oSIST prEN ISO 13160:2026

• Abstract:

  This document specifies conditions for the determination of 90Sr and 89Sr activity concentration in samples of environmental water using liquid scintillation counting (LSC) or proportional counting (PC).; The method is applicable to test samples of drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling and handling, and test sample preparation. Filtration of the test sample and a chemical separation are required to separate and purify strontium from a test portion of the sample.; The detection limit depends on the sample volume, the instrument used, the sample count time, the background count rate, the detection efficiency and the chemical yield. The method described in this document, using currently available LSC counters, has a detection limit of approximately 10 mBq l−1 and 2 mBq l−1 for 89Sr and 90Sr, respectively, which is lower than the WHO criteria for safe consumption of drinking water (100 Bq·l−1 for 89Sr and 10 Bq·l−1 for 90Sr)[3]. These values can be achieved with a counting time of 1 000 min for a sample volume of 2 l.; The methods described in this document are applicable in the event of an emergency situation. When fallout occurs following a nuclear accident, the contribution of 89Sr to the total amount of radioactive strontium is not negligible. This document provides test methods to determine the activity concentration of 90Sr in presence of 89Sr.; The analysis of 90Sr and 89Sr adsorbed to suspended matter is not covered by this method.; It is the user’s responsibility to ensure the validity of this test method selected for the water samples tested.

• Status: Not Published
• Public Enquiry End Date: 01-Oct-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: 05-Aug-2026
• Due Date: 23-Dec-2026
• Ref Project: prEN ISO 13160 - Water quality - Strontium 90 and strontium 89 - Test methods using liquid scintillation counting or proportional counting (ISO/DIS 13160:2026)

• Revises: SIST EN ISO 13160:2021 - Water quality - Strontium 90 and strontium 89 - Test methods using liquid scintillation counting or proportional counting (ISO 13160:2021)
• Effective Date: 01-Sep-2026

Overview

oSIST prEN ISO 13160:2026:2026 - Water Quality – Strontium 90 and Strontium 89 – Test Methods Using Liquid Scintillation Counting or Proportional Counting is an international draft standard developed by CEN and ISO. It specifies validated laboratory test methods for the determination of strontium-90 (^90Sr) and strontium-89 (^89Sr) activity concentrations in environmental water samples. The document details procedures employing liquid scintillation counting (LSC) and proportional counting (PC), ensuring sensitive detection of these radionuclides in a range of water types.

Strontium-89 and strontium-90 are radioactive isotopes commonly monitored in water quality assessments, particularly due to their potential health risks and regulatory guidance by authorities such as the World Health Organization (WHO). These methods cater to routine environmental monitoring and emergency response following nuclear incidents.

Key Topics

• Applicable Water Types: The test methods are suitable for drinking water, rainwater, surface water, groundwater, seawater, cooling water, industrial water, as well as domestic and industrial wastewater, after appropriate sample preparation.

• Sample Preparation: The process requires preliminary filtration and selective chemical separation to isolate strontium from potential interferences in the test sample.

• Analytical Techniques:

  • Liquid Scintillation Counting (LSC): Preferred for its sensitivity and ability to distinguish between beta-emitters using spectral analysis.
  • Proportional Counting (PC): Utilized for direct beta-particle emission measurement but less effective than LSC in identifying interfering radionuclides.

• Detection Limits: Using current LSC instruments, the method achieves detection limits as low as 10 mBq/l for ^89Sr and 2 mBq/l for ^90Sr with a 2-liter sample and approximately 1,000 minutes of counting-well below WHO maximum limits for safe drinking water.

• Emergency and Routine Use: These standardized methods are applicable for routine monitoring, regulatory compliance, and assessment in emergency situations, such as fallout following nuclear accidents.

• Limitations: The documented methods do not cover measurement of strontium isotopes adsorbed to suspended matter; only dissolved forms in water samples are measured.

Applications

• Regulatory Water Monitoring: Ensures compliance with national and international guidelines for radioactivity in water, protecting public health by observing limits set by WHO and environmental agencies.

• Post-Accident Environmental Assessment: Provides reliable methodologies for quantifying radioactive strontium isotopes after nuclear accidents (e.g., Chernobyl, Fukushima), supporting prompt risk assessment and mitigation.

