SIST-TP CEN ISO/TR 22930-2:2021

Evaluating the performance of continuous air monitors - Part 2: Air monitors based on flow-through sampling techniques without accumulation (ISO/TR 22930-2:2020)

The use of a continuous air monitor (CAM) is mainly motivated by the need to be alerted quickly and in the most accurate way possible with an acceptable false alarm rate when significant activity concentration value is exceeded, in order to take appropriate measures to reduce exposure of those involved.
The performance of this CAM does not only depend on the metrological aspect characterized by the decision threshold, the limit of detection and the measurement uncertainties but also on its dynamic capacity characterized by its response time as well as on the minimum detectable activity concentration corresponding to an acceptable false alarm rate.
The ideal performance is to have a minimum detectable activity concentration as low as possible associated with a very short response time, but unfortunately these two criteria are in opposition. It is therefore important that the CAM and the choice of the adjustment parameters and the alarm levels be in line with the radiation protection objectives.
This document describes
—   the dynamic behaviour and the determination of the response time,
—   the determination of the characteristic limits (decision threshold, detection limit, limits of the coverage interval), and
—   a possible way to determine the minimum detectable activity concentration and the alarms setup.
Finally the annexes of this document show actual examples of CAM data which illustrate how to quantify the CAM performance by determining the response time, the characteristics limits, the minimum detectable activity concentration and the alarms setup.

Ermittlung der Leistungsfähigkeit kontinuierlicher Luftmonitore - Teil 2: Luftmonitore basierend auf Durchfluss-Sammeltechnik ohne Anreicherung (ISO/TR 22930-2:2020)

Die Verwendung eines kontinuierlichen Luftmonitors (CAM, en: continuous air monitor) ist hauptsächlich darin begründet, bei der Überschreitung eines signifikanten Werts der Aktivitätskonzentration schnell und mit einer akzeptablen Fehlalarmrate möglichst genau alarmiert zu werden, um geeignete Maßnahmen zu ergreifen, um die Exposition der Beteiligten zu verringern.
Die Leistungsfähigkeit dieser kontinuierlichen Luftmonitore hängt nicht nur vom metrologischen Aspekt, der durch die Erkennungsgrenze, die Nachweisgrenze und die Messunsicherheiten charakterisiert ist, ab, son¬dern auch von der dynamischen Kapazität, die durch die Ansprechzeit charakterisiert ist, sowie von der kleinsten nachweisbaren Aktivitätskonzentration, die einer akzeptablen Fehlalarmrate entspricht.
Eine ideale Leistungsfähigkeit wäre eine möglichst geringe nachweisbare Aktivitätskonzentration, die mit einer sehr kurzen Ansprechzeit verbunden ist, jedoch stehen diese beiden Kriterien zueinander im Wider-spruch. Es ist daher wichtig, die kontinuierlichen Luftmonitore und die Wahl der Einstellparameter und Alarm¬schwellen in Einklang mit den Strahlenschutzzielen zu bringen.
Dieses Dokument beschreibt:
–   das dynamische Verhalten und die Ermittlung der Ansprechzeit,
–   die Bestimmung der charakteristischen Grenzen (Erkennungsgrenze, Nachweisgrenze, Grenzen des Überdeckungsintervalls) und
–   einen möglichen Weg, die kleinste nachweisbare Aktivitätskonzentration und die Alarmeinstellungen zu bestimmen.
Abschließend zeigen die Anhänge dieses Dokuments aktuelle Beispiele von CAM-Daten, die aufzeigen, wie die Leistungsfähigkeit eines kontinuierlichen Luftmonitors anhand der Bestimmung der Ansprechzeit, der cha¬rakteristischen Grenzen, der kleinsten nachweisbaren Aktivitätskonzentration und der Alarmeinstellungen quantifiziert werden kann.

Évaluation des performances des dispositifs de surveillance de l'air en continu - Partie 2: Dispositifs de surveillance de l’air basés sur des techniques d’échantillonnage par circulation sans accumulation (ISO/TR 22930-2:2020)

L'utilisation d'un dispositif de surveillance de l'air en continu (CAM) est principalement motivée par la nécessité d'être alerté rapidement et de la façon la plus précise possible avec un taux acceptable de fausses alarmes lorsqu'une valeur d'activité volumique significative est dépassée, afin de prendre des mesures appropriées pour réduire l'exposition des personnes concernées.
Les performances de ce CAM dépendent non seulement de l'aspect métrologique caractérisé par le seuil de décision, la limite de détection et les incertitudes de mesure, mais aussi de sa capacité dynamique caractérisée par son temps de réponse ainsi que de l'activité volumique minimale détectable correspondant à un taux de fausses alarmes acceptable.
La situation idéale serait d'avoir une activité volumique minimale détectable aussi faible que possible et un temps de réponse associé très court, mais ces deux critères sont malheureusement en opposition. Il est donc important que le CAM et le choix des paramètres de réglage et des niveaux d'alarme soient alignés sur les objectifs de la radioprotection.
Le présent document décrit
—          le comportement dynamique et la détermination du temps de réponse,
—          la détermination des limites caractéristiques (seuil de décision, limite de détection, limites de l'intervalle élargi), et
—          une méthode possible pour déterminer l'activité volumique minimale détectable et le paramétrage des alarmes.
Les annexes du présent document présentent ensuite des exemples actuels de données de CAM qui illustrent la quantification des performances d'un CAM en déterminant le temps de réponse, les limites caractéristiques, l'activité volumique minimale détectable et le paramétrage des alarmes.

