SIST EN ISO 13164-3:2020

SLOVENSKI STANDARD
01-maj-2020
Kakovost vode - Radon Rn-222 - 3. del: Preskusna metoda z emanometrijo (ISO
13164-3:2013)
Water quality - Radon-222 - Part 3: Test method using emanometry (ISO 13164-3:2013)
Wasserbeschaffenheit - Radon-222 - Teil 2: Verfahren mittels Emanometrie (ISO 13164-
3:2013)
Qualité de l’eau - Radon 222 - Partie 3: Méthode d’essai par émanométrie (ISO 13164-
3:2013)
Ta slovenski standard je istoveten z: EN ISO 13164-3:2020
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.

EN ISO 13164-3
EUROPEAN STANDARD
NORME EUROPÉENNE
February 2020
EUROPÄISCHE NORM
ICS 13.060.60; 17.240; 13.280
English Version
Water quality - Radon-222 - Part 3: Test method using
emanometry (ISO 13164-3:2013)
Qualité de l'eau - Radon 222 - Partie 3: Méthode d'essai Wasserbeschaffenheit - Radon-222 - Teil 2: Verfahren
par émanométrie (ISO 13164-3:2013) mittels Emanometrie (ISO 13164-3:2013)
This European Standard was approved by CEN on 6 October 2019.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2020 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 13164-3:2020 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 13164-3:2013 has been prepared by Technical Committee ISO/TC 147 "Water quality”
of the International Organization for Standardization (ISO) and has been taken over as EN ISO 13164-
3:2020 by Technical Committee CEN/TC 230 “Water analysis” the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by August 2020, and conflicting national standards shall
be withdrawn at the latest by August 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 13164-3:2013 has been approved by CEN as EN ISO 13164-3:2020 without any
modification.
INTERNATIONAL ISO
STANDARD 13164-3
First edition
2013-09-01
Water quality — Radon-222 —
Part 3:
Test method using emanometry
Qualité de l’eau — Radon 222 —
Partie 3: Méthode d’essai par émanométrie
Reference number
ISO 13164-3:2013(E)
©
ISO 2013
ISO 13164-3:2013(E)
© ISO 2013
All rights reserved. Unless otherwise specified, 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
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Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
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Published in Switzerland
ii © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
Contents Page
Foreword .iv
Introduction .v
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
5 Sampling . 3
5.1 General requirement . 3
5.2 Sampling requirement . 3
5.3 Sample volume . 3
5.4 Container characteristics . 3
6 Transportation and storage . 4
7 Transfer of radon by degassing . 4
7.1 Purpose . 4
7.2 Principle . 4
8 Detection . 4
8.1 Objective . 4
8.2 Principle . 4
8.3 Silver-activated zinc sulfide ZnS(Ag) scintillation . 4
8.4 Air ionization . 5
8.5 Semiconductor (alpha-detection). 5
9 Quality assurance and quality control programme . 5
9.1 General . 5
9.2 Influence quantities . 5
9.3 Instrument verification. 6
9.4 Method verification . 6
9.5 Demonstration of analyst capability . 6
10 Expression of results . 6
10.1 Activity concentration . 6
10.2 Standard uncertainty of the activity concentration . 7
10.3 Decision threshold and detection limit . 7
10.4 Confidence limits. 7
11 Calibration . 7
12 Test report . 7
Annex A (informative) Examples of measurement methods using scintillation cells .9
Annex B (informative) Example of a measurement method using an ionization chamber .17
Bibliography .23
ISO 13164-3:2013(E)
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, www.iso.org/directives.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received, www.iso.org/patents.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
The committee responsible for this document is ISO/TC 147, Water quality, Subcommittee SC 3,
Radioactivity measurements.
ISO 13164 consists of the following parts, under the general title Water quality — Radon-222:
— Part 1: General principles
— Part 2: Test method using gamma-ray spectrometry
— Part 3: Test method using emanometry
The following part is under preparation:
— Part 4: Test method using two-phase liquid scintillation counting
iv © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
Introduction
Radioactivity from several naturally occurring and human-made sources is present throughout the
environment. Thus, water bodies (surface waters, groundwaters, sea waters) can contain radionuclides
of natural and human-made origin.
— Natural radionuclides, including potassium-40, and those of the thorium and uranium decay series,
in particular radium-226, radium-228, uranium-234, uranium-238, lead-210, can be found in water
for natural reasons (e.g. desorption from the soil and wash-off by rain water) or releases from
technological processes involving naturally occurring radioactive materials (e.g. the mining and
processing of mineral sands or phosphate fertilizer production and use).
— Human-made radionuclides such as transuranium elements (americium, plutonium, neptunium,
curium), tritium, carbon-14, strontium-90 and gamma-emitting radionuclides can also be found in
natural waters as they can be authorized to be routinely released into the environment in small
quantities in the effluent discharged from nuclear fuel cycle facilities and following their used in
unsealed form in medicine or industry. They are also found in water due to the past fallout of the
explosion in the atmosphere of nuclear devices and the accidents at Chernobyl and Fukushima.
