Overview
EN ISO 9161:2021 (identical to ISO 9161:2019) specifies a laboratory method for determining the apparent density (loose bulk density) and tap density of free‑flowing uranium dioxide (UO2) powder used for pelleting and sintering UO2 nuclear fuel pellets. The method is applicable to a range of powder morphologies (grains, granules, spheres) and can also be used for other fuel powders such as PuO2, ThO2, and mixtures like UO2–PuO2 and UO2–Gd2O3. The procedure is based on use of a flowmeter funnel (or alternative apparatus such as a Scott volumeter) and defines sampling, apparatus, test steps, and expression of results.
Key topics and requirements
- Measured properties: apparent (bulk) density and tapped density - reported as dry mass per unit volume.
- Principle:
- Apparent density: powder poured through a flowmeter funnel into a tared, graduated density cup; mass and known volume are used to calculate density.
- Tap density: a weighed portion in a calibrated cup is tapped under fixed conditions and the compacted volume is measured.
- Apparatus & dimensions (specified ranges):
- Flowmeter funnel with orifice diameter options: 2.5 mm, 5.0 mm, 10 mm, or 15 mm; 60° conical angle.
- Density cup volumes: 10 cm3, 25 cm3, 50 cm3, or 100 cm3.
- Tapping device: baseplate tapped with stroke ~2–3 mm, cam‑shaft speed around (250 ± 15) min⁻¹, and an adjustable counter (1–9 999 taps).
- Balance sensitivity: 0.01 g or better.
- Sampling: representative laboratory test portion from production batch; test portion should exceed cup volume (≈ twice the density cup volume) and measures taken to avoid particle segregation during transport.
- Quality & calibration: periodic calibration of balances and equipment; adherence to laboratory quality practices (ISO/IEC 17025 recommended).
- Safety: containment and PPE when handling radioactive powders.
Practical applications and users
This standard is used to:
- Verify powder physical properties required by fuel manufacturing specifications.
- Support quality control and acceptance testing for UO2 powder suppliers and nuclear fuel fabricators.
- Aid process control in pellet pressing and sintering by correlating powder packing behaviour with sintered density and pellet quality.
- Provide standardized data for R&D, material qualification, and regulatory reporting.
Typical users:
- Nuclear fuel manufacturers and mills
- Analytical and QC laboratories in the nuclear supply chain
- Research institutions working on ceramic fuel materials
- Regulators and certification bodies assessing compliance
Related standards
- ISO 9161:2019 (international text adopted as EN ISO 9161:2021)
- ASTM C753 (guidance on UO2 sample collection referenced)
- ISO/IEC 17025 (laboratory calibration and quality management guidance)
Keywords: uranium dioxide powder, apparent density, tap density, EN ISO 9161:2021, flowmeter funnel, Scott volumeter, nuclear fuel, UO2 pellets, powder characterization.
