5.1 The most prevalent of the five radium isotopes in ground water, having a half life greater than one day, are 226Ra and 228Ra. These two isotopes also present the greatest health risk compared to the other naturally occurring nuclides of equal concentrations if ingested via the water pathway.5.2 Although primarily utilized on a water medium, this technique may be applicable for the measurement of the 226Ra content of any medium once the medium has been completely decomposed and put into an aqueous solution.5.3 This test method is based on a method previously published by Rushing, et al. (1).3 The general methodology and basis of the technique are similar to that of Ref (2).1.1 This test method covers the measurement of soluble, suspended, and total 226Ra in water in concentrations above 3.7 × 10−3 Bq/L. This test method is not applicable to the measurement of other radium isotopes.1.2 This test method may be used for quantitative measurements by calibrating with a 226Ra standard, or for relative measurements by comparing the measurements made with each other.1.3 This test method does not meet the current requirements of Practice D2777.1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.1.5 Hydrofluoric acid (HF) is very hazardous and should be used in a well-ventilated hood. Wear rubber gloves, safety glasses or goggles, and a laboratory coat. Avoid breathing any HF fumes. Clean up all spills promptly and wash thoroughly after using HF.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

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5.1 Radium is one of the most radiotoxic elements. Its isotope of mass 226 is the most hazardous because of its long half-life. The isotopes 223 and 224, although not as hazardous, are of some concern in appraising the quality of water. 5.2 The alpha-particle-emitting isotopes of radium other than that of mass 226 may be determined by difference if radium-226 is measured separately, such as by Test Method D3454. Note that one finds 226Ra and 223Ra together in variable proportions (5, 6), but 224Ra does not normally occur with them. Thus, 223Ra often may be determined by simply subtracting the 226Ra content from the total: and if 226Ra and 223Ra are low, 224Ra may be determined directly. The determination of a single isotope in a mixture is less precise than if it occurred alone. 1.1 This test method covers the separation of dissolved radium from water for the purpose of measuring its radioactivity. Although all radium isotopes are separated, the test method is limited to alpha-particle-emitting isotopes by choice of radiation detector. The most important of these radioisotopes are 223Ra, 224Ra, and 226Ra. The lower limit of concentration to which this test method is applicable is 3.7 × 10-2 Bq/L (1 pCi/L). 1.2 This test method may be used for absolute measurements by calibrating with a suitable alpha-emitting radioisotope such as 226 Ra, or for relative methods by comparing measurements with each other. Mixtures of radium isotopes may be reported as equivalent 226Ra. Information is also provided from which the relative contributions of radium isotopes may be calculated. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For a specific precautionary statement, see Section 9.

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