Overview
ISO 13169:2018 - Water quality - Uranium - Test method using alpha liquid scintillation counting specifies a validated laboratory procedure to determine the total activity concentration of uranium isotopes in non-saline waters. The method uses liquid–liquid extraction into an extractant scintillation cocktail (containing HDEHP) followed by alpha liquid scintillation counting (alpha LSC). Typical performance covers soluble uranium activity concentrations from approximately 2·10−3 Bq/kg to 10 Bq/kg when analysing a 1 L sample with a 60 000 s counting time on a typical alpha LSC instrument. The standard also supports determination of the 234U/238U ratio by spectral deconvolution.
Key technical topics and requirements
- Scope and applicability: non-saline waters (surface water, groundwater, drinking water, effluents) and soluble uranium isotopes; method not tested for other uranium isotopes.
- Analytical principle: acidify sample, optional pre‑concentration by evaporation, liquid–liquid extraction into an organic scintillation cocktail, alpha counting by LSC.
- Reagents & equipment: analytical‑grade reagents (nitric acid, laboratory water), LSC instrument, extractant cocktail containing bis(2‑ethylhexyl) hydrogen phosphate (HDEHP).
- Calibration & quality control: use of uranium standard solutions (e.g., 236U standard for calibration), preparation of alpha and beta calibration sources, blank controls, and optimization of counting conditions.
- Performance metrics: calculations for activity per unit mass, standard and expanded uncertainties (ISO/IEC Guide 98‑3), decision threshold, detection limit and confidence limits (ISO 11929).
- Procedure variants: direct analysis without pre‑concentration and analysis after evaporation for lower detection limits.
- Interference control, sampling, reporting: guidance on sampling practices, interference checks, quality assurance and the required content of the test report.
Practical applications and users
- Environmental and radiological monitoring of drinking water, groundwater, surface water, and liquid effluents.
- Routine surveillance to verify compliance with national or WHO guidance levels (document cites WHO guidance for uranium isotopes).
- Emergency and post‑incident monitoring when rapid, reliable uranium activity data are required.
- Intended users: accredited testing laboratories, water utilities, environmental regulators, nuclear facility effluent monitoring teams, and research laboratories performing uranium radioactivity analyses.
Related standards (useful cross‑references)
- ISO 11929 - determination of decision threshold and detection limit for ionizing radiation measurements
- ISO 5667 series - water sampling guidance
- ISO 3696 - laboratory water quality
- ISO/IEC 17025 - laboratory competence
- ISO/IEC Guide 98‑3 (GUM) - expression of measurement uncertainty
- ISO 80000‑10 - units and symbols for atomic and nuclear physics
Keywords: ISO 13169:2018, uranium test method, alpha liquid scintillation counting, water quality, uranium isotopes, 234U/238U ratio, detection limit, liquid scintillation counting, HDEHP, environmental monitoring.