IEC 61577-4:2009

IEC 61577-4 ®
Edition 1.0 2009-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Radiation protection instrumentation – Radon and radon decay product
measuring instruments –
Part 4: Equipment for the production of reference atmospheres containing radon
isotopes and their decay products (STAR)

Instrumentation pour la radioprotection – Instruments de mesure du radon et
des descendants du radon –
Partie 4: Dispositif pour la réalisation d’atmosphères de référence contenant des
isotopes du radon et leurs descendants (STAR)

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IEC 61577-4 ®
Edition 1.0 2009-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Radiation protection instrumentation – Radon and radon decay product
measuring instruments –
Part 4: Equipment for the production of reference atmospheres containing
radon isotopes and their decay products (STAR)

Instrumentation pour la radioprotection – Instruments de mesure du radon et
des descendants du radon –
Partie 4: Dispositif pour la réalisation d’atmosphères de référence contenant
des isotopes du radon et leurs descendants (STAR)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
U
CODE PRIX
ICS 13.280 ISBN 978-2-88910-545-8
– 2 – 61577-4 © IEC:2009
CONTENTS
FOREWORD.4
INTRODUCTION.6
1 Scope and object.7
2 Normative references .7
3 Terms, definitions and units.8
3.1 General terms and definitions.8
3.2 Specific terms and definitions.9
3.3 Units and conversion factors .12
4 General description of a System for Test Atmospheres with Radon (STAR).13
4.1 General .13
4.2 Mode of operation of a STAR .14
4.2.1 Static mode of operation.14
4.2.2 Dynamic mode of operation .14
5 Characteristics of a STAR .15
5.1 General .15
5.2 STAR for radon .16
5.2.1 General .16
5.2.2 Technical characteristics of STAR containers .16
5.2.3 Radon sources .16
222 220
5.2.4 Rn and Rn analysis and control.17
5.2.5 Analysis and control of climatic parameters .18
5.3 STAR for radon and RnDP .18
5.3.1 General .18
5.3.2 Technical characteristics of STAR containers .18
5.3.3 RnDP sources .18
5.3.4 RnDP analysis and control.19
5.3.5 Sampling flow rate of equipment under test .19
5.3.6 Analysis and control of climatic parameters .20
6 Requirements for the reference atmosphere provided by STAR .20
6.1 General .20
6.2 Reference conditions.20
6.3 Influence quantities .21
6.3.1 General .21
6.3.2 Temperature.22
6.3.3 Relative humidity.22
6.3.4 Atmospheric pressure.22
6.3.5 Ambient gamma field .23
6.3.6 Working range for exposure to RnDP.23
6.3.7 Working range for aerosols.23
6.3.8 Exposure time for the instrument under test.23
7 Calibration and traceability of measurement methods and instruments used in a
STAR .23
7.1 Traceability chains .23
7.2 Quality assurance .24
Annex A (informative) Characteristics of atmospheres that can be simulated in a
STAR.25

61577-4 © IEC:2009 – 3 –
Bibliography.27

Figure 1 – Components of a STAR: general case.13
Figure 2 – Minimum requirements for a STAR.14
Figure 3 – Dynamic mode of operation of a STAR.15

Table 1 – Reference and standard test conditions.21
Table 2 – Tests with variation of the influence quantities .21
Table A.1 – Atmosphere characteristic ranges (typical values).26

– 4 – 61577-4 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RADIATION PROTECTION INSTRUMENTATION –
RADON AND RADON DECAY PRODUCT
MEASURING INSTRUMENTS –
Part 4: Equipment for the production of reference atmospheres
containing radon isotopes and their decay products (STAR)

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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6) All users should ensure that they have the latest edition of this publication.
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Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61577-4 has been prepared by subcommittee 45B: Radiation
protection instrumentation, of IEC technical committee 45: Nuclear instrumentation.
The text of this standard is based on the following documents:
FDIS Report on voting
45B/598/FDIS 45B/606/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

