ISO/FDIS 13169

• Abstract:

  This document specifies the measurement method for the determination of total activity concentration of uranium isotopes in non-saline waters by extraction and liquid scintillation counting. This method covers the measurement of soluble uranium isotopes in water in activity concentrations between approximately 2·10−3 Bq/kg and 10 Bq/kg when analysing a 1 l test sample volume with a 60 000 s counting time with a typical alpha LSC instrument. The ratio 234U/238U can also be determined. This method has not been tested for the measurement of other uranium isotopes.

• Status: Not Published
• ICS: 13.060.60 - Examination of physical properties of water
• ICS: 17.240 - Radiation measurements
• Technical Committee: ISO/TC 147/SC 3 - Radioactivity measurements
• Drafting Committee: ISO/TC 147/SC 3/WG 15 - Liquid scintillation counting and proportional counting
• Current Stage: 5000 - FDIS registered for formal approval
• Start Date: 02-Jul-2026
• Completion Date: 01-Jul-2026

• Consolidates: prEN ISO 13169 - Water quality - Uranium - Test method using alpha liquid scintillation counting (ISO/DIS 13169:2025)
• Effective Date: 12-Feb-2026
• Consolidates: ISO 7124:2023 - Eggs and egg products — Determination of fipronil and metabolites residues — Liquid chromatography tandem mass spectrometry method
• Effective Date: 16-Oct-2025
• Revises: ISO 13169:2018 - Water quality — Uranium — Test method using alpha liquid scintillation counting
• Effective Date: 22-Jun-2024

Overview

ISO/FDIS 13169:2026, published by the International Organization for Standardization (ISO), specifies a standardized method for determining the total activity concentration of uranium isotopes in non-saline water. The method utilizes alpha liquid scintillation counting (LSC) after chemical extraction and allows for the quantification of soluble uranium in water samples within a broad range of activity concentrations. It can also be used to determine the ratio of uranium-234 to uranium-238. This water quality testing standard is essential for laboratories monitoring radiological contaminants in environmental and drinking waters.

Key Topics

• Scope: Measurement of dissolved uranium isotopes (especially U-234 and U-238) in non-saline water samples using alpha LSC.
• Method Range: Activity concentrations between approximately 0.002 Bq/kg and 10 Bq/kg, based on a 1-liter sample and 60,000 seconds counting time.
• Sample Preparation: Includes acidification, potential pre-concentration by evaporation, filtration, and extraction using specialized scintillation cocktails.
• Calibration and Quality Control: Details preparation of calibration standards, instrument calibration, blank sample measurement, and quality assurance procedures aligned with ISO/IEC 17025.
• Result Expression: Provides guidance on calculating activity per mass or volume, assessing uncertainty, detection limits, and result reporting.
• Safety and Competence: Emphasizes the necessity for qualified staff and adherence to laboratory safety practices.

Applications

The test method specified in ISO/FDIS 13169 is valuable in a variety of practical contexts where uranium may present a human or ecological health risk, including:

• Drinking Water Monitoring: Ensuring compliance with national and international safety standards, including World Health Organization (WHO) guidelines and local regulatory limits.
• Environmental Surveillance: Routine assessment of surface, ground, and effluent waters for radiological contamination from both natural and anthropogenic sources.
• Emergency Response: Rapid evaluation of water supplies in the event of nuclear incidents or unplanned releases, supporting timely public health interventions.
• Regulatory Compliance: Fulfilling legal requirements for testing and documentation of water quality in municipal, industrial, and laboratory settings.
• Research and Baseline Studies: Supporting scientific studies on natural radioactivity distribution and impact in various hydrogeological and climatic environments.

