prEN ISO 13164-2

• Abstract:

  ISO 13164-2:2013 specifies a test method for the determination of radon-222 activity concentration in a sample of water following the measurement of its short-lived decay products by direct gamma-spectrometry of the water sample.; The radon-222 activity concentrations, which can be measured by this test method utilizing currently available gamma-ray instruments, range from a few becquerels per litre to several hundred thousand becquerels per litre for a 1 l test sample.; This test method can be used successfully with drinking water samples. The laboratory is responsible for ensuring the validity of this test method for water samples of untested matrices.; An annex gives indications on the necessary counting conditions to meet the required sensitivity for drinking water monitoring.

• Status: Not Published
• Publication Date: 06-Dec-2027
• ICS: 13.060.60 - Examination of physical properties of water
• ICS: 13.280 - Radiation protection
• ICS: 17.240 - Radiation measurements
• Technical Committee: CEN/TC 230 - Water analysis
• Current Stage: 4020 - Submission to enquiry - Enquiry
• Start Date: 18-Jun-2026
• Completion Date: 18-Jun-2026
• Ref Project: oSIST prEN ISO 13164-2:2026 - Water quality - Radon-222 - Part 2: Test method using gamma-ray spectrometry (ISO/DIS 13164-2:2026)

• Revises: EN ISO 13164-2:2020 - Water quality - Radon-222 - Part 2: Test method using gamma-ray spectrometry (ISO 13164-2:2013)
• Effective Date: 05-Nov-2024

Overview

prEN ISO 13164-2:2026 is an international standard developed by CEN and ISO that specifies a reliable test method for the determination of radon-222 activity concentration in water samples using direct gamma-ray spectrometry. This method is applicable to a range of water types, including drinking water, and offers laboratories a scientifically robust approach for monitoring radon-222, a naturally occurring radioactive isotope that presents potential health risks if present in elevated concentrations. The standard provides clear procedures for sampling, detection, measurement, and quality assurance, supporting compliance with national and international regulations concerning water quality and radiological safety.

Key Topics

• Radon-222 Monitoring in Water: Provides guidelines for detecting and quantifying radon-222 by measuring the gamma-ray emissions from its short-lived decay products within a sealed water sample.
• Gamma-ray Spectrometry: Details a direct measurement technique using high-resolution gamma spectrometers as described in ISO 10703, ensuring accurate energy discrimination and quantification.
• Sample Collection and Handling: Stresses rigorous protocols for representative water sampling in line with ISO 5667-1 and ISO 5667-3, as well as proper sample transportation and storage to minimize radon loss and decay.
• Quality Assurance (QA): Describes essential QA/QC elements under ISO/IEC 17025, including instrument calibration, participation in proficiency tests, and controls to account for potential sources of error (e.g., sample handling, background radiation, and laboratory atmospheric conditions).
• Measurement Sensitivity: Indicates methods and necessary counting conditions to achieve sensitivity required for regulatory monitoring, particularly for drinking water safety.

Applications

This standard is highly relevant for:

• Water Utilities and Regulators: Ensuring compliance with health and safety regulations by routinely monitoring radon-222 in public water supplies, especially where geological or anthropogenic factors may raise radon levels.
• Environmental Laboratories: Implementing standardized, validated procedures for radiological assessment of water samples as part of environmental monitoring and quality assurance programs.
• Emergency and Incident Response: Guiding rapid and accurate assessment of water radioactivity in emergency situations, such as accidental releases from nuclear installations, to support public health protection.
• Research and Environmental Studies: Facilitating robust data collection for studies investigating waterborne radionuclide behavior, environmental dispersion, and potential human health impacts.
• Industrial Sectors: Supporting industries such as mining, oil and gas, and land remediation in meeting regulatory requirements for water discharge and workplace safety.

Related Standards

To ensure comprehensive and accurate radon-222 testing in water, prEN ISO 13164-2 references and complements several other key international standards:

• ISO 13164-1: General principles for radon-222 testing in water.
• ISO 10703: Methods for testing gamma-ray emitting radionuclides using high-resolution spectrometry.
• ISO 5667-1 & ISO 5667-3: Sampling program design and water sample preservation.
• ISO 11929: Determination of characteristic limits for measurements of ionizing radiation.
• ISO/IEC 17025: Laboratory competence requirements.
• IEC 61577-1 & 61577-2: General and specific requirements for radon measurement instruments.
• ISO 80000-10: Atomic and nuclear quantities and units for consistency in reporting.

Practical Value

By following prEN ISO 13164-2, laboratories and organizations can ensure:

• Accurate and reproducible results for radon-222 activity concentration in water.
• Compliance with legal and regulatory limits set for public health and environmental protection.
• High-quality data for risk assessment and decision-making in water quality management.
• Harmonization with international best practices for radiological monitoring, supporting both local and cross-border environmental initiatives.

