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.