Overview
ISO 22875:2017 specifies a validated analytical method for the determination of chlorine and fluorine in uranium dioxide (UO2) powder and sintered fuel pellets. The standard covers sample preparation by pyrohydrolysis (steam-assisted thermal decomposition at 850 °C–1 000 °C) with subsequent measurement of chloride and fluoride ions by liquid ion chromatography (IC) or ion-selective electrode (ISE). It is applicable for chlorine mass fractions from 5 µg/g to 500 µg/g and fluorine from 2 µg/g to 500 µg/g.
Key topics and technical requirements
- Principle: Pyrohydrolysis traps halogens as acids, which are collected in aqueous solution for analysis.
- Measurement options:
- Ion chromatography (IC) - requires an eluent, suppressor and conductivity detection; calibration with chloride/fluoride standards.
- Ion-selective electrodes (ISE) - requires millivoltmeter calibration and appropriate buffer/conditioning.
- Apparatus: tubular furnace (up to 1 000 °C), steam generator, pyrohydrolysis tube (example: 400 mm × 20 mm), combustion boats, IC system or ISE setup, balances and volumetric glassware.
- Reagents and standards: Type 1 water, anhydrous NaCl and NaF, Na2CO3/NaHCO3 eluents, acetic acid/potassium acetate buffers, and calibration solutions prepared fresh.
- Procedural elements: calibration (IC and millivoltmeter), blank tests, separate procedures for powder and pellet samples, measurement of pyrohydrolysis solutions, and calculation of results including pyrohydrolysis yield if required.
- Quality control: validation limits, detection/ determination limits, and estimation of measurement uncertainty; formal test report requirements are specified.
- Updates in 2017 edition: lowered pyrohydrolysis temperature, added information on species decomposition, and result calculation adjustments for pyrohydrolysis yield.
Applications and users
ISO 22875 is intended for laboratories and quality assurance teams in the nuclear industry involved in:
- Fuel fabrication and quality control of uranium dioxide powders and sintered fuel pellets.
- Regulatory compliance testing where accurate halogen analysis (chlorine and fluorine) impacts corrosion, sintering behaviour, or fuel performance.
- Analytical service providers supporting reactor fuel manufacturers and research facilities performing trace halogen quantification.
Typical users: analytical chemists, nuclear fuel engineers, laboratory managers, and inspectors responsible for uranium fuel quality control.
Related standards
- ISO 3696 - Water for analytical laboratory use (reagent water quality).
- ISO 9892:1992 - Fluoride determination in uranium materials (ISE method), referenced for methodology alignment.
Keywords: ISO 22875, chlorine fluorine determination, uranium dioxide analysis, pyrohydrolysis, ion chromatography, ion-selective electrode, uranium fuel pellets, halogen analysis.
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