SIST EN ISO 20044:2024

SLOVENSKI STANDARD
01-september-2024
Merjenje radioaktivnosti v okolju - Zrak: aerosolni delci - Preskusna metoda z
vzorčenjem s filtrirnimi mediji (ISO 20044:2022)
Measurement of radioactivity in the environment - Air: aerosol particles - Test method
using sampling by filter media (ISO 20044:2022)
Bestimmung der Radioaktivität in der Umwelt - Luft: Aerosole - Messverfahren mittels
Sammlung auf Filtern (ISO 20044:2022)
Mesurage de la radioactivité dans l'environnement - Air: particules d'aérosol - Méthode
d’essai utilisant l’échantillonnage par un média filtrant (ISO 20044:2022)
Ta slovenski standard je istoveten z: EN ISO 20044:2024
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 20044
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2024
EUROPÄISCHE NORM
ICS 17.240; 13.040.01
English Version
Measurement of radioactivity in the environment - Air:
aerosol particles - Test method using sampling by filter
media (ISO 20044:2022)
Mesurage de la radioactivité dans l'environnement - Bestimmung der Radioaktivität in der Umwelt - Luft:
Air: particules d'aérosol - Méthode d'essai utilisant Aerosole - Messverfahren mittels Sammlung auf Filtern
l'échantillonnage par un média filtrant (ISO (ISO 20044:2022)
20044:2022)
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.

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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 20044:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
The text of ISO 20044:2022 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 20044:2024 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 20044:2022 has been approved by CEN as EN ISO 20044:2024 without any modification.

INTERNATIONAL ISO
STANDARD 20044
First edition
2022-12
Measurement of radioactivity in the
environment — Air: aerosol particles
— Test method using sampling by
filter media
Mesurage de la radioactivité dans l'environnement — Air: particules
d'aérosol — Méthode d’essai utilisant l’échantillonnage par un média
filtrant
Reference number
ISO 20044:2022(E)
ISO 20044:2022(E)
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 20044:2022(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 5
5 Principle . 6
6 Sampling . 9
6.1 General . 9
6.2 Choice of criteria for sampling location . 9
6.3 Criteria for sampling duration . . 9
6.4 Criteria for sampling equipment . 9
6.5 Criteria for filter .12
6.6 Criteria for air volume and flow-rate measurement .12
7 From filter collecting to deferred deposited activity measurement report .12
8 Determination of the activity concentration in the air from deferred measurement
results .13
8.1 General .13
8.2 Model of evaluation . 13
8.3 Relative standard uncertainty . 14
8.4 Decision threshold . 14
8.5 Detection limit . 14
8.6 Expression of activity concentration results . 14
[11]
9 Real time measurement with continuous air monitor .14
9.1 Context . 14
9.2 Description of CAM .15
9.3 Operating use of CAM . 17
10 Quality assurance and quality control .17
10.1 General . 17
10.2 Sample identification, handling, and storage . 17
10.3 Sampling equipment . 17
10.4 Documentation and record keeping . 18
[16]
Annex A (informative) Radionuclides in the atmosphere .19
Annex B (informative) General information on aerosol behaviour .21
Annex C (informative) Example of sampling head and characterizations .25
Annex D (informative) Examples of some sampling filters characteristics .27
Annex E (informative) Example of sampling information sheet .30
Annex F (informative) Characterization of the transport line .31
Annex G (informative) Example of calculation of the activity concentration in the air from
deferred measurement .33
Annex H (informative) Illustration of CAM empirical minimum detectable activity
concentration setup and its associated response time .37
Bibliography .43
iii
ISO 20044:2022(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 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, Subcommittee 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.
iv
ISO 20044:2022(E)
Introduction
Everyone is exposed to natural radiation. The natural sources of radiation are cosmic rays and naturally
occurring radioactive substances that exist in the earth and flora and fauna, including 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 effluent and
waste during operation and decommissioning. The use of radioactive materials in industry, 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 crew during
air travel. The average level of occupational exposures is generally similar to the global average level of
[1]
natural radiation exposure .
