BS EN ISO 9696-2015 pdf – Water quality — Measurement of gross alpha activity in non-saline water — Thick source method.
1 Scope This International Standard specifies a method for the determination of gross alpha activity in non- saline waters for alpha-emitting radionuclides which are not volatile up to 350 °C. The method is applicable to raw and potable waters. The range of application depends on the amount of total soluble salts in the water and on the performance characteristics (background count rate and counting efficiency) of the counter. It is the laboratory’s responsibility to ensure the suitability of this method for the water samples tested. 2 Normatives references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3696, Water for analytical laboratory use — Specification and test methods ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and sampling techniques ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples ISO 5667-14, Water quality — Sampling — Part 14: Guidance on quality assurance of environmental water sampling and handling ISO 11929, Determination of the characteristic limits (decision threshold, detection limit and limits of the confidence interval) for measurements of ionizing radiation — Fundamentals and application ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated terms (VIM)
5 Reagents and equipment 5.1 Reagents Except for the certified reference solution, all reagents shall be of recognized analytical grade and shall not contain any measurable alpha activity. NOTE A method for preparing reagent blanks to check for endemic radioactivity or contamination is given in Clause 7. 5.1.1 Water, distilled or deionized, for all applications. 5.1.2 Certified reference solution A calibration laboratory establishes traceability of its own measurement standards and measuring instruments to the International System of Units (SI) by means of an unbroken chain of calibrations or comparisons linking them to relevant primary standards of the SI units of measurement. The link to SI units may be achieved by reference to national measurement standards. National measurement standards may be primary standards, which are primary realizations of the SI units or agreed representations of SI units based on fundamental physical constants, or they may be secondary standards which are standards calibrated by another national metrology institute. When using external calibration services, traceability of measurement shall be assured by the use of calibration services from laboratories that can demonstrate competence, measurement capability and traceability. The calibration certificates issued by these laboratories shall contain the measurement results, including the measurement uncertainty and/or a statement of compliance with an identified metrological specification.
The choice of alpha standard depends on knowledge of the type of radioactive contaminant likely to be present in the waters being tested. In general, this amounts to a choice between naturally occurring and man-made alpha emitters. Among standard solutions of artificial alpha-emitting radionuclides, 241 Am and 239 Pu are commonly used. The presence of other impurities in the chosen alpha standard, which may emit alpha particles or decay to an alpha-emitting progenies, shall be taken into account. When 241 Am is used, the potential interferences of its gamma emission, or alpha-beta crosstalk shall be taken into account (see Reference ). NOTE 1 A uranium compound of certified natural or known isotopic composition has one arguable advantage, as its specific activity can be calculated from established physical constants and isotopic abundance data which are independent of the calibration procedures of a particular organization. NOTE 2 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 transuranics. When the true composition is unknown, some authorities prefer to overestimate the results as a conservative approach. 5.1.3 Nitric acid, c(HNO 3 ) = 8 mol/l. 5.1.4 Sulfuric acid, c(H 2 SO 4 ) = 18 mol/l, r = 1,84 g/ml, mass fraction w(H 2 SO 4 ) = 95 %.