61577-4 © IEC:2009 – 5 –
A list of all parts of the IEC 61577 series, under the general title Radiation protection
instrumentation – Radon and radon decay product measuring instruments, can be found on
the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – 61577-4 © IEC:2009
INTRODUCTION
226 223 224
Radon is a radioactive gas produced by the decay of Ra, Ra and Ra, respectively
238 235 232
decay products of U, U and Th which are present in the earth's crust. By decay,
222 219 220
radon isotopes (i.e. Rn, Rn, Rn) produce three decay chains, each ending in a stable
lead isotope.
NOTE In normal conditions, due to the very short half-life of Rn, its activity and the activity of its RnDP are
considered negligible compared to the activity of the two other series. Its health effects are therefore not important.
Thus in this standard Rn and its decay products are not considered.
Radon isotopes and their corresponding short-lived Radon Decay Products (RnDP) (i.e.
218 214 214 214 222 216 212 212 212 208 220
Po, Pb, Bi, Po for Rn, and Po, Pb, Bi, Po, Tl for Rn) are of
considerable importance, as they constitute the major part of the radiological exposure to
natural radioactivity for the general public and workers. In some workplaces, for instance in
underground mines, spas and waterworks, the workers are exposed to very significant levels
of RnDP. These radionuclides are present in variable quantities in the air, in a gaseous form
for the radon isotopes, and as very fine particles for the decay products. It is worthwhile for
health physicists to be able to measure with a great accuracy the level of this kind of natural
radioactivity in the atmosphere. Because the very particular behaviour of these radioactive
elements in the atmosphere and in the corresponding measuring instruments, it is necessary
to formalize the way such instruments could be tested.
Remark:
In order to facilitate its use, the IEC 61577 series is divided into the following different parts:
IEC 61577-1: This emphasizes the terminology and units of the specific field of radon and
radon decay products (RnDP) measurement techniques and presents briefly the concept of
System for Test Atmospheres with Radon (STAR) used for test and calibration of radon and
RnDP measuring devices.
222 220
IEC 61577-2: This part is dedicated to the tests of Rn and Rn measuring instruments.
IEC 61577-3: This part is dedicated to the tests of RnDP and RnDP measuring
222 220
instruments.
IEC 61577-4: Details how a STAR is constructed and how it can be used for testing.

———————
RnDP is the acronym of Radon Decay Products and it is equivalent to Radon Progeny (see [1] in the
Bibliography).
61577-4 © IEC:2009 – 7 –
RADIATION PROTECTION INSTRUMENTATION –
RADON AND RADON DECAY PRODUCT
MEASURING INSTRUMENTS –
Part 4: Equipment for the production of reference atmospheres
containing radon isotopes and their decay products (STAR)

1 Scope and object
The IEC 61577 series covers the general features concerning test and calibration of radon
and radon decay products measuring instruments. It is also intended to help define type tests,
which have to be conducted in order to qualify these instruments. These type tests are
described in IEC 61577-2 and IEC 61577-3. This standard addresses only the instruments
and associated methods for measuring isotopes 220 and 222 of radon and their subsequent
short-lived decay products in gases.
IEC 61577-4 concerns the System for Test Atmospheres with Radon (STAR) needed for
testing, in a reference atmosphere, the instruments measuring radon and RnDP. The clauses
that follow do neither claim to solve all the problems involved in the production of equipment
for setting up reference atmospheres for radon and its decay products, nor to describe all the
methods for doing so. They do however set out to be a guide enabling those faced with such
problems to choose the best methods for adoption in full knowledge of the facts.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 60050-111:1996, International Electrotechnical Vocabulary (IEV) – Chapter 111: Physics
and chemistry
IEC 60050-393:2003, International Electrotechnical Vocabulary (IEV) – Part 393: Nuclear
instrumentation – Physical phenomena and basic concepts
IEC 60050-394:2007, International Electrotechnical Vocabulary (IEV) – Part 394: Nuclear
instrumentation – Instruments, systems, equipment and detectors
IEC 61577 (all parts), Electrical safety in low voltage distribution systems up to 1 000 V a.c.
and 1 500 V d.c. – Equipment for testing, measuring or monitoring of protective measures
ISO/IEC Guide 99:2007, International vocabulary of metrology – Basic and general concepts
and associated terms (VIM)
ISO/IEC 17025, General requirements for the competence of testing and calibration
laboratories
ICRP 32: Annals of the ICRP, Publication N° 32, Limits for inhalation of Radon Daughters by
Workers, Vol. 6, N°1, 1981, Pergamon Press
ICRP 38: Annals of the ICRP, Publication N° 38, Radionuclides transformations, Energy and
Intensity of Emissions, Vol. 11 - 13, 1983, Pergamon Press

