ISO 9698:2019

Overview

ISO 9698:2019 specifies a laboratory test method for measuring tritium (3H) activity concentration in water using liquid scintillation counting (LSC). It applies to marine, surface, ground, rain and drinking waters, and to tritiated water ([3H]H2O) in effluents. The standard defines sampling and sample‑preparation options (including distillation), counting procedures, calibration and expression of results. It notes that organically bound tritium requires additional chemical processing (e.g., chemical oxidation or combustion) before analysis. With suitable instrumentation and technique, the method can achieve a detection limit as low as 1 Bq·L−1, and concentrations up to 10^6 Bq·L−1 can be measured without dilution.

Key topics and requirements

• Principle: measurement of tritium beta emissions by liquid scintillation counting.
• Sample types and handling: guidance on sampling, transportation and storage consistent with ISO 5667 series recommendations.
• Sample preparation: direct measurement or pre‑treatment (distillation, optional concentration); annexes cover distillation for small/large volumes and simplified procedures.
• Reagents and equipment: scintillation cocktail, quenching agents, calibration source solutions, counting vials and LSC instrument requirements.
• Calibration and quality control: use of calibration sources, internal standards (annex C), blank controls and quench correction.
• Performance metrics: calculation of activity concentration, decision threshold, detection limit and confidence interval; guidance on uncertainty evaluation.
• Limitations: not directly applicable to organically bound tritium without chemical conversion.

Applications and users

ISO 9698:2019 is designed for:

• Environmental and radiochemical laboratories performing routine monitoring of water quality for tritium.
• Water utilities and drinking‑water testing laboratories verifying compliance with regulatory or guidance levels.
• Nuclear industry operators and effluent control teams measuring tritiated discharges.
• Emergency response and public‑health agencies assessing tritium after incidents.
• Accreditation bodies and laboratories seeking/maintaining validated tritium measurement procedures.

Practical uses include routine surveillance of surface and groundwater, effluent monitoring prior to discharge, compliance checks against WHO or national guidance levels, and emergency assessment where rapid, reliable tritium quantification is required.

Related standards

• ISO 5667 series (water sampling and handling)
• ISO/IEC Guide 98‑3 (uncertainty of measurement)
• ISO 9698 is part of ISO/TC 147 (Water quality) radionuclide measurement suite

Keywords: ISO 9698:2019, tritium, liquid scintillation counting, water quality, tritium testing, detection limit 1 Bq·L−1, tritiated water, organically bound tritium.