Evaluating the performance of continuous air monitors - Part 1: Air monitors based on accumulation sampling techniques (ISO/TR 22930-1:2020)

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 a 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.
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.
Among those factors, it is important to know the half-lives of the radionuclides involved, in order to select the appropriate detection system and its associated model of evaluation.
CAM using filter media accumulation sampling techniques are usually of two types:
a)   fixed filter;
b)   moving filter.
This document first describes the theory of operation of each CAM type i.e.:
—   the different models of evaluation considering short or long radionuclides half-lives values,
—   the dynamic behaviour and the determination of the response time.
In most case, CAM is used when radionuclides with important radiotoxicities are involved (small value of ALI). Those radionuclides have usually long half-life values.
Then the determination of the characteristic limits (decision threshold, detection limit, limits of the coverage interval) of a CAM is described by the use of long half-life models of evaluation.
Finally, a possible way to determine the minimum detectable activity concentration and the alarms setup is pointed out.
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 1: Luftmonitore basierend auf Sammeltechnik mittels Anreicherung (ISO/TR 22930-1:2020)

Évaluation des performances des dispositifs de surveillance de l'air en continu - Partie 1: Dispositifs de surveillance de l'air basés sur des techniques de prélèvement avec accumulation (ISO/TR 22930-1:2020)

Ugotavljanje zmogljivosti neprekinjeno delujočih zračnih nadzornikov - 1. del: Zračni nadzorniki na podlagi tehnik vzorčenja kopičenja zraka (ISO/TR 22930-1:2020)

General Information

Status
Published
Public Enquiry End Date
14-Jul-2021
Publication Date
19-Sep-2021
Technical Committee
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
15-Sep-2021
Due Date
20-Nov-2021
Completion Date
20-Sep-2021

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SLOVENSKI STANDARD
SIST-TP CEN ISO/TR 22930-1:2021
01-november-2021
Ugotavljanje zmogljivosti neprekinjeno delujočih zračnih nadzornikov - 1. del:
Zračni nadzorniki na podlagi tehnik vzorčenja kopičenja zraka (ISO/TR 22930-
1:2020)

Evaluating the performance of continuous air monitors - Part 1: Air monitors based on

accumulation sampling techniques (ISO/TR 22930-1:2020)

Ermittlung der Leistungsfähigkeit kontinuierlicher Luftmonitore - Teil 1: Luftmonitore

basierend auf Sammeltechnik mittels Anreicherung (ISO/TR 22930-1:2020)

Évaluation des performances des dispositifs de surveillance de l'air en continu - Partie 1:

Dispositifs de surveillance de l'air basés sur des techniques de prélèvement avec

accumulation (ISO/TR 22930-1:2020)
Ta slovenski standard je istoveten z: CEN ISO/TR 22930-1:2021
ICS:
13.280 Varstvo pred sevanjem Radiation protection
SIST-TP CEN ISO/TR 22930-1:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST-TP CEN ISO/TR 22930-1:2021
---------------------- Page: 2 ----------------------
SIST-TP CEN ISO/TR 22930-1:2021
CEN ISO/TR 22930-1
TECHNICAL REPORT
RAPPORT TECHNIQUE
August 2021
TECHNISCHER BERICHT
ICS 13.280
English Version
Evaluating the performance of continuous air monitors -
Part 1: Air monitors based on accumulation sampling
techniques (ISO/TR 22930-1:2020)

Évaluation des performances des dispositifs de Ermittlung der Leistungsfähigkeit kontinuierlicher

surveillance de l'air en continu - Partie 1: Dispositifs de Luftmonitore - Teil 1: Luftmonitore basierend auf

surveillance de l'air basés sur des techniques de Sammeltechnik mittels Anreicherung (ISO/TR 22930-

prélèvement avec accumulation (ISO/TR 22930- 1:2020)
1:2020)

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 22930-1:2021 E

worldwide for CEN national Members.
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SIST-TP CEN ISO/TR 22930-1:2021
CEN ISO/TR 22930-1:2021 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

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SIST-TP CEN ISO/TR 22930-1:2021
CEN ISO/TR 22930-1:2021 (E)
European foreword

