Overview
ISO 9894:1996 specifies a controlled method for subsampling uranium hexafluoride (UF6) in the liquid phase to obtain representative aliquots for laboratory analysis. The standard describes equipment, conditioning, leak and purge procedures, aliquoting steps and safety controls needed to produce subsamples suitable for isotopic analysis, impurity (chemical) analysis, and uranium assay while minimizing isotopic and chemical contamination.
Key topics and technical requirements
- Subsample quantities and container sizes
- Isotopic analysis: 1–3 g (container/tube volume ≈ 0.005–0.100 L).
- Uranium assay: 5–10 g (tube volume ≈ 0.002–0.005 L).
- Impurity (chemical) analysis: 10–200 g (PTFCE container ≈ 0.1 L).
- Apparatus
- Metal sample cylinders (types per ISO 7195 / ANSI N14.11) or CEA 23D.
- PTFCE (polytrifluorochloroethylene) containers and sampling tubes.
- Heated vacuum manifold, valves, micrometer valve for controlled run-off.
- Pump unit with liquid‑nitrogen cold trap, chemical trap (NaF + Al2O3) and vacuum pump.
- Conditioning and pressure control
- Temperature zones: liquefaction 90–100 °C, liquid-phase subsampling 80–90 °C, gaseous-phase aliquoting/recovery 65–75 °C.
- Pump down to low pressure (system capable of ~0.1 Pa); perform pressure-rise tests (≤ 0.1 Pa over specified interval).
- Purge, passivation and cleanliness
- Purge lines with UF6 from the sample cylinder prior to aliquoting.
- Optional passivation with ClF3 or N2 doped with ~25% F2 after maintenance.
- Dedicated containers for isotopic aliquots; passivate and keep system scrupulously clean.
- Analytical notes and safety
- Carbon halides, hydrocarbons and certain metal halides can be measured directly from the subsample.
- Hydrolysis (for impurity preparation) uses double‑distilled water (approx. 5 g H2O per 1 g U) and must be performed under a hood in a ventilated area.
- Minimize cross‑contamination and handle UF6 under controlled ventilation and fume extraction.
Applications and users
ISO 9894 is intended for organizations involved in:
- Nuclear fuel production and quality control
- Safeguards and isotopic verification laboratories
- Analytical chemistry labs performing uranium assay, isotopic ratio measurement and impurity profiling
- Transport/packaging and regulatory bodies overseeing UF6 handling and sampling
This standard helps ensure representative, reproducible subsamples for accurate isotopic, assay and impurity determinations while maintaining safety and traceability.
Related standards
- ISO 7195 - Packaging of uranium hexafluoride (reference for cylinder types)
- ANSI N14.11 / ANSI N14.1 (referenced packaging and handling guidance)
- Prepared by ISO/TC 85 (Nuclear energy), SC 5 (Nuclear fuel technology)
