid solution, c(H 2 SO 4 ) = 1 mol/l. Iron carrier, solution of 5 mg of iron per millilitre. Barium carrier, solution of 5 mg of barium per millilitre.
5.2 Equipment
5.2.1 Laboratory equipment for direct evaporation
Usual laboratory apparatus to store and prepare the sample as specified in ISO 5667-3.
A hot plate, an automatic evaporator or any other appropriate apparatus.
5.2.2 General equipment Filters, of pore size 0,45 µm. Planchet (counting trays).
The planchet shall be lipped and of stainless steel. The diameter of the planchet is determined taking  account of the detector diameter and source holder dimensions of the counter used. In the specific case of co-precipitation, an annular support is used to fix the filter on to a filter holder or on to the planchet.
As the source, test portion and standard, is spread directly on to the planchet for evaporation, it is easier to produce an even deposit on a roughened metal surface; sand blasting or chemical etching can be applied for this purpose, alternatively, a rippled planchet can be used.
5.2.3 Special equipment for alpha-emitting radionuclide co-precipitation Hot plate with stirring equipment. Infrared lamp. Vacuum filtration system. Filters, of pore size 0,45 µm.
5.2.4 Measurement equipment Alpha-beta counter.
Gross alpha and gross beta activity can be measured using either a silicon surface barrier (SSB) detector or a proportional counter (windowless). Ion-implanted Si detectors and window-proportional counters (between 80 µg cm −2 to 400 µg cm −2 ) may also be used. Gross alpha and gross beta activity can also be counted using a silver-activated zinc sulfide scintillation screen and plastic scintillation detector,respectively.BS EN ISO 10704 pdf download.