– 8 – 61577-4 © IEC:2009
ICRP 65: Annals of the ICRP, Publication N° 65, ICRP Publication 65: Protection Against
Radon-222 at Home and at Work, Vol. 23/2, 1994, Pergamon Press
3 Terms, definitions and units
For the purposes of this document, the following terms, definitions and units apply.
Throughout the whole standard, the term RADON is used to denote all the radon isotopes,
which are covered by this standard. When a particular isotope is to be referred to, it will be
220 222
indicated by its chemical symbol preceded by its mass number (e.g. Rn, Rn). For
historical reasons, Rn is also called thoron.
The term RADON DECAY PRODUCTS or its abbreviation (RnDP) denotes the whole set of
short-lived decay products, which are concerned by this standard. A particular isotope is
indicated by its chemical symbol preceded by its mass number. The subscripts , added
222 220
to the symbol RnDP refer to the whole set of short-lived decay products of the corresponding
218 214 214 214 216 212 212 212 208
radon isotope ( Po, Pb, Bi, Po), ( Po, Pb, Bi, Po, Tl).
All the nuclear data used in this standard refers to ICRP 38, as this standard applies mainly to
instruments used for radiation protection purposes.
3.1 General terms and definitions
3.1.1
activity
A
quotient, for an amount of radionuclide in a particular energy state at a given time, of dN by
dt, where dN is the expectation value of the number of spontaneous nuclear transitions from
this energy state in the time interval of duration dt:

dN
A =
dt
NOTE This quantity is expressed in becquerels (Bq).
[IEV 393-14-12]
3.1.2
volumic activity
activity concentration
C
A
quotient of the activity by the total volume of the sample
NOTE 1 For a gas, it is necessary to indicate the temperature and pressure conditions for which the volumic
activity, expressed in becquerel per cubic metre, is measured, for example standard temperature and pressure
(STP).
–3
NOTE 2 This quantity is expressed in becquerels per cubic metre (Bq·m ).
[IEV 393-14-16]
3.1.3
primary standard
standard that is designed or widely acknowledged as having the highest metrological qualities
and whose value is accepted without reference to other standards of the same quantity
NOTE The concept of primary standard is equally valid for base quantities and derived quantities.
[VIM, 5.4, modified]
61577-4 © IEC:2009 – 9 –
3.1.4
secondary standard
standard whose value is assigned by comparison with a primary standard of the same
quantity
[VIM, 5.5, modified]
3.1.5
reference standard
standard generally having the highest metrological quality available at a given location or in a
given organization, from which measurements made there are derived
[VIM, 5.6, modified]
3.1.6
mass flow rate
–1
(kg·s )
mass of a gas flowing in a conduit during a unit time
3.1.7
volume flow rate
3 –1
(m ·s )
volume of gas flowing in a conduit during a unit time
3.1.8
aerosol
set of solid or liquid particles in suspension in a gaseous medium
NOTE The range of particle diameter is generally from a few nanometres up to 10 μm.
[IEV 393-11-37]
3.1.9
homogeneous
qualifies a physical medium in which the relevant properties are independent of the position in
the medium
[IEV 111-13-08]
3.1.10
conventionally true value of a quantity
v
c
value attributed to a particular quantity and accepted, sometimes by convention, as having an
uncertainty appropriate for a given purpose
NOTE "Conventionally true value of a quantity" is sometimes called assigned value, best estimate of the value,
conventional value or reference value.
[IEV 394-40-10]
3.2 Specific terms and definitions
3.2.1
Potential Alpha Energy
PAE or ε
p
total alpha energy emitted during the decay of RnDP atoms along the decay chain through to
210 208 222 220
Pb or Pb respectively for the decay chains of the Rn and Rn
–13
ε =[(6,003 + 7,687)×N +7,687×(N +N )+7,687 × N ]×1,602×10 (J)
p
222 218Po 214Pb 214Bi 214Po
–13
ε =[(6,779 + 7,804)×N +7,804×(N +N )+8,785 × N ]×1,602×10 (J)
p
220 216Po 212Pb 212Bi 212Po
– 10 – 61577-4 © IEC:2009
where N is the number of atoms
NOTE 1 The 7,804 MeV alpha energy corresponds to a virtual alpha emission due to the branching ratio of Bi.
NOTE 2 Annual Limits of Intake (ALI) can be expressed in the term of PAE and PAE . For this reason,
222 220
PAE and PAE are used as health risk indicator.
222 220
[ICRP 32]
3.2.2
Potential Alpha Energy Concentration
PAEC or c
p
concentration of any mixture of short-lived radon decay products in air in terms of the alpha
210 208
energy released during decay through Pb or Pb
–3
NOTE This quantity is expressed in the SI unit J·m .
[ICRP 32]
3.2.3
Potential alpha energy exposure
P (T)
p
time integral of the potential alpha energy concentration in air, c to which an individual is
,
p
exposed over a given time period T, e.g. one year
P (T ) = c (t).dt
p p
∫
T
–3
NOTE This quantity is expressed in the SI unit J·m ·h.
[ICRP 65]
3.2.4
equilibrium equivalent concentration
c
eq
activity concentration of radon, in radioactive equilibrium with its short-lived decay products
that has the same potential alpha energy concentration as the non-equilibrium mixture to
which the c refers
eq
–3
NOTE This quantity is expressed in the SI unit Bq·m .
[ICRP 32]
3.2.5
equilibrium factor
F
ratio of equilibrium equivalent concentration to the radon gas concentration
c
eq
F =
C
Rn
[ICRP 65]
3.2.6
emanating power (or emanation coefficient)
ratio between the number of radon atoms (n) transferred to the pore space of the material and
the number (N) of radon atoms present in the material itself, including the pores’ space

61577-4 © IEC:2009 – 11 –
n
τ =
N
3.2.7
emanation rate
value of the activity of radon atoms leaving a material per unit mass per unit time
–1 –1
NOTE This is expressed in Bq·kg ·s .
3.2.8
deconvolution
mathematical treatment of a set of data resulting from a measurement (i.e. counted events)
allowing, through the use of a particular set of equations, to get the value of the original
quantity to be measured
3.2.9
Activity Median Aerodynamic Diameter
AMAD [2]
–3
median of the activity distribution of diameters of the unit density (kg·m ) spheres that have
the same settling velocity as the aerosol particle concerned
3.2.10
Activity Median Thermodynamic Diameter
AMTD
–3
median of the activity distribution of diameters of the unit density (kg·m ) spheres that have
the same thermodynamic properties as the aerosol particle concerned
3.2.11
unattached fraction of PAEC
fraction of the potential alpha energy concentration of short-lived RnDP that is not attached to
the ambient aerosol
NOTE The particle size concerned is in the order of magnitude of nm.
[ICRP 65]
3.2.12
attached fraction
fraction of the potential alpha energy concentration of short-lived RnDP that is attached to the
ambient aerosol.
NOTE The sizes of the carrier aerosol, to which most of RnDP are attached, are generally in the 0,1 μm to 0,3 μm
range.
3.2.13
grab sampling
collection of a sample (e.g. of air containing radon or aerosol particles) during a period
considered short compared with the fluctuations of the quantity under study (e.g. volumic
activity of the air)
3.2.14
continuous method
method which ensures a continuous recording of the parameter to be measured, over a
defined period of time, and with a time resolution adapted to the phenomenon to be studied
———————
Numbers in brackets refer to the bibliography.

