Overview - ISO 24460:2023 (Radioactive tracer methods for closed conduits)
ISO 24460:2023 specifies how to measure single-phase fluid flow rate in closed conduits (pipe systems) using radioactive tracer methods. The standard documents three principal approaches - transit time (pulse) method, constant rate injection method, and integration (dilution) method - and provides guidance on tracer selection, detector arrangement, data acquisition, uncertainty evaluation and radiation dose considerations. For steady single-phase flow the standard enables determination of volumetric flow rate (Q) and, if density is known, mass flow rate.
Key technical topics and requirements
- Methods covered
- Transit time method: pulse injection of radioactive tracer; two downstream detection cross-sections record response curves and the transit time between them is used to compute Q (Q = V / t).
- Constant rate injection method: continuous tracer injection at a known rate with downstream dilution measurement.
- Integration method: measurement of tracer concentration over time to obtain total transported volume.
- Tracer selection: guidance on radionuclide type, emitted radiation, and appropriate half-life to balance detectability and dose.
- Mixing length: definition and requirements for adequate mixing upstream of measurement cross-sections to ensure uniform cross‑section concentration.
- Detection and instrumentation:
- Gamma radiation detectors and recommended detector arrangements.
- Data acquisition systems for recording response curves and performing time-correlation analysis.
- Procedures and calculation:
- Location of injection and detection cross-sections, injection techniques, activity estimation, measuring length selection, and transit time calculation.
- Uncertainty: methods for evaluating and propagating measurement uncertainty for each tracer method; annex provides calculation examples.
- Radiation protection: Annex B addresses radiation dose considerations and the need for regulatory compliance and safety practices.
Practical applications and users
- Applications
- Calibration of installed flowmeters (ultrasonic, electromagnetic, Venturi, etc.)
- Flow balancing in pipe networks and distribution systems
- Measurement of pump/turbine performance and process flow auditing
- Online, non-intrusive flow verification in harsh industrial environments without process shutdown
- Who will use this standard
- Flow measurement engineers and metrologists
- Nuclear/radiation safety officers and regulatory specialists
- Process engineers in oil & gas, chemical, power generation, water/wastewater, and heavy industries
- Service providers performing tracer-based flowmeter calibration and diagnostic testing
Related standards and notes
- ISO 24460 complements other ISO/IEC standards on flow measurement and instrumentation. Implementers should ensure compliance with national radiation protection regulations and consult their national standards body for additional guidance.