The text of ISO/TR 22930-1:2020 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 22930-1:2021 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 22930-1:2020 has been approved by CEN as CEN ISO/TR 22930-1:2021 without any

modification.
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SIST-TP CEN ISO/TR 22930-1:2021
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SIST-TP CEN ISO/TR 22930-1:2021
TECHNICAL ISO/TR
REPORT 22930-1
First edition
2020-05
Evaluating the performance of
continuous air monitors —
Part 1:
Air monitors based on accumulation
sampling techniques
Évaluation de la performance des dispositifs de surveillance de l'air
en continu —
Partie 1: Moniteurs d'air basés sur des techniques d'échantillonnage
par accumulation
Reference number
ISO/TR 22930-1:2020(E)
ISO 2020
---------------------- Page: 7 ----------------------
SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(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
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Published in Switzerland
ii © ISO 2020 – All rights reserved
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SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols .......................................................................................................................................................................................................................... 4

5 Measuring principle .......................................................................................................................................................................................... 6

6 Fixed-media filter monitor ........................................................................................................................................................................ 7

6.1 Preliminary note .................................................................................................................................................................................... 7

6.2 Study of the dynamic behaviour .............................................................................................................................................. 7

6.2.1 General...................................................................................................................................................................................... 7

6.2.2 Short half-life model of evaluation of the activity concentration .......................................... 8

6.2.3 Long half-life radionuclide activity concentration model of evaluation .......................11

6.2.4 Intermediate half-life radionuclide activity concentration model of evaluation ..14

6.2.5 Comparison of the three fixed filter models of evaluation .......................................................15

7 Moving filter monitor ...................................................................................................................................................................................17

7.1 Preliminary note .................................................................................................................................................................................17

7.2 Study of the dynamic behaviour ...........................................................................................................................................17

7.3 Activity concentration model of evaluation ................................................................................................................20

8 Evaluation of the characteristic limits ........................................................................................................................................23

8.1 General ........................................................................................................................................................................................................23

8.2 Fixed media filter model of evaluation ............................................................................................................................24

8.2.1 General...................................................................................................................................................................................24

8.2.2 Definition of the model ............................................................................................................................................24

8.2.3 Standard uncertainty ................................................................................................................................................24

8.2.4 Decision threshold.......................................................................................................................................................25

8.2.5 Detection limit ................................................................................................................................................................26

8.2.6 Limits of the coverage interval .........................................................................................................................26

8.3 Moving filter model of evaluation ........................................................................................................................................28

8.3.1 Definition of the measurand ...............................................................................................................................28

8.3.2 Standard uncertainty ................................................................................................................................................28

8.3.3 Decision threshold.......................................................................................................................................................29

8.3.4 Detection limit ................................................................................................................................................................29

8.3.5 Limits of the coverage interval .........................................................................................................................29

9 Alarms setup, minimum detectable activity concentration and PME ........................................................29

Annex A (informative) Numerical example of gross beta emitting activity concentration

measurement on fixed filter ..................................................................................................................................................................32

Annex B (informative) Numerical example of gross alpha emitting activity concentration

measurement on moving filter ...........................................................................................................................................................37

Annex C (informative) Numerical example of iodine 131 activity concentration gamma

spectrometry measurement on fixed charcoal cartridge .......................................................................................41

Annex D (informative) Determination of the detectable activity concentration and its

associated response time by the use a linear regression and statistical test method ..............44

Bibliography .............................................................................................................................................................................................................................52

© ISO 2020 – All rights reserved iii
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SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(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.

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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SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
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 accumulation sampling techniques.

© ISO 2020 – All rights reserved v
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SIST-TP CEN ISO/TR 22930-1:2021
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SIST-TP CEN ISO/TR 22930-1:2021
TECHNICAL REPORT ISO/TR 22930-1:2020(E)
Evaluating the performance of continuous air monitors —
Part 1:
Air monitors based on accumulation sampling techniques
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 a 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.

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.

Among those factors, it is important to know the half-lives of the radionuclides involved, in order to

select the appropriate detection system and its associated model of evaluation.

CAM using filter media accumulation sampling techniques are usually of two types:

a) fixed filter;
b) moving filter.
This document first describes the theory of operation of each CAM type i.e.:

— the different models of evaluation considering short or long radionuclides half-lives values,

— the dynamic behaviour and the determination of the response time.

In most case, CAM is used when radionuclides with important radiotoxicities are involved (small value

of ALI). Those radionuclides have usually long half-life values.

