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1.1 This test method covers the determination of the concentration of gamma-ray emitting special nuclear materials dissolved in homogeneous solutions. The test method corrects for gamma-ray attenuation by the solution and its container by measurement of the transmission of a beam of gamma rays from an external source (Refs. (1), (2), and (3)).2

1.2 Two solution geometries, slab and cylinder, are considered. The solution container that determines the geometry may be either a removable or a fixed geometry container. This test method is limited to solution containers having walls or a top and bottom of equal transmission through which the gamma rays from the external transmission correction source must pass.

1.3 This test method is typically applied to radionuclide concentrations ranging from a few milligrams per litre to several hundred grams per litre. The assay range will be a function of the specific activity of the nuclide of interest, the physical characteristics of the solution container, counting equipment considerations, assay gamma-ray energies, solution matrix, gamma-ray branching ratios, and interferences.

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. For specific hazards, see Section 9.

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.

5.1 This test method is a nondestructive means of determining the nuclide concentration of a solution for special nuclear material accountancy, nuclear safety, and process control.

5.2 It is assumed that the nuclide to be analyzed is in a homogeneous solution (Practice C1168).

5.3 The transmission correction makes the test method independent of matrix (solution elemental composition and density) and useful over several orders of magnitude of nuclide concentrations. However, a typical configuration will normally span only two to three orders of magnitude because of detector dynamic range.

5.4 The test method assumes that the solution-detector geometry is the same for all measured items. This can be accomplished by requiring that the liquid height in the sidelooking geometry exceeds the detector field of view defined by the collimator. For the upward-looking geometry, a fixed solution fill height must be maintained and vials of identical radii must be used unless the vial radius exceeds the field of view defined by the collimator.

5.5 Since gamma-ray systems can be automated, the test method can be rapid, reliable, and not labor intensive.

5.6 This test method may be applicable to in-line or off-line situations.