– 12 – 61577-4 © IEC:2009
3.2.15
integrating method
method that relies on the measurement of the integral over a defined sampling and
measurement time of the quantity under study
3.2.16
passive sampling
sampling that applies to instruments using no active device like pumps for sampling the
atmosphere
NOTE In this case, the sampling is in most instruments mainly made by diffusion.
3.2.17
active sampling
sampling applies to instruments using active devices like pumps for sampling the atmosphere
3.2.18
reference source
radioactive secondary standard source for use in the calibration of the measuring instrument
[IEV 394-40-19]
3.2.19
reference atmosphere
radioactive atmosphere in which the influencing parameters (aerosols, radioactivity, climatic
conditions, etc.) are sufficiently well-known or controlled to allow its use in a testing
procedure for radon or RnDP measuring instruments. The parameter values concerned are
traceable to recognized standards
3.2.20
System for Test Atmospheres with Radon
STAR
system that designates the equipment needed for the creation and the use of a reference
atmosphere
3.2.21
High Efficiency Particulate Air filters (HEPA filters)
filters used for the aerosol collection, with a minimum efficiency of 99,97 % for particle size of
0,3 μm
3.3 Units and conversion factors
This standard uses the International System of Units (SI).
NOTE The following "non-standard" units are still sometimes used:
Curie (Ci), a unit of activity: 1 Ci = 3,7 × 10 Bq
– –1 –4 –3
MeV·l , a unit of potential alpha energy concentration 1 MeV·l = 1,6 × 10 μJ·m
The following conversion factors are given for information:
–3
Working Level (WL), a quantity of volume potential alpha energy 1 WL = 20,8 μJ·m
–3
Working Level Month (WLM), a quantity of exposure to potential alpha energy 1 WLM = 3,6 mJ·h·m
222 –3
- A Rn activity concentration of 1 Bq·m  in equilibrium with its RnDP , is equivalent to a Potential Alpha
–9 –3
Energy,Concentration, PAEC of 5,62 × 10 J⋅m .
220 –3
- A Rn activity concentration of 1 Bq.m in equilibrium with its RnDP , is equivalent to a Potential Alpha
–9 –3
Energy,Concentration, PAEC of 75,8 × 10 J⋅m .
61577-4 © IEC:2009 – 13 –
4 General description of a System for Test Atmospheres with Radon (STAR)
4.1 General
The need for a reference atmosphere arises from the necessity for a complete and
standardized testing, under controlled conditions, of the measuring instruments concerned.
The various examples illustrated indicate a need for a test facility related directly to the
four inseparable parts:
elements to be measured. Such a facility will consist of
– the equipment for producing the atmosphere;
– the equipment for containing the atmosphere;
– the reference atmosphere thus created;
– the equipment and methods for monitoring this atmosphere.
Equipment used to characterise the atmosphere shall be traceable to a primary standard.
In order to simplify the text of this standard, such a system is referred to as a "STAR" (an
acronym for System for Test Atmospheres with Radon).
The Figure 1 shows the general components of a complete STAR.
It is also called “Radon Chamber”; however, this term does not imply the same integrated
concept.
Traceability to a reference standard
Reference radon
Radon source
measuring
instruments
Reference RnDP
Climatic conditioning
measuring
system
instruments
Reference atmosphere
Reference aerosol
Aerosol generation
measuring
system
instruments
Instrument
under test
Reference climatic
parameter Reference flow rates
measuring measuring instrument
Container
instruments
STAR
Not always necessary
For RnDP tests
IEC  270/09
Figure 1 – Components of a STAR: general case
In some cases, a STAR may comprise only parts of the complete scheme. As an example,
STAR used only for testing radon instruments, which are not affected by aerosols and RnDP
in the atmosphere, do not need special equipment for controlling quantities relating to these
effects. Figure 2 illustrates this minimum configuration.

