ASTM D7939-15

5.1 This test method is considered a rapid method when compared to other classical methods for the determination of ²⁴¹Am in aqueous solutions. During the method validation of this method, a test batch of fourteen test samples plus quality control samples was chemically processed in ~7.5 hours. Additional time for counting the samples depends on the measurement quality objectives.

5.2 This test method is specific for Americium-241 (²⁴¹Am) in drinking water and other aqueous samples. However, if any isotopes of curium are present in the sample, they will be carried with americium during the analytical separation process and will be observed in the final alpha spectrum.

5.3 This test method is capable of achieving a required method uncertainty for ²⁴¹Am of 0.070 Bq/L at an analytical action level of 0.555 Bq/L. This test method is capable of achieving a required relative method uncertainty, φ_MR, 13 % above 0.555 Bq/L. This test method is capable of achieving a “required” minimum detectable concentration (MDC) of 0.055 Bq/L.

5.4 To attain these stated measurement quality objectives (MQOs), a sample volume of approximately 200 mL and count time of at least 1 to 3 hours are recommended. The sample turnaround time and throughput may vary based on additional project MQOs, the time for analysis of the final counting form, and initial sample volume. This test method should be validated before use following the protocols provided in Method Validation Guide for Qualifying Methods Used by Radiological Laboratories Participating in Incident Response Activities.4

5.5 This test method is intended to be used for water samples that are similar in composition to drinking water. This method was evaluated following the guidance presented for “Level E Method Validation: Adapted or Newly Developed Methods, Including Rapid Methods” in Method Validation Guide for Qualifying Methods Used by Radiological Laboratories Participating in Incident Response Activities and Chapter 6 of MARLAP, 2004.1.1 This test method is specifically for Americium-241 (²⁴¹Am) in drinking water and other aqueous samples. However, if any isotopes of curium are present in the sample, they will be carried with americium during the analytical separation process and will be observed in the final alpha spectrum. The presence of ²⁴³Am in the water sample will bias the results obtained by this test method.

1.2 This test method is applicable to samples in which radioactive contamination is from either known or unknown origins. If any filtration of the sample is performed before starting the analysis, those solids should be analyzed separately. The results from the analysis of these solids should be reported separately (as a suspended activity concentration for the water volume filtered) but identified with the filtrate results.

1.3 This test method is applicable to the determination of soluble ²⁴¹Am. This test method is not applicable to the determination of ²⁴¹Am in highly insoluble particulate matter possibly present in water samples contaminated as a result of a radiological dispersal device (RDD) event.

1.4 This test method uses rapid radiochemical separation techniques for determining americium in water samples following a radiological or nuclear incident. Although, with this test method, concentrations of ²⁴¹Am on the same order of magnitude as methods used for the Safe Drinking Water Act (SDWA) can be detected, this test method is not a substitute for SDWA-approved methods for ²⁴¹Am.

1.5 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.

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 and health practices and determine the applicability of regulatory limitations prior to use.