ISO 19361-2025 PDF

Full title and description

Measurement of radioactivity — Determination of beta emitters activities — Test method using liquid scintillation counting. This International Standard specifies a laboratory test method that uses liquid scintillation counting (LSC) to determine the activity concentration of beta-emitting radionuclides in prepared scintillation sources made from liquid or suitably prepared solid samples.

Abstract

This document defines conditions and procedural requirements for measuring beta-emitter activities by mixing a test portion with an appropriate scintillation cocktail and counting the resulting scintillation events with an LSC system. It covers liquid (aqueous or organic) samples and prepared solid forms (e.g., particles, filters, planchets) and addresses typical activity ranges and interferences; specific radiochemical test-portion preparations (for example distillation for 3H or benzene synthesis for 14C) are excluded and covered by separate methods.

General information

• Status: Published.
• Publication date: 11 July 2025 (Edition 2 published July 2025).
• Publisher: International Organization for Standardization (ISO).
• ICS / categories: 17.240 (Radiation measurements).
• Edition / version: Edition 2 (2025).
• Number of pages: 22 pages.

Scope

The standard is applicable to the determination of activity concentration of beta-emitting radionuclides using liquid scintillation counting for prepared scintillation sources. It applies to direct measurement of mixed scintillation sources from liquid samples (which may be diluted to fit instrument range) and to suitably prepared solids (particles, filters, planchets) provided the resulting source activity is compatible with the counting assembly. Typical applicable activity concentrations extend from about 1 Bq·L⁻¹ up to 1×10⁶ Bq·L⁻¹, subject to instrument performance and sample preparation. The standard excludes specialised test-portion preparation procedures for particular radionuclides that are covered by separate methods.

Key topics and requirements

• Principle: preparation of a scintillation source by combining the test portion with a scintillation cocktail and measurement using a liquid scintillation counter.
• Sample types: aqueous and organic liquids, and prepared solid sources (particles, filters, planchets) provided preparation yields a suitable scintillation source.
• Activity range and instrument compatibility: intended for low-to-high activity concentrations subject to instrument dynamic range and counting assembly characteristics; dilution or other preparation may be required.
• Interference management: procedures require consideration of co-existing alpha, beta and gamma emitters and, where necessary, radiochemical separation or extraction to isolate the radionuclide of interest.
• Calibration and efficiency: requirements for calibration, counting efficiency determination, and application of quench-correction or spectral-shift corrections as appropriate for the LSC system.
• Quality assurance: routine checks, blanks, calibrants, control samples and uncertainty estimation are required to support result traceability and validity.
• Counting geometry and background: instructions to control source geometry, background minimization and measurement timing to achieve stated decision thresholds and detection limits.
• Limitations and exclusions: explicit exclusions for specialised test-portion pre-treatments (e.g., distillation, solvent synthesis) which are addressed in specific methods outside this standard.

These topics are derived from the standard's procedural and applicability statements.

Typical use and users

Used by accredited radiochemistry and environmental laboratories, regulatory and monitoring agencies, nuclear industry analytical units, research institutions and any laboratory performing quantitative beta-emitter analysis by liquid scintillation counting. Typical applications include environmental water monitoring, routine laboratory radionuclide assays, emergency monitoring where LSC provides rapid results, and support for regulatory compliance and waste characterization.

Related standards

Standards often used alongside or referenced when applying LSC methods include the ISO 11929 series (characteristic limits, detection limits and decision thresholds for ionizing radiation measurements), ISO 11704 (gross alpha and beta activity in water using LSC), ISO 9696 / ISO 10704 (gross alpha/gross beta methods by thick/thin source techniques) and other ISO/IEC documents addressing uncertainty, sampling and laboratory quality (for example ISO/IEC 17025). These related documents provide complementary guidance on detection limits, sampling, and screening methods used in radioactivity measurement workflows.

Keywords

liquid scintillation counting; LSC; beta emitters; beta activity concentration; quench correction; counting efficiency; radiochemical separation; detection limit; decision threshold; environmental monitoring; radionuclide analysis; ISO 19361.

FAQ

Q: What is this standard?

A: ISO 19361:2025 is an International Standard that specifies a test method using liquid scintillation counting for the determination of activity concentrations of beta-emitting radionuclides in prepared scintillation sources.

Q: What does it cover?

A: It covers preparation of scintillation sources from liquid and prepared solid samples, measurement conditions for LSC, calibration and corrections (including quench correction), considerations for interferences and applicable activity ranges. It excludes specialised sample-specific pre-treatments that are described in separate methods.

Q: Who typically uses it?

A: Accredited radiochemistry laboratories, environmental and regulatory monitoring organizations, nuclear industry labs, research groups and emergency response laboratories that perform quantitative beta-emitter measurements using LSC.

Q: Is it current or superseded?

A: Current. Edition 2 was published in July 2025 (the 2017 edition was withdrawn and replaced by this 2025 edition).

Q: Is it part of a series?

A: It is one standard within the broader set of ISO documents on measurement of radioactivity and radiological laboratory practice; users commonly apply it alongside ISO documents such as the ISO 11929 series (detection limits) and ISO 11704 (gross alpha/beta by LSC).

Q: What are the key keywords?

A: Liquid scintillation counting, beta emitters, activity concentration, quench correction, counting efficiency, detection limit, radiochemical separation, environmental monitoring.