Overview
ISO 21847-2:2007, "Nuclear fuel technology - Alpha spectrometry - Part 2: Determination of plutonium in uranium and its compounds," specifies a radiochemical alpha‑spectrometry method for measuring trace amounts of 238Pu and the combined 239Pu + 240Pu in uranium hexafluoride (UF6), uranium oxides and uranyl nitrate. The standard describes sample preparation, chemical separations, source preparation and alpha counting, plus calculation and reporting of activity per gram of uranium.
Key topics and technical requirements
- Analytes and matrices: Trace determination of 238Pu and 239Pu + 240Pu in UF6, uranium oxides and uranyl nitrate.
- Sample preparation: Hydrolysis of UF6 and dissolution of solids to obtain uranyle/nitrate solutions.
- Redox chemistry: Reduction of Pu(VI) and Pu(IV) to Pu(III) using hydroxylamine hydrochloride, followed by controlled oxidation back to Pu(IV) with sodium nitrite to optimize extraction.
- Solvent extraction: Liquid–liquid extraction of Pu(IV) using thenoyltrifluoroacetone (TTA) in xylene; stepwise washing and optional re‑extraction to purify the Pu fraction.
- Source formation: Deposition of 0.2 ml of the extracted phase onto a stainless steel disk or watch glass and drying under an infrared/epiradiator.
- Detection: Alpha spectrometry using a Frisch‑grid ionization chamber (argon/methane 90/10) or semiconductor detector; multichannel analyzer energy window recommended 4–7 MeV.
- Quality and performance: Use of certified Pu reference solution as tracer to measure extraction efficiency; yields ≥ 90% indicate method performance; reproducibility example: standard deviation of 0.8 Bq/g for 20 Bq/g U.
- Calculations and reporting: Formula provided to convert counts to activity per gram of uranium, accounting for sample and aliquot volumes, uranium concentration, extraction and detection efficiencies.
Applications
- Routine radiochemical analysis in nuclear fuel technology: quality control of uranium feed materials and fuel cycle intermediates.
- Laboratories performing safeguards, nuclear materials accounting and forensics, where accurate plutonium assay in uranium matrices is required.
- Metrology and calibration labs establishing tracer recoveries and detection efficiencies for alpha spectrometry.
Who should use this standard
- Analytical chemists and radiochemists in the nuclear industry
- Nuclear fuel fabrication and processing laboratories
- Regulatory, safeguards and accreditation bodies involved in nuclear materials measurement
Related standards
- ISO 21847-1 - Determination of neptunium in uranium and its compounds (Part 1)
- ISO 21847-3 - Determination of uranium‑232 in uranium and its compounds (Part 3)
- ISO 3696 - Water for analytical laboratory use (referenced for reagent water quality)
Keywords: ISO 21847-2:2007, alpha spectrometry, plutonium determination, uranium compounds, UF6, TTA extraction, radiochemical analysis, nuclear fuel technology.