Keywords: water quality, radon-222, gamma-ray spectrometry, radiological monitoring, ISO 13164-2, drinking water, regulatory compliance, environmental laboratory, radioactive isotopes, water sampling.

SLOVENSKI STANDARD
01-september-2026
Kakovost vode - Radon Rn-222 - 2. del: Preskusna metoda z gama spektrometrijo
(ISO/DIS 13164-2:2026)
Water quality - Radon-222 - Part 2: Test method using gamma-ray spectrometry
(ISO/DIS 13164-2:2026)
Wasserbeschaffenheit - Radon-222 - Teil 2: Verfahren mittels Gammaspektrometrie
(ISO/DIS 13164-2:2026)
Qualité de l'eau - Radon 222 - Partie 2: Méthode d'essai par spectrométrie gamma
(ISO/DIS 13164-2:2026)
Ta slovenski standard je istoveten z: prEN ISO 13164-2
ICS:
13.060.60 Preiskava fizikalnih lastnosti Examination of physical
vode properties of water
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 13164-2
ISO/TC 147/SC 3
Water quality — Radon-222 —
Secretariat: AFNOR
Part 2:
Voting begins on:
Test method using gamma-ray 2026-04-10
spectrometry
Voting terminates on:
2026-07-03
Qualité de l'eau — Radon 222 —
Partie 2: Méthode d'essai par spectrométrie gamma
ICS: 13.060.60; 13.280; 17.240
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 13164-2:2026(en)
DRAFT
ISO/DIS 13164-2:2026(en)
International
Standard
ISO/DIS 13164-2
ISO/TC 147/SC 3
Water quality — Radon-222 —
Secretariat: AFNOR
Part 2:
Voting begins on:
Test method using gamma-ray
2026-04-10
spectrometry
Voting terminates on:
2026-07-03
Qualité de l'eau — Radon 222 —
Partie 2: Méthode d'essai par spectrométrie gamma
ICS: 13.060.60; 13.280; 17.240
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2026
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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BE CONSIDERED IN THE LIGHT OF THEIR
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NATIONAL REGULATIONS.
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RECIPIENTS OF THIS DRAFT ARE INVITED
CP 401 • Ch. de Blandonnet 8
TO SUBMIT, WITH THEIR COMMENTS,
CH-1214 Vernier, Geneva
NOTIFICATION OF ANY RELEVANT PATENT
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Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 13164-2:2026(en)
ii
ISO/DIS 13164-2:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 2
5 Principle . 3
6 Sampling . 4
6.1 General requirement .4
6.2 Sampling requirement .4
6.3 Sample volume .4
6.4 Container characteristics .4
7 Transportation and storage . 4
8 Detection . 5
9 Measurement procedure . 5
10 Quality assurance and quality control programme . 5
10.1 General .5
10.2 Influence quantities .5
10.3 Instrument verification .6
10.4 Method verification .6
10.5 Demonstration of analyst capability . .7
11 Expression of results . 7
11.1 Activity concentration .7
11.2 Standard uncertainty of the activity concentration .7
11.3 Decision threshold .8
11.4 Limit of detection .8
11.5 Limits of the coverage intervals .9
11.5.1 Limits of the probabilistically symmetric coverage interval .9
11.5.2 The shortest coverage interval .9
12 Calibration . 9
13 Test report . 10
Annex A (informative) Sample spectra .11
Annex B (informative) Sample accuracy and precision data .13
Bibliography . 14

