Overview
EN ISO 15651:2017 (identical to ISO 15651:2015) specifies a laboratory method for the determination of total hydrogen content in nuclear fuel materials: PuO2 and UO2 powders and UO2, (U,Gd)O2 and (U,Pu)O2 sintered pellets. The method uses inert gas extraction (argon or nitrogen carrier gas) and thermal conductivity (conductivity) detection with a hydrogen analyser. Reported measurement ranges cover powders (up to 2 000 µg H/g oxide) and sintered pellets (up to 10 µg H/g oxide).
Key topics and technical requirements
- Measurement principle: Rapid high‑temperature decomposition (>1 770 °C) in a graphite crucible to release hydrogen from adsorbed water, water of crystallization, hydrocarbons and other hydrogenated impurities; separation and detection of hydrogen by chromatography and a thermal conductivity cell.
- Temperature control: Heating to >1 770 °C within ≈5 s is required to ensure complete decomposition; avoid temperatures >2 200 °C to prevent CO2 formation from UO2–graphite reactions that interfere with detection.
- Carrier gas and purity: Use argon (≥99.995% v/v) or nitrogen (≥99.998% v/v). Calibration gases or certified mixes with known hydrogen are required for instrument calibration.
- Apparatus & consumables:
- Furnace and hydrogen analyser with thermal conductivity detector; furnace capable of at least 2 200 °C.
- High‑purity graphite crucibles (impurities ≤2 µg/g).
- Hydrogen‑free tin, copper or nickel capsules; analytical balance (1 mg resolution).
- Purification reagents/columns: CuO, anhydrone (Mg(ClO4)2), Schutze reagent, Hopcalite, NaOH over clay.
- Sampling and sample handling:
- Powder samplers with diameter >2.5× maximum particle size; exposure to ambient air limited to ≤5 minutes unless handled in a glove box.
- Store samples in tight containers with minimal headspace; check mass before/after storage when delayed analysis.
- Calibration and quality control: Calibration by gas or certified reference materials (e.g., Ti or Zr standards); blank tests and calibration checks specified. Measurement uncertainty guided by ISO/IEC Guide 98‑3 (GUM).
Applications
- Quality control and acceptance testing of nuclear fuel powders and sintered pellets.
- Fuel manufacturing process monitoring (drying, sintering, storage) to detect hydrogen-related impurities.
- Safety and performance assessments where hydrogen content affects fuel behavior (oxidation, thermal properties).
Who uses it
- Nuclear fuel manufacturers, fuel technologists, R&D laboratories, and regulatory testing facilities involved in nuclear fuel quality assurance, characterization of fissile materials, and material certification.
Related standards
- ISO 15651:2015 (original international text adopted as EN ISO 15651:2017)
- ISO/IEC Guide 98-3:2008 (GUM: uncertainty of measurement)