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:
— improve the understanding of global levels and temporal trends of public and worker exposure;
— evaluate the components of exposure so as to provide a measure of their relative importance;
— 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 measurements of the activity concentration in or specific activity of waste, effluent and/
or environmental samples.
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 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
apply them to demonstrate their technical competences and to complete proficiency tests successfully
during interlaboratory comparisons, two prerequisites for obtaining national accreditation.
Today, over a hundred International Standards are available to testing laboratories for measuring the
activity concentration or specific activity of radionuclides in different matrices.
Generic standards help testing laboratories to manage the measurement process by setting out the
general requirements and methods to calibrate equipment and validate techniques. These standards
underpin specific standards that describe the test methods to be performed by staff, for example, for
different types of samples. The specific standards cover test methods for:
40 3 14
— naturally-occurring radionuclides (including K, H, C and those originating from the thorium and
226 228 234 238 210 210
uranium decay series, in particular Ra, Ra, U, U, Po 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);
v
ISO 20044:2022(E)
— human-made radionuclides, such as transuranium elements (americium, plutonium, neptunium,
3 14 90
and curium), H, C, Sr and gamma-ray emitting radionuclides found in waste, liquid and gaseous
effluent, 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 fallout from accidents, such as those that occurred in Chernobyl and Fukushima.
A reliable monitoring of activity concentration in the air is necessary to assess the potential human
exposure, to verify compliance with radiation protection and environmental protection regulations
or to provide guidance on reducing health risks. Accurate measurement of the activities of the
radionuclides is also needed for homeland security and in connection with the Non-Proliferation Treaty
(NPT).
NOTE The Non-Proliferation Treaty (NPT) is a landmark international treaty whose objective is to prevent
the spread of nuclear weapons and weapons technology, to promote cooperation in the peaceful uses of nuclear
energy and to further the goal of achieving nuclear disarmament and general and complete disarmament.
Many radionuclides are present in ambient air in gaseous form or bound to aerosol particles. They have
a natural or artificial origin with half-lives ranging from less than a second ( Po) to 15,7 million years
( I). Examples of activity concentration values of these background levels are presented in Annex A.
If the potential source of release is known, the measurement programme of the environment provides
data to compare the activity in the environment with the released radionuclides. In case of an
emergency, these measuring programmes provide data to calculate the expected dose.
In all cases, a correction for radon and/or radon progeny interference is taken into account when
analysing only the count results, statistics or types of particle, or when no specific information is
available, e.g. from spectrometric measurements.
The specific techniques used in a sampling programme are based on the purpose(s) of the sampling.
Even if airborne radionuclide concentrations are very low, sampling may be conducted routinely due to
the potential for high exposures and doses if an incident or accident release should occur. Sampling in
the environment can be used to determine the following parameters:
— controls of the confinement of radioactive substances;
— measurement of activity concentrations of airborne radioactive substance in the environment for
assessment of dose calculations and the recommendation of measures;
— environmental monitoring for preparedness for a nuclear/radiological emergency or making radio-
ecological investigation
The continuous measurement of radionuclides in the atmosphere enables very fast provision of
measurement data in case of an emergency. In the general measurement programme the detection of
activity concentrations near to the limit of detection is demanded. The sampling/measuring-sites have
to be distributed in such a way that the sum of the results allows an interpretation of the situation
which is representative for the area due to the meteorological conditions.
Aims are:
— monitoring of radionuclides in the atmosphere;
— trend detection;
— baseline determination;
— dose assessment in case of air contamination caused by long-distance sources (e.g. Chernobyl,
Algeciras, Fukushima, nuclear weapons, etc.);
— data collection for radio-ecological application and research.
vi
INTERNATIONAL STANDARD ISO 20044:2022(E)
Measurement of radioactivity in the environment — Air:
aerosol particles — Test method using sampling by filter
media
1 Scope
This document provides guidance for
— the sampling process of the aerosol particles in the air using filter media. This document takes into
account the specific behaviour of aerosol particles in ambient air (Annex B).