• Industrial and Nuclear Facilities: Essential for monitoring radioactive discharges and effluents in facilities handling radiological materials, optimizing process control and environmental safety.

• Research and Public Health: Supports studies on the distribution and impact of radionuclides in the water cycle, aiding epidemiological research and long-term environmental surveillance.

Related Standards

• EN ISO 11929-1:2021 – Characteristic limits for measurements of ionizing radiation; fundamentals and applications.
• ISO 80000-10:2019 – Quantities and units for atomic and nuclear physics.
• ISO 5667-1, ISO 5667-3, ISO 5667-14 – Water quality sampling guidelines.
• ISO/IEC Guide 98-3:2008 – Uncertainty of measurement.
• ISO 13160:2021 – Previous edition, technically revised in this new draft.

Practical Value

By following oSIST prEN ISO 13160:2026:2026, laboratories, water utilities, environmental agencies, and industry stakeholders can:

• Achieve accurate, sensitive testing for ^90Sr and ^89Sr in diverse water matrices.
• Meet regulatory and safety requirements for radioactivity in water.
• Respond efficiently to radiological contamination events.
• Maintain comparability of results through harmonized test procedures.

This standard represents a comprehensive framework for ensuring water safety and protecting human health through the reliable determination of critical radiological contaminants.

SLOVENSKI STANDARD
01-september-2026
Kakovost vode - Stroncij Sr-90 in stroncij Sr-89 - Preskusne metode s štetjem s
tekočinskim scintilatorjem ali proporcionalnim štetjem (ISO/DIS 13160:2026)
Water quality - Strontium 90 and strontium 89 - Test methods using liquid scintillation
counting or proportional counting (ISO/DIS 13160:2026)
Wasserbeschaffenheit - Strontium-90 und Strontium-89 - Verfahren mittels
Flüssigszintillationszählung oder Proportionalzählung (ISO/DIS 13160:2026)
Qualité de l'eau - Strontium 90 et strontium 89 - Méthodes d'essai par comptage des
scintillations en milieu liquide ou par comptage proportionnel (ISO/DIS 13160:2026)
Ta slovenski standard je istoveten z: prEN ISO 13160
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 13160
ISO/TC 147/SC 3
Water quality — Strontium 90 and
Secretariat: AFNOR
strontium 89 — Test methods using
Voting begins on:
liquid scintillation counting or
2026-07-27
proportional counting
Voting terminates on:
2026-10-19
Qualité de l'eau — Strontium 90 et strontium 89 — Méthodes
d'essai par comptage des scintillations en milieu liquide ou par
comptage proportionnel
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 has not been edited by the ISO Central 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 13160:2026(en)
DRAFT
ISO/DIS 13160:2026(en)
International
Standard
ISO/DIS 13160
ISO/TC 147/SC 3
Water quality — Strontium 90 and
Secretariat: AFNOR
strontium 89 — Test methods using
Voting begins on:
liquid scintillation counting or
proportional counting
Voting terminates on:
Qualité de l'eau — Strontium 90 et strontium 89 — Méthodes
d'essai par comptage des scintillations en milieu liquide ou par
comptage proportionnel
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 has not been edited by the ISO Central 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
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
BE CONSIDERED IN THE LIGHT OF THEIR
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
or ISO’s member body in the country of the requester.
NATIONAL REGULATIONS.
ISO copyright office
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
Phone: [phone]
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION.
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ISO/DIS 13160:2026(en)
ii
ISO/DIS 13160:2026(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 2
3.1 Terms and definitions .2
3.2 Symbols .2
4 Principle . 3
4.1 General .3
4.2 Chemical separation .3
4.3 Detection .3
5 Chemical reagents and equipment . 3
6 Procedure . 4
6.1 Test sample preparation .4
6.2 Chemical separation .4
6.2.1 General .4
6.2.2 Precipitation techniques .5
6.2.3 Liquid–liquid extraction technique .6
6.2.4 Chromatographic techniques .6
6.3 Preparation of the source for test.6
6.3.1 Source preparation for liquid scintillation counter .6
6.3.2 Source preparation for proportional counter .6
6.4 Measurement .7
6.4.1 General .7
6.4.2 Liquid scintillation counter .7
6.4.3 Proportional counter .7
6.4.4 Efficiency calculation .7
6.4.5 Determination of the chemical yield .8
7 Expression of results . 8
90 90
7.1 Determination of Sr in equilibrium with Y .8
7.1.1 Calculation of the activity concentration .8
7.1.2 Standard uncertainty .9
7.1.3 Decision threshold .10
7.1.4 Detection limit .10
90 90
7.2 Determination of Sr from separated Y .10
7.2.1 Calculation of the activity concentration .10
7.2.2 Standard uncertainty .11
7.2.3 Decision threshold .11
7.2.4 Detection limit .11
90 89 90 90
7.3 Determination of Sr and Sr utilizing Sr/ Y equilibrium . 12
7.3.1 Calculation of the activity concentration . 12
7.3.2 Standard uncertainty . 12
7.3.3 Decision threshold . 13
7.3.4 Limit of detection .14
8 Limits of the coverage intervals . 14
8.1 Limits of the probabilistically symmetric coverage interval.14
8.2 Limits of the shortest coverage interval . 15
9 Quality control .15
10 Test report .15

