Overview
ISO 21847-3:2007 - "Nuclear fuel technology - Alpha spectrometry - Part 3: Determination of uranium 232 in uranium and its compounds" specifies a radioanalytical alpha‑spectrometry method for measuring trace amounts of uranium‑232 (232U) in nuclear‑purity uranium materials. The scope covers uranium hexafluoride (UF), uranium oxides and uranyl nitrate. The procedure combines liquid–liquid extraction, electro‑deposition of a source and alpha spectrometric measurement to quantify 232U relative to total uranium.
Key topics and technical requirements
- Sample types: uranium hexafluoride (after hydrolysis), uranium oxides, uranyl nitrate (nuclear‑grade).
- Chemical preparation: removal of interfering elements (e.g., thorium) by liquid–liquid extraction using thenoyltrifluoroacetone (TTA) in xylene; several nitric acid strengths and cleaning steps are specified.
- Source preparation: electro‑deposition onto stainless steel disks or watch glasses using an ammonium chloride medium and controlled current/time conditions; parameters depend on cell geometry.
- Detection: use of a Frisch‑grid ionization chamber (argon–methane gas mixture) or a semiconductor detector coupled to a multichannel analyser. The multichannel analyser is set to the 4–6 MeV energy band.
- Spectral markers: identification and integration of the 232U alpha peak at about 5.320 MeV and the 238U alpha peak at about 4.196 MeV.
- Calculation: mass fraction of 232U is derived from measured activities (A232, A238) and the standard’s provided massic‑activity constants; the standard includes the explicit equation and constants to compute w(232U).
- Quality & precision: example reproducibility reported (19 measurements, 10‑hour counting) - standard deviation ≈ 0.03 ng 232U per g U at ~1.22 ng/g 232U; strict cleanliness and measurement control required.
- Reporting: mandatory test‑report items include sample ID, reference to ISO 21847‑3, results and units, unusual features and deviations.
Applications and users
- Practical applications: trace determination of 232U for nuclear fuel quality control, safeguards, forensic investigations and radiochemical characterisation of feed/stored materials.
- Who uses it: nuclear fuel manufacturers, analytical laboratories in the nuclear industry, safeguards and regulatory laboratories, and environmental or forensic labs involved in uranium isotopic analysis.
- Benefits: standardized sample prep, controlled electro‑deposition and measurement parameters enable reproducible, comparable trace analysis of 232U across labs.
Related standards
- ISO 21847‑1: Determination of neptunium in uranium and its compounds (alpha spectrometry)
- ISO 21847‑2: Determination of plutonium in uranium and its compounds (alpha spectrometry)
Keywords: ISO 21847-3:2007, uranium‑232, alpha spectrometry, nuclear fuel technology, uranium hexafluoride, uranyl nitrate, uranium oxides, electro‑deposition, trace analysis, TTA extraction, Frisch grid ionization chamber.