Ugotavljanje zmogljivosti neprekinjeno delujočih zračnih nadzornikov - 2. del: Zračni nadzorniki na podlagi tehnik vzorčenja pretoka zraka brez kopičenja (ISO/TR 22930-2:2020)

General Information

• Status: Published
• Public Enquiry End Date: 14-Jul-2021
• Publication Date: 19-Sep-2021
• ICS: 13.280 - Radiation protection
• Technical Committee: I13 - Imaginarni 13
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 15-Sep-2021
• Due Date: 20-Nov-2021
• Completion Date: 20-Sep-2021
• Ref Project: CEN ISO/TR 22930-2:2021 - Evaluating the performance of continuous air monitors - Part 2: Air monitors based on flow-through sampling techniques without accumulation (ISO/TR 22930-2:2020)

Standards Content (Sample)

SLOVENSKI STANDARD
SIST-TP CEN ISO/TR 22930-2:2021
01-november-2021
Ugotavljanje zmogljivosti neprekinjeno delujočih zračnih nadzornikov - 2. del:
Zračni nadzorniki na podlagi tehnik vzorčenja pretoka zraka brez kopičenja
(ISO/TR 22930-2:2020)
Evaluating the performance of continuous air monitors - Part 2: Air monitors based on
flow-through sampling techniques without accumulation (ISO/TR 22930-2:2020)
Ermittlung der Leistungsfähigkeit kontinuierlicher Luftmonitore - Teil 2: Luftmonitore
basierend auf Durchfluss-Sammeltechnik ohne Anreicherung (ISO/TR 22930-2:2020)
Évaluation des performances des dispositifs de surveillance de l'air en continu - Partie 2:
Dispositifs de surveillance de l’air basés sur des techniques d’échantillonnage par
circulation sans accumulation (ISO/TR 22930-2:2020)
Ta slovenski standard je istoveten z: CEN ISO/TR 22930-2:2021
ICS:
13.280 Varstvo pred sevanjem Radiation protection
SIST-TP CEN ISO/TR 22930-2:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST-TP CEN ISO/TR 22930-2:2021


CEN ISO/TR 22930-2
TECHNICAL REPORT

RAPPORT TECHNIQUE

August 2021
TECHNISCHER BERICHT
ICS 13.280
English Version

Evaluating the performance of continuous air monitors -
Part 2: Air monitors based on flow-through sampling
techniques without accumulation (ISO/TR 22930-2:2020)
Évaluation des performances des dispositifs de Ermittlung der Leistungsfähigkeit kontinuierlicher
surveillance de l'air en continu - Partie 2: Dispositifs de Luftmonitore - Teil 2: Luftmonitore basierend auf
surveillance de l'air basés sur des techniques Durchfluss-Sammeltechnik ohne Anreicherung
d'échantillonnage par circulation sans accumulation (ISO/TR 22930-2:2020)
(ISO/TR 22930-2:2020)


This Technical Report was approved by CEN on 16 August 2021. It has been drawn up by the Technical Committee CEN/TC 430.

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
© 2021 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN ISO/TR 22930-2:2021 E
worldwide for CEN national Members.

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CEN ISO/TR 22930-2:2021 (E)
Contents Page
European foreword . 3

2

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CEN ISO/TR 22930-2:2021 (E)
European foreword
The text of ISO/TR 22930-2:2020 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 CEN ISO/TR 22930-2:2021 by Technical Committee
CEN/TC 430 “Nuclear energy, nuclear technologies, and radiological protection” the secretariat of
which is held by AFNOR.
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.
Endorsement notice
The text of ISO/TR 22930-2:2020 has been approved by CEN as CEN ISO/TR 22930-2:2021 without any
modification.