Then the determination of the characteristic limits (decision threshold, detection limit, limits of the

coverage interval) of a CAM is described by the use of long half-life models of evaluation.

Finally, a possible way to determine the minimum detectable activity concentration and the alarms

setup is pointed out.

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.
© ISO 2020 – All rights reserved 1
---------------------- Page: 13 ----------------------
SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
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 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 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
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 http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .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]
2 © ISO 2020 – All rights reserved
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SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
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

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]
3.5
detection alarm level

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]
© ISO 2020 – All rights reserved 3
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SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
3.8
measurand
quantity intended to be measured
[SOURCE: ISO 11929-1:2019, 3.3]
3.9
minimum detectable activity concentration

time-integrated activity concentration or activity concentration measurements and their associated

coverage intervals for a given probability (1−γ) corresponding to the detection 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]
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
[SOURCE: IEC 60761-1:2002, 3.15]

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).

3.13
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 speed and L the detector aperture or length of the deposition area

considering a constant width w then the time transit t = .
4 Symbols
a(t) Activity deposited on the media filter at a time t, in Bq

b Slope of the linear regression line obtained from a set of n successive points (i, y ), y being

i i
th −2
the i measurement of the counting pulse (i = 1, ..., n), in s

C Correlation coefficient of the line resulting from the linear regression, dimensionless

4 © ISO 2020 – All rights reserved
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SIST-TP CEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
C Coefficient of Student, dimensionless
c Activity concentration, in Bq·m
c* Decision threshold of the activity concentration, in Bq·m
# −3
c Detection limit of the activity concentration, in Bq·m

Lower limit of the coverage interval of the activity concentration for a given probability (1−γ),

in Bq·m

Upper limit of the coverage interval of the activity concentration for a given probability (1−γ),

in Bq·m
c(t) Activity concentration measured at a time t, in Bq·m
c(t ), c Activity concentration measured at a time t , in Bq·m
j j j
c (t) Actual activity concentration measured at a time t, in Bq·m
c Detectable activity concentration, in Bq·m
det
c Activity concentration of a gross measurement, in Bq·m
c Minimum detectable activity concentration, in Bq·m

Lower limit of the coverage interval of the minimum detectable activity concentration for a

min
given probability (1−γ), in Bq·m

Upper limit of the coverage interval the minimum detectable activity concentration for a

min
given probability (1−γ), in Bq·m

Activity concentration of the i measurement of a series of gross measurements (with

0,i
i = 1, …, n) which represent a background situation, in Bq·m
Mean value of c in Bq·m
0,i
D Diameter the circular window deposition area viewed by the detector, in m

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

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
 
Quantile of a standard normal distribution for a probability 1− , dimensionless
 
 2
L Length of the rectangular window deposition area vi
...

SLOVENSKI STANDARD
kSIST-TP FprCEN ISO/TR 22930-1:2021
01-julij-2021
Ugotavljanje zmogljivosti neprekinjeno delujočih zračnih nadzornikov - 1. del:
Zračni nadzorniki na podlagi tehnik vzorčenja kopičenja zraka (ISO/TR 22930-
1:2020)

Evaluating the performance of continuous air monitors - Part 1: Air monitors based on

accumulation sampling techniques (ISO/TR 22930-1:2020)

Ermittlung der Leistungsfähigkeit kontinuierlicher Luftmonitore - Teil 1: Luftmonitore

basierend auf Sammeltechnik mittels Anreicherung (ISO/TR 22930-1:2020)

Évaluation des performances des dispositifs de surveillance de l'air en continu - Partie 1:

Dispositifs de surveillance de l'air basés sur des techniques de prélèvement avec

accumulation (ISO/TR 22930-1:2020)
Ta slovenski standard je istoveten z: FprCEN ISO/TR 22930-1
ICS:
13.280 Varstvo pred sevanjem Radiation protection
kSIST-TP FprCEN ISO/TR 22930-1:2021 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
kSIST-TP FprCEN ISO/TR 22930-1:2021
---------------------- Page: 2 ----------------------
kSIST-TP FprCEN ISO/TR 22930-1:2021
TECHNICAL ISO/TR
REPORT 22930-1
First edition
2020-05
Evaluating the performance of
continuous air monitors —
Part 1:
Air monitors based on accumulation
sampling techniques
Évaluation de la performance des dispositifs de surveillance de l'air
en continu —
Partie 1: Moniteurs d'air basés sur des techniques d'échantillonnage
par accumulation
Reference number
ISO/TR 22930-1:2020(E)
ISO 2020
---------------------- Page: 3 ----------------------
kSIST-TP FprCEN ISO/TR 22930-1:2021
ISO/TR 22930-1:2020(E)
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ISO/TR 22930-1:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols .......................................................................................................................................................................................................................... 4