— Two methods for sampling procedures with subsequent or simultaneous measurement:
— the determination of the activity concentration of radionuclides bound to aerosol particles in
the air knowing the activity deposited in the filter;
— the operating use of continuous air monitoring devices used for real time measurement.
-3
The activity concentration is expressed in becquerel per cubic metre (Bq∙m ).
This document describes the test method to determine activity concentrations of radionuclides bound
to aerosol particles after air sampling passing through a filter media designed to trap aerosol particles.
The method can be used for any type of environmental study or monitoring.
[2]
The test method is used in the context of a quality assurance management system (ISO/IEC 17025 ).
This document does not cover the details of measurement test techniques (gamma spectroscopy,
global alpha and beta counting, liquid scintillation, alpha spectrometry) used to determine the activity
deposited in the media filter, which are either based on existing standards or internal methods
developed by the laboratory in charge of those measurements. Also, this document does not cover the
variability of the aerosol particle sizes as given by the composition of the dust contained in ambient
[3][4]
air . This document does not address to sampling of radionuclides bound to aerosol particles in the
[5]
effluent air of nuclear facilities [see ISO 2889:2021] .
The procedures described here facilitate the sampling of aerosol bound radionuclides. It is supposed to
conform to the national and international requirements for monitoring programmes safety standards
[6]
of IAEA .
The characteristics of the sampling location (coordinates, type of vegetation, obstacles) need to
be documented prior to commencing the monitoring. The guidelines of the World Meteorology
Organization (WMO) include the criteria for representative measurements of temperature, wind-speed,
[7]
wind direction, humidity and precipitation for all the weather stations in the world .
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 11929-1, Determination of the characteristic limits (decision threshold, detection limit and limits of
the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 1:
Elementary applications
ISO 20044:2022(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
accuracy
closeness of agreement between a measured quantity value and the true quantity value of the
measurand
[SOURCE: ISO 2889:2021, 3.4, modified — Correction of “measured quantity” in “measured quantity
[5]
value” and “true quantity” in “true quantity value” .]
3.2
activity median aerodynamic diameter
AMAD
d̅
a,A
median aerodynamic diameter (MAD) (3.14) for the airborne activity in a given aerosol (3.4)
3.3
aerodynamic diameter
AD
d
a
-3
diameter of a sphere with density 1 000 kg·m that has
the same sedimentation velocity in quiescent air as the arbitrary particle
3.4
aerosol
system of solid and/or liquid particles suspended in air or other gas
[8]
[SOURCE: ISO 15900:2020, 3.1 ]
3.5
aerosol particle
solid or liquid particle constituents of an aerosol (3.4)
[5]
[SOURCE: ISO 2889:2021, 3.11 ]
3.6
collection efficiency of the sampling line
ratio between the concentration of aerosol particles (3.5) arriving on the media filter via the transport
line and the outdoor concentration of aerosol particles near the sampling head, for a given "size" of
aerosol particles (3.5) as part of aerosols (3.4)
3.7
collection efficiency of the filter
ratio between the amount of aerosol particles (3.5) deposited in the filter and the amount of aerosol
particles (3.5) arriving on the filter
3.8
continuous air monitor
CAM
instrument that continuously monitors the airborne activity concentration on a near real-time basis
Note 1 to entry: This approach uses continuous air monitors to assess activity concentration in air and can alarm
when predetermined levels are exceeded.
ISO 20044:2022(E)
[9]
[SOURCE: ISO 16639:2017, 3.10 ]
3.9
decision threshold
value of the estimator of the measurand, which when exceeded by the result of an actual measurement
using a given measurement procedure of a measurand quantifying a physical effect, it is decided that
the physical effect is present
Note 1 to entry: The decision threshold is defined in such a way that in cases where the measurement result
exceeds the decision threshold, the probability of a wrong decision, namely that the true value of the measurand
is not zero if in fact it is zero, is less or equal to a chosen probability, α.