3

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SIST-TP CEN ISO/TR 22930-2:2021
TECHNICAL ISO/TR
REPORT 22930-2
First edition
2020-05
Evaluating the performance of
continuous air monitors —
Part 2:
Air monitors based on flow-through
sampling techniques without
accumulation
Évaluation de la performance des dispositifs de surveillance de l'air
en continu —
Partie 2: Moniteurs d'air basés sur des techniques d'échantillonnage
par circulation sans accumulation
Reference number
ISO/TR 22930-2:2020(E)
©
ISO 2020

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ISO/TR 22930-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 Measuring principle . 6
6 Study of dynamic behaviour . 7
7 Evaluation of the characteristic limits .13
7.1 General .13
7.2 Single detector .13
7.2.1 General.13
7.2.2 Definition of the model .14
7.2.3 Standard uncertainty .14
7.2.4 Decision threshold.15
7.2.5 Detection limit .17
7.2.6 Limits of the coverage interval .17
7.3 Double detector .17
7.3.1 General.17
7.3.2 Definition of the model .18
7.3.3 Standard uncertainty .18
7.3.4 Decision threshold.19
7.3.5 Detection limit .20
7.3.6 Limits of the coverage interval .20
8 Alarms setup, minimum detectable concentration and potential missed exposure .20
Annex A (informative) Application example: Single detector with a proportional counter .23
Annex B (informative) Application example: Double detector in current mode .26
Bibliography .32
© ISO 2020 – All rights reserved iii

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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, Subcommittee SC 2, Radiological protection.
A list of all the parts in the ISO/TR 22930 series can be found on the ISO website.
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 2020 – All rights reserved

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Introduction
Sampling and monitoring of airborne activity concentration in workplaces are critically important for
maintaining worker safety at facilities where dispersible radioactive substances are used.
The first indication of a radioactive substance dispersion event comes, in general, from a continuous
air monitor (CAM) and its associated alarm levels. In general, the response of a CAM is delayed in time
compared to the actual situation of release.
The knowledge of a few factors is needed to interpret the response of a CAM and to select the appropriate
CAM type and its operating parameters.
The role of the radiation protection officer is to select the appropriate CAM, to determine when effective
release of radioactive substances occurs, to interpret measurement results and to take corrective
action appropriate to the severity of the release.
The objective of ISO/TR 22930 series is to assist radiation protection officer in evaluating the
performance of a CAM.
ISO/TR 22930 series describes the factors and operating parameters and how they influence the
response of a CAM.
This document deals with monitoring systems based on flow-through sampling techniques without
accumulation.
© ISO 2020 – All rights reserved v

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TECHNICAL REPORT ISO/TR 22930-2:2020(E)
Evaluating the performance of continuous air monitors —
Part 2:
Air monitors based on flow-through sampling techniques
without accumulation
1 Scope
The use of a continuous air monitor (CAM) is mainly motivated by the need to be alerted quickly
and in the most accurate way possible with an acceptable false alarm rate when significant activity
concentration value is exceeded, in order to take appropriate measures to reduce exposure of those
involved.
The performance of this CAM does not only depend on the metrological aspect characterized by the
decision threshold, the limit of detection and the measurement uncertainties but also on its dynamic
capacity characterized by its response time as well as on the minimum detectable activity concentration
corresponding to an acceptable false alarm rate.
The ideal performance is to have a minimum detectable activity concentration as low as possible
associated with a very short response time, but unfortunately these two criteria are in opposition. It is
therefore important that the CAM and the choice of the adjustment parameters and the alarm levels be
in line with the radiation protection objectives.
This document describes
— the dynamic behaviour and the determination of the response time,
— the determination of the characteristic limits (decision threshold, detection limit, limits of the
coverage interval), and
— a possible way to determine the minimum detectable activity concentration and the alarms setup.
Finally the annexes of this document show actual examples of CAM data which illustrate how to quantify
the CAM performance by determining the response time, the characteristics limits, the minimum
detectable activity concentration and the alarms setup.
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 16639, Surveillance of the activity concentrations of airborne radioactive substances in the workplace
of nuclear facilities
IEC 60761-1, Equipment for continuous monitoring of radioactivity in gaseous effluents — Part 1: General
requirements
© ISO 2020 – All rights reserved 1

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3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11929-1, ISO 16639,
IEC 60761-1 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/o bp
— IEC Electropedia: available at http:// www.e lectropedia. org/
3.1
annual limit on intake
ALI
derived limit for the amount of radioactive substance (in Bq) taken into the body of an adult worker by
inhalation or ingestion in a year
[SOURCE: ISO 16639:2017, 3.7]
3.2
continuous air monitor
CAM
instrument that continuously monitors the airborne activity concentration on a near real-time basis
[SOURCE: ISO 16639:2017, 3.10]
3.3
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 such that in cases where the measurement result, y, exceeds
the decision threshold, y*, 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, y, is below the decision threshold, y*, 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]
3.4
derived air concentration
DAC
concentration of a radionuclide in air that, if breathed over the period of a work year, would result in the
intake of one ALI for that radionuclide
Note 1 to entry: The DAC is calculated by dividing the ALI by the volume of air breathed by reference man under
−3
light-activity work during a working year (in Bq m ).
Note 2 to entry: The parameter values recommended by the International Commission on Radiological Protection
3 −1 3
for calculating the DAC are a breathing rate of 1,2 m ·h and a working year of 2 000 h (i.e. 2 400 m ).
Note 3 to entry: The air concentration can be expressed in terms of a number of DAC. For example, if the DAC for
−3 −3
a given radionuclide in a particular form is 0,2 Bq m and the observed concentration is 1,0 Bq m , then the
observed concentration can also be expressed as 5 DAC (i.e. 1,0 divided by 0,2).
Note 4 to entry: The derived air concentration-hour (DAC-hour) is an integrated exposure and is the product of the
concentration of a radioactive substance in air (expressed as a fraction or multiple of DAC for each radionuclide)
and the time of exposure to that radionuclide, in hours.
[SOURCE: ISO 16639:2017, 3.12]
2 © ISO 2020 – All rights reserved

