IEC 60951-2:2009

IEC 60951-2 ®
Edition 2.0 2009-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Nuclear power plants – Instrumentation important to safety – Radiation
monitoring for accident and post-accident conditions –
Part 2: Equipment for continuous off-line monitoring of radioactivity in gaseous
effluents and ventilation air
Centrales nucléaires de puissance – Instrumentation importante pour la sûreté –
Surveillance des rayonnements pour les conditions accidentelles et post-
accidentelles –
Partie 2: Matériels pour la surveillance des rayonnements en continu avec
prélèvements dans les effluents gazeux et l’air de ventilation

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IEC 60951-2 ®
Edition 2.0 2009-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Nuclear power plants – Instrumentation important to safety – Radiation
monitoring for accident and post-accident conditions –
Part 2: Equipment for continuous off-line monitoring of radioactivity in gaseous
effluents and ventilation air
Centrales nucléaires de puissance – Instrumentation importante pour la sûreté –
Surveillance des rayonnements pour les conditions accidentelles et post-
accidentelles –
Partie 2: Matériels pour la surveillance des rayonnements en continu avec
prélèvements dans les effluents gazeux et l’air de ventilation

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
Q
CODE PRIX
ICS 27.120.20 ISBN 978-2-88910-347-8
– 2 – 60951-2 © IEC:2009
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.7
2 Normative references .7
3 Terms and definitions .8
4 Design principles.8
4.1 General .8
4.2 Basic requirements related to functions .8
4.3 Sampling assembly .8
4.3.1 General .8
4.3.2 Measurement technique requirements .9
4.3.3 Requirements on filters and collecting devices .9
4.3.4 Requirements on sampling circuit and materials .10
5 Functional Testing .11
5.1 General .11
5.2 Reference sources .11
5.3 Performance characteristics : Response to other radioactive gases or
particles .11
5.3.1 Requirements .11
5.3.2 Test method .11
5.4 Air circuit performance test.12
5.4.1 General .12
5.4.2 Monitor sampling efficiency .12
5.4.3 Susceptibility to gas or particles retention.13
5.4.4 Relative error of the volume and flow rate measurement .14
5.4.5 Flow-rate stability .15
5.4.6 Effect of filter pressure drop .15
5.4.7 Effect of power supply voltage on the flow rate .15
5.4.8 Effect of power supply frequency on the flow rate .16

Table 1 – Overview of the standards covering the domain of radiation monitoring.5
Table 2 – Additional tests to complement the general tests required in IEC 60951-1.16

60951-2 © IEC:2009 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
NUCLEAR POWER PLANTS –
INSTRUMENTATION IMPORTANT TO SAFETY –
RADIATION MONITORING FOR ACCIDENT
AND POST-ACCIDENT CONDITIONS –

Part 2: Equipment for continuous off-line monitoring of
radioactivity in gaseous effluents and ventilation air

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
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
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between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
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 60951-2 has been prepared by subcommittee 45A: Instrumentation
and control of nuclear facilities, of IEC technical committee 45: Nuclear instrumentation.
This second edition cancels and replaces the first edition published in 1988, as well as
IEC 60951-5, published in 1994. This edition constitutes a technical revision.
The main technical changes with regard to the previous edition are as follows:
• To clarify the definitions.
• To update the references to new standards published since the first issue.
• To update the units of radiation.

