SIST EN ISO 20045:2024

SLOVENSKI STANDARD
01-september-2024
Merjenje radioaktivnosti v okolju - Zrak: tritij - Preskusna metoda z vzorčenjem z
mehurčki (ISO 20045:2023, vključno s popravljeno različico 2023-09)
Measurement of the radioactivity in the environment - Air: tritium - Test method using
bubbler sampling (ISO 20045:2023, vključno s popravljeno različico 2023-09)
Bestimmung der Radioaktivität in der Umwelt - Luft: Tritium - Messverfahren mit
Sammlung mittels Gaswaschflaschen (ISO 20045:2023, vključno s popravljeno različico
2023-09)
Mesurage de la radioactivité dans l’environnement - Air : tritium - Méthode d’essai à
l’aide d’un prélèvement par barbotage (ISO 20045:2023, vključno s popravljeno različico
2023-09)
Ta slovenski standard je istoveten z: EN ISO 20045:2024
ICS:
13.040.01 Kakovost zraka na splošno Air quality in general
17.240 Merjenje sevanja Radiation measurements
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 20045
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2024
EUROPÄISCHE NORM
ICS 13.040.01; 17.240
English Version
Measurement of the radioactivity in the environment - Air:
tritium - Test method using bubbler sampling (ISO
20045:2023, including corrected version 2023-09)
Mesurage de la radioactivité dans l'environnement - Bestimmung der Radioaktivität in der Umwelt - Luft:
Air : tritium - Méthode d'essai à l'aide d'un Tritium - Messverfahren mit Sammlung mittels
prélèvement par barbotage (ISO 20045:2023, y Gaswaschflaschen (ISO 20045:2023, einschließlich der
compris version corrigée 2023-09) korrigierten Fassung von 2023-09)
This European Standard was approved by CEN on 7 July 2024.

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, Türkiye 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
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 20045:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 20045:2023, including corrected version 2023-09 has been prepared by Technical
Committee ISO/TC 85 “Nuclear energy, nuclear technologies, and radiological protection” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 20045:2024 by
Technical Committee CEN/TC 430 “Nuclear energy, nuclear technologies, and radiological protection”
the secretariat of which is held by AFNOR.
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 January 2025, and conflicting national standards shall
be withdrawn at the latest by January 2025.
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.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
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, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 20045:2023, including corrected version 2023-09 has been approved by CEN as
INTERNATIONAL ISO
STANDARD 20045
First edition
2023-05
Corrected version
2023-09
Measurement of the radioactivity in
the environment — Air: tritium — Test
method using bubbler sampling
Mesurage de la radioactivité dans l’environnement — Air : tritium —
Méthode d’essai à l’aide d’un prélèvement par barbotage
Reference number
ISO 20045:2023(E)
ISO 20045:2023(E)
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Phone: +41 22 749 01 11
Email: copyright@iso.org
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Published in Switzerland
ii
ISO 20045:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms, definitions and symbols . 1
3.1 Terms and definitions . 2
3.2 Symbols, definitions and units . 3
4 Principle . 4
5 Influence quantities . 5
6 Equipment . 6
6.1 Description and requirements of the sampling system . 6
6.2 Location of sampling head . 6
6.3 Air flow rate, sampling duration and air volume sampling . 6
6.4 Trapping water solution . 7
6.5 Specifications for use . 7
7 Procedure .8
7.1 Sampling . 8
7.2 Sample collection and transportation . 9
7.3 Receipt. 9
7.4 Conservation . 9
7.5 Tritium activity concentration measurement . 9
8 Expression of results . 9
8.1 General . 9
8.2 Calculations for tritiated water vapour . 10
8.2.1 Activity concentration . . 10
8.2.2 Decision threshold . 10
8.2.3 Detection limit . 11
8.2.4 Coverage intervals limits . 11
8.2.5 Conditions of use .12
8.3 Calculation for tritiated gas compounds .12
8.3.1 Tritiated gas without significant HTO level .13
8.3.2 Tritiated gas compounds with significant HTO level . 14
8.3.3 Coverage intervals limits . 16
8.3.4 Conditions of use . 16
9 Test report .17
Annex A (informative) Technical data for tritium .19
Annex B (informative) Determination of trapping efficiency .21
Annex C (informative) Preserving of tritiated water solutions .25
Annex D (informative) Example of sampling and calculations forms .26
Annex E (informative) Examples of calculations of air tritium activity concentrations .29
Bibliography .35
iii
ISO 20045:2023(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 (see 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 (see 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.
