oSIST prEN ISO 13169:2026

• 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
• Public Enquiry End Date: 02-Feb-2026
• ICS: 13.060.60 - Examination of physical properties of water
• ICS: 17.240 - Radiation measurements
• Technical Committee: KAV - Water quality
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 08-Dec-2025
• Due Date: 27-Apr-2026
• Completion Date: 20-Feb-2026
• Ref Project: prEN ISO 13169 - Water quality - Uranium - Test method using alpha liquid scintillation counting (ISO/DIS 13169:2025)

Overview

oSIST prEN ISO 13169:2026 – Water Quality – Uranium – Test Method Using Alpha Liquid Scintillation Counting specifies a standardized laboratory procedure for determining the total activity concentration of uranium isotopes in non-saline water samples. Developed by the Slovenian Institute for Standardization (SIST), this method uses extraction and alpha liquid scintillation counting (LSC) to measure the presence of soluble uranium isotopes. The standard is aimed at supporting regular water quality monitoring, environmental protection, and compliance with safety regulations regarding uranium levels in drinking water and environmental water bodies.

Key Topics

• Measurement of Uranium Isotopes: The standard defines procedures for measuring uranium isotope activity concentrations between approximately 0.002 Bq/kg and 10 Bq/kg. It enables the determination of the 234U/238U ratio, aiding in environmental and health risk assessments.
• Sample Preparation and Handling: Detailed requirements are set for sampling, acidification, filtration, and storage to ensure samples are representative and uncontaminated. Proper handling is critical for accurate uranium detection and quantification.
• Extraction and Scintillation Counting: The method uses liquid-liquid extraction followed by measurement with LSC equipment capable of alpha/beta discrimination. The procedure includes stringent calibration and quality control protocols.
• Quality Assurance: The document highlights the importance of laboratory competence, regular blank testing, interference control (especially thorium), and adherence to ISO/IEC 17025 for laboratory quality assurance.
• Detection Limits: With current LSC technology, the detection limit for uranium activity in water is lower than the WHO guideline values, providing sensitivity for both routine monitoring and emergency responses.

Applications

The test method outlined in oSIST prEN ISO 13169:2026 is widely applicable to:

• Drinking Water Safety: Ensuring that water supply systems comply with regulatory thresholds for uranium, reducing health risks.
• Environmental Monitoring: Assessing the impact of natural processes or anthropogenic activities (such as mining or nuclear power generation) on surface waters and groundwater.
• Routine and Emergency Analysis: The method is suitable for planned, ongoing, or emergency assessments of uranium in water due to its sensitivity and reliability.
• Regulatory Compliance: Supporting regulatory authorities, laboratories, and water utilities in meeting national and international standards for safe uranium concentrations in water resources.

Related Standards

This standard is complemented by other international guidelines and standards that enhance sampling, uncertainty estimation, and laboratory competency:

• ISO 5667 Series: Guidance on the design of sampling programs, water sample preservation, and quality control in environmental water sampling.
• ISO 80000-10: Specifies quantities and units in atomic and nuclear physics for consistency in reporting radioactivity.
• ISO 11929: Procedures for determining characteristic limits (decision threshold, detection limit, and confidence intervals) for ionizing radiation measurements.
• ISO/IEC 17025: General requirements for the competence of testing and calibration laboratories.
• ISO/IEC Guide 98-3: Guide to the expression of uncertainty in measurement (commonly known as the GUM).

Practical Value

Adopting the procedures specified in oSIST prEN ISO 13169:2026 enhances water quality assessment reliability, improves public health protection, and supports compliance with regulatory requirements. Laboratories benefit from a harmonized, validated approach to uranium testing, aligning with international best practices and facilitating data comparability across borders. This standard is a valuable resource for environmental scientists, health authorities, water utilities, and regulatory agencies focused on water safety and radiological protection.