Related Standards

ISO/FDIS 13169 is designed to be used in conjunction with several other important international standards:

• ISO/IEC Guide 98-3: Guide to the expression of uncertainty in measurement (GUM)
• ISO 11929-1: Determination of characteristic limits for measurements of ionizing radiation
• ISO/IEC 17025: General requirements for competence of testing and calibration laboratories
• ISO 5667 series: Water quality sampling and handling (including ISO 5667-1, ISO 5667-3, and ISO 5667-10)
• ISO 80000-10: Atomic and nuclear physics terms and units
• ISO 13166: Test methods for other radionuclides in water (as an alternative for samples with potential thorium interference)

Summary

ISO/FDIS 13169:2026 offers a robust, validated approach for the measurement of uranium isotopes in non-saline waters, supporting effective monitoring for water safety and environmental compliance. This standard enhances the reliability and comparability of radiological water quality data worldwide, fostering best practices for public health protection and environmental stewardship. Laboratories and regulatory bodies are encouraged to utilize and reference this standard within water monitoring programs.

For more detailed requirements and technical guidance, consult the full ISO/FDIS 13169 document and related international standards.

FINAL DRAFT
International
Standard
ISO/TC 147/SC 3
Water quality — Uranium —
Secretariat: AFNOR
Test method using alpha liquid
Voting begins on:
scintillation counting
2026-10-02
Qualité de l'eau — Uranium — Méthode d'essai par comptage des
Voting terminates on:
scintillations alpha en milieu liquide
2026-11-27
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 SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
ISO/TC 147/SC 3
Water quality — Uranium —
Secretariat: AFNOR
Test method using alpha liquid
Voting begins on:
scintillation counting
Qualité de l'eau — Uranium — Méthode d'essai par comptage des
Voting terminates on:
scintillations alpha en milieu liquide
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 SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 3
6 Sampling . 4
7 Chemical reagents and equipment . 4
7.1 Chemical reagents .4
7.2 Equipment and apparatus .5
8 Instrument set up and calibration . 5
8.1 Preparation of extractant scintillation cocktail .5
8.2 Preparation of alpha emitter calibration source .6
8.3 Preparation of beta emitter calibration source .6
8.4 Optimization of counting conditions .6
8.5 Detection efficiency .6
8.6 Blank sample preparation and measurement.7
9 Procedure . 7
9.1 Without pre-concentration .7
9.2 Pre-concentration by evaporation .7
9.3 Sample preparation .8
9.4 Sample measurement .8
10 Quality assurance and quality control program . 8
10.1 Interference control .8
10.2 Quality control .8
11 Expression of results . 8
11.1 Calculation of activity per unit of mass .8
11.2 Standard uncertainty .8
11.3 Decision threshold .9
11.4 Limit of detection .9
11.5 Limits of the coverage intervals .9
11.5.1 Limits of the probabilistically symmetric coverage interval .9
11.5.2 Shortest coverage interval .10
11.6 Calculations using the activity concentration .10
12 Test report .11
Annex A (informative) Set-up parameters and validation data .12
Bibliography .16