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3.5
detection alarm level
S0
value of time-integrated activity concentration activity concentration corresponding to an acceptable
false alarm rate
Note 1 to entry: When S0 increases false alarm rate decreases.
Note 2 to entry: Others values of alarm level higher than S0 can also be set up for operational reasons.
3.6
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 according to 3.3, 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 one
has to state according to which standard they are used.
[SOURCE: ISO 11929-1:2019, 3.13]
3.7
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 standard
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 interval containing the set of true
quantity values of a measurand with a stated probability, based on the information available.
[SOURCE: ISO 11929-1:2019, 3.16 modified – Note 3 to entry has been added]
3.8
measurand
quantity intended to be measured
[SOURCE: ISO 11929-1:2019, 3.3]
3.9
minimum detectable concentration
time-integrated activity concentration or activity concentration measurements and their associated
coverage intervals for a given probability (1−γ) corresponding to the first alarm level S0
3.10
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]
© ISO 2020 – All rights reserved 3

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3.11
potential missed exposure
PME
time-integrated activity concentration or maximum activity concentration, as applicable, that can
acceptably be missed
Note 1 to entry: the value of PME is defined according to ALARA/ALARP principles, and below legal limits.
Note 2 to entry: In order to be alerted when a measurement is likely to exceed the value of PME, an alarm level S1
is set up. The PME is then the upper limit of the coverage interval for a given probability (1−γ) of time-integrated
activity concentration or activity concentration measurements corresponding to S1.
[SOURCE: ISO 16639:2017, 3.18]
3.12
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
Note 1 to entry: The intrinsic response time is related to the measurement principle and its associated model of
evaluation of an ideal detector (without taking account of the counting time of the detector).
[SOURCE: IEC 60761-1:2002, 3.15]
4 Symbols
at() Activity going through the detection volume at a time t, in Bq
−3
c Activity concentration, in Bq·m
−3
c Actual activity concentration, in Bq·m
ac
−3
*
Decision threshold of the activity concentration, in Bq·m
c
−3
#
Detection limit of the activity concentration, in Bq·m
c

Lower limit of the coverage interval of the activity concentration for a given prob-
c
−3
ability (1−γ), in Bq·m

Upper limit of the coverage interval of the activity concentration for a given prob-
c
−3
ability (1−γ), in Bq·m
−3
ct Activity concentration measured at a time t, in Bq·m
()
−3
ct Actual activity concentration measured at a time t, in Bq·m
()
ac
−3
c Gross primary measurement of the activity concentration, in Bq·m
g
−3
c Minimum detectable activity concentration, in Bq·m
min

Lower limit of the coverage interval of the minimum detectable activity concentra-
c
min
−3
tion for a given probability (1−γ), in Bq·m

Upper limit of the coverage interval the minimum detectable activity concentration
c
min
−3
for a given probability (1−γ), in Bq·m
th
c Activity concentration of the i measurement of a series of gross measurements
0,i
−3
(with i = 1, …, n) which represent a background situation, in Bq·m
−3
Mean value of c , in Bq·m
c
0,i
0
4 © ISO 2020 – All rights reserved

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I Minimum amount of current registered by the measuring detector (with
min
Q
min
I = in A
min
t
C
I Minimum amount of current registered by the compensating detector (with
minc, d
Q
minc, d
I = ), in A
minc, d
t
Ccd
,
It
() Instantaneous gross current of the measuring detector at a time t, in A
g
Gross current during the counting time t of the measuring detector at a time t, in A
It,,tI
()
C
gC g
It() Instantaneous gross current of the compensating detector at a time t, in A
gc, d
Gross current during the counting time t of the compensating detector at a time t, in A
It,,tI
C,cd
()
gc,,dC cd gc, d
I Background current of the measuring detector, in A
0
I Background current of the compensating detector, in A
0,cd
K Detection alarm setup parameter corresponding to the chosen acceptable false
alarm rate level, dimensionless
k Quantile of a standard normal distribution, if kk= , dimensionless
11−−αβ
k Quantile of a standard normal distribution for a probability (1−α), dimensionless
1−α
k Quantile of a standard normal distribution for a probability (1−β), dimensionless
1−β
k γ
 