Drinking-water can thus contain radionuclides at activity concentration which could present a risk to
human health. In order to assess the quality of drinking-water (including mineral waters and spring
waters) with respect to its radionuclide content and to provide guidance on reducing health risks by
taking measures to decrease radionuclide activity concentrations, water resources (groundwater, river,
lake, sea, etc.) and drinking water are monitor for their radioactivity content as recommended by the
World Health Organization (WHO).
Standard test methods for radon-222 activity concentrations in water samples are needed by test
laboratories carrying out such measurements in fulfillment of national authority requirements.
Laboratories may have to obtain a specific accreditation for radionuclide measurement in drinking
water samples.
−1
The radon activity concentration in surface water is very low, usually below 1 Bq l . In groundwater, the
−1 −1 −1
activity concentration varies from 1 Bq l up to 50 Bq l in sedimentary rock aquifers, from 10 Bq l
−1 −1 −1
up to 300 Bq l in wells, and from 100 Bq l up to 1 000 Bq l in crystalline rocks. The highest activity
concentrations are normally measured in rocks with high concentration of uranium (Reference [15]).
High variations in the activity concentrations of radon in aquifers have been observed. Even in a region
with relatively uniform rock types, some well water may exhibit radon activity concentration greatly
higher than the average value for the same region. Significant seasonal variations have also been
recorded (see Annex A).
Water may dissolve chemical substances as it passes from the soil surface to an aquifer or spring waters.
The water may pass through or remain for some time in rock, some formations of which may contain a
high concentration of natural radionuclides. Under favourable geochemical conditions, the water may
selectively dissolve some of these natural radionuclides.
Guidance on radon in drinking-water supplies provided by WHO in 2008 suggests that controls should be
−1
implemented if the radon concentration of drinking-water for public water supplies exceeds 100 Bq l .
It also recommended that any new, especially public, drinking-water supply using groundwater should
be tested prior to being used for general consumption and that if the radon concentration exceeds
−1
100 Bq l , treatment of the water source should be undertaken to reduce the radon levels to well below
that level (Reference [16]).
This International Standard is one of a series dealing with the measurement of the activity concentration
of radionuclides in water samples.
The origin of radon-222 and its short-lived decay products in water and other measurement methods
are described generally in ISO 13164-1.
INTERNATIONAL STANDARD ISO 13164-3:2013(E)
Water quality — Radon-222 —
Part 3:
Test method using emanometry
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
ensure compliance with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document
be carried out by suitably qualified staff.
1 Scope
This part of ISO 13164 specifies a test method for the determination of radon-222 activity concentration
in a sample of water following its transfer from the aqueous phase to the air phase by degassing and its
detection. It gives recommendations for rapid measurements performed within less than 1 h.
The radon-222 activity concentrations, which can be measured by this test method utilizing currently
−1
available instruments, range from 0,1 Bq l to several hundred thousand becquerels per litre for a
100 ml test sample.
This test method is used successfully with drinking water samples. The laboratory is responsible for
ensuring the validity of this test method for water samples of untested matrices.
This test method can be applied on field sites or in the laboratory.
Annexes A and B give indications on the necessary counting conditions to meet the required sensitivity
for drinking water monitoring.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and
sampling techniques
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 11929, Determination of the characteristic limits (decision threshold, detection limit and limits of the
confidence interval) for measurements of ionizing radiation — Fundamentals and application
ISO 13164-1, Water quality — Radon-222 — Part 1: General principles
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
IEC 61577-1, Radiation protection instrumentation — Radon and radon decay product measuring
instruments — Part 1: General principles
ISO 13164-3:2013(E)
IEC 61577-2, Radiation protection instrumentation — Radon and radon decay product measuring
instruments — Part 2: Specific requirements for radon measuring instruments
3 Terms, definitions and symbols
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 80000-10 and ISO 13164-1 apply.
3.2 Symbols
For the purposes of this document, the symbols defined in ISO 80000-10. ISO 13164-1, and the
following apply.
c measured radon activity concentration in the air of the measuring system after degassing,
in becquerels per cubic metre
c radon activity concentration in the air of the measuring system before degassing, in becque-
rels per cubic metre
c activity concentration of radon in water, in becquerels per litre
A
∗
c
decision threshold, in becquerels per litre
A
#
c
detection limit, in becquerels per litre
A