iii
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, in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 230, Water analysis, in accordance with the Agreement on technical
cooperation between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 13169:2018), which has been technically
revised.
The main changes are as follows:
— the introduction has been modified;
— the expression of results has been updated in Clause 8;
— the Bibliography has been updated.
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
Introduction
Radionuclides are present throughout the environment, thus, water bodies (e.g. surface waters, ground
waters and 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 and runoff by
rain water) or released from technological processes involving naturally occurring radioactive materials
(e.g. mining, mineral processing, oil, gas and coal production, water treatment, and production and use
of phosphate fertilisers).
55 59 63 90 99
— Anthropogenic radionuclides such as Fe, Ni, Ni, Sr, Tc, transuranic elements (e.g. 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 into
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 for medical and industrial applications can be released into the environment after
use. Anthropogenic radionuclides are also found in waters due to contamination fallout resulting from
above-ground nuclear detonations and accidents such as those that have 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 can 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. As an example, during either a planned or existing situation,
−1 238 −1 324 [4]
the WHO guidance level in drinking water is 10 Bq·l for U and 1 Bq·l for U , see NOTES 1 and 2.
Conformity to these limits is assessed by measuring radioactivity in water samples and by comparing the
[5]
results obtained, with their associated uncertainties, as specified by ISO/IEC Guide 98-3 and ISO 5667-20 .
−1
The provisional guideline value for total content of uranium in drinking water is 30 µg·l based on its
chemical toxicity, which is predominant compared with its radiological toxicity.
NOTE 1 If the value is not specified in Annex 6 of Reference [4], the value has been calculated using the formula
provided in Reference [4] and the dose coefficient data from References [6] and [7].
NOTE 2 The guidance level calculated in Reference [4] is the activity concentration that results in an effective dose
−1 −1
of 0,1 mSv·a to members of the public for an intake of 2 l·d of drinking water for one year. This is an effective
dose that represents a very low level of risk to human health and which is not expected to give rise to any detectable
[4]
adverse health effects .
This document contains a test method to support laboratories which need to determine uranium isotopes
activity 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 decision threshold, limit of detection 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
FINAL DRAFT International Standard ISO/FDIS 13169:2026(en)
Water quality — Uranium — Test method using alpha liquid
scintillation counting
WARNING — Persons using this document should be familiar with normal laboratory practice. 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.
IMPORTANT — Tests conducted according to this document shall be carried out by suitably trained
staff.
1 Scope
This document specifies a method to measure uranium isotopes in non-saline waters by extraction and
liquid scintillation counting. This document covers the measurement of soluble uranium isotopes in water
−3 −1 −1
in activity concentrations between approximately 2·10 Bq·kg and 10 Bq·kg when analysing a 1 l test
sample volume with a 60 000 s counting time using a liquid scintillation counting instrument with α/β
234 238
discrimination function. This method can be used to determine the ratio of U/ U.
NOTE This method has not been tested for the measurement of other uranium isotopes.
This document applies to test samples of non-saline waters after proper sampling, handling and preparation.
This document is also applicable in the event of an emergency situation.
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/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
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 5667-10, Water quality — Sampling — Part 10: Guidance on sampling of waste water
ISO 11929-1, Determination of the characteristic limits (decision threshold, detection limit and limits of
the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 1:
Elementary applications
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC Guide 98-3, ISO 11929-1 and
ISO 80000-10 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
236 −1
A activity concentration of U, the standard solution Bq·g
S
−1
a total massic activity of uranium isotopes Bq·g
−1

a
possible or assumed true quantity values of the activity per mass Bq·g
−1
a* decision threshold of the measurand Bq·g
# −1
a limit of detection of the measurand Bq·g
−1

Bq·g
lower and upper limits of the probabilistically symmetric coverage interval
aa,
−1

lower and upper limits of the shortest coverage interval Bq·g
aa,
−1
c total activity concentration of the uranium isotopes Bq·l
A
ε alpha efficiency —
φ
distribution function of the standardized normal distribution, Φ(k ) = p applies —
p
α false positive probability —
β false negative probability —
m sample mass g
standard solution mass g
m
S
m mass of U standard solution used for the preparation of the calibration sample g
S(U)
m mass of Sr standard solution used for the preparation of the calibration sample g
S(Sr)
−1
r sample count rate in the alpha window s
g
−1
r count rate of the calibration sample in the alpha window s
S
−1
r blank sample count rate in the alpha window s
−1
background count rate from the alpha window s
r
0,α
−1
background count rate of the beta window s
r
0,β
−1
background count rate from the total window s
r
0,T
−1
r alpha emitter count rate in beta window when measuring alpha standard s
Sα,β
−1
r alpha emitter count rate in total (alpha+beta) window when measuring alpha standard s
Sα,T
−1
r beta emitter count rate in alpha window when measuring beta standard s
Sβ,α
−1
r beta emitter count rate in total (alpha+beta) window when measuring beta standard s
Sβ,T
t blank sample counting time s
t sample counting time s
g
t calibration or sample counting time s
s
−1
u(a) standard uncertainty associated with the measurand Bq·g
—
u relative standard uncertainty
rel
−1
ua  standard uncertainty of a as a function of its true value Bq·g