5 Measuring principle .......................................................................................................................................................................................... 6

6 Fixed-media filter monitor ........................................................................................................................................................................ 7

6.1 Preliminary note .................................................................................................................................................................................... 7

6.2 Study of the dynamic behaviour .............................................................................................................................................. 7

6.2.1 General...................................................................................................................................................................................... 7

6.2.2 Short half-life model of evaluation of the activity concentration .......................................... 8

6.2.3 Long half-life radionuclide activity concentration model of evaluation .......................11

6.2.4 Intermediate half-life radionuclide activity concentration model of evaluation ..14

6.2.5 Comparison of the three fixed filter models of evaluation .......................................................15

7 Moving filter monitor ...................................................................................................................................................................................17

7.1 Preliminary note .................................................................................................................................................................................17

7.2 Study of the dynamic behaviour ...........................................................................................................................................17

7.3 Activity concentration model of evaluation ................................................................................................................20

8 Evaluation of the characteristic limits ........................................................................................................................................23

8.1 General ........................................................................................................................................................................................................23

8.2 Fixed media filter model of evaluation ............................................................................................................................24

8.2.1 General...................................................................................................................................................................................24

8.2.2 Definition of the model ............................................................................................................................................24

8.2.3 Standard uncertainty ................................................................................................................................................24

8.2.4 Decision threshold.......................................................................................................................................................25

8.2.5 Detection limit ................................................................................................................................................................26

8.2.6 Limits of the coverage interval .........................................................................................................................26

8.3 Moving filter model of evaluation ........................................................................................................................................28

8.3.1 Definition of the measurand ...............................................................................................................................28

8.3.2 Standard uncertainty ................................................................................................................................................28

8.3.3 Decision threshold.......................................................................................................................................................29

8.3.4 Detection limit ................................................................................................................................................................29

8.3.5 Limits of the coverage interval .........................................................................................................................29

9 Alarms setup, minimum detectable activity concentration and PME ........................................................29

Annex A (informative) Numerical example of gross beta emitting activity concentration

measurement on fixed filter ..................................................................................................................................................................32

Annex B (informative) Numerical example of gross alpha emitting activity concentration

measurement on moving filter ...........................................................................................................................................................37

Annex C (informative) Numerical example of iodine 131 activity concentration gamma

spectrometry measurement on fixed charcoal cartridge .......................................................................................41

Annex D (informative) Determination of the detectable activity concentration and its

associated response time by the use a linear regression and statistical test method ..............44

Bibliography .............................................................................................................................................................................................................................52

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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 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.
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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 accumulation sampling techniques.

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kSIST-TP FprCEN ISO/TR 22930-1:2021
TECHNICAL REPORT ISO/TR 22930-1:2020(E)
Evaluating the performance of continuous air monitors —
Part 1:
Air monitors based on accumulation sampling techniques
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 a 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.

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.

Among those factors, it is important to know the half-lives of the radionuclides involved, in order to

select the appropriate detection system and its associated model of evaluation.

CAM using filter media accumulation sampling techniques are usually of two types:

a) fixed filter;
b) moving filter.
This document first describes the theory of operation of each CAM type i.e.:

— the different models of evaluation considering short or long radionuclides half-lives values,

— the dynamic behaviour and the determination of the response time.

In most case, CAM is used when radionuclides with important radiotoxicities are involved (small value

of ALI). Those radionuclides have usually long half-life values.

Then the determination of the characteristic limits (decision threshold, detection limit, limits of the

coverage interval) of a CAM is described by the use of long half-life models of evaluation.

Finally, a possible way to determine the minimum detectable activity concentration and the alarms

setup is pointed out.

