ASTM C 1855:2018

1.1 This test method specifies the determination of the volumetric uranium and plutonium concentrations, typically, in nitric acid solutions through the combination of K-Edge absorption Densitometry (KED) and K X-Ray fluorescence (XRF) using an X-Ray generator. It is known as the "Hybrid K-Edge" (HKED) technique whose original implementation is described in Ref ( 1 ) . 2 The method is applicable to dissolver (input) solutions and product solutions. The test method also specifies the determination of low concentrations (50 g/L) of U and Pu using XRF measurements alone (the "stand-alone XRF" mode). Using the XRF measurement in the stand-alone mode, solutions in the 0.2 g/L to 50 g/L range of Pu with or without U and solutions in the 0.2 g/L to 50 g/L range of U with or without Pu are commonly measured. 1.2 This test method is applicable to the following common-use conditions: 1.2.1 Spent nuclear fuel reprocessing and fuel production. 1.2.2 Homogeneous aqueous solutions contained in cylindrical vials or cuvettes. HKED systems may use two separate sample containers, namely a rectangular cuvette for KED and a cylindrical vial for XRF. Alternatively, there are HKED systems that use a sample contained in a single cylindrical vial, for both K-Edge and XRF. 1.2.3 The results produced by the two sample configuration (a rectangular cuvette for K-Edge densitometry and a cylindrical vial for XRF) are compliant with the International Target Values (ITV) ( 1 ) . 1.2.4 The precision results produced by the single cylindrical vial configuration are degraded in comparison to the two container system. 1.2.5 This test method is applicable to facilities that do not adopt the ITVs, but have their own Data Quality Objectives (DQO). 1.2.6 Solutions which contain uranium and plutonium with uranium concentration of 150 to 250 g/L and a U:Pu ratio of 100:1 typically, in the presence of fission products with β, γ, activity of up to 10 TBq/L. 1.2.6.1 This test method is not applicable to samples where a minor element such as U needs to be quantified in which Pu is the major element. 1.2.6.2 This test method is applicable for common use process control applications for quantifying Pu in the 5 g/L to 30 g/L range using XRF only in the presence of up to ~10% (~100 000 ppm) of transuranic impurities (predominantly U and Am). In this application, the impurity concentration in the Pu samples is not quantified. Additional uncertainties must be estimated and factored in the Pu concentration results. 1.2.7 Solutions containing 50 g/L to 400 g/L of uranium alone. 1.2.8 Solutions containing 50 g/L to 400 g/L of plutonium alone. 1.2.9 Solutions with low concentrations of U and Pu, typically in the 0.2 g/L to 50 g/L range. 1.2.10 The concentration ranges given in 1.2.6 - 1.2.9 are application of the HKED technique for Materials Control and Accountancy (MC&A) purposes. For process control applications where precision requirements are less stringent, KED method can be used to assay samples with lower concentrations of U or Pu (down to 30 g/L). 1.3 Units- The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 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. 1.5 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.