−1
#
standard uncertainty of a when the true value is the detection limit Bq·g

ua

−1
U(a) expanded uncertainty of the measurand, calculated by U = k u(a) with k = 2, …, Bq·g
τ alpha spillover parameter —
α
τ beta spillover parameter —
β
quantiles of the standardized normal distribution for the probabilities p (for instance —
k
p
p = 1 − α, 1 − β or 1 − γ/2)
k quantiles of the standardized normal distribution for the probabilities q (for instance —
q
q = 1−α, 1− β or 1−γ/2)
ρ −1
density of water samples g·l
s(ε) standard deviation of the alpha efficiency —
−1
s
s  standard deviation of alpha net count rate
 cps
ω auxiliary quantity —
V volume of test sample l
−1
w calibration factor l
5 Principle
5.1 The limit of detection depends on the sample volume, the instrument used, the background count
rate, the detection efficiency, the counting time and the chemical yield. The limit of detection of the method
described in this document, using currently available liquid scintillation apparatus, is approximately
−1 −1
0,002 Bq·l , which is lower than the WHO criteria for safe consumption of drinking water (10 Bq·l for
238 −1 234 [4]
U and 1 Bq·l for U) . This value can typically be achieved with a counting time of 60 000 s for a test
sample volume of 1 l, as shown in Table A.2.
234 235 238
5.2 Uranium has three natural isotopes, which are all radioactive: U, U and U. Details of these are
reported in Table 1.
Human activity can modify the natural ratio of uranium isotopes. As well, dissolved uranium in natural
waters can show isotope ratios different from natural ones due to leaching mechanisms.

Table 1 — Uranium isotopes features
Isotope Natural mass Half-life Specific activity concen-
abundance tration per gram of isotope
−1
% year Bq·g
238 9 4
U 99,27 4,468·10 1,235·10
235 8 2
U 0,72 7,04·10 5,579·10
234 5 4
U 0,005 4 2,455 ·10 1,243·10
The water sample is first acidified with a fixed amount of nitric acid and then, if a lower detection limit is
required, concentrated by evaporation. Uranium isotopes are then separated by a liquid-liquid extraction
using a scintillation cocktail containing a complexing agent such as bis(2-ethylhexyl) hydrogen phosphate
(HDEHP) and measured by liquid scintillation. The total activity of uranium isotopes can be thus determined.
U standard solution is used for calibration (external standard).
234 238
Spectral deconvolution can be performed using a suitable software to assess the U/ U ratio.
6 Sampling
Sampling, handling and storage of the water shall be done as specified in ISO 5667-1, ISO 5667-3 and
ISO 5667-10. guidance is given for the different types of waters in References [8] to [14]. The laboratory
must receive a sample that is truly representative and has neither been damaged or modified during
transportation or storage.
Store the water sample (from 0,1 l to 1 l) in a plastic bottle in accordance with ISO 5667-3. Acidify the sample
with HNO : if the sample is not supposed to be concentrated by evaporation, add 5 ml of HNO (7.1.1) to 95 g
3 3
of sample; if pre-concentration has to be carried out, add 5 ml of HNO (7.1.1) to 1 000 g of sample (see 9.1
and 9.2). The sample is filtered to remove suspended matter using a 0,45 μm filter. A smaller pore size filter
can also be used, but the filtration can take longer.
The sample shall be a
...

ISO/DISFDIS 13169:2026(en)
ISO/TC 147/SC 3
Secretariat: AFNOR
ISO TC 147/SC 3/WG 15
Date: 2026-09-18
Water quality — Uranium — Test method using alpha liquid
scintillation counting
Second edition
Date: 2026-07-01
Qualité de l'eau — Uranium — Méthode d'essai par comptage des scintillations alpha en milieu liquide
TThhiiss d drraft iaft iss su subbmmiitted tted to to a pa parallearallel vl vote ote iinn IS ISOO, CE, CENN.