Note 2 to entry: If the result, A, is below the decision threshold, it is decided to conclude that the result cannot be
attributed to the physical effect; nevertheless, it cannot be concluded that it is absent.
[SOURCE: ISO 11929-1:2019, 3.12, modified — The definition and the Notes to entry have been slightly
reworded.]
3.10
detection limit
smallest true value of the measurand which ensures a specified probability of being detectable by the
measurement procedure
Note 1 to entry: With the decision threshold, the detection limit is the smallest true value of the measurand for
which the probability of wrongly deciding that the true value of the measurand is zero is equal to a specified value,
β, when, in fact, the true value of the measurand is not zero. The probability of being detectable is consequently
(1 − β).
Note 2 to entry: The terms detection limit and decision threshold are used in an ambiguous way in different
standards (e.g. standards related to chemical analysis or quality assurance). If these terms are referred to, it is
necessary to state according to which standard they are used.
[SOURCE: ISO 11929-1:2019, 3.13]
3.11
hot particle
small particle containing a specific activity significantly higher than the rest of the sample
Note 1 to entry: If not detected, the activity of the hot particle would be assigned to the total sample and,
therefore, results in a non-representative measurement.
3.12
limits of the coverage interval
values which define a coverage interval
Note 1 to entry: The limits are calculated in the ISO 11929 series to contain the true value of the measurand with
a specified probability (1 − γ).
Note 2 to entry: The definition of a coverage interval is ambiguous without further stipulations. In this document,
two alternatives, namely the probabilistically symmetric and the shortest coverage interval are used.
Note 3 to entry: The coverage interval is defined in ISO 11929-1:2019, 3.4, as the set of quantity values within
which the true value of the measurand is contained with a stated probability, based on the information available.
[SOURCE: ISO 11929-1:2019, 3.16, modified — Note 3 to entry has been added.]
3.13
measurand
quantity intended to be measured
[SOURCE: ISO 11929-1:2019, 3.3]
ISO 20044:2022(E)
3.14
median aerodynamic diameter
MAD
d̅
a
value of aerodynamic diameter (3.3) for which 50 % of the quantity in a given aerosol (3.4) is associated
with particles smaller than the MAD, and 50 % of the quantity is associated with particles larger than
the MAD
3.15
minimum detectable activity concentration
time-integrated activity concentration or activity concentration measurements and their associated
coverage intervals for a given probability (1 − γ) to the detection alarm level
[11]
[SOURCE: ISO TR 22930-1:2020, 3.9 ]
3.16
mass median aerodynamic diameter
MMAD
d̅
a,m
point in an aerodynamic particle size distribution where half of the mass lies in particles with a
diameter less than the MMAD and half in particles with a diameter greater than the MMAD
[12]
[SOURCE: ISO 16972:2020, 3.140 ]
3.17
model of evaluation
set of mathematical relationships between all measured and other quantities involved in the evaluation
of measurements
[SOURCE: ISO 11929-1:2019, 3.11]
3.18
response time
time required after a step variation in the measured quantity for the output signal variation to reach a
given percentage for the first time, usually 90 %, of its final value
[5]
[SOURCE: ISO 2889:2021, 3.64 ]
3.19
sampling
collection of radioactive substances on filter, absorbers or adsorbers that is analysed for radioactive
material
3.20
sampling head
device through which aerosol particle (3.5) as part of the aerosols (3.4) in the atmosphere contained in
ambient air are pumped
3.21
standard reference conditions
STP
conditions of temperature and pressure to which measurements are referred for standardization
Note 1 to entry: Standard reference conditions used in this document are of 273,15 K temperature and
1 013,25 hPa pressure.