iii
ISO/DIS 13160:2026(en)
90 89
Annex A (informative) Determination of Sr and Sr by precipitation and proportional
counting . 17
90 89
Annex B (informative) Determination of Sr and Sr by precipitation and liquid scintillation
counting .21
90 90
Annex C (informative) Determination of Sr from its decay progeny Y at equilibrium by
organic extraction and liquid scintillation counting .25
Annex D (informative) Determination of Sr after ionic exchange separation by proportional
counting .28
Annex E (informative) Determination of Sr after separation on a crown ether-based
extraction resin for strontium and liquid scintillation counting .31
90 90
Annex F (informative) Determination of Sr from its decay progeny Y at equilibrium by
organic extraction and proportional counting and liquid scintillation counting .34
90 90
Annex G (informative) Determination of Sr from its decay product Y at equilibrium to
specific octyldiglycolamide resin and liquid scintillation counting .38
Annex H (informative) Correction factor for Sr purity using proportional counting . 41
Bibliography .44

iv
ISO/DIS 13160:2026(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).
Attention is drawn to the possibility that some of the elements of this document may be the subject 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 third edition cancels and replaces the second edition (ISO 13160:2021), which has been technically
revised. The main changes compared to the previous edition are as follows:
— the Clause has been completely revised;
90 90
— Annex G dealing with Sr analysis from its decay product Y in based on extraction chromatography
has been added;
— the has been enhanced.
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/DIS 13160:2026(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 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 fertilizers).
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 to the
environment as a result of discharged 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 to the environment after use.
Anthropogenic radionuclides are also found in waters due to contamination from fallout resulting from
above-ground nuclear detonations and accidents such as those that have occurred at the Chornobyl and
Fukushima nuclear facilities.
Radionuclide activity concentration 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
−1 89
situation, the WHO guidance level in drinking water is 100 Bq·l for Sr activity concentration and 10
−1 90 [4]
Bq·l for Sr , 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
[5] [6]
ISO/IEC Guide 98-3:2008 and ISO 5667-20:2008 .
[4]
NOTE 1 If the value is not specified in Annex 6 of Reference , the value has been calculated using the formular
[4] [7] [8]
provided in Reference and the dose coefficient data from References and .
−1
NOTE 2 The guidance level is the activity concentration with an intake of 2 l·d of drinking water for one year that
−1
results in an effective dose of 0,1 mSv·a for members of the public. This is an effective dose that represents a very low
[4]
level of risk and which is not expected to give rise to any detectable adverse health effects
.
90 89
This document contains methods to support laboratories, which need to determine Sr and Sr in water
samples. The methods 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.