For an explanation on 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 the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 85, Nuclear energy, nuclear technologies,
and radiological protection, SC 2, Radiological protection.
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.
This corrected version of ISO 20045:2023 incorporates the following corrections:
— editorial corrections have been made in Clause 1, 3.2, Table 2, 8.3.1.1, 8.3.2.1, 8.3.3.2 and Clause 9;
— Formula (17) and Formula (B.10) have been corrected.
iv
ISO 20045:2023(E)
Introduction
Everyone is exposed to natural radiation. The natural sources of radiation include cosmic rays and
naturally occurring radioactive substances which exist on Earth such as flora, fauna or the human body.
Human activities involving the use of radiation and radioactive substances add to the radiation exposure
from this natural exposure. Some of those activities, such as the mining and use of ores containing
naturally-occurring radioactive materials (NORM) and the production of energy by burning coal that
contains such substances, simply enhance the exposure from natural radiation sources. Nuclear power
plants and other nuclear installations use radioactive materials and produce radioactive effluents and
waste during operation and decommissioning. The use of radioactive materials in industry, medicine,
agriculture and research is expanding around the globe.
All these human activities give rise to radiation exposures that are only a small fraction of the global
average level of natural exposure. The medical use of radiation is the largest and a growing man-made
source of radiation exposure in developed countries. It includes diagnostic radiology, radiotherapy,
nuclear medicine and interventional radiology.
Radiation exposure also occurs as a result of occupational activities. It is incurred by workers in
industry, medicine and research using radiation or radioactive substances, as well as by passengers
and crew during air travel. The average level of occupational exposures is generally below the global
average level of natural radiation exposure (see Reference [2]).
As uses of radiation increase, so do the potential health risk and the public's concerns. Thus, all these
exposures are regularly assessed in order to
a) improve the understanding of global levels and temporal trends of public and worker exposure,
b) evaluate the components of exposure so as to provide a measure of their relative impact, and
c) identify emerging issues that may warrant more attention and study. While doses to workers
are mostly directly measured, doses to the public are usually assessed by indirect methods
using the results of radioactivity measurements of waste, liquid and/or gaseous effluents and/or
environmental samples.
Radioactivity from several naturally-occurring and anthropogenic sources is present throughout the
environment. Thus, atmosphere can contain radionuclides of natural, human-made, or both origins.
40 3 14
— Natural radionuclides including K, H, C and those originating from the thorium and uranium
226 228 234 238 210
decay series, in particular Ra, Ra, U, U and Pb which can be found in materials from
natural sources or can be released 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 transuranic elements (americium, plutonium, neptunium, and
3 14 90
curium), H, C, Sr and gamma-ray emitting radionuclides can also be found gaseous effluent
discharges, in environmental matrices (water, air, soil and biota), in food and in animal feed as a
result of authorized releases into the environment, fallout from the explosion in the atmosphere of
nuclear devices and radionuclides releases from accidents of nuclear reactors, such as those that
occurred in Chernobyl and Fukushima.