FDIS stage
ISO/DISFDIS 13169:2026(en)
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication
may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO
at the address below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
EmailE-mail: [e-mail]
Website: www.iso.org
Published in Switzerland
iii
ISO/DISFDIS 13169:2025(E2026(en)
Contents
Foreword . Error! Bookmark not defined.
Introduction . Error! Bookmark not defined.
1 Scope . Error! Bookmark not defined.
2 Normative references . Error! Bookmark not defined.
3 Terms and definitions . Error! Bookmark not defined.
4 Symbols . Error! Bookmark not defined.
5 Principle. Error! Bookmark not defined.
6 Sampling . Error! Bookmark not defined.
7 Chemical reagents and equipment . Error! Bookmark not defined.
7.1 Chemical reagents . Error! Bookmark not defined.
7.2 Equipment and apparatus . Error! Bookmark not defined.
8 Instrument set up and calibration . Error! Bookmark not defined.
8.1 Preparation of extractant scintillation cocktail . Error! Bookmark not defined.
8.2 Preparation of alpha emitter calibration source . Error! Bookmark not defined.
8.3 Preparation of beta emitter calibration source . Error! Bookmark not defined.
8.4 Optimization of counting conditions . Error! Bookmark not defined.
8.5 Detection efficiency . Error! Bookmark not defined.
8.6 Blank sample preparation and measurement . Error! Bookmark not defined.
9 Procedure . Error! Bookmark not defined.
9.1 Without pre-concentration . Error! Bookmark not defined.
9.2 Pre-concentration by evaporation . Error! Bookmark not defined.
9.3 Sample preparation . Error! Bookmark not defined.
9.4 Sample measurement . Error! Bookmark not defined.
10 Quality assurance and quality control program . Error! Bookmark not defined.
10.1 Interference control . Error! Bookmark not defined.
10.2 Quality control . Error! Bookmark not defined.
11 Expression of results . Error! Bookmark not defined.
11.1 Calculation of activity per unit of mass . Error! Bookmark not defined.
11.2 Standard uncertainty. Error! Bookmark not defined.
11.3 Decision threshold . Error! Bookmark not defined.
11.4 Limit of detection . Error! Bookmark not defined.
11.5 Limits of the coverage intervals . Error! Bookmark not defined.
11.6 Calculations using the activity concentration . Error! Bookmark not defined.
12 Test report . Error! Bookmark not defined.
(informative) Set-up parameters and validation data . Error! Bookmark not defined.
Bibliography . Error! Bookmark not defined.

iv
ISO/DISFDIS 13169:2026(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., in collaboration with the European Committee for Standardization (CEN)
Technical Committee CEN/TC 230, Water analysis, in accordance with the Agreement on technical cooperation
between ISO and CEN (Vienna Agreement).
This second edition cancels and replaces the first edition (ISO 13169:2018), which has been technically
revised.
The main changes are as follows:
— — the introduction has been modified;
— — the expression of results has been updated in 8Clause 8;;
— — the Bibliography has been updated.
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.
v
ISO/DISFDIS 13169:2025(E2026(en)
Introduction
Radionuclides are present throughout the environment, thus, water bodies (e.g. surface waters, ground waters
and 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 and runoff by rain
water) or released from technological processes involving naturally occurring radioactive materials (e.g.
mining, mineral processing, oil, gas and coal production, water treatment, and production and use of
phosphate fertilisers).
55 59 63 90 99
— — Anthropogenic radionuclides such as Fe, Ni, Ni, Sr, Tc, transuranic elements (e.g. 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 into the
environment as a result of authorized routine releases. The radionuclides present in liquid effluents are
[1]
usually controlled before being discharged to the environment[1] and water bodies. Anthropogenic
radionuclides used for medical and industrial applications can be released into the environment after use.
Anthropogenic radionuclides are also found in waters due to contamination fallout resulting from above-
ground nuclear detonations and accidents such as those that have 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 during
[2][3]
planned, existing and emergency exposure situations[2][3]. . Some drinking-water sources can thus
contain radionuclides at activity concentrations that can present a human health risk. The World Health
[4]
Organization (WHO) recommends to routinely monitor radioactivity in drinking waters[4] 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. As an example, during either a planned or existing situation, the
-−1 238 -−1 324 [4]
WHO guidance level in drinking water is 10 Bq·l for U and 1 Bq·l for U[4], , see NOTES 1 and 2.
Conformity withto these limits is assessed by measuring radioactivity in water samples and by comparing the
results obtained, with their associated uncertainties, as specified by ISO/IEC Guide 98-3 and ISO 5667-
[5]
20[5] .
-−1
The provisional guideline value for total content of uranium in drinking water is 30 µg·l based on its
chemical toxicity, which is predominant compared with its radiological toxicity.
NOTE 1 If the value is not specified in Annex 6 of Reference [4][4],, the value has been calculated using the formula
provided in Reference [4][4] and the dose coefficient data from References [6][6] and[7] [7].
NOTE 2 The guidance level calculated in Reference [4][4] is the activity concentration that results in an effective dose
-−1 −1
of 0,1 mSv·a to members of the public for an intake of 2 l·d of drinking water for one year. This is an effective dose
that represents a very low level of risk to human health and which is not expected to give rise to any detectable adverse
[4]
health effects[4] .
This document contains a test method to support laboratories which need to determine uranium isotopes
activity in water samples. The method described in this document can be used for various types of waters (see
1Clause 1).). Minor modifications such as sample volume and counting time can be made if needed to ensure
that the decision threshold, limit of detection 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.
vi
DRAFT International Standard ISO/DIS 13169:2026(en)