γ
Quantile of a standard normal distribution for a probability 1− , dimensionless
1−  
2
2  
N Number of atoms on the media filter, dimensionless
Gross count during the counting time t of the measuring detector at a time t, di-
nt,t
()
C
gC
mensionless
Q Minimum amount of electric charge that induces a pulse registered by the measuring
min
detector, in C
Q Minimum amount of electric charge that induces a pulse registered by the compen-
minc, d
sating detector, in C
3 −1
q Flow rate, in m ·s
−1
rt() Instantaneous gross count rate of the measuring detector at a time t, in s
g
−1
Gross count rate during the counting time t of the measuring detector at a time t, in s
rt,,tr
()
C
gC g
−1
rt Instantaneous gross count rate of the compensating detector at a time t, in s
()
gc, d
Gross count rate during the counting time t of the compensating detector at a
rt,,tr
() C,cd
gc,,dC cd gc, d
−1
time t, in s
−1
r Background count rate of the measuring detector, in s
0
−1
r Background count rate of the compensating detector, in s
0,cd
s Standard deviation of the activity concentration at a series of i measurements which
0
represent a background situation
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ISO/TR 22930-2:2020(E)

t Counting time of the measuring detector, in s
C
t
Counting time of the compensating detector, in s
Cc, d
t Duration of airborne release, in s
F
t Response time, in s
R
t Intrinsic response time, in s
RI
t Counting time of the measuring detector for background measurement, in s
0
t Counting time of the compensating detector for background measurement, in s
0,cd
t Half-life, in s
12/
3
V
Detection volume, in m
−3 −3 −1
w Calibration factor, in Bq·m ·s or Bq·m ·A
δ Correction factor related to sampling (sampling point representativity, radioactive
decay, …), dimensionless
−1 −1 −1
ε Detector efficiency, in Bq ·s or A·Bq
D
−1
λ Decay constant, in s
5 Measuring principle
A representative sample of ambient air to be monitored containing an activity concentration ct at a
()
ac
time t is continuously captured through a transport line then goes through a detection volume without
being retained. In parallel, a detector continuously measures the activity going through the detection
volume. Then a processing algorithm calculates the activity concentration ct() and the suited alarms
on the basis of the evolution of the activity going through the detection volume of air sampled and the
installation or not of an ambient compensating detector. The processing algorithm can also, if necessary,
take into account influence quantities which may perturb the measurement result (see Figure 1).
6 © ISO 2020 – All rights reserved

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SIST-TP CEN ISO/TR 22930-2:2021
ISO/TR 22930-2:2020(E)

Key
1 transport line
2 detector
3 sampling pump
4 media filter
5 processing algorithm
6 alarm processing unit
Figure 1 — Model of the sampling and alarming
6 Study of dynamic behaviour
This clause describes the evolution over time of the activity concentration ct during the sudden
()
app
...

SLOVENSKI STANDARD
kSIST-TP FprCEN ISO/TR 22930-2:2021
01-julij-2021
Ugotavljanje zmogljivosti neprekinjeno delujočih zračnih nadzornikov - 2. del:
Zračni nadzorniki na podlagi tehnik vzorčenja pretoka zraka brez kopičenja
(ISO/TR 22930-2:2020)
Evaluating the performance of continuous air monitors - Part 2: Air monitors based on
flow-through sampling techniques without accumulation (ISO/TR 22930-2:2020)
Ermittlung der Leistungsfähigkeit kontinuierlicher Luftmonitore - Teil 2: Luftmonitore
basierend auf Durchfluss-Sammeltechnik ohne Anreicherung (ISO/TR 22930-2:2020)
Évaluation des performances des dispositifs de surveillance de l'air en continu - Partie 2:
Dispositifs de surveillance de l’air basés sur des techniques d’échantillonnage par
circulation sans accumulation (ISO/TR 22930-2:2020)
Ta slovenski standard je istoveten z: FprCEN ISO/TR 22930-2
ICS:
13.280 Varstvo pred sevanjem Radiation protection
kSIST-TP FprCEN ISO/TR 22930-2:2021 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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kSIST-TP FprCEN ISO/TR 22930-2:2021
TECHNICAL ISO/TR
REPORT 22930-2
First edition
2020-05
Evaluating the performance of
continuous air monitors —
Part 2:
Air monitors based on flow-through
sampling techniques without
accumulation
Évaluation de la performance des dispositifs de surveillance de l'air
en continu —
Partie 2: Moniteurs d'air basés sur des techniques d'échantillonnage
par circulation sans accumulation
Reference number
ISO/TR 22930-2:2020(E)
©
ISO 2020

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kSIST-TP FprCEN ISO/TR 22930-2:2021
ISO/TR 22930-2:2020(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2020
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: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved

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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 Measuring principle . 6
6 Study of dynamic behaviour . 7
7 Evaluation of the characteristic limits .13
7.1 General .13
7.2 Single detector .13
7.2.1 General.13
7.2.2 Definition of the model .14
7.2.3 Standard uncertainty .14
7.2.4 Decision threshold.15
7.2.5 Detection limit .17
7.2.6 Limits of the coverage interval .17
7.3 Double detector .17
7.3.1 General.17
7.3.2 Definition of the model .18
7.3.3 Standard uncertainty .18
7.3.4 Decision threshold.19
7.3.5 Detection limit .20
7.3.6 Limits of the coverage interval .20
8 Alarms setup, minimum detectable concentration and potential missed exposure .20
Annex A (informative) Application example: Single detector with a proportional counter .23
Annex B (informative) Application example: Double detector in current mode .26
Bibliography .32
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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, Subcommittee SC 2, Radiological protection.
A list of all the parts in the ISO/TR 22930 series can be found on the ISO website.
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 2020 – All rights reserved

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kSIST-TP FprCEN ISO/TR 22930-2:2021
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Introduction
Sampling and monitoring of airborne activity concentration in workplaces are critically important for
maintaining worker safety at facilities where dispersible radioactive substances are used.
The first indication of a radioactive substance dispersion event comes, in general, from a continuous
air monitor (CAM) and its associated alarm levels. In general, the response of a CAM is delayed in time
compared to the actual situation of release.
The knowledge of a few factors is needed to interpret the response of a CAM and to select the appropriate
CAM type and its operating parameters.
The role of the radiation protection officer is to select the appropriate CAM, to determine when effective
release of radioactive substances occurs, to interpret measurement results and to take corrective
action appropriate to the severity of the release.
The objective of ISO/TR 22930 series is to assist radiation protection officer in evaluating the
performance of a CAM.
ISO/TR 22930 series describes the factors and operating parameters and how they influence the
response of a CAM.
This document deals with monitoring systems based on flow-through sampling techniques without
accumulation.
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kSIST-TP FprCEN ISO/TR 22930-2:2021
TECHNICAL REPORT ISO/TR 22930-2:2020(E)
Evaluating the performance of continuous air monitors —
Part 2:
Air monitors based on flow-through sampling techniques
without accumulation
1 Scope
The use of a continuous air monitor (CAM) is mainly motivated by the need to be alerted quickly
and in the most accurate way possible with an acceptable false alarm rate when significant activity
concentration value is exceeded, in order to take appropriate measures to reduce exposure of those
involved.
The performance of this CAM does not only depend on the metrological aspect characterized by the
decision threshold, the limit of detection and the measurement uncertainties but also on its dynamic
capacity characterized by its response time as well as on the minimum detectable activity concentration
corresponding to an acceptable false alarm rate.
The ideal performance is to have a minimum detectable activity concentration as low as possible
associated with a very short response time, but unfortunately these two criteria are in opposition. It is
therefore important that the CAM and the choice of the adjustment parameters and the alarm levels be
in line with the radiation protection objectives.
This document describes
— the dynamic behaviour and the determination of the response time,
— the determination of the characteristic limits (decision threshold, detection limit, limits of the
coverage interval), and
— a possible way to determine the minimum detectable activity concentration and the alarms setup.
Finally the annexes of this document show actual examples of CAM data which illustrate how to quantify
the CAM performance by determining the response time, the characteristics limits, the minimum
detectable activity concentration and the alarms setup.
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 16639, Surveillance of the activity concentrations of airborne radioactive substances in the workplace
of nuclear facilities
IEC 60761-1, Equipment for continuous monitoring of radioactivity in gaseous effluents — Part 1: General
requirements
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3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 11929-1, ISO 16639,
IEC 60761-1 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/o bp
— IEC Electropedia: available at http:// www.e lectropedia. org/
3.1
annual limit on intake
ALI
derived limit for the amount of radioactive substance (in Bq) taken into the body of an adult worker by
inhalation or ingestion in a year
[SOURCE: ISO 16639:2017, 3.7]
3.2
continuous air monitor
CAM
instrument that continuously monitors the airborne activity concentration on a near real-time basis
[SOURCE: ISO 16639:2017, 3.10]
3.3
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 such that in cases where the measurement result, y, exceeds
the decision threshold, y*, 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, y, is below the decision threshold, y*, 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]
3.4
derived air concentration
DAC
concentration of a radionuclide in air that, if breathed over the period of a work year, would result in the
intake of one ALI for that radionuclide
Note 1 to entry: The DAC is calculated by dividing the ALI by the volume of air breathed by reference man under
−3
light-activity work during a working year (in Bq m ).
Note 2 to entry: The parameter values recommended by the International Commission on Radiological Protection
3 −1 3
for calculating the DAC are a breathing rate of 1,2 m ·h and a working year of 2 000 h (i.e. 2 400 m ).
Note 3 to entry: The air concentration can be expressed in terms of a number of DAC. For example, if the DAC for
−3 −3
a given radionuclide in a particular form is 0,2 Bq m and the observed concentration is 1,0 Bq m , then the
observed concentration can also be expressed as 5 DAC (i.e. 1,0 divided by 0,2).
Note 4 to entry: The derived air concentration-hour (DAC-hour) is an integrated exposure and is the product of the
concentration of a radioactive substance in air (expressed as a fraction or multiple of DAC for each radionuclide)
and the time of exposure to that radionuclide, in hours.
[SOURCE: ISO 16639:2017, 3.12]
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3.5
detection alarm level
S0
value of time-integrated activity concentration activity concentration corresponding to an acceptable
false alarm rate
Note 1 to entry: When S0 increases false alarm rate decreases.
Note 2 to entry: Others values of alarm level higher than S0 can also be set up for operational reasons.
3.6
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 according to 3.3, 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 one
has to state according to which standard they are used.
[SOURCE: ISO 11929-1:2019, 3.13]
3.7
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 standard
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 interval containing the set of true
quantity values of a measurand with a stated probability, based on the information available.
[SOURCE: ISO 11929-1:2019, 3.16 modified – Note 3 to entry has been added]
3.8
measurand
quantity intended to be measured
[SOURCE: ISO 11929-1:2019, 3.3]
3.9
minimum detectable concentration
time-integrated activity concentration or activity concentration measurements and their associated
coverage intervals for a given probability (1−γ) corresponding to the first alarm level S0
3.10
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]
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3.11
potential missed exposure
PME
time-integrated activity concentration or maximum activity concentration, as applicable, that can
acceptably be missed
Note 1 to entry: the value of PME is defined according to ALARA/ALARP principles, and below legal limits.
Note 2 to entry: In order to be alerted when a measurement is likely to exceed the value of PME, an alarm level S1
is set up. The PME is then the upper limit of the coverage interval for a given probability (1−γ) of time-integrated
activity concentration or activity concentration measurements corresponding to S1.
[SOURCE: ISO 16639:2017, 3.18]
3.12
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
Note 1 to entry: The intrinsic response time is related to the measurement principle and its associated model of
evaluation of an ideal detector (without taking account of the counting time of the detector).
[SOURCE: IEC 60761-1:2002, 3.15]
4 Symbols
at() Activity going through the detection volume at a time t, in Bq
−3
c Activity concentration, in Bq·m
−3
c Actual activity concentration, in Bq·m
ac
−3
*
Decision threshold of the activity concentration, in Bq·m
c
−3
#
Detection limit of the activity concentration, in Bq·m
c