SLOVENSKI STANDARD
01-januar-2026
Kakovost vode - Uran - Preskusna metoda s štetjem alfa delcev s tekočinskim
scintilatorjem (ISO/DIS 13169:2025)
Water quality - Uranium - Test method using alpha liquid scintillation counting (ISO/DIS
13169:2025)
Wasserbeschaffenheit - Uran - Verfahren mittels AlphaFlüssigszintillationszählung
(ISO/DIS 13169:2025)
Qualité de l'eau - Uranium - Méthode d'essai par comptage des scintillations alpha en
milieu liquide (ISO/DIS 13169:2025)
Ta slovenski standard je istoveten z: prEN ISO 13169
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 13169
ISO/TC 147/SC 3
Water quality — Uranium —
Secretariat: AFNOR
Test method using alpha liquid
Voting begins on:
scintillation counting
2025-12-01
Qualité de l'eau — Uranium — Méthode d'essai par comptage des
Voting terminates on:
scintillations alpha en milieu liquide
2026-02-23
ICS: 17.240; 13.060.60
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.
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STANDARDS MAY ON OCCASION HAVE TO
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BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
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RECIPIENTS OF THIS DRAFT ARE INVITED
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NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Reference number
ISO/DIS 13169:2025(en)
DRAFT
ISO/DIS 13169:2025(en)
International
Standard
ISO/DIS 13169
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
ICS: 17.240; 13.060.60
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 2025
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
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NOTIFICATION OF ANY RELEVANT PATENT
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Published in Switzerland Reference number
ISO/DIS 13169:2025(en)
ii
ISO/DIS 13169:2025(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions, symbols and units . 2
4 Principle . 3
5 Sampling . 4
6 Chemical reagents and equipment . 4
6.1 Chemical reagents .4
6.2 Equipment and Apparatus .5
7 Instrument set up and calibration . 5
7.1 Preparation of extractant scintillation cocktail .5
7.2 Preparation of alpha emitter calibration source .5
7.3 Preparation of beta emitter calibration source .6
7.4 Optimization of counting conditions .6
7.5 Detection efficiency .6
7.6 Blank sample preparation and measurement.7
8 Procedure . 7
8.1 Without pre-concentration .7
8.2 Pre-concentration by evaporation .7
8.3 Sample preparation .7
8.4 Sample measurement .8
9 Quality assurance and quality control program . 8
9.1 Interference control .8
9.2 Quality control .8
10 Expression of results . 8
10.1 Calculation of activity per unit of mass .8
10.2 Standard uncertainty .8
10.3 Decision threshold .9
10.4 Limit of detection .9
10.5 Limits of the coverage intervals . .9
10.5.1 Limits of the probabilistically symmetric coverage interval .9
10.5.2 The shortest coverage interval .10
10.6 Calculations using the activity concentration .10
11 Test report . 10
Annex A (informative) Set-up parameters and validation data .12
Bibliography .16

iii
ISO/DIS 13169:2025(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
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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 13169:2018), which has been technically
revised.
The main changes are as follows:
— Modification of the introduction
— Clause 8: updating of the expression of results
— Updating of the Bibliography
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 13169:2025(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 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 the 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 -1 [4]
the WHO guidance level in drinking water is 10 Bq·l for uranium 238 and 1 Bq·l for uranium 234 see
NOTES 1 and 2. Compliance with 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
[5]
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 method(s) 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, 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 13169:2025(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 tests conducted according to this document be carried
out by suitably qualified staff.
1 Scope
This document specifies a method to measure 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
−3 -1 -1
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 with a LSC instrument with α/β discrimination function.
234 238
The ratio U/ U can also be determined. This method has not been tested for the measurement of other
uranium isotopes.
The method is applicable to test samples of non-saline waters after proper sampling, handling, and
preparation.
The detection limit 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
-1
in this document, using currently available liquid scintillation apparatus, is approximately 0,03 Bq·l , which
-1 238 -1
is lower than the WHO criteria for safe consumption of drinking water (10 Bq·l for U and 1 Bq·l for
234 [4]
U). This value can typically be achieved with a counting time of 30 000 s for a test sample volume of 1 l.
The method described in 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 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 preservation and handling of water samples
ISO 5667-14, Water quality — Sampling — Part 14: Guidance on quality assurance and quality control of
environmental water sampling and handling
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
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/IEC 17025, General requirements for the competence of testing and calibration laboratories

ISO/DIS 13169:2025(en)
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
measurement (GUM:1995)
3 Terms, definitions, symbols and units
For the purposes of this document, the terms and definitions given in ISO 80000-10, ISO 11929 series and
ISO/IEC Guide 98-3 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/
236 -1
A activity concentration of U, the standard solution Bq·g
S
-1
a total mass 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
distribution function of the standardized normal distribution, Φ(k ) = p ap-
p
φ
plies
α, β false positive and false negative probability respectively
m sample mass g
m
standard solution mass g
S
mass of U standard solution used for the preparation of the calibration g
m
S(U)
sample
mass of Sr standard solution used for the preparation of the calibration g
m
S(Sr)
sample
r sample count rate in the alpha window
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
ISO/DIS 13169:2025(en)
-1
alpha emitter count rate in total (alpha+beta) window when measuring alpha s
r
Sα,T
standard
-1
r beta emitter count rate in alpha window when measuring beta standard s
Sβ,α
-1
beta emitter count rate in total (alpha+beta) window when measuring beta s
r
Sβ,T
standard
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
expanded uncertainty of the measurand, calculated by U = ku (c ) with k= 2, Bq·g
A
U(a)
…,
τ alpha spillover parameter
α
τ beta spillover parameter
β
quantiles of the standardized normal distribution for the probabilities p (for
k
p
instance p = 1 − α, 1 − β or 1 − γ/2)
k quantiles of the standardized normal distribution for the probabilities q (for
q
instance 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
s standard deviation of net alpha cps
αcps
ω auxiliary quantity
V volume of test sample L
-1
w Calibration factor L
4 Principle
234 235 238
Natural uranium is composed of a mixture of three isotopes, all radioactive: U, U and U.
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.

ISO/DIS 13169:2025(en)
Table 1 — Uranium isotopes features
Isotope Mass abundance (%) Half-life (a) Specific activity of natural
-1
uranium (Bq·g )
238 9 4
U 99,3 4,468·10 1,235·10
235 8 2
U 0,7 7,04·10 5,579·10
234 5 4
U <0,1 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 (liquid-liquid extraction) by
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.
5 Sampling
Sampling, handling, and storage of the water shall be done as specified
...