Overview
ISO 9891:1994 specifies standardized analytical procedures for the determination of carbon content in uranium dioxide (UO2) powder and sintered pellets using high-frequency induction furnace combustion. The standard covers three measurement routes - titrimetric, coulometric, and infrared (IR) absorption - all based on combusting a sample in oxygen at elevated temperature and quantifying the evolved CO2. Applicable range: 5 µg to 500 µg of carbon per sample.
Key topics and technical requirements
- Combustion principle: Heat a test portion at ≥ 1100 °C to 1200 °C in an oxygen atmosphere using a high-frequency induction furnace; typical crucibles are quartz-encapsulated tungsten or platinum.
- Gas purification and traps: Evolved gases pass over a manganese dioxide layer and silver permanganate catalyst (oxidises CO to CO2 and removes sulfur/halogen interferences) before CO2 trapping.
- CO2 capture and measurement:
- Titrimetric/coulometric: CO2 is trapped in barium perchlorate solution (pH ≈ 10); pH change is corrected continuously by potentiostatic titrimetry or coulometry.
- Infrared: CO2 measured directly by IR absorption with signal integration.
- Ancillary systems: Oxygen purification and flow-control, calibrated gas injection valves (50 µl and 500 µl), buffer vessels and six‑way backflush valves to avoid atmospheric CO2 ingress.
- Calibration and quality control: Use certified reference materials (SRM steels) and blank checks; required absorption efficiency ≥ 95%. Precision: repeat measurements by one analyst should agree within 2 µg/g carbon or 5% of content, whichever is greater.
- Practical notes: UO2 powder can adsorb atmospheric CO2 and should be pre-treated; fluoride traces can damage IR detectors.
Applications
- Nuclear fuel production QA/QC: Control carbon impurities in UO2 powder and sintered pellets used for fuel fabrication.
- Materials characterization: Routine elemental carbon analysis in uranium dioxide for research, process optimization and failure analysis.
- Regulatory & forensic testing: Documented method for trace carbon quantification in nuclear materials required by standards bodies and regulators.
- Analytical chemists and technicians in nuclear fuel laboratories
- Quality assurance and process-control teams at fuel fabrication plants
- Metrology institutes and test laboratories performing certified elemental analysis
- R&D groups studying UO2 materials and sintering processes
Related standards
ISO 9891 was prepared by ISO Technical Committee ISO/TC 85, Subcommittee SC 5 (Nuclear fuel technology). It complements other international standards and methods for combustion and elemental analysis used in nuclear materials testing and industrial laboratory practice.
Keywords: ISO 9891, carbon content, uranium dioxide, UO2 powder, sintered pellets, high-frequency induction furnace, titrimetric, coulometric, infrared absorption, combustion analysis, nuclear fuel QA/QC.