Lower limit of the coverage interval of the activity concentration for a given prob-
c
−3
ability (1−γ), in Bq·m

Upper limit of the coverage interval of the activity concentration for a given prob-
c
−3
ability (1−γ), in Bq·m
−3
ct Activity concentration measured at a time t, in Bq·m
()
−3
ct Actual activity concentration measured at a time t, in Bq·m
()
ac
−3
c Gross primary measurement of the activity concentration, in Bq·m
g
−3
c Minimum detectable activity concentration, in Bq·m
min

Lower limit of the coverage interval of the minimum detectable activity concentra-
c
min
−3
tion for a given probability (1−γ), in Bq·m

Upper limit of the coverage interval the minimum detectable activity concentration
c
min
−3
for a given probability (1−γ), in Bq·m
th
c Activity concentration of the i measurement of a series of gross measurements
0,i
−3
(with i = 1, …, n) which represent a background situation, in Bq·m
−3
Mean value of c , in Bq·m
c
0,i
0
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I Minimum amount of current registered by the measuring detector (with
min
Q
min
I = in A
min
t
C
I Minimum amount of current registered by the compensating detector (with
minc, d
Q
minc, d
I = ), in A
minc, d
t
Ccd
,
It
() Instantaneous gross current of the measuring detector at a time t, in A
g
Gross current during the counting time t of the measuring detector at a time t, in A
It,,tI
()
C
gC g
It() Instantaneous gross current of the compensating detector at a time t, in A
gc, d
Gross current during the counting time t of the compensating detector at a time t, in A
It,,tI
C,cd
()
gc,,dC cd gc, d
I Background current of the measuring detector, in A
0
I Background current of the compensating detector, in A
0,cd
K Detection alarm setup parameter corresponding to the chosen acceptable false
alarm rate level, dimensionless
k Quantile of a standard normal distribution, if kk= , dimensionless
11−−αβ
k Quantile of a standard normal distribution for a probability (1−α), dimensionless
1−α
k Quantile of a standard normal distribution for a probability (1−β), dimensionless
1−β
k γ
 
