Overview
ISO 9463:2019 specifies a validated spectrophotometric method for the determination of plutonium (Pu) in nitric acid solutions. The procedure is designed for use with spectrophotometers installed in hot cells or glove boxes so that it can be applied to high-activity samples from nuclear fuel reprocessing and other nuclear facilities. The method measures the Pu(VI) absorption peak at 831 nm and is applicable for original-sample plutonium concentrations above 0.5 mg·L−1, with a standard uncertainty (k = 1) typically below 5%.
Key topics and technical requirements
- Oxidation chemistry: Plutonium is quantitatively oxidized to Pu(VI) using either cerium(IV) (Ce(IV)) or silver(II)/silver oxide (Ag(II)/AgO).
- Ag(II) is more powerful and faster; Ce(IV) is compatible with certain acid matrices and does not require destruction of excess reagent.
- When AgO is used, excess oxidant is destroyed (e.g., with sulfamic acid) before measurement.
- Measurement principle: Optical density of Pu(VI) at 831 nm; calibration by comparison with a plutonium reference solution prepared in the same nitrate matrix.
- Analytical conditions:
- Calibration and sample dilution commonly use 3.0 ± 0.05 mol·L−1 HNO3.
- Recommended minimum plutonium calibration concentration: ≈5 mg·L−1.
- Typical spectrophotometer specs: double-beam, spectral slit ≤2 nm, absorbance capability 0.001–1.5, spectral coverage including 800–860 nm.
- Measurement cells: standard 1 cm pathlength (longer paths can be used to increase sensitivity).
- Molar extinction coefficient: Nominally in the range ~400–500 L·mol−1·cm−1; sensitive to nitrate concentration (notably), temperature (≈0.5% change per °C), and acidity.
- Interferences & performance: Method is commonly free of interference from many cations/anions when calibration and sample nitrate content are matched. Reproducibility and detection-limit guidance are provided in the standard.
Applications and users
- Intended primarily for process control during steps of nuclear fuel reprocessing.
- Used in radiochemical laboratories, hot-cell analytical facilities, and glove-box operations for quality control and monitoring of plutonium-bearing streams.
- Target users: radiochemists, laboratory managers, nuclear facility process control engineers, and metrology personnel responsible for plutonium assay.
Related standards and references
- ISO 1042 (laboratory glassware - volumetric flasks) is cited for equipment requirements.
- ISO 3696 referenced for water grade.
- Annex A of ISO 9463 provides a procedure for preparing AgO if commercial silver(II) oxide is not available.
Keywords: ISO 9463:2019, plutonium determination, spectrophotometry, nitric acid solutions, Pu(VI), silver(II) oxide, cerium(IV), nuclear fuel reprocessing, hot cell analysis, glove box analysis.
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