Overview
ISO 8300:2013 defines a gravimetric method for the determination of plutonium content in nuclear‑grade plutonium dioxide (PuO2). The procedure is intended for PuO2 containing less than 0.65% mass fraction of non‑volatile impurities and is primarily used to cross‑check material accountancy and assay results. The method yields a stoichiometric, stable, non‑hygroscopic PuO2 by controlled high‑temperature treatment and subsequent weighing, with overall single‑determination standard deviation on the order of 0.05% for the gravimetric step.
Key Topics
- Principle: sampling and precise weighing in a dry atmosphere, heating in air at 1 200 °C to 1 250 °C to constant mass, impurity measurement and correction, and calculation of plutonium concentration using a gravimetric conversion factor that depends on isotopic composition.
- Sampling & handling: transfer of bulk material to sealed vials, rapid movement to a dry glovebox (dew point ≤ −40 °C), and sub‑sampling (typical sub‑sample ≈ 1.5 g).
- Weighing & apparatus: analytical balance accurate to ±0.1 mg, platinum crucibles pre‑tared by heating to constant mass, muffle furnace capable of 1 200–1 250 °C, desiccators and stainless steel sampling vials.
- Heating regime: repeated 1‑hour heatings at 1 200–1 250 °C followed by cooling and weighing until mass change is ≤ ±0.1 mg, ensuring stoichiometric PuO2.
- Impurity correction: measure non‑volatile impurities (µg·g−1) and apply conversion factors (see Annex A) to correct the gravimetric result; uncorrected non‑volatile impurities produce a positive bias.
- Isotopic analysis: determine mean relative atomic mass of plutonium (Ā(Pu))-commonly by mass spectrometry-to calculate the gravimetric conversion factor.
- Precision and uncertainty: gravimetric repeatability ≈ 0.05%. Total uncertainty including impurity correction can remain below 0.1% if impurity analyses meet specified precision levels.
Applications
- Cross‑checking accountancy measurements of nuclear‑grade PuO2 in fuel cycle facilities and laboratories.
- Independent verification of plutonium assays used for safeguards, inventory control, and regulatory compliance.
- Reference method for laboratories requiring a high‑accuracy, stoichiometry‑based plutonium determination.
Related Standards
- ISO/TC 85 committee publications on nuclear fuel technology and safeguards procedures.
- National and international guidance on isotopic measurement (mass spectrometry) for mean atomic mass determination.
For implementation, laboratories should follow the documented procedure for sampling, taring, heating and weighing, perform a complete impurity analysis when necessary, and include full uncertainty reporting and test‑report elements as specified in the standard.
Open preview (PDF)Nuclear fuel technology — Determination of plutonium content in plutonium dioxide of nuclear grade quality — Gravimetric method