vi
DRAFT International Standard ISO/DIS 13160:2026(en)
Water quality — Strontium 90 and strontium 89 — Test
methods using liquid scintillation counting or proportional
counting
1 Scope
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 and to determine
the applicability of any other restrictions.
Warning — It is absolutely essential that tests conducted according to this document be carried out
by suitably trained staff.
90 89
This document specifies methods to determine Sr and Sr by liquid scintillation counting (LSC) or
proportional counting (PC) in supply water, drinking water, rainwater, surface and ground water, marine
water, as well as cooling water, industrial water, domestic, and industrial wastewater after proper sampling,
handling and test sample preparation.
The detection limit depends on the sample volume, the instrument used, the sample counting time, the
background count rate, the detection efficiency and the chemical yield. The method described in this
document, using currently available LSC and PC instruments, has a detection limit of approximately
−1 −1 90 89
2 mBq·l and 10 mBq·l for Sr and Sr, respectively, for a volume of 2 l and a measuring time of 60 000
−1 89
s, which is lower than the WHO criteria for safe consumption of drinking water (100 Bq·l for Sr and
−1 90 [4]
10 Bq·l for Sr) .
The methods described in this document are applicable in the event of an emergency situation. When
contamination contains fresh fission products, the contribution of Sr to the total amount of radioactive
Sr is not negligible. This document provides test methods to determine the activity concentration of Sr in
89 90
presence of Sr, and to determine the activity concentration of Sr in large volume of water sample (>50 L).
90 89
The analysis of Sr and Sr adsorbed to suspended matter is not covered by this method. Filtration of
the test sample and a chemical separation are required to separate and purify Sr from a test portion of the
sample as the analysis of 90Sr and 89Sr adsorbed to suspended matter is not covered by this method.
It is the user’s responsibility to ensure the validity of this test method selected for the water samples tested.
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 80000-10:2019/Amd 1:2025, Quantities and units — Part 10: Atomic and nuclear physics — Amendment 1
EN ISO 11929-1:2021, 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 11929-1:2019)