Water quality — Uranium — Test method using alpha liquid
scintillation counting
WARNING — Persons using this document should be familiar with normal laboratory practice. 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.
IMPORTANT — It is absolutely essential that testsTests conducted in accordance withaccording to this
document shall be carried out by suitably qualifiedtrained staff.
1 Scope
This document specifies a method to measure uranium isotopes in non-saline waters by extraction and liquid
scintillation counting. This methoddocument covers the measurement of soluble uranium isotopes in water
−3 -−1 -−1
in activity concentrations between approximately 2·10 Bq·kg and 10 Bq·kg when analysing a 1 l test
sample volume with a 60 000 s counting time using a Liquid Scintillation Countingliquid scintillation counting
234 238
instrument with α/β discrimination function. This method can be used to determine the ratio of U/ U.
NOTE This method has not been tested for the measurement of other uranium isotopes.
This document applies to test samples of non-saline waters after proper sampling, handling and preparation.
This document is also applicable in the event of an emergency situation.
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/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
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: Guidance on the preservationPreservation and
handling of water samples
ISO 5667-10, Water quality — Sampling — Part 10: Guidance on sampling of waste water
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
ISO 11929-1Determination1, Determination of the characteristic limits (decision threshold, detection limit and
limits of the confidencecoverage interval) for measurements of ionizing radiation — Fundamentals and
application — Part 1: Elementary applications
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO/DISFDIS 13169:2025(E2026(en)
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80000-10/IEC Guide 98-3, ISO
11929-1 and ISO/IEC Guide 98-3 80000-10 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
236 −1
A activity concentration of U, the standard solution Bq·g
S
−1
a total massic activity of uranium isotopes Bq·g
−1
𝑎˜ possible or assumed true quantity values of the activity per mass Bq·g
−1
a* decision threshold of the measurand Bq·g
# −1
a limit of detection of the measurand Bq·g
⊲ ⊳
−1
𝑎 , 𝑎 lower and upper limits of the probabilistically symmetric coverage interval Bq·g
< >
−1
𝑎 , 𝑎 lower and upper limits of the shortest coverage interval Bq·g
−1
c total activity concentration of the uranium isotopes Bq·l
A
ε alpha efficiency —
𝜙 distribution function of the standardized normal distribution, Φ(k ) = = p applies —
p
α false positive probability —
β false negative probability —
m sample mass g
𝑚 standard solution mass g
S
m mass of U standard solution used for the preparation of the calibration sample g
S(U)
m mass of Sr standard solution used for the preparation of the calibration sample g
S(Sr)
-−1
r sample count rate in the alpha window s
g
−1
r count rate of the calibration sample in the alpha window s
S
−1
r blank sample count rate in the alpha window s
−1
𝑟 background count rate from the alpha window s
0,𝛼
−1
𝑟 background count rate of the beta window s
0,𝛽
−1
𝑟 background count rate from the total window s
0,T
−1
r alpha emitter count rate in beta window when measuring alpha standard s
Sα,β
−1
r alpha emitter count rate in total (alpha+beta) window when measuring alpha standard s
Sα,T
−1
