ISO 7097-2:2022

Overview - ISO 7097-2:2022 (iron(II)/cerium(IV) titrimetric method)

ISO 7097-2:2022 defines a validated analytical method for the determination of uranium in solutions, uranium hexafluoride (UF6) and solid uranium materials using an iron(II) reduction / cerium(IV) oxidation titration. Intended for nuclear fuel technology and safeguards, the method is precise enough for nuclear materials accountability and for analysis of common feed and product forms (U metal, UO2, UO3, U3O8, uranyl nitrate hexahydrate and UF6). The titration is performed as a mass titration to a potentiometric end point, and the procedure emphasizes accuracy, interference control and calibration with certified reference material.

Key topics and technical requirements

• Principle: Uranium(VI) is reduced to U(IV) with Fe(II) in phosphoric acid; excess Fe(II) is removed, then U(IV) is titrated by standardized Ce(IV) solution to a potentiometric end point. Vanadium is used to promote reaction kinetics.
• Sample size and titration scale: Typical aliquots contain ~15–25 mg U for the titration to optimize precision.
• Mass titration recommendation: Weighing an aliquot and using mass titration is recommended to improve reproducibility and accuracy.
• Interferences and limits: The method tolerates many matrix elements; fission products equivalent to up to 10% burn-up do not interfere. Specific impurity tolerances and potential interferents (e.g., As, Sb, Mo, Mn, halides, platinum-group elements) are specified and should be considered for each sample.
• Reagents and safety: Use analytical-grade reagents and high-purity water (ISO 3696 grade). The document includes handling considerations for aggressive reagents such as hydrofluoric and nitric acids.
• Automation and routine use: The standard recognizes advantages of using automatic devices for critical steps in routine laboratory workflows.
• Environmental benefit: Unlike the dichromate-based method in Part 1, this procedure does not produce a toxic mixed waste stream from potassium dichromate.

Applications - who uses ISO 7097-2:2022

• Nuclear fuel manufacturers and converters performing product quality control (U metal, UO2 pellets, UF6, uranyl nitrate).
• Safeguards, regulatory and accounting laboratories needing accurate uranium assay for inventory and accountability.
• Research and analytical labs working on reactor fuel materials and process control where uranium analysis, precision and low interference are required.

Related standards and references

• ISO 7097-1 (potassium dichromate titration method)
• ISO 10980 (reference material calibration guidance)
• ISO 3696 (water for analytical laboratory use)
• ISO 9894 (UF6 subsampling)
• ISO 5725-1 (accuracy, trueness and precision)

Keywords: ISO 7097-2:2022, uranium determination, cerium(IV) titration, iron(II) reduction, potentiometric titration, uranium hexafluoride, nuclear fuel analysis, mass titration, nuclear materials accountability.