ISO/DIS 13160:2026(en)
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in EN ISO 11929-1:2021 and
ISO 80000-10:2019/Amd 1:2025 apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.2 Symbols
The symbols are given in Table 1.
Table 1
Symbol Definition Unit
A calibration source activity of radionuclide i, at the time of calibration Bq
i
-1
c activity concentration of radionuclide i Bq·l
A,i
-1
decision threshold of radionuclide i Bq·l
-1
detection limit of radionuclide i Bq·l
-1
lower and upper limits of the probabilistically symmetric coverage interval of radionuclide i Bq·l
-1
lower and upper limits of the shortest coverage interval of radionuclide i Bq·l
k quantile of the standardized normal distribution for the probability p (for instance p=1-α, 1-β
p
or 1-γ/2)
R chemical yield of the extraction of radionuclide i
c,i
-1
r background count rate s
-1
r background count rate for measurement j s
0j
-1
r gross count rate s
g
-1
r gross count rate for measurement j s
gj
-1
r net count rate for measurement j s
j
-1
r calibration source count rate s
s
90 90
t time elapsed between separation of Sr/ Y (t = 0) and mid-point of counting s
t background counting time s
t , t start and finish time respectively of the measurement, referred to t = 0 s
d f
t sample counting time s
g
t start time of the measurement j, referred to t = 0 s
j
t calibration source counting time s
s
-1
U expanded uncertainty, calculated by U = ku(c ) with k = 1, 2 . Bq·l
A
-1
u(c ) standard uncertainty associated with the measurement result Bq·l
A
u (c ) relative standard uncertainty
rel A
V volume of the test sample l
α, β probability of a false positive and false negative decision, respectively
ε counting efficiency for radionuclide i
i
λ decay constant of radionuclide i
i
ISO/DIS 13160:2026(en)
4 Principle
4.1 General
90 90 89
The radionuclides Sr, Y and Sr are all pure beta-particle emitters. Their beta-emission energies and
half-lives are given in Table 2.
90 90 89 [9]
Table 2 — Half-lives, maximum energies, and average energies of Sr, Y, and Sr
90 90 89
Parameter Sr Y Sr
Maximum energy 546,0 keV 2 283,9 keV 1 491,0 keV
Average energy 196,4 keV 935,3 keV 586,3 keV
Half-life 28,80 (7) a 2,6684 (13) d 50,57 (3) d
Strontium-90 can either be measured directly or calculated through the measurement of its decay
progeny Y. All the test methods are based on a chemical separation step followed by beta-counting using
proportional counting (PC) or liquid scintillation counting (LSC). See Table 3 which contains guidance over
method selection.
4.2 Chemical separation
Strontium is isolated from the water using precipitation, ion exchange or specific chromatographic
[10]
separation by crown ether resin . Yttrium can then be isolated by precipitation, liquid–liquid extraction,
or extraction chromatography. Alternatively, yttrium can be isolated directly from the sample.
The method chosen shall be selective with a high chemical yield. When certain radionuclides such of
thorium, lead or bismuth radioisotopes are present at high activity levels, they can interfere with Sr,
90 89
Y or Sr detection. Other matrix constituents, such as other alkaline earth metals, particularly calcium
which interferes with Sr separation; or transuranic and lanthanide elements which interfere with yttrium
separation, reduce the chemical yield of the various extraction steps.
The radiochemical separation yield is calculated using either a stable element (e.g. Sr or Y), which can
be used as both a carrier or as a tracer, or a radioactive tracer such as Sr. Techniques such as atomic
absorption spectroscopy (AAS), inductively coupled plasma–atomic emission spectroscopy (ICP–AES) EN
[11] [12]
ISO 11885:2009 or inductively coupled plasma–mass spectrometry (ICP–MS) EN ISO 17294-1:2024
to measure the carrier, and gamma-spectrometry to measure Sr, are recommended. A carrier can also be
measured by gravimetric methods, which can be an easy, fast, and cost effective method to determine the
chemical recovery. However, the element to measure (Sr or Y) has to be well separated or the presence of
stable elements, notably alkaline earth elements in the leaching solutions, can lead to an overestimation of
the radiochemical separation yields, particularly for the measurement of Sr.
4.3 Detection
The use of LSC, which provides spectra and can allow the detection of interference from unwanted
radionuclides, is recommended in preference to PC, which does not does not allow emissions from different
beta-emitters to be identified. When PC instrument is used, it is recommended that the purity of the
precipitate is checked by monitoring the ingrowth of Y, even though this is time consuming.
Seven test methods are presented in Annex A, Annex B, Annex C, Annex D, Annex E, Annex F and Annex G.
5 Chemical reagents and equipment
The necessary chemical reagents and equipment for each Sr or Y measurement method are specified in
Annex A, Annex B, Annex C, Annex D, Annex E, Annex F and Annex G.
During the analyses use only reagents of recognized analytical grade and laboratory ultrapure water with a
resistivity of more than 18 MΩ·cm at 25 °C.

ISO/DIS 13160:2026(en)
6 Procedure
6.1 Test sample preparation
Strontium-89/90 activity concentration is determined from the water test sample after appropriate
[13] [14] [15]
sampling procedures ISO 5667-1 , ISO 5667-3 and ISO 5667-14:2014 .
Filtration of the test sample should be done prior to the addition of the tracer or carrier and then sufficient
time should be allowed for the tracer or carrier to reach chemical equilibrium with the Sr initial present in
the sample before starting the test sample preparation.
90 90 90
Unlike the direct determination of Sr, indirect determination of Sr from its decay product Y at
equilibrium requires to set aside the sample for over 20 days or longer before analysis, by which time Y
will be in equilibrium with Sr, particularly in the case of a fresh contamination.
When stable Sr is added as a carrier, the original Sr concentration in the test sample shall be known in order
to determine the chemical yield. In the case of separation based on extraction chromatography, the total Sr
content shall be below the sorption capacity of the resin to avoid saturation of the resin.
6.2 Chemical separation
6.2.1 General
89 90
There are several approaches Table 3 to the routine analysis of Sr and Sr involving the separation and
purification of Sr or Y: precipitation, liquid–liquid extraction or chromatographic techniques (ion exchange
or chromatographic extraction). Annex A, Annex B, Annex C, Annex D, Annex E, Annex F and Annex G
describe a test method for each of these techniques.