[13]
[SOURCE: ISO 13443:1996, Clause 3 ]
ISO 20044:2022(E)
3.22
test sample
sample obtained from the collected filter by an appropriate treatment which makes it possible to
determine the activity deposited in the filter
Note 1 to entry: If no appropriate treatment is needed, the filter is the test sample.
3.23
transit time
duration corresponding to the complete scrolling of the moving filter in front of the detector, in case of
moving filter, and considering that the entire deposition area is viewed by the detector
Note 1 to entry: If v is the moving filter velocity and L the diameter of the circular area of the exposed filter or the
length of a rectangular area in the direction of the transported filter tape with a constant width w of the
D
L
exposed area below the detector then the time transit is: t = (see Clause 4)
T
ν
[11]
[SOURCE: ISO/TR 22930-1:2020, 3.13 , modified — Note 1 to entry has been modified with respect to
ISO/TR 22930-1:2020, 3.13.]
3.24
transport line
pipe or set of pipes connecting the sampling head (3.20) to the media filter
3.25
uncertainty of measurement
parameter associated with the result of measurements that characterizes the dispersion of the values
that could reasonably be attributed to the measurand (3.13)
[14]
Note 1 to entry: The uncertainty of a measurement derived according to the GUM comprises, in general, many
components. Some of these components are evaluated from the statistical distribution of the results of series of
measurements and can be characterized by experimental standard deviations. The other components, which also
can be characterized by standard deviations, are evaluated from assumed or known probability distributions
[15]
based on experience and other information .
[SOURCE: ISO 11929-1:2019, 3.10, modified — Definition and Note 3 to entry were reworded and Notes
1, 2 and 4 to entry were deleted.]
4 Symbols
Symbols used in formulae in this document are defined in Table 1.
Table 1 — Symbols used in formulae
α, β Probability of a false positive and false negative decision, respectively —
A Activity deposited in the filter at the time of measurement Bq
A* Decision threshold of the activity deposited in the media filter at the time of meas- Bq
urement
#
A Detection limit of the activity deposited in the media filter at the time of measurement Bq
a Cross section area of the suction pipe m
-3
Averaged activity concentration in the air over the sampling duration Bq·m
C
-3
Decision limit of the averaged activity concentration in the air over the sampling Bq·m
C *
duration
-3
#
Decision threshold of the averaged activity concentration in the air over the sampling Bq·m
C
duration
d Inner diameter of the pipe m
-1
λ Radioactive constant decay of the measured radionuclide s
ISO 20044:2022(E)
TTabablele 1 1 ((ccoonnttiinnueuedd))
ε Collection efficiency of the sampling line —
S
Collection efficiency of the filter —
ε
F
-1 -1
η Dynamic viscosity kg∙m ∙s
G
Quantile of the standardized normal distribution for the probability p (for instance —
k
p
p = 1-α, 1-β or 1-γ/2)
L Diameter of the circular area of the exposed filter or the length of a rectangular area
in the direction of the transported filter tape with a constant width w of the exposed
m
D
area below the detector
3 -1
q Volume flow rate at standard reference conditions with T = 273,15 K and p = 1 013,25 hPa m ∙s
STP
Re Reynolds number, dimensionless —
-3
Gas density kg∙m
ρ
G
t (= T1) Sampling duration s
S
Period of time from the end of sampling to the end of the measurement s
t (= T2)
t Counting time s
C
Sampling time of CAM s
t
t Transit time of the filter s
T
Standard uncertainty of the quantity x —
ux()
ux Relative standard uncertainty of the quantity x —
()
r
V Air volume m
-1
v Moving filter velocity m∙s
-1
v Air velocity m∙s
a
Conversion factor for the measurement of the activity deposited on the media filter.