– 4 – 60951-2 © IEC:2009
This standard is to be read in conjunction with IEC 60951-1.
The text of this standard is based on the following documents:
FDIS Report on voting
45A/735/FDIS 45A/757/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.
A list of all parts of IEC 60951 series, under the general title Nuclear power plants –
Instrumentation important to safety – Radiation monitoring for accident and post-accident
conditions, 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.
60951-2 © IEC:2009 – 5 –
INTRODUCTION
a) Technical background, main issues and organisation of the standard
This IEC standard specifically focuses on radiation monitoring systems used for accident and
post-accident operations.
This standard is intended for use by purchasers in developing specifications for their plant-
specific radiation monitoring systems and by manufacturers to identify needed product
characteristics when developing systems for accident monitoring conditions. Some specific
instrument characteristics such as measurement range, required energy response, and
ambient environment requirements will depend upon the specific application. In such cases.
guidance is provided on determining the specific requirements, but specific requirements
themselves are not stated.
This standard is one in a series of standards covering post-accident radiation monitors
important to safety. The full series is comprised of the following standards.
• IEC 60951-1 – General requirements
• IEC 60951-2 – Equipment for continuous off-line monitoring of radioactivity in gaseous
effluents and ventilation air
• IEC 60951-3 – Equipment for continuous high range area gamma monitoring
• IEC 60951-4 – Equipment for continuous in-line or on-line monitoring of radioactivity in
process streams
b) Situation of the current standard in the structure of the IEC SC 45A standard series
The IEC 60951 series of standards are at the third level in the hierarchy of SC 45A standards.
They provide guidance on the design and testing of radiation monitoring equipment used for
accident and post-accident conditions. Other standards developed by SC 45A and SC 45B
provide guidance on instruments used for monitoring radiation as part of normal operations.
The IEC 60761 series provide requirements for equipment for continuous off-line monitoring
of radioactivity in gaseous effluents in normal conditions. IEC 60861 provides requirements
for equipment for continuous off-line monitoring of radioactivity in liquid effluents in normal
conditions. IEC 60768 provides requirements for equipment for continuous in-line and on-line
monitoring of radioactivity in process streams in normal and incident conditions. Finally,
ISO 2889 gives guidance on gas and particulate sampling. The relationship between these
various radiation monitoring standards is given in Table 1 below.
Table 1 – Overview of the standards covering the domain of radiation monitoring
Developer ISO SC 45A – Process and safety monitoring SC 45B – Radiation
protection and
Scope Sampling circuits Accident and post- Normal and incident
effluents monitoring
and methods accident conditions conditions
Gas, particulate and ISO 2889 IEC 60951-1 and IEC 60761 series and IEC 62302 (noble
iodine with sampling IEC 60951-2 gases only)
(OFF LINE)
Liquid with sampling N/A N/A IEC 60861
(OFF LINE)
Process streams N/A IEC 60951-1 and IEC 60768 N/A
(gaseous effluents, IEC 60951-4
steam or liquid)
without sampling
(ON or IN-LINE)
Area monitoring N/A IEC 60951-1 and IEC 60532
IEC 60951-3
– 6 – 60951-2 © IEC:2009
Developer ISO SC 45A – Process and safety monitoring SC 45B – Radiation
protection and
Scope Sampling circuits Accident and post- Normal and incident
effluents monitoring
and methods accident conditions conditions
Central system N/A IEC 61504 IEC 61559 series

For more details on the structure of the IEC SC 45A standard series, see item d) of this
introduction.
c) Recommendations and limitations regarding the application of this standard
It is important to note that this Standard establishes no additional functional requirements for
safety systems.
d) Description of the structure of the IEC SC 45A standard series and relationships
with other IEC documents and other bodies documents (IAEA, ISO)
The top-level document of the IEC SC 45A standard series is IEC 61513. It provides general
requirements for I&C systems and equipment that are used to perform functions important to
safety in NPPs. IEC 61513 structures the IEC SC 45A standard series.
IEC 61513 refers directly to other IEC SC 45A standards for general topics related to
categorization of functions and classification of systems, qualification, separation of systems,
defence against common cause failure, software aspects of computer-based systems,
hardware aspects of computer-based systems, and control room design. The standards
referenced directly at this second level should be considered together with IEC 61513 as a
consistent document set.
At a third level, IEC SC 45A standards not directly referenced by IEC 61513 are standards
related to specific equipment, technical methods, or specific activities. Usually these
documents, which make reference to second-level documents for general topics, can be used
on their own.
A fourth level extending the IEC SC 45A standard series, corresponds to the Technical
Reports which are not normative.
IEC 61513 has adopted a presentation format similar to the basic safety publication
IEC 61508 with an overall safety life-cycle framework and a system life-cycle framework and
provides an interpretation of the general requirements of IEC 61508-1, IEC 61508-2 and
IEC 61508-4, for the nuclear application sector. Compliance with IEC 61513 will facilitate
consistency with the requirements of IEC 61508 as they have been interpreted for the nuclear
industry. In this framework, IEC 60880 and IEC 62138 correspond to IEC 61508-3 for the
nuclear application sector.
IEC 61513 refers to ISO standards as well as to IAEA 50-C-QA (now replaced by IAEA GS-R-
3) for topics related to quality assurance (QA).
The IEC SC 45A standards series consistently implements and details the principles and
basic safety aspects provided in the IAEA code on the safety of NPPs and in the IAEA safety
series, in particular the Requirements NS-R-1, establishing safety requirements related to the
design of Nuclear Power Plants, and the Safety Guide NS-G-1.3 dealing with instrumentation
and control systems important to safety in Nuclear Power Plants. The terminology and
definitions used by SC 