To ensure that the data obtained from radioactivity monitoring programs support their intended use, it
is essential that the stakeholders (for example nuclear site operators, regulatory and local authorities)
agree on appropriate methods and procedures for obtaining representative samples and for sampling,
handling, storing, preparing and measuring the test samples. An assessment of the overall measurement
uncertainty also needs to be carried out systematically. As reliable, comparable and ‘fit for purpose’
data are an essential requirement for any public health decision based on radioactivity measurements,
international standards of tested and validated radionuclide test methods are an important tool for
the production of such measurement results. The application of standards serves also to guarantee
comparability of the test results over time and between different testing laboratories. Laboratories
v
ISO 20045:2023(E)
apply them to demonstrate their technical competencies and to complete proficiency tests successfully
during interlaboratory comparisons, two prerequisites for obtaining national accreditation.
Today, over a hundred International standards, prepared by Technical Committees of the International
Organization for Standardization, including those produced by ISO/TC 85, and the International
Electrotechnical Commission (IEC), are available to testing laboratories for measuring radionuclides in
different matrices.
Tritium ( H) is a radioactive isotope of hydrogen. It is a pure beta emitting radionuclide, with a
maximum energy equal to 18,591 ± 1 keV and a radiological half-life equal to 12,312 (0,025) years
(see Reference [3]). It is naturally occurring and continuously produced in the upper atmosphere by
interaction of cosmic rays with nitrogen and oxygen nuclei (see Reference [4]).
Two main chemical species of both natural and anthropogenic tritium are present in the environment.
The most abundant chemical form is tritiated water (HTO) (see Reference [5]). Tritium can also be
present in the form of tritiated gas (HT or T ) usually present in the vicinity of tritium-emitting facilities
(see Reference [6]), tritiated methane (CH T), or in other various organic forms of tritium commonly
observed in terrestrial, aquatic continental, and marine ecosystems (see References [7], [8] and [9]).
Anthropogenic tritium compounds come from radioactive releases of nuclear facilities i.e., nuclear
power plants, irradiated fuel reprocessing and recycling plants, military defence, medical research
applications, and past atmospheric testing of nuclear devices (see Annex A).
This document describes the method to assess the activity concentration of atmospheric tritium via air
sampling by bubbler devices which trap tritiated water vapour and tritiated gas in a water solution. The
method can be used for any type of environmental study or monitoring.
The test method is used in the context of a quality assurance management system (ISO/IEC 17025). It
can be adapted so that the characteristic limits, decision threshold, detection limit and uncertainties
ensure that the test results of the atmospheric tritium activity concentrations can be verified to be
below guidance levels required by a national authority for either planned or existing situations or for
an emergency situation.
vi
INTERNATIONAL STANDARD ISO 20045:2023(E)
Measurement of the radioactivity in the environment —
Air: tritium — Test method using bubbler sampling
1 Scope
This document describes a test method to determine the activity concentration of atmospheric
tritium by trapping tritium in air by bubbling through a water solution. Atmospheric tritium activity
-3
concentration levels are expressed in becquerel per cubic metre (Bq∙m ).
The formulae are given for a sampling system with four bubblers. They can also be applied to trapping
systems with only one trapping module consisting of two bubblers if only tritiated water vapour (HTO)
is in the atmosphere to be sampled.
This document does not cover laboratory test sample results, in becquerel per litre of trapping solution,
according to ISO 9698 or ISO 13168.
-3 -3
The test method detection limit result is between 0,2 Bq∙m and 0,5 Bq∙m when the sampling duration
is about one week.