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.
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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 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 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
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 http:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .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]
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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

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]
3.5
detection alarm level

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]
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3.8
measurand
quantity intended to be measured
[SOURCE: ISO 11929-1:2019, 3.3]
3.9
minimum detectable activity concentration

time-integrated activity concentration or activity concentration measurements and their associated

coverage intervals for a given probability (1−γ) corresponding to the detection 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]
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
[SOURCE: IEC 60761-1:2002, 3.15]

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).

3.13
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 speed and L the detector aperture or length of the deposition area

considering a constant width w then the time transit t = .
4 Symbols
a(t) Activity deposited on the media filter at a time t, in Bq

b Slope of the linear regression line obtained from a set of n successive points (i, y ), y being

i i
th −2
the i measurement of the counting pulse (i = 1, ..., n), in s

C Correlation coefficient of the line resulting from the linear regression, dimensionless

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C Coefficient of Student, dimensionless
c Activity concentration, in Bq·m
c* Decision threshold of the activity concentration, in Bq·m
# −3
c Detection limit of the activity concentration, in Bq·m

Lower limit of the coverage interval of the activity concentration for a given probability (1−γ),

in Bq·m

Upper limit of the coverage interval of the activity concentration for a given probability (1−γ),

in Bq·m
c(t) Activity concentration measured at a time t, in Bq·m
c(t ), c Activity concentration measured at a time t , in Bq·m
j j j
c (t) Actual activity concentration measured at a time t, in Bq·m
c Detectable activity concentration, in Bq·m
det
c Activity concentration of a gross measurement, in Bq·m
c Minimum detectable activity concentration, in Bq·m

Lower limit of the coverage interval of the minimum detectable activity concentration for a

min
given probability (1−γ), in Bq·m

Upper limit of the coverage interval the minimum detectable activity concentration for a

min
given probability (1−γ), in Bq·m

Activity concentration of the i measurement of a series of gross measurements (with

0,i
i = 1, …, n) which represent a background situation, in Bq·m
Mean value of c in Bq·m
0,i
D Diameter the circular window deposition area viewed by the detector, in m

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

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
 
Quantile of a standard normal distribution for a probability 1− , dimensionless
 
 2

L Length of the rectangular window deposition area viewed by the detector, considering a

constant width w , in m
N Number of atoms on the media filter, dimensionless

n (t, t ) Gross count during the counting time t of the media filter at a time t, dimensionless

g c c

p Student test acceptance parameter of the linear regression with a risk less than one out of

ten thousand to be aberrant, dimensionless
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3 −1
q Flow rate, in m ·s
r (t) Instantaneous gross count rate of the media filter at a time t, in s

r (t, t ) Gross count rate during the counting time t of the media filter at a time t, in s

g c c

r (t, t ), r Gross count rate during the counting time t of the media filter at a time t , in s

g c j c j
r Background count rate, in s

s Standard deviation of the activity concentration at a series of i measurements which repre-

sent a background situation

t, t Time, in year (YYYY)-month (MM)-day (DD) T hour (hh):minute (mm): second (ss)

t Counting time, in s
t Duration of airborne release, in s
t Time interval, in s
t Response time, in s
t Intrinsic response time, in s
t Transit time, in s
t Counting time for background measurement in s
t Half-life, in s
1/2
v Moving filter speed, in m·s
w Calibration factor, in Bq·m ·s
w Width of the rectangular deposition area viewed by the detector, in m
y Counting pulse measurement at the initiation of a linear regression process

Correction factor related to sampling (sampling point representativity, aerosol deposition in

the transport line, …), dimensionless
−1 −1
Detector efficiency, in Bq ·s
λ Decay constant, in s
5 Measuring principle

A representative sample of ambient air to be monitored containing an actual activity c (t) at a time t

is continuously captured through a transport line which deposits the radioactive substance on a media

filter. In parallel, a detector continuously measures the activity deposited on the media filter which

can be fixed or moving. Then a processing algorithm calculates the activity concentration c(t) and the

appropriate alarms on the basis of the evolution of the deposited activity and the volume of air sampled.

The processing algorithm can also, if necessary, take into account parameters which may perturb the

measurement result (see Figure 1).
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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 Fixed-media filter monitor
6.1 Preliminary note

In Clause 6, fixed-media filter means any type of fixed trapping method of radioactive contaminant (e.g.

“filter” used for aerosols monitoring, “charcoal cartridge” used for iodine, etc.).

6.2 Study of the dynamic behaviour
6.2.1 Genera
...

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