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. Designation: C1855 - 18 INTERNATIONAL Standard Test Method for Determination of Uranium and Plutonium Concentration in Aqueous Solutions Using Hybrid K-Edge Densitometry and X-Ray Fluorescence1 This standard is issued under the fixed designation C1855; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. 1. Scope 1.2.6 Solutions which contain uranium and plutonium with 1.1 This test method specifies the determination of the uranium concentration of 150 to 250 g/L and a U:Pu ratio of volumetric uranium and plutonium concentrations, typically, in 100:1 typically, in the presence of fission products with β, , nitric acid solutions through the combination of K-Edge activity of up to 10 TBq/L. absorption Densitometry (KED) and K X-Ray fluorescence 1.2.6.1 This test method is not applicable to samples where (XRF) using an X-Ray generator. It is known as the “Hybrid a minor element such as U needs to be quantified in which Pu K-Edge" (HKED) technique whose original implementation is is the major element. described in Ref (1).2 The method is applicableto dissolver 1.2.6.2 This test method is applicable for common use (input) solutions and product solutions.The test method also process control applications for quantifying Pu in the 5 g/L to specifiesthedeterminationoflowconcentrations(<50g/L)of 30 g/L range using XRF only in the presence of up to ~10 % U and Pu using XRF measurements alone (the “stand-alone (~100 000 ppm) of transuranic impurities (predominantly U XRF"'mode).UsingtheXRFmeasurement inthestand-alone and Am). In this application, the impurity concentration in the mode, solutions in the 0.2 g/L to 50 g/L range of Pu with or Pu samples is not quantified. Additional uncertainties must be without U and solutions in the 0.2 g/L to 50 g/L range of U with estimated and factored in the Pu concentration results. or without Pu are commonly measured. 1.2.7 Solutions containing 50 g/L to 400 g/L of uranium 1.2 This test method is applicable to the following common- alone. 1.2.8 Solutions containing 50 g/L to 400 g/L of plutonium use conditions: 1.2.1 Spent nuclear fuel reprocessing and fuel production. alone. 1.2.2 Homogeneous aqueous solutions contained in cylin- 1.2.9 Solutions with low concentrations of U and Pu, drical vials or cuvettes. HKED systems may use two separate typically in the 0.2 g/L to 50 g/L range. sample containers, namely a rectangular cuvette for KED and 1.2.10 The concentration ranges given in 1.2.6 - 1.2.9 are a cylindrical vial for XRF. Alternatively, there are HKED application of the HKED technique for Materials Control and systems that use a sample contained in a single cylindrical vial, Accountancy(MC&A)purposes.Forprocesscontrolapplica- for both K-Edge and XRF. tionswhereprecisionrequirements arelessstringent,KED 1.2.3 The results produced by the two sample configuration method can be used to assay samples with lower concentrations (arectangular cuvetteforK-Edgedensitometryandacylindri- of U or Pu (down to 30 g/L). cal vial for XRF) are compliant with the International Target 1.3 Units-The values stated in SI units are to be regarded Values (ITV) (1) as standard. No other units of measurement are included in this 1.2.4 The precision results produced by the single cylindri- standard. cal vial configuration are degraded in comparison to the two 1.4 This standard does not purport to address all of the container system. 1.2.5 This test method is applic