ISO 10704:2019 pdf free.Water quality一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 coprecipitate deposited on the planchet being measured WI.
When suspended matter is present, filtration through 0,45 itii filter media is required and the gross alpha and gross beta activity can also be determined for the material retained on the filter.
IMPORTANT — Gross alpha and gross beta determinations are not absolute determinations of the sample alpha and beta radioactive contents, but relative determinations referenced to specific alpha and beta emitters that constitute the standard calibration sources.
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 olaipha standard depends on the knowledge 01 the type 01 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
241Am solutions and 239Pu solutions. When 239Pu is used, the presence of 241Pu as an impurity shall be taken Into account as it leads to growth of 241Am in prepared standard solutions of sources. When 241Am is used, take into account the interferences of its x and y emission.
NOTE A uranium compound of certified natural or known isotopic composition has one arguable advantage, in that its specfic activity can he 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.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.The laboratory sample is not usually acidified as the test portion is directly evaporated on the planchet. Acidification minimizes the loss of radioactive material from solution by adsorption on the wall of the vial, but is done after filtration, as otherwise it desorbs radioactive material already adsorbed on the particulate material and, also, increases the salt content of the test sample, and thus the thickness of the deposit. If necessary, concentrated nitric acid can be used (it is recommended to avoid hydrochloric acid).ISO 10704 pdf download.