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 4788, Laboratory glassware — Graduated measuring cylinders
ISO 9698, Water quality — Tritium — Test method using liquid scintillation counting
ISO 13168, Water quality — Simultaneous determination of tritium and carbon 14 activities — Test method
using liquid scintillation counting
ISO/IEC Guide 98-3, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in
me a s ur ement (GUM: 1995)
ISO/IEC Guide 99, International vocabulary of metrology — Basic and general concepts and associated
terms (VIM)
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics
3 Terms, definitions and symbols
For the purposes of this document, the definitions, symbols and abbreviations given in,
ISO/IEC Guide 98-3, ISO/IEC Guide 99, ISO 80000-10 and the following 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 https:// www .electropedia .org/
ISO 20045:2023(E)
3.1 Terms and definitions
3.1.1
aerosol
dispersion of very fine solid particles or liquid droplets in air or gases
3.1.2
air sample
representative part of the atmosphere sampled routinely, intermittently or continuously to examine its
various characteristics
3.1.3
bubbler
glass container that holds the trapping water solution (3.1.11)
3.1.4
bubbler sample
bubbler (3.1.3) which an air sample (3.1.2) bubbled through
3.1.5
oxidizing efficiency
ratio of atmospheric tritium gas compounds converted into tritiated water vapour (3.1.13), oxidized
with a catalytic converter furnace, to tritium gas compounds in the atmosphere during the sampling
period
3.1.6
sampling module
module composed of two bubblers (3.1.3) connected in series to trap tritium species HTO (3.1.13) or no-
HTO (3.1.12)
3.1.7
sampling system
device for sampling atmospheric tritium by bubbling through a water solution that consists of a
sampling head which is the air inlet, a transport line, collector, and flow conditioning system
Note 1 to entry: Recorded samples are analysed off-line in a testing laboratory.
3.1.8
standard conditions
temperature of 273,13 K (0 °C) and a pressure of 101 325 Pa
Note 1 to entry: Used to convert air densities into a common basis. Other temperature and pressure conditions
may be used and should be applied consistently.
3.1.9
test sample
representative volume taken from the bubbler sample (3.1.4) to analyse the tritium activity
concentration by a testing laboratory
3.1.10
trapping efficiency
ratio of tritiated water vapour (3.1.13) activity concentration collected, during the sampling period, to
atmospheric tritiated water vapour (3.1.13) activity concentration
3.1.11
trapping water solution
any types of colourless water with no apparent biological activities to trap atmospheric tritium by
molecular and/or isotopic exchange between the tritium atoms in water vapour of the air and the
hydrogen atoms of the water molecules in solution
ISO 20045:2023(E)
3.1.12
tritiated gas
no-HTO
tritium gas compounds where HT and CH T molecules are predominant chemical gas species in
atmosphere
3.1.13
tritiated water vapour
HTO
water vapour where one hydrogen atom of a water molecule is substituted by one tritium atom
3.2 Symbols, definitions and units
Table 1 — Symbols, definitions and units
Symbol Definition and unit
A tritium activity of the bubbler sample, B , in becquerel (Bq) where i =1, 2, 3 or 4
i i
A reference tritium activity of tritiated water vapour (HTO) in the atmosphere in becquerel (Bq)
ref
−1
c tritium activity concentration of the test sample, i, in becquerel per litre (Bq·l )
i
decision threshold of the tritium activity concentration of the test sample, i, in becquerel per litre
*
c
−1
i
(Bq·l )
detection limit of the tritium activity concentration of the test sample, i, in becquerel per
#
c
−1
i
litre (Bq·l )
reference tritium activity concentration of tritiated water vapour (HTO) in the atmosphere in
c
ref −3
becquerel per cubic metre (Bq·m ) at standard conditions
tritium activity concentration of tritiated water vapour (HTO) in the atmosphere in becquerel per
c
w
−3
cubic metre (Bq·m ) at standard conditions
tritium activity concentration of tritiated gas compounds (no-HTO) in the atmosphere in becquer-
c
g
−3
el per cubic metre (Bq·m ) at standard conditions
decision threshold of the tritium activity concentration of HTO and no-HTO respectively in the
* *
c and c
−3
w g
atmosphere in becquerel per cubic metre (Bq·m ) at standard conditions
detection limit of the tritium activity concentration of HTO and no-HTO respectively in the atmos-
# #
c and c
−3
w g
phere in becquerel per cubic metre (Bq·m ) at standard conditions

cc,
ww
lower and upper limits of the probabilistically symmetric coverage interval of HTO and no-HTO
and
−3
respectively in the atmosphere in becquerel per cubic metre (Bq·m ) at standard conditions

cc,
gg
<>
cc,
ww
lower and upper limits of the shortest coverage interval of HTO and no-HTO respectively in the
and
−3
atmosphere in becquerel per cubic metre (Bq·m ) at standard conditions
<>
cc,
gg
ε trapping efficiency of each bubbler sample, i
Bi
ε oxidizing efficiency of the catalytic converter furnace
F
coverage factor with k = 1, 2, 3, .