c c lower and upper limits of the confidence interval, in becquerels per litre
A A
,
f conversion factor from cubic metre to litre: 0,001
c
f correction factor for the decay of radon during time interval t, dimensionless
d
k , k quantiles of the standardized normal distribution for the probabilities, p and q, respectively
p q
L Ostwald coefficient
T water temperature, in Celsius
HO
t time interval between the sampling and the measurement, in seconds
U expanded uncertainty calculated by U = ku(c ) with k = 2
A
u(c ) standard uncertainty associated with the measurement result
A
V volume of test sample, in litres
HO
V volume of air in the measurement system, in cubic metres
a
α, β probability of the error of the first and second kind, respectively
γ probability for the confidence interval of the activity concentration
λ decay constant of radon-222, in reciprocal second
Φ distribution function of the standardized normal distribution
2 © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
4 Principle
The determination of radon-222 activity concentration in water by degassing into the air phase is
based on the:
— collection of a representative sample of the water at time t in a suitable container;
— transfer of radon dissolved in the water to the air phase by degassing;
— detection of the alpha-radiation emitted by the radon or its solid decay products present in the air.
The radon activity concentration in the water is determined from the activity concentration in the air
phase, taking account of the Ostwald coefficient (see ISO 13164-1).
5 Sampling
5.1 General requirement
The sample shall be representative of the environment to be analysed at a given time.
5.2 Sampling requirement
The sampling shall be carried out in compliance with the conditions and techniques specified in
ISO 5667-1, ISO 5667-3, and ISO 13164-1. The temperature of the water shall be measured and recorded
during the sampling process.
Fill the container completely and fit the cap in such a way as to avoid the presence of air above the sample.
The container shall be filled in such a way as to avoid degassing the radon in the water sample. The
sampling techniques to be used vary according to the actual situation.
When the analytical laboratory is not in charge of sampling, the laboratory shall supply the container for
the measurement and specify the sampling procedure to the person carrying out the sampling operation.
It is recommended that several discrete samples be taken in case of problems arising in relation to the
sampling conditions or transportation of the samples.
5.3 Sample volume
Experience shows that a sample volume of at least 1 l is needed for the sample to be representative of
the environment to be analysed.
At least 1 l samples are recommended, but for the effective determination smaller test portions are used.
5.4 Container characteristics
The choice and preparation of a suitable container are important (see ISO 5667-3).
The container and cap used to contain the sample shall comply with the following requirements.
— They shall be made from inert materials, impermeable to radon, non-hydrophobic, and conductive
(in order not to adsorb radon and its decay products from the surrounding atmosphere).
— They shall be shock-proof.
The volume of the container should be compatible with the water volume required by the degassing
technique used.
ISO 13164-3:2013(E)
6 Transportation and storage
During transportation and storage, the sample shall be maintained at a temperature below that of the
original water (but above 0 °C) until it is ready for analysis. The container shall be protected and tightly
sealed. The container shall be packed in an appropriate manner in order to prevent any leakage.
The period of transportation and storage prior to analysis shall be as short as possible given the half-
life of radon-222, the expected activity concentration, and the detection limit of the measurement
method to be used.
On arrival at the laboratory, the sample shall be maintained at a temperature below that of the original water
(but above 0 °C), if it cannot be analysed immediately. The sample shall be analysed as soon as possible.
Experience indicates that it is essential that the time between sampling and analysis not exceed 48 h.
7 Transfer of radon by degassing
7.1 Purpose
This technique is used to transfer the radon dissolved in the water into the air so that it can be detected
and measured in its gaseous state.
7.2 Principle
As the Ostwald coefficient of radon in water is fairly low, the dissolved radon degasses naturally into the
air with relatively slow kinetics (over a few hours) (see ISO 13164-1).
In order to accelerate the degassing process, several means may be used:
— shaking the sample;
— sparging radon-free air through the water sample using a fine air bubble to increase the air
exchange surface;
— decreasing the pressure in the air phase.