ISO/DIS 13160:2026(en)
Table 3 — Determination procedures for radioactive Sr depending on its origin
NOTE Strontium-89 is not considered in old contamination due to its short half-life, but should be included in fresh
contamination scenarios. The number of counts indicated in this Table 3 is valid only in cases of effective separation,
i.e. when no interferents are present. In practice, verifying the absence of interference requires monitoring the re-
growth or decay of Y. In the case of liquid scintillation counting, spectrum examination may occasionally reveal the
presence of an interferent, but this method is less sensitive than monitoring the re-growth or decay of Y.
6.2.2 Precipitation techniques
The precipitation of Sr with nitrate is a very common method to separate Sr even for water samples with
high mineral salt contents. This technique is very efficient, but not selective for Sr.
The addition of fuming nitric acid leads to a Sr precipitate with other interfering elements. Successive
dissolution–precipitation cycles concentrate Sr in the precipitate, while yttrium and other elements remain
in the supernatant fraction. After further separation of Sr, Sr is usually precipitated as SrCO .
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For the test method with Sr and Y in equilibrium, either the total concentration of Sr and Y is directly
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measured in the precipitate or Y activity is measured after a separation from Sr. In this latter case, the
chemical yield is estimated by the addition of an yttrium carrier to the source before the yttrium separation.
The final product is an yttrium precipitate, usually in the form of an oxalate.
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In the absence of Sr, Sr is measured by counting the beta-emission of Y or of Y and Sr. In the latter
case, the sample can be counted at equilibrium or counted at any time if a mathematical correction for Y
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ingrowth and Sr decay is applied. When Sr in the water test sample cannot be neglected, the direct
measurement method of Sr at two different times shall be chosen.
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Two precipitation methods are described: Annex A employs PC for Sr and Sr; Annex B employs LSC for
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Sr and Sr.
ISO/DIS 13160:2026(en)
6.2.3 Liquid–liquid extraction technique
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This technique is based on the extraction of Y in equilibrium with its radioactive parent Sr using an
organic solvent. The chemical separation is fast and requires few technical resources. A provisional result
can be achieved after 3 d (approximately one Y decay period). However, total selectivity of the extraction
is not always possible. In the presence of high levels of natural radioactivity, interference can occur, making
it difficult to determine very low levels of Sr activity.
Yttrium-90 is extracted from the water test sample fraction using an organic solvent, and then after
re-extraction, recovered in the form of an yttrium precipitate. Test methods are presented in Annex C
and Annex F.
After the source preparation, the Y is measured by PC (Annex F) or LSC (Annex C). The absence of other
interfering beta-emitters is verified during the decay of Y by measuring the decrease in count rate of the
Y and once the decay is complete (about 20 days), comparing it with the background level activity.
6.2.4 Chromatographic techniques
6.2.4.1 Ion exchange resin
This technique is based on Sr(II) exchange on a cation exchange resin and is used for the separation and
purification of Sr in large volume samples. A method is presented in Annex D in which the measurement is
carried out with PC.
6.2.4.2 Crown ether resin
This technique is based on the selective chromatographic separation of Sr using a specific crown ether resin.
However, this method has limited application for samples containing high amounts of stable Sr and Ca in
amounts exceeding the resin sorption capacity. A method is presented in Annex E in which the measurement
is carried out by LSC.
6.3 Preparation of the source for test
6.3.1 Source preparation for liquid scintillation counter
The Sr or Y precipitate is dissolved and mixed with a liquid scintillation cocktail. When Sr or Y is already in
solution, it is mixed directly with the liquid scintillator. The volume of the analysed aliquot depends on the
equipment (vial size) and the specific scintillation cocktail used.
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The calibration source shall be prepared from a known activity of tracer ( Sr, Sr, Sr + Y or Y) with
the same geometry and chemical composition as the source to be measured.
The blank source should be prepared following the method chosen starting with a clean test sample
(or water).
6.3.2 Source preparation for proportional counter
The Sr or Y precipitate is deposited on a filter by filtration or on a stainless steel planchet by direct
evaporation.
The filter or planchet size diameter should be similar to the detector size (see Annex A, Annex D and
Annex H).
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A calibration source shall be prepared from a known amount of tracer ( Sr, Sr, Sr + Y or Y) with the