r beta emitter count rate in alpha window when measuring beta standard s
Sβ,α
ISO/DISFDIS 13169:2026(en)
−1
r beta emitter count rate in total (alpha+beta) window when measuring beta standard s
Sβ,T
t blank sample counting time s
t sample counting time s
g
t calibration or sample counting time s
s
−1
u(a) standard uncertainty associated with the measurand Bq·g
𝑢 relative standard uncertainty —
rel
−1
𝑢˜ (𝑎˜) standard uncertainty of a as a function of its true value Bq·g
#
−1
standard uncertainty of a when the true value is the detection limit Bq·g
𝑢˜ (𝑎 )
−1
U(a) expanded uncertainty of the measurand, calculated by U = = k u(a) with k= = 2, …, Bq·g
τα alpha spillover parameter —
τ beta spillover parameter —
β
quantiles of the standardized normal distribution for the probabilities p (for instance p —
k
p
= = 1 − α, 1 − β or 1 − γ/2)
k quantiles of the standardized normal distribution for the probabilities q (for instance —
q
q = 1−α, 1− β or 1−γ/2)
−1
𝜌 density of water samples g·l
s(ε) standard deviation of the alpha efficiency —
-−1
s s
α
standard deviation of alpha net count rate
𝑠
cps
𝛼 cps
ω auxiliary quantity —
V volume of test sample l
−1
w calibration factor l
5 Principle
5.1 The limit of detection depends on the sample volume, the instrument used, the background count rate,
the detection efficiency, the counting time, and the chemical yield. The limit of detection of the method
described in this document, using currently available liquid scintillation apparatus, is approximately
-−1 -−1 238
0,002 Bq·l , which is lower than the WHO criteria for safe consumption of drinking water (10 Bq·l for U
-−1 234 [4]
and 1 Bq·l for U)[4]). . This value can typically be achieved with a counting time of 60 000 s for a test
sample volume of 1 l, as shown in Table A.2 Table A2.
234 235 238
5.2 Uranium has three natural isotopes, which are all radioactive: U, U and U. Details of these are
reported in Table 1 Table 1 below. .
Human activity can modify the natural ratio of uranium isotopes. As well, dissolved uranium in natural waters
can show isotope ratios different from natural ones due to leaching mechanisms.
Table 1 — Uranium isotopes features
Isotope Natural mass Half-life, yr Specific activity
abundance concentration per
gram of isotope
-−1
% year Bq·g
238 9 4
U 99,27 4,468·10 1,235·10
ISO/DISFDIS 13169:2025(E2026(en)
Isotope Natural mass Half-life, yr Specific activity
abundance concentration per
gram of isotope
-−1
% year Bq·g
235 8 2
U 0,72 7,04·10 5,579·10
234 5 4
U 0,0054005 4 2,455 ·10 1,243·10
The water sample is first acidified with a fixed amount of nitric acid and then, if a lower detection limit is
required, concentrated by evaporation. Uranium isotopes are then separated by a liquid-liquid extraction
using a scintillation cocktail containing a complexing agent such as bis(2-ethylhexyl) hydrogen phosphate
(HDEHP) and measured by liquid scintillation. The total activity of uranium isotopes can be thus determined.
U standard solution is used for calibration (external standard).
234 238
Spectral deconvolution can be performed using a suitable software to assess the U/ U ratio.
6 Sampling
Sampling, handling and storage of the water shall be done as specified in ISO 5667-1, ISO 5667-3 and
ISO 5667-10. guidance is given for the different types of waters in References [8][8] to[14] [14]. The
laboratory must receive a sample that is truly representative and has neither been damaged or modified
during transportation or storage.