In order to improve the detection limit of the measurement method, it is necessary for the radon activity
concentration in the air used for the degassing process to be as low as possible and to be measured
before degassing the radon from the water.
8 Detection
8.1 Objective
The purpose of the detector is to quantify the alpha-radiation emitted by the radon and/or its solid
decay products that is directly related to the activity concentration of the radon in the air phase.
8.2 Principle
[1]
A number of detection techniques can be used (see ISO 11665-1 ).
8.3 Silver-activated zinc sulfide ZnS(Ag) scintillation
Some electrons in scintillating media, such as ZnS(Ag), have the particular feature of emitting photons
by returning to their ground state when they are excited by an alpha-particle. These emitted photons
can be detected using a photomultiplier.
4 © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
This is the principle adopted for scintillation cells (such as Lucas cells) used for radon spot measurement
[3]
(see References [5]–[7] and ISO 11665-6 ).
8.4 Air ionization
When it travels through the air, each alpha-particle creates several tens of thousands of ion pairs which,
under some experimental conditions, produce an ionization current. Although very low, this current can
be measured using an ionization chamber that gives the activity concentration of radon and its decay
products. When the sampling is performed through a filtering medium, only radon diffuses into the
ionization chamber and the signal is proportional to the radon activity concentration (see References
[2]
[8]–[10] and ISO 11665-5 ).
8.5 Semiconductor (alpha-detection)
A semiconductor detector, e.g. made of silicon, converts the energy from an incident alpha-particle into
electric charges. These are converted into pulses with an amplitude proportional to the energy of the
alpha-particles emitted by the radon and its short-lived decay products (see References [11]–[13]).
NOTE This detection principle is occasionally associated with electrostatic precipitation of the alpha-
emitter isotopes.
9 Quality assurance and quality control programme
9.1 General
Quality control operations shall meet the requirements of ISO/IEC 17025.
9.2 Influence quantities
Various quantities can lead to measurement bias that could induce non-representative results. In the
specific case of the emanometric method, influence quantities can affect the following stages in the
measurement process: sampling; transportation and storage of the sample; transfer of radon from the
aqueous phase to another; and the measurement of the radon activity concentration.
During the sampling, consider particularly the:
— water temperature;
— turbulence in the water;
— volume of air in the container.
During the transfer of the radon from the water to the air by degassing, the influence of the water
temperature shall be taken into account.
During measurement, consider particularly the:
— detector storage conditions prior to beginning the measurement;
— stability of the characteristics of the detection system (contamination of the detection surface,
saturation, etc.);
— possible presence of other alpha-emitters (radon isotopes) in the detection volume.
When the delay between the sampling and the analysis is too long, it is possible that the presence of
dissolved radium in the water needs to be taken into account as an influence quantity.
When the presence of Ra is suspected, take a second measurement of the same sample after a period
equal to 10 half-lives of Rn (38 days). If the radon activity concentration is insignificant relative to
ISO 13164-3:2013(E)
the initial measurement result, the contribution of Ra is considered to be negligible. If this is not the
case, determine the activity concentration of Ra present in the water sample.
9.3 Instrument verification
Major instrument parameters (efficiency, background) shall be periodically checked within a quality
assurance programme established by the laboratory and following the manufacturer’s instructions.
9.4 Method verification
Periodically verify the accuracy of the method by:
— participating in intercomparison exercises;
— analysing reference materials.
Method repeatability shall also be checked, e.g. by replicate measurements.
The acceptance limits of the tests mentioned in the preceding shall be defined.
9.5 Demonstration of analyst capability
If an analyst has not used this procedure before, a precision and bias test shall be performed by running a
duplicate measurement of a reference or spiked material. Acceptance limits shall be defined by the laboratory.
A similar test shall be performed by analysts routinely using this procedure with a periodicity defined
by the laboratory. Acceptance limits shall be defined.
10 Expression of results
10.1 Activity concentration
The activity concentration of radon in the water, c , expressed at the date and time of sampling can be
A
obtained using Formula (1):
 
