ISO 24460:2023

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.