– 14 – 61577-4 © IEC:2009
Traceability to a reference standard
Reference radon Reference atmosphere
measuring
instruments
Radon source
Instrument
under test
Reference climatic
parameter
measuring
instruments
Container
STAR
IEC  271/09
Figure 2 – Minimum requirements for a STAR
The equipment used for containing the reference atmosphere can be classified into two main
categories:
– large containers (internal volume of several m ), often designed as "walk in", allow the
equipment to be handled inside it, by operators;
– small containers only for the equipment under test.
4.2 Mode of operation of a STAR
4.2.1 Static mode of operation
With the static mode of operation, the conditions inside the container are settled at the
beginning of the operation.
The radon sources are placed inside or outside the container. The static mode of operation
may include the use of an internal fan for the purpose of homogenisation of the atmosphere.
NOTE Containers for static mode of operation are relatively simple to set up and to use, and they enable a
diverse set of atmospheres to be created and manipulated. However, there are only limited possibilities when it
comes to controlling the internal conditions (atmospheres, aerosols, etc.).
4.2.2 Dynamic mode of operation
With the dynamic mode of operation, atmosphere conditions in the container can be controlled
and modified during the exposition of the apparatus to be tested.
Dynamic mode of operation always incorporates some method of renewing, totally or partially,
the internal atmosphere (Figure 3).
Dynamic mode can be used in two ways (Figure 3):
– with a closed loop (recirculation of the atmosphere),
– with an open loop (partial or total evacuation).

61577-4 © IEC:2009 – 15 –
Exhaust
Flow rate
Open loop
meter
222 220
Rn and/or Rn source
Aerosol
Closed loop
source
Instruments under test
Container
Flow rate
Air inlet
meter
IEC  272/09
Figure 3 – Dynamic mode of operation of a STAR
The radon sources are generally located outside the container, thus allowing some control, or
at least a continuous monitoring, of the internal conditions.
The aerosol source is located inside or outside the container.
The use of an open-air circuit may have influence on the radioactive releases to the
environment.
The closed loop is used to control the aerosol concentration or the equilibrium factor in the
container.
The different modes of operation of a STAR may involve various air-flow conditions that
influence the homogeneity or the behaviour of RnDP:
a) Convection
Convection shall be taken into account in static or very low air exchange rate conditions. This
phenomenon may, in these experimental conditions, modify the homogeneity of the STAR
atmosphere.
b) Forced air movement
Forced air movement may have an influence on aerosol behaviour, mainly by turbulent
diffusion and impaction phenomena, leading to changes in the deposition of RnDP on
surfaces (walls, instrument, etc.). It may also be important for the homogeneity of the
atmosphere.
Air exchange rates have a strong influence on the RnDP concentration in the reference
atmosphere.
5 Characteristics of a STAR
5.1 General
This clause describes the characteristics for STARs dedicated to radon reference atmosphere
and, for STARs dedicated to radon and RnDP reference atmosphere.

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5.2 STAR for radon
5.2.1 General
This type of STAR shall be used only for testing instruments that do not depend on aerosol
parameters. Therefore, instruments measuring radon with an open detector cannot be tested
with this STAR.
5.2.2 Technical characteristics of STAR containers
A STAR container shall be sufficiently leak proof:
– to ensure safety through the effective confinement of any radioactivity it might contain;
– to prevent any unforeseen change due to leakage of the reference atmosphere.
If, in addition, the container is to be provided with means for carrying out tests under
pressure, it shall withstand the internal pressure required for such tests and be in conformity
with all relevant regulations related to pressure vessels.
2 –1
The walls shall be thermally insulated (for example with R > 3 m ·K·W ) when tests with
th
variation of temperature and humidity, according to Table 2, are conducted. Where the
atmosphere in the container is to be continuously renewed, its internal shape should be
designed so as to avoid badly ventilated "dead" zones capable of leading to a non-uniform
distribution of activities throughout the volume. Such a design might also facilitate the
processes of evacuation and decontamination of the atmosphere.
The internal walls of the container should be made of a smooth material which cannot corrode
and is a good electrical conductor. These qualities not only facilitate decontamination and
limit the trapping of aerosols by diffusion to a minimum, but they also prevent any stray
collection of RnDPs through electrostatic effects.
Whatever the type of container used, the manipulation of equipment during tests shall as far
as possible be carried out from the outside, either by remote control or by the use of glove
apertures so as to cause the least possible disturbance to the internal conditions.
For the same reason, the largest containers should be fitted with an airlock, both for the
introduction of instruments and for the entrance and exit of operators.
The electricity supply should be stable both in voltage and frequency and should provide
sufficient power.
NOTE A suitable location shall be available to store passive integrating detectors where the radon level is
minimal.
5.2.3 Radon sources
5.2.3.1 Solid sources
226 228 222 220
Solid sources generally consist of a salt of Ra or Th to generate Rn and Rn,
respectively. The salt may be pure or it may be mixed with, or trapped on a matrix. The nature
of the material will determine the value of the emanating power and of emanation rate and
thus the capacity of the source to supply large amounts of radon.
The emanation rate should be constant. But, since the emanating power is highly dependent
on certain physical parameters (relative humidity, etc), the use of such sources will require
considerable precautions to be taken (control of temperature, humidity, etc). Nevertheless,
these sources are very widely used because of easily handling.