V
a
cc=−cL +  ff =−cc ω (1)
() ()
A 00cd
 
V
HO
 2 
where
 
V
a
ω =+L  ff (2)
cd
 
V
HO
 2 
ft=exp λ (3)
()
d
The Ostwald coefficient may be expressed by Formula (4) (Reference [14]):
LT=+0,,105 0 403exp,−00502 (4)
()
HO
6 © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
10.2 Standard uncertainty of the activity concentration
[4]
According to ISO/IEC Guide 98-3, the standard uncertainty of c is calculated as given in Formula (5):
A
22 2 2 2
 
uc = ωωuc +uc +cu (5)
() () () ()
AA0 rel
 
where
2 2
 2 
Vu V
uV ()
() a HO
2 a 2 2
 
u ωω= + (6)
()
rel
2 4
 
V V
HO HO
2 2
 
where the standard uncertainties of the Ostwald coefficient, L, f , and f are neglected.
c d
10.3 Decision threshold and detection limit
Calculate the characteristic limits associated with the activity concentration in accordance with
ISO 11929. An example of the calculations of uncertainties and characteristic limits is detailed in
Annexes A and B for two specific measurement methods.
10.4 Confidence limits


The lower, c , and upper, c , confidence limits are calculated using Formulae (7) and (8) (see ISO 11929):
A A
 γ 

cc=−ku c  with  p=−ω 1 (7)
()
AA pA
 
 
ωγ

cc=+ku c  with  q=−1 (8)
()
AA qA
where
ω = Φ[y/u(y)] in which Φ is the distribution function of the standardized normal distribution;
ω can be assumed to be 1 if c ≥ 4u(c ).
A A
In this case:

cc=±ku c (9)
()
AA 12−γ A
γ = 0,05 with k = 1,96 are often chosen by default.
1 − γ/2
11 Calibration
Calibrations shall be carried out under conditions specified in IEC 61577-1 and IEC 61577-2.
12 Test report
The test report shall be in accordance with ISO/IEC 17025 requirements and shall contain at least the
following information:
a) the test method used, together with a reference to this part of ISO 13164 (ISO 13164-3:2013);
b) measurement method;
c) identification of the sample;
ISO 13164-3:2013(E)
d) measuring date and time;
e) units in which the results are expressed;
f) test result, c ± u(c ) or c ± U, with the associated k value.
A A A
Complementary information can be provided such as the following:
g) sampling date and time;
h) sampling location;
i) probabilities α, β, and (1 − γ);
j) the decision threshold and the detection limit — depending on the needs of the customer, there are
different ways to present the result:
— when the activity concentration is compared with the decision threshold (see ISO 11929), the result
*
of the measurement shall be expressed as ≤c when the result is below the decision threshold,
A
— when the activity concentration is compared with the detection limit, the result of the measurement
#
can be expressed as ≤c when the result is below the detection limit — if the detection limit exceeds
A
the guideline value, it shall be documented that the method is not suitable for the measurement purpose;
k) activity concentration of Ra if its presence is detected in the water sample;
l) mention of any relevant information likely to have affected the results.
The results are expressed in a similar format to that shown in ISO 13164-1 (see Annex B).
8 © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
Annex A
(informative)
Examples of measurement methods using scintillation cells
A.1 General
This annex deals only with the scintillation cells methods among the various methods able to meet the
requirements of this part of ISO 13164. The two methods described differ in the degassing technique used
and the volume of test sample. These methods are suitable for use either in the laboratory or on field sites.
For the purpose of this annex, the following symbols and those given in Clause 3 apply.
F calibration factor per alpha for a counting carried out with a radioactive equilibrium between
c
the radon and its short-lived decay products, in pulses per second per becquerel
f correction factor for the decay of radon in the volume detection, dimensionless
d
f correction factor for atmospheric pressure, dimensionless
p
N number of background counts
N average number of background counts
N number of gross counts
s
average number of gross counts
N
s
n number of counting of each sample
n (t) number of alpha-emitters present in the cell per becquerel of radon after a waiting time
α
between filling and counting the cell (n is approximately 3 at a waiting time of 3 h for 1 Bq of
α
radon)
t counting duration (common to N , N ), in seconds
c s 0
V cell volume, in cubic metres
sc
p pressure measured in the cell after sampling, in hectopascals
r
p pressure measured in the cell once under vacuum, in hectopascals
v
Δt elapsed time between the end of the sampling, t = 0, and the cell counting, in seconds
λ decay constant of radon-222, in reciprocal seconds
A.2 Method A
A.2.1 General
−1
This test method covers the measurement of radon in water in activity concentrations above 10 Bq l
using a small test sample volume. The degassing technique used is the decrease of the air phase pressure.
ISO 13164-3:2013(E)
A.2.2 Equipment
Usual laboratory equipment and in particular the following.
A.2.2.1 Borosilicate glass sample container fitted with a self-healing rubber stopper.
A.2.2.2 Hypodermic syringe to take the test sample.
A.2.2.3 Holder for filter medium for taking the air sample in the detection volume.
A.2.2.4 Scintillation cell fitted with a cap containing a hydrophilic cotton plug to enclose the
detection volume.
A scintillation cell is a hermetically sealed glass flask with defined geometry and volume. The internal
surface of the cell, apart from the bottom, is covered in silver-activated zinc sulfide [ZnS(Ag)].
A.2.2.5 Vacuum-creating device for the cell.
A.2.2.6 Pressure-measuring device for the cell.
A.2.2.7 Counting chain equipped with a photomultiplier.
A.2.2.8 Thermometer to measure the temperature of the water to be analysed.
A.2.3 Principle
A test portion of the water to be analysed (1 ml to 2 ml) is introduced into the scintillation cell (A.2.2.4)
by injecting the water with a syringe (A.2.2.2) into the hydrophilic cotton plug placed in the cap. Because
of the partial vacuum created in the cell prior the injection, radon is extracted from the water. Radon-
free filtered air is then introduced into the scintillation cell to allow the pressure to return to normal
(see Figure A.1).
The alpha-particles produced by the decay the radon and its short-lived decay products transfer their energy
as they pass through the scintillation medium. As they return to their ground state, the excited electrons
in the scintillation medium emit photons from the ZnS coating that can be detected by a photomultiplier
(A.2.2.7). The photomultiplier converts the photons into electrical pulses that are then counted. The pulse
count is directly proportional to the radon activity concentration in the air inside the cell.
A.2.4 Sampling
Sampling shall be performed in accordance with the requirements specified in Clause 5.
The test portion consists of 1 ml or 2 ml of water, taken through the self-healing rubber stopper using a
hypodermic syringe.
A.2.5 Transfer of the radon from the water phase to the air phase
A partial vacuum at least 10 kPa (100 mbar) below ambient is created inside the scintillation cell
using a vacuum pump. The test water sample is then injected into the cotton plug inside the cap of
the scintillation cell. Because of the partial vacuum in the cell, radon is extracted from the water. The
pressure in the cell returns to normal by allowing the introduction of clean radon-free filtered air. The
radon equilibrium, governed by the Ostwald coefficient, is achieved between radon dissolved in water
and radon in the air phase.
10 © ISO 2013 – All rights reserved

