Overview
ISO 13164-2:2013 defines a laboratory test method for determining radon-222 (222Rn) activity concentration in water by direct gamma‑ray spectrometry of the water sample. The method quantifies gamma emissions from the short‑lived decay products of radon (e.g., 214Pb, 214Bi) and converts those measurements into radon activity per litre. Using currently available gamma spectrometers, measurable activity concentrations range from a few becquerels per litre to several hundred thousand Bq·L−1 for a 1 L test sample. The standard is suitable for drinking water monitoring, with laboratory responsibility to validate the method for untested sample matrices. Annexes provide sample spectra, accuracy/precision data and guidance on counting conditions for required sensitivity.
Key topics and technical requirements
- Principle: Measure gamma lines from radon short‑lived progeny and compute radon‑222 activity for the sample volume.
- Detection energies: Typical photon energies used include lines from 214Pb (≈295 keV, ≈352 keV) and 214Bi (≈609 keV, ≈1 764 keV), among others, as indicators of radon equilibrium.
- Sampling & sample handling: Follow representative sampling, container selection, transport and storage practices to preserve radon and its decay‑product equilibrium.
- Sample volume and sensitivity: Standard examples use a 1 L test sample; Annex B gives indications on counting conditions to meet drinking‑water sensitivity.
- Measurement procedure: Direct gamma spectrometry of the water sample with appropriate detector efficiency, background subtraction and calibration.
- Quality assurance / quality control: Instrument verification, method verification, analyst competence, influence quantities and routine QA/QC procedures.
- Expression of results: Report activity concentration, standard uncertainty, decision threshold, detection limit and confidence limits.
- Laboratory competence: Compliance with ISO/IEC 17025 and validation of the method for specific matrices.
Applications and users
- Water quality laboratories performing radionuclide analyses for public water supplies, bottled/mineral water, groundwater and springs.
- Environmental and public health authorities assessing radon exposure from drinking water and implementing corrective actions.
- Water utilities and consultants performing source evaluation, monitoring and treatment verification.
- Research groups studying radon distribution in aquifers and seasonal/geo‑chemical variations.
Practical keywords: ISO 13164-2, radon-222 in water, gamma-ray spectrometry, radon measurement, drinking water monitoring, radon testing method.
Related standards
- ISO 13164-1 - Water quality - Radon‑222 - General principles
- ISO 10703 - High‑resolution gamma‑ray spectrometry for radionuclide activity in water
- ISO 5667 series - Water sampling guidance and preservation
- ISO/IEC 17025 - Laboratory competence
- IEC/IEC standards for germanium detectors and spectrometer calibration (e.g., IEC 61452, IEC 60973)