k
3 −1
q
air flow rate of sampling system in cubic metre per hour (m ·h ) at standard conditions
p
t counting duration of the test sample, i, in seconds (s)
i
t
sampling duration in hour (h)
p
standard uncertainty of the tritium activity concentration of the test sample, i, in becquerel per
uc()
i −1
litre (Bq·l )
uy() standard uncertainty associated with quantity, y, result (k = 1)
Uy expanded uncertainty calculated by Uy =⋅ku y with k > 1
() () ()
ISO 20045:2023(E)
TTabablele 1 1 ((ccoonnttiinnueuedd))
Symbol Definition and unit
−1
uy()
relative standard uncertainty associated with quantity, y, result calculated by uy()=uy()⋅ y
rel
rel
Uy() relative expanded uncertainty calculated by Uy()=⋅ku ()ykwith >1
rel relrel
sampled air volume in cubic metre (m ) at standard conditions
V
where Vq=⋅t
pp
V water volume of bubbler sample, B , at the end of sampling duration in litre (l)
Bi i
V initial same volume of water in each bubbler, B , in litre (l)
Bref i
−1
w correction factor for the tritium activity concentration of the test sample, i, in per litre (l )
i
4 Principle
The bubbler sampling method consists of trapping airborne tritium compounds in water solution.
The sampled air is continuously pumped through a series of bubblers containing trapping water and
transformed as micro-bubbles in the water. The micro bubbles allow for the efficient capture of airborne
tritium water vapour in the trapping solution by molecular and isotopic exchanges.
After filtering of solid aerosol particles by the dust filter, the sampled air passes through a first sampling
module of two bubblers. This unit collects tritiated water vapour from the air. A second module,
specifically for no-HTO compounds, can also be connected in series. In this case, the sampled air shall
pass through a catalytic converter furnace which converts no-HTO compounds into HTO. This second
module collects residual HTO not trapped by the first module and no-HTO compounds that have been
converted into HTO.
The flow of air through the sampling system is controlled by a mass flow metre.
The Figure 1 shows a diagram of an example of a sample system. Other air flow control and injection
configurations can be used.
Key
1 atmospheric air to monitor at temperature, T, and relative humidity RH in %
2 sampling head
3 connection pipe
4 anti-dust filter
5 hydrophobic filter
ISO 20045:2023(E)
6 mass flow meter
7 bubbler with trapping water solution
8 micro-bubbles generator
9 catalytic converter furnace
10 pump
11 cooling module
12 first module for HTO trapping (bubblers B1 and B2)
13 second module for no-HTO and residual HTO trapping (bubblers B3 and B4)
Figure 1 — Example of an atmospheric air sampling system diagram with two sampling
modules
At the end of the sampling period, trapping solutions shall be collected separately and transported as
soon as possible to the testing laboratory.
Tritium activity concentration of water from each bubbler sample, in becquerel per litre of bubbler
sample, shall be estimated by liquid scintillation in accordance with ISO 9698 or ISO 13168.
Activity concentrations of atmospheric tritium shall be calculated taking into account:
— air volume sampled;
— water volume of each bubbler sample at the start and end of sampling period;
— activity concentration of each bubbler sample;
— HTO trapping efficiency and if required;
— oxidizing efficiency of the catalytic converter furnace.
