Uranium hexafluoride used to produce nuclear fuel must meet certain criteria for its isotopic composition as described in Specifications C 787 and C 996.

1.1 This method applies to the determinations of isotopic composition in hydrolyzed nuclear grade uranium hexafluoride. It covers isotopic abundance of ²³⁵U between 0.1 and 5.0% mass fraction, abundance of ²³⁴U between 0.0055 and 0.05% mass fraction, and abundance of ²³⁶U between 0.0003 and 0.5% mass fraction. This test method may be applicable to other isotopic abundance providing that corresponding standards are available.

1.2 This test method can apply to uranyl nitrate solutions. This can be achieved either by transforming the uranyl nitrate solution to a uranyl fluoride solution prior to the deposition on the filaments or directly by depositing the uranyl nitrate solution on the filaments. In the latter case, a calibration with uranyl nitrate standards must be performed.

1.3 This test method can also apply to other nuclear grade matrices (for example, uranium oxides) by providing a chemical transformation to uranyl fluoride or uranyl nitrate solution.

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