ISO 13164-3:2013(E)
It is essential that the partial vacuum not be too high in order to avoid vaporizing the water inside the
cell and damaging the zinc sulfide coating.
a) b) c)
Key
1 scintillation cell 5 syringe containing the test sample
2 hydrophilic cotton plug 6 air sampling device
3 cap 7 air filter
4 vacuum pump 8 air circulation
Figure A.1 — Principle of measuring radon in water by degassing and detection using a
scintillation cell
A.2.6 Detection and counting
Before using the scintillation cell, its background count is checked by recording the count from a pre-
calibrated photomultiplier placed in a lightproof enclosure for a suitable period of time.
For an optimum count, 3 h should elapse after injecting the water into the cotton. The accuracy sought
dictates the counting duration and the number of counting for the sample.
A.2.7 Measurement procedure
The measurement procedure is as follows:
a) before using the cells, determination of the background of each scintillation cell by counting the
photons emitted before sampling for a suitable duration with a pre-calibrated photomultiplier in a
lightproof enclosure;
b) creation of a vacuum of 10 kPa (100 mbar) in the scintillation cell;
c) measurement of the residual pressure in the cells;
d) choice and location of the sampling place;
e) taking of one or more water samples;
f) taking a test portion using a syringe;
g) injection of the water into the hydrophilic cotton plug;
ISO 13164-3:2013(E)
h) introduction of clean filtered air (free of radon) into the scintillation cell so that pressure
returns to normal;
i) measurement of the pressure after filling the cells and maintenance of the pressure at
atmospheric pressure;
j) recording of the location, date, and time of the sampling;
k) establishment of a radioactive equilibrium between the Rn and its short-lived decay products
214 218
( Po, Po) in the cell by waiting, for an optimum counting, 3 h after the sampling;
l) counting, by means of a pre-calibrated photomultiplier placed in a lightproof enclosure, of the
number of photons emitted by the scintillation medium when excited by alpha-particles produced
by the decay of radon and its short-lived decay products present in the cells;
m) determination of the activity concentration by calculation.
It is assumed that the sample counting time and the
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