5 Influence quantities
Numerous parameters can affect the sampling of atmospheric air. These influencing quantities may be
categorized as controllable or uncontrollable parameters. Controllable parameters can be monitored
by applying the requirements of this document. Uncontrollable parameters are closely linked with
environmental conditions such as atmospheric air temperature and humidity or ambient temperature
at the sampling location.
Controllable quantities are:
— air flow rate;
— height of trapping solution into each bubbler;
— micro-bubbling into each bubbler;
— temperature of the bubbler sample during sampling;
— oxidizing efficiency of the catalytic converter furnace during heating;
— hermetically sealing of sampling system;
— conditions of sampling and filtration of atmospheric air upstream of sampling device.
ISO 20045:2023(E)
6 Equipment
6.1 Description and requirements of the sampling system
The sampling system shall include:
— a sampling head equipped with protection against direct rainfall or splashing;
— a connection pipe as short as possible, between the sampling head and the sampling system,
watertight, airtight and dustproof. The composition of the connection line shall reduce the retention
of water vapour and isotopic exchanges with hydrogen. The connection pipe shall be protected from
condensation and frost in the winter season;
— a dust filter upstream of the first module to limit chemical luminescence and quenching during
sample analysis via liquid scintillation counting. The dust filter shall be periodically changed to
protect it from clogging-up;
— a mass flow meter, associated with a pump flow rate control, protected by hydrophobic filters
located upstream and downstream of the mass flow meter. The mass flow meter shall be periodically
calibrated to ensure their accuracy;
— a minimum of one sampling module consisting of two bubblers connected in series each with a
micro-bubble generator to improve exchanges between atmospheric tritiated water vapour and
trapping water. It is recommended to use glass bubblers to reduce the risk of cross contamination
after use, washing and drying;
— if required, to collect no-HTO and residual HTO not trapped by the first module;
— a catalytic converter furnace to convert no-HTO tritium compounds to HTO by oxidizing;
— a second module of two bubblers connected in series each with a micro-bubble generator to
improve the exchange between HTO, converted by the catalytic converter furnace, and trapping
water. The oxidizing efficiency shall be known (see Table B.1). Efficiency of the conversion
catalyst depends of furnace temperature and material type used as catalyst to convert tritium
species of interest see References [12], [13], [14], [15] and [16].
— a pump located downstream of sampling module(s);
— a cooling system to reduce evaporation of water into bubblers and to ensure a temperature range
between 2 °C and 15 °C.
6.2 Location of sampling head
Sampling head shall be located in accordance with aeraulic conditions at the sampling point (cleared
area, dominant wind, etc.). To limit clogging-up of dust filter and rain splashing, the sampling head shall
be located at one metre above the sampling zone (roof or other).
6.3 Air flow rate, sampling duration and air volume sampling
The air flow rate shall be known, continuous and constant to ensure the representativeness of sampling.
The air volume sampled is calculated from the mass flow meter and the sampling duration data. The
result of this volume is expressed in cubic metre (m ) in standard conditions. The mass flow meter shall
be calibrated at standard conditions, i.e. temperature of 273,13 K (0 °C) and a pressure of 101 325 Pa.
A periodically verification of flow meter calibration according to the international system shall ensure
the accuracy and uncertainty of sampling volume measurements.
ISO 20045:2023(E)
6.4 Trapping water solution
Any type of water acceptable to the measurement by the test laboratory (e.g. deionized water, mineral
water or deep aquifer water) that does not generate unacceptable chemical luminescence or quenching
phenomena may be used. The tritium activity of the trapping solution shall be negligible related to the
tritium activities to be monitored. Tritium activity of the trapping water solution shall be monitored
with appropriate performances before use as trapping water solution to ensure that the decision
threshold or the detection limit are in accordance with customer request.
If the sampling system operates under ambient temperatures less than 0 °C, it may be necessary to
add antifreeze into trapping solution. This addition can generate chemical luminescence and quenching
phenomena influencing the detection efficiency of the liquid scintillation measurement. The user shall
ensure that the corresponding test sample is acceptable to the measurement by the test laboratory.
Before the start of sampling and at the end of the sampling period, the volume or the mass of the
trapping solution in each bubbler shall be measured with a known accuracy, by graduated cylinder in
accordance with ISO 4788 requirements or by mass.
6.5 Specifications for use
Specifications for use shall be defined and shall take into account:
— an unambiguous identification of bubblers;
— a hermetically sealed sampling system;
— a sufficient volume of trapping water to ensure a minimum vertical path of bubbles;
— a sufficient clearing height above the air-water interface to limit mechanical transfers of water from
one bubbler to the next one;
— an air flow rate in accordance with a good exchange of HTO between bubbles and trapping water.
NOTE 1 The clearing height above the air-water interface and the vertical path of bubbles depend on the
design of the bubbling system. They shall be optimized by the manufacturer.
-1 -1
NOTE 2 For example, air flow rate at standard conditions can range from 10 l·h to 50 l·h for a sampling
period ranging from few hours to a week.
Figure 2 gives an example of a bubbler diagram.
ISO 20045:2023(E)
Key
1 micro-bubbles generator
2 vertical path of bubbles
3 clearing height
a
Air input.
Figure 2 — Example of bubbler diagram
Precautions shall be taken to avoid equipment cross-contamination. For example, the following
precautions may be used:
— a systematic cleaning of the sample container (e.g. dishwasher and drying);
— a systematic cleaning of the micro-bubble generators (e.g. absorbent paper);
— a control of “absence” of contamination of the sampling system (e.g. by sampling an atmospheric
air with a low-level tritium activity concentration during maintenance operations or after the
sampling system is replaced). It is also advisable to check for the “absence” of contamination when
the sampling system has been subjected to unusual tritium atmospheric activity concentration.
7 Procedure
7.1 Sampling
The purpose of the sampling is to collect atmospheric tritium of various forms for a quantitative
analysis by a testing laboratory.
Bubbler samples shall be representative of the monitored or studied site. Consequently, the sampling
system shall be located taking into account environmental characteristics such as local landscapes,
barriers or dominant winds.
The sampling shall be done uninterrupted and with a constant air flow rate.
Air flow rate and sampling duration shall be adjusted to achieve appropriate performances; a sampled
3 -1
volume of 5 m corresponding to an air flow rate about 30 l∙h and a sampling duration of one week,
-3
allows to reach an HTO detection limit of 0,2 Bq∙m .
Atmospheric sampling for monitoring or studying operations, often, take place outside directly in the
environment. Generally, in controlled conditions of use, recommended controllable parameters values
ISO 20045:2023(E)
are sufficient to neglect humidity and temperature parameters. However, extreme climatic conditions
may affect the sampling system and can disrupt the air sampling (e.g. a warm moist atmospheric air or
a dry cold atmospheric air causes strong variations of relative humidity). These variations may have
a significant impact on the final water volume collected at the end of sampling duration in the first
bubbler sample (see References [10] and [11]).
7.2 Sample collection and transportation
At the end of the sampling period bubbler samples are disconnected from the sampling system and
hermetically sealed as soon as possible. Optionally, a volume of bubbler samples’ trapping solution
can be removed and stored into an acceptable container. The container shall be, as soon as possible,
hermetically sealed and unambiguously identified. Moreover, it is recommended to fill the container
completely, leaving no headspace to minimize tritium exchange with atmospheric moisture.
Samples and associated information are given to the testing laboratory (see Annex D). Transport
and conservation shall be carried out in accordance with testing laboratory recommendations (see
Annex C).
7.3 Receipt
Bubbler samples shall be delivered to the testing laboratory as soon as possible after sampling. The
laboratory shall check the completeness of samples received such as the number of samples, their
integrity, identification or other useful information.
The laboratory should have procedures in place to handle these types of samples and prevent cross-
contamination during handling or test sample preparation.
7.4 Conservation
Analysis of samples are achieved as soon as possible after re
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