same geometry and chemical composition as the source to be measured.
A blank source shall be prepared with the same geometry and chemical composition as the source to be
measured.
ISO/DIS 13160:2026(en)
6.4 Measurement
6.4.1 General
The same equipment conditions should be used for the sample, the background and the calibration source
measurements.
The counting time depends on the sample and background count rates and also on the detection limit and
decision threshold required.
6.4.2 Liquid scintillation counter
The scintillation phenomenon results from interactions of ionizing radiations with solvents and compounds
having fluorescent properties (scintillators). The solvents and scintillators constitute the scintillation
cocktail. The scintillation mixture is achieved by adding the scintillation cocktail to the test sample in order
to obtain a homogeneous mixture.
The scintillation cocktail is chosen according to the characteristics of the sample to be analysed and
[16]
according to the properties of the detection equipment (see ISO 19361:2017 ). It is recommended that a
hydrophilic scintillation cocktail be used, especially for the measurement of natural water.
The characteristics of the scintillation cocktail shall allow the mixture to be homogeneous and stable.
It is recommended that the scintillation cocktail be stored in the dark and, particularly just before use,
exposure to direct sunlight or fluorescent light be avoided in order to prevent interfering luminescence and
to comply with the storage conditions specified by the scintillation cocktail supplier.
The measurement can be affected by chemiluminescence phenomena, quench due to chemical entities, and
the presence of other radionuclides than Y. It is then necessary to take into account the characteristics of
the water sample.
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When assessing the Sr activity by its measurement with Y in equilibrium, two cases arise:
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— If Sr activity is negligible, the relevant contribution of Y in equilibrium with Sr can be assessed
using LSC;
— If Sr activity is not negligible, it is necessary to measure the Sr at two different times, to estimate the
Sr activity through its decay.
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When assessing Sr activity by Y measurement, it is preferable to measure the Cerenkov radiation from
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the Y, as there is negligible interference from Sr.
6.4.3 Proportional counter
A PC measures directly the beta-radiation, without energy discrimination, from a source usually prepared
as a thin layer deposit.
Dual-window alpha/beta discrimination allows the presence of alpha-emitter contaminants in the source
to be monitored. If other beta-emitters are present, they can be detected by performing successive
measurements of the source over time.
6.4.4 Efficiency calculation
The procedure to calibrate the counters is as follows:
— count the sample until at least 10 counts are obtained;
— determine the beta-count rate of the calibration source (in the same chemical and physical form as the
samples);
ISO/DIS 13160:2026(en)
— calculate the counting efficiency of the counter by dividing the count rate measured by the activity of the
calibration source given in Formula (1):
(1)
— and the relative standard uncertainty of ε is calculated using Formula (2):
i
(2)
6.4.5 Determination of the chemical yield
The chemical yield of Sr, R , is calculated from Sr carrier or tracer by one of the following procedures:
c,Sr
a) chemical yield calculated as the ratio of the mass of the collected Sr to the mass of the Sr at the start
of the procedure, i.e. the mass of Sr in the test sample plus the mass of Sr carrier added as given in
Formula (3):
(3)
where
m is the mass of the Sr collected and then determined by an appropriate method (gravimetric, AA,
c,p
ICP–AES or ICP–MS);
m is the mass of Sr in the processed aliquot, i.e. the mass of Sr in the test sample plus the mass of
c,Sr
Sr in the added carrier;
and the relative uncertainty of R is calculated using Formula (4):
C,Sr
(4)
b) chemical yield calculated as the ratio of the activity of the Sr collected and then measured by gamma-
spectrometry, over the activity of the Sr added as a tracer at the start of the procedure. See Formula (5):
(5)
where
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is the activity of Sr measured by gamma-spectrometry taking into account the Sr decay
from the start of procedure;
is the activity of Sr added at the start of the procedure.
and the relative uncertainty of R is calculated using Formula (6):
C,Sr
(6)
The chemical yield of yttrium, R , is calculated from the yttrium carrier by a procedure similar to that
c,Y
presented for the chemical yield of Sr.
7 Expression of results
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7.1 Determination of Sr in equilibrium with Y
7.1.1 Calculation of the activity concentration
The activity per unit mass in source samples where the Y has been completely separated from the parent
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radionuclide Sr is most easily assessed when the decay progeny Y h
...