iii
ISO/DIS 13164-2:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 147, Water Quality, Subcommittee SC 3,
Radioactivity measurements.
This second edition cancels and replaces the first edition (ISO 13164-2:2013), which has been technically
revised.
The main changes are as follows:
— A common Introduction template for the ISO 13164 series parts under revision was implemented
— Edits to improve consistency with content of other ISO 13164 parts
— Updates to Symbols clause content
— Clarified decay correction calculations
— Annex and Bibliography updates
— Additional clarifying edits.
A list of all parts in the ISO 13164 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO/DIS 13164-2:2026(en)
Introduction
Radionuclides are present throughout the environment; thus, water bodies (e.g. surface waters, ground
waters, sea waters) contain radionuclides, which can be of either natural or anthropogenic origin:
3 14 40
— naturally occurring radionuclides, including H, C, K and those originating from the thorium and
210 210 222 226 228 227 232 231 234 238
uranium decay series, in particular Pb, Po, Rn, Ra, Ra, Ac, Th, Pa, U, and U
can be found in water bodies due to either natural processes (e.g., desorption from the soil, runoff by rain
water) or released from technological processes involving naturally occurring radioactive materials (e.g.
mining, mineral processing, oil, gas and production, water treatment and the production and the use of
phosphate fertilisers);
55 59 63 90 99
— anthropogenic radionuclides such as Fe, Ni, Ni, Sr, Tc, transuranic elements (Np, Pu, Am,
60 137
and Cm)and some gamma emitting radionuclides such as Co and Cs can also be found in natural
waters. Small quantities of anthropogenic radionuclides can be discharged from nuclear facilities to the
environment as a result of authorized routine releases. The radionuclides present in liquid effluents
[1]
are usually controlled before being discharged to the environment and water bodies. Anthropogenic
radionuclides used in medical and industrial applications can be released to the environment after use.
Anthropogenic radionuclides are also found in waters due to the contamination from fallout resulting
above-ground nuclear detonations and accidents such as those that occurred at the Chornobyl and
Fukushima nuclear facilities.
Radionuclide activity concentrations in water bodies can vary according to local geological characteristics
and climatic conditions and can be locally and temporally enhanced by releases from nuclear facilities
[2][3]
during planned, existing, and emergency exposure situations . Some drinking water sources can thus
contain radionuclides at activity concentrations that could present a human health risk. The World Health
[4]
Organization (WHO) recommends to routinely monitor radioactivity in drinking waters and to take
proper actions when needed to minimize the health risk.
National regulations usually specify the activity concentration limits that are authorized in drinking waters,
water bodies, and liquid effluents to be discharged to the environment. These limits can vary for planned,
existing, and emergency exposure situations. The WHO does not have a current recommended specific
activity concentration limit for radon in water as radon exposure through indoor air is considered a more
[4]
pressing concern, while in Europe, the implementation of European Council Directive 2013/51/EURATOM,
-1
establishes a radon concentration limit of 100 Bq·l . Compliance with such limits is assessed by measuring
radioactivity in water samples and by comparing the results obtained with their associated uncertainties as
[5] [6]
specified by ISO/IEC Guide 98-3 and ISO 5667-20 .
This document contains method to support laboratories which need to determine Rn in water samples.
The method described in this document can be used for various types of waters (see Clause 1). Minor
modifications such as sample volume and counting time can be made if needed to ensure that the
characteristic limit, decision threshold, detection limit, and uncertainties are below the required limits.
This can be done for several reasons such as emergency situations, lower national guidance limits, and
operational requirements.
v
DRAFT International Standard ISO/DIS 13164-2:2026(en)
Water quality — Radon-222 —
Part 2:
Test method using gamma-ray spectrometry
WARNING — Persons using this document should be familiar with normal laboratory practices. This
document does not purport to address all of the safety problems, if any, associated with its use. It is
the responsibility of the user to establish appropriate safety and health practices and to determine
the applicability of any other restrictions.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document be
carried out by suitably qualified staff.
1 Scope
This part of ISO 13164 specifies a test method for the determination of Rn activity concentration in a
sample of water by the measurement of its short-lived decay products by direct gamma-spectrometry of a
water sample (see Annex A).
The Rn activity concentrations, which can be measured by this test method utilizing currently available
gamma-ray instruments, range from a few becquerels per litre to several hundred thousand becquerels per
litre for a 1 l test sample.
This test method can be used successfully with drinking water samples. The laboratory is responsible for
ensuring the validity of this test method for water samples of untested matrices.
Annex B gives indication on the necessary counting conditions to meet the required sensitivity for drinking
water monitoring.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and sampling
techniques
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 10703, Water quality — Gamma-ray emitting radionuclides — Test method using high resolution gamma-
ray spectrometry
ISO 11929 (all parts), Determination of the characteristic limits (decision threshold, detection limit and limits of
the confidence interval) for measurements of ionizing radiation — Fundamentals and application
ISO 13164-1, Water quality — Radon-222 — Part 1: General principles
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
IEC 60973, Test procedures for germanium gamma-ray detectors

ISO/DIS 13164-2:2026(en)
IEC 61151, Nuclear instrumentation — Amplifiers and preamplifiers used with detectors of ionizing radiation —
Test procedures
IEC 61452, Nuclear instrumentation — Measurement of gamma-ray emission rates of radionuclides —
Calibration and use of germanium spectrometers
IEC 61577-1, Radiation protection instrumentation — Radon and radon decay product measuring instruments
— Part 1: General principles
IEC 61577-2, Radiation protection instrumentation — Radon and radon decay product measuring instruments
— Part 2: Specific requirements for radon measuring instruments
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80000-10 and ISO 13164-1 apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
4 Symbols
For the purposes of this document, the symbols defined in ISO 80000-10, ISO 13164-1, and the following
apply.
A activity of each radionuclide in calibration source, at the Bq
calibration time
222 −1
c activity concentration of Rn in water Bq·l
A
−1
*
Bq·l
decision threshold
c
A
−1
# Bq·l
limit of detection
c
A
−1
 
Bq·l
lower and upper limits of the probabilistically symmetric coverage interval
c , c
A A
−1

Bq·l
lower and upper limits of the shortest coverage interval
cc,
AA
f correction factor for the decay of radon during time
...