61577-4 © IEC:2009 – 17 –
NOTE Some other solid sources are simply constructed using uranium or thorium ore or tailings packed in a
closed container; although this kind of source may be cheap to build and easy to operate, its stability is difficult to
obtain.
5.2.3.2 Liquid sources
226 228
Liquid sources generally consist of an acid solution of a salt of Ra or Th in order to
222 220
obtain Rn or Rn, respectively. After a time that depends on the half-life of the radon
isotope in question, the daughters are in secular equilibrium with the parent nuclide forming
the source.
By careful degassing of the solution, it is then possible to recover the radon formed either:
– in a single operation, or
– continuously.
In the latter case, a simple calculation enables the radon flow rate to be obtained in terms of
the activity of the source and the flow rate of the carrier gas.
The main application of these types of sources is the calibration of the reference instruments.
Precaution shall be taken to avoid contamination risks.
Permeation capsules containing Ra in solution with a certified emanation rate are also
used for calibration purposes.
5.2.3.3 Gaseous sources
Ampoules containing radon are also used as a gaseous source for generation of the STAR
atmosphere. Properly calibrated radon sources in glass bulbs or stainless steel containers
can be used for the standardisation of the STAR atmosphere [3, 4, 14].
NOTE Using this type of source, care shall be taken to ensure the complete transfer of the radon contained in the
ampoule.
Standard Rn gas sources are available to be used for calibration purposes.
222 220
5.2.4 Rn and Rn analysis and control
The radon activity concentration in a STAR is chosen according to the mode of operation.
This radon activity concentration in the STAR container can be:
– kept at a constant level;
– modified in order to reach several constant levels;
– allowed to decrease with radon decay constant after injection of the radon activity in the
container;
– allowed to increase until a plateau is reached.
The means used to analyse the radioactivity of the STAR will be chosen according to the tests
that are planned. The conventionally true value of radon activity concentration of the
reference atmosphere is traceable to national or international standards.
Auxiliary measuring equipment, if possible traceable to reference standards, will be added
according to the tests to be carried out.
If, for example, a significant quantity to be investigated is the gamma radiation, an instrument
for measuring this type of radiation will then be required.
In order to compare the conventionally true value of the radon activity concentration with the
value measured by the instrument to be tested, the radon activity concentration in the

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container shall be homogeneous. In order to ensure homogeneity of the reference
atmosphere, this homogeneity shall be tested.
5.2.5 Analysis and control of climatic parameters
The main climatic parameters, temperature, pressure, and relative humidity shall be
measured.
Because the temperature, relative humidity and, atmospheric pressure are influence
quantities for the response of the detectors and sampling system of the instrument under test,
the value of those quantities shall be taken into account for the determination of the radon or
thoron activity concentration of the reference atmosphere.
When a STAR is used for the determination of the influence of climatic parameters, those
parameters shall be controlled.
5.3 STAR for radon and RnDP
5.3.1 General
This type of STAR includes, at least, all the requirements of STAR for radon described in 5.2
and special requests related to RnDP that are described below.
5.3.2 Technical characteristics of STAR containers
Technical characteristics of STAR containers are defined in 5.2.2.
In addition, internal dimensions of STAR containers should achieve the best possible
compromise between two contradictory requirements:
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