γ
Quantile of a standard normal distribution for a probability 1− , dimensionless
1−  
2
2  
N Number of atoms on the media filter, dimensionless
Gross count during the counting time t of the measuring detector at a time t, di-
nt,t
()
C
gC
mensionless
Q Minimum amount of electric charge that induces a pulse registered by the measuring
min
detector, in C
Q Minimum amount of electric charge that induces a pulse registered by the compen-
minc, d
sating detector, in C
3 −1
q Flow rate, in m ·s
−1
rt() Instantaneous gross count rate of the measuring detector at a time t, in s
g
−1
Gross count rate during the counting time t of the measuring detector at a time t, in s
rt,,tr
()
C
gC g
−1
rt Instantaneous gross count rate of the compensating detector at a time t, in s
()
gc, d
Gross count rate during the counting time t of the compensating detector at a
rt,,tr
() C,cd
gc,,dC cd gc, d
−1
time t, in s
−1
r Background count rate of the measuring detector, in s
0
−1
r Background count rate of the compensating detector, in s
0,cd
s Standard deviation of the activity concentration at a series of i measurements which
0
represent a background situation
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t Counting time of the measuring detector, in s
C
t
Counting time of the compensating detector, in s
Cc, d
t Duration of airborne release, in s
F
t Response time, in s
R
t Intrinsic response time, in s
RI
t Counting time of the measuring detector for background measurement, in s
0
t Counting time of the compensating detector for background measurement, in s
0,cd
t Half-life, in s
12/
3
V
Detection volume, in m
−3 −3 −1
w Calibration factor, in Bq·m ·s or Bq·m ·A
δ Correction factor related to sampling (sampling point representativity, radioactive
decay, …), dimensionless
−1 −1 −1
ε Detector efficiency, in Bq ·s or A·Bq
D
−1
λ Decay constant, in s
5 Measuring principle
A representative sample of ambient air to be monitored containing an activity concentration ct at a
()
ac
time t is continuously captured through a transport line then goes through a detection volume without
being retained. In parallel, a detector continuously measures the activity going through the detection
volume. Then a processing algorithm calculates the activity concentration ct() and the suited alarms
on the basis of the evolution of the activity going through the detection volume of air sampled and the
installation or not of an ambient compensating detector. The processing algorithm can also, if necessary,
take into account influence quantities which may perturb the measurement result (see Figure 1).
6 © ISO 2020 – All rights reserved

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Key
1 transport line
2 detector
3 sampling pump
4 media filter
5 processing algorithm
6 alarm processing unit
Figure 1 — Model of the sampling and alarming
6 Study of dynamic behaviour
This clause describes the evolution over time of the activity concentration ct during the sudden
()
appearance of an actual activity concentration c . The dynamic behaviour is quantified by the
ac
response time. The response time t is due to the intrinsic response time t related to the measurement
R RI
principle and its associated model of evaluation, the time delay provided by the counting time t of the
C
activity going through the detection volume, the renewal rate of the detection volume and also the
duration of the processing algorithm. This latter duration is not taken into account in this document but
it should be kept in mind.
It is considered in the following that the actual concentration to be measured c changes over time in
ac
steps of duration t :
F
ct()=≤ctwhen0 ac ac F
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ct()=≥0 whentt (2)
ac F
The differential equations describing the number of atoms N of the radionuclide considered in the
detection volume of the detector can be formulated as a function of the concentration c at the
ac
sampling point according to the following relationships:
qCδ
dNt() Nt()q
ac
=−λNt()− when0≤ F
dt λ V
NOTE 1 The monitor flow rate q is taken to be constant over the interval of interest.
and
dNt() Nt()q
=−λNt − whentt≥ (4)
()
F
dt V
Moreover, the evolution of the activity present in the detection volume is given by the relationship
rt()−r
g 0
at =λNt = (5)
() ()
ε
D
NOTE 2 The detector efficiency ε is supposed to be constant meaning that at any time the activity is
D
distributed uniformly throughout the detection volume.
Considering that N(0) = 0 at the beginning of the sampling, the solutions of the differential Formulae (3)
and (4) are:
q
 
 
−+λ t
εδqc
 
Dac
 V 
 
rt −=rNελ t = 1−ewhen0≤t< () ()
gD0 F
q
 
λ+
 
V
q q
   
 
−+λλt −+ ()tt−
εδqc
   
F F
Dac
 V   V 
 
rt −=rNελ t = 1−ee whentt≥ (7)
() ()
gD0 F
q
 
λ +
 
V
From the Formulae (5), (6) and (7), the model of evaluation of the activity concentration over time can
be expressed as
q
λ+
V
 
ct()= rt()−r (8)
g0
 
εδ q
D
When an ionization detector is used, instead of the count rate, the current may be the output. Then the
model of evaluation of the activity concentration becomes to
q
λ+
V
 
ct()= It()−I (9)
g0
 
εδ q
D
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with
q
 
 
−+λ t
 
 V 
 
ct()=−ct1 ewhen0≤ ac F
 
 
q q
   
 
−+λλt −+ ()tt−
   
FF
V V
   
 
ct()=−ct1 ee when ≥t (11)
ac F
 
 
The evolution of the ratio of the activity concentration and the actual one according to Formula (10) by
considering an infinite duration release ( t → ∞) is given in Table 1.
F
ct()
Table 1 — Evolution of the ratio of the measured activity concentration and the actual
ct
()
ac
one according to Formula (10)
Ratio Time
% s
0 0
06, 9
50
q
λ +
V
23,
~t
RI
90
q
λ+
V
3
95
q
λ +
V
46, 1
99
q
λ +
V
69
...