Store the water sample (from 0,1 l to 1 l) in a plastic bottle in accordance with ISO 5667--3. Acidify the sample
with HNO : if the sample is not supposed to be concentrated by evaporation, add 5 ml of HNO (7.1.1(7.1.1))
3 3
to 95 g of sample; if pre-concentration has to be carried out, add 5 ml of HNO3 (7.1.1(7.1.1)) to 1 000 g of
sample (see 9.19.1 and 9.29.2).). The sample is filtered to remove suspended matter using a 0,45 μm filter. A
smaller pore size filter can also be used, but the filtration can take longer.
The sample shall be acidified after filtration to pH less than 2 with HNO (7.1.1(7.1.1).). The water test sample
should be stored at 3± ± 2 °C if not immediately analysed.
7 Chemical reagents and equipment
7.1 Chemical reagents
Use only reagents of recognisedrecognized analytical grade.
It is recommended to use acids and bases of trace metal grade or equivalent (a better purity grade can also be
employed).
-−1 -−1
7.1.1 7.1.1 Nitric acid, c(HNO ) = = 15,8 mol·l , ρ = 1,42 g·ml , mass fraction w(HNO ) = 70 %.
3 3
-−1
7.1.2 7.1.2 Nitric acid, c(HNO3) = 0,7 mol·l .
-−1
7.1.3 7.1.3 Hydrochloric acid, c(HCl) = 0,1 mol·l .
7.1.4 7.1.4 Ultrapure water with a resistivity of more than 18,2 MΩ cm at 25 °C and total organic carbon
−1
less than 1 μg∙l .
Unless otherwise stated, water refers to ultrapure water.
Water can contain detectable amounts of Rn and short-lived progeny. It is therefore strongly recommended
to boil it under vigorous stirring and let it stand for one day before its use. An alternative option is to purge it
with nitrogen for about 1 h for 2 l volume.
ISO/DISFDIS 13169:2026(en)
7.1.5 7.1.5 Scintillation cocktail, to be prepared (see 7.17.1).).
7.1.6 7.1.6 Ethanol, 95 %.
7.1.7 7.1.7 p-xylene, 99 %, for spectroscopy or scintillation grade.
7.1.8 7.1.8 Bis(2-ethylhexyl) hydrogen phosphate, 95 %.
7.1.9 7.1.9 Naphthalene, 99 %, scintillation grade.
7.1.10 7.1.10 2-(4-biphenylyl)-6-phenyl benzoxazole (PBBO), scintillation grade.
7.1.11 7.1.11 Radioactive standard solution.
236 90 90
Alpha and beta emitter standard solutions (respectively U and Sr/ Y or others suitable uranium isotopes
and beta emitting radionuclides) shall be provided with either calibration certificates containing at least the
activity concentration and measurement uncertainty, or statement of conformity with an identified
metrological specification, or both.
7.2 Equipment and apparatus
7.2.1 7.2.1 Balance.
7.2.2 7.2.2 Hot plate with magnetic stirrer and stirring bar.
7.2.3 7.2.3 Liquid scintillation counter, with α/β discrimination option, with preferably thermostated
counting chamber and preferably a commercially available low background counter to achieve better
detection limits.
7.2.4 7.2.4 Polyethylene scintillation vials, PTFE coated, 20 ml.
PTFE coated polyethylene vials are the best choice of scintillation vials because they prevent both the diffusion
of the cocktail into the wall of the vial and the absorption of radon from the outer environment. Glass vials
exhibit a considerably higher background and generally degrade both α/β discrimination and α peaks
resolution.
8 Instrument set up and calibration
8.1 Preparation of extractant scintillation cocktail
To prepare 500 ml of cocktail, weigh in a beaker:
— naphthalene (7.1.9Naphthalene (7.1.9):): 90,0 g;
— PBBO (7.1.10(7.1.10):): 2,0 g;
— HDEHP (7.1.8(7.1.8):): 25,0 g.
Add approximately 450 ml of p-xylene (7.1.7(7.1.7)) and stir for about 1 h with a magnetic stirrer. Transfer to
a 500 ml tared flask, coarsely filtering (e.g. with glass wool), and bring to volume
...