ISO 9006:1994

Overview

ISO 9006:1994 specifies an analytical method for determining nitrogen content in uranium metal and uranium dioxide (UO2) powder and pellets. The method targets nitrogen present as nitride, converting it to ammonium during acidic dissolution and quantifying it as ammonia using an ammonia‑sensing electrode with a standard‑addition procedure. The method is applicable over the concentration range 9 µg to 600 µg N per gram of sample.

Key topics and requirements

• Scope: Uranium metal, UO2 powder and UO2 pellets; nitride-origin nitrogen only.
• Principle: Dissolve sample in HCl + H2O2 to convert nitride → NH4+. Make solution alkaline (K2CO3) to convert NH4+ → NH3, retain U(VI) as carbonate complex; measure ammonia with an ammonia electrode using standard additions.
• Reagents & apparatus: Analytical‑grade reagents and distilled water; millivoltmeter (0.1 mV resolution), ammonia‑sensing electrode, magnetic stirrer, micrometer syringe (0.2 µL increments). EDTA is used to complex metals that form ammines.
• Sample preparation: Procedures specified for uranium metal (cleaning, nitric acid pre‑treatment) and UO2 pellets (crushing and 75 µm sieve); UO2 powder is analysed as received.
• Measurement protocol: Standard addition until electrode response change ~17–33 mV; blank determination and correction; electrode slope determination (Annex A) using cumulative additions and regression or Nernst fit. Measurements should be made within ~30 minutes of preparing the alkaline solution.
• Accuracy & limitations: Potential interference from metals that form complex ammines (though rarely significant). No certified reference materials available for method verification; checks with uranium nitride additions indicate no significant bias. Report includes reproducibility figures: e.g., uranium metal (40 µg/g) reproducibility ≈ ±12 µg/g; UO2 powder (63 µg/g) ≈ ±14.4 µg/g; UO2 pellets (6 µg/g) ≈ ±6 µg/g.

Applications and users

• Quality control and chemical analysis of nuclear fuel materials (uranium metal and UO2).
• Nuclear fuel technologists, analytical chemists, regulatory and laboratory personnel involved in material certification and process control.
• Useful where accurate determination of nitride-derived nitrogen is required for safety, material specification, or research into fuel behavior.

Related standards

• Prepared by ISO/TC 85 (Nuclear energy), Subcommittee SC 5 (Nuclear fuel technology).
• Often used alongside other ISO and national standards for nuclear materials analysis and fuel specification (refer to organization‑specific lists for exact cross‑references).

Keywords: ISO 9006:1994, nitrogen content, uranium metal, uranium dioxide, UO2, ammonia‑sensing electrode, nitride, analytical method, nuclear fuel analysis.