It takes into account the detector calibration, the emission intensity and various
-1
w s·Bq
correction factors useful for the measurement such as, for example, self-attenuation,
geometry correction, chemical precipitation efficiency, true coincidences
Filter tape width m
w
D
5 Principle
The activity concentration monitoring of the aerosols in the atmosphere consists of passing a known
volume of air through a filter placed in a transport line and measuring the activity deposited on this
media. In general, two methods are applied:
— A system referred to as continuous sampling and off-line measurement (see Figure 1), in which the
filter medium is collected at the end of the batch sampling process and then sent to a laboratory for
measurement of the activity deposited on it. The average activity concentrations over the sampling
period can be determined only when the measurement result of the activity deposited on the filter
is available;
ISO 20044:2022(E)
Key
P1 sampling phase
P2 filter collecting, packaging, transfer and conservation phase
P3 filter treatment and activity determination phase
sampling duration
T
period of time from the end of sampling to the end of the measurement
T
A1 activity result of the test sample at the time of measurement
A activity deposited on and in the filter media at the time of sampling (deduced from A1)
1 sampling head
2 transport line
3 filter holder
4 filter
5 pump and flow meter
6 filter packaging and transport box
7 treatment of the filter for sampling test
8 test sample
9 activity measurement device
Figure 1 — Principle of continuous sampling with deferred measurement
[10]
[SOURCE: NF M 60-760]
— Another system referred to as real-time measurement using continuous air monitors (CAM) for
aerosol particles (see Figure 2), which consists of continuously and simultaneously measuring the
volume of air passing through the filter and the activity deposited therein by a radiation detector.
[10][11]
The results of the activity concentrations are made available in real time .
ISO 20044:2022(E)
Key
1 sampling head
2 transport line
3 filter holder
4 filter
5 pump and flow meter
6 radiation detector
A activity deposited on the filter
Figure 2 — Principle of continuously sampling and simultaneous detection
The determination of the activity concentration requires the knowledge of the various parameters
regarding
— the sampling process: the representativeness of the sampling location, the capture efficiency of the
transport line, the trapping efficiency of the filter, the volume of air sampled and their respective
uncertainties, and
— the activity measurement process: the treatment efficiency (if needed) of the filter, the activity
deposited on the filter at the end of the sampling period and their associated characteristic limits
(decision threshold, detection limit and limits of the coverage interval) for the deferred measurement
method and the CAM performance for real-time measurement.
ISO 20044:2022(E)
6 Sampling
6.1 General
Sampling has to be continuous when measurement is performed simultaneously. In addition, a
daily or weekly sampling period may be acceptable (except for very short-lived radionuclides) when
measurements are performed after sampling. Monthly or quarterly sampling can be acceptable for
areas in which average activity concentrations of airborne radioactive material are expected to be
-3
below a few mBq∙m .
6.2 Choice of criteria for sampling location
If the measurement results should be representative for a large area, the directives of the WMO
[7]
should be taken as a guideline for the choice of a sampling site for aerosol bound radionuclides. The
representativeness of an observation is the degree to which it accurately describes the value of the
variable needed for a specific purpose. Therefore, it is not a fixed quality of any observation, but results
from joint appraisal of instrumentation, measurement interval and exposure against the requirements
of some particular application. For instance, synoptic observations should typically be representative
of an area up to 100 km around the station, but for small-scale or local applications the considered area
can have dimensions of 10 km or less.
Each sampling location, as well as their number, shall be chosen according to environmental monitoring
objectives and strategies, in particular:
— monitoring the environment around nuclear sites;
— monitoring of sites with a problem of additional natural radioactivity due to their present or past
activities;
— monitoring activity concentration on a national scale (regional background levels, radiological
events).
Their location depends on the topography, the climate, types of environment (industrial, agricultural,
accessibility, etc.), the potential discharge points, etc.
If a potential source of release is monitored, the sampling locations should be chosen so that the
area surrounding the sampling air intake is free of any obstructions. If this condition cannot be met
omnidirectionally, it shall be met for the most likely and least likely wind direction from the source of
release to be monitored. In case of the continuous release of radionuclides the probability of sampling
radionuclides bound to aerosol particles are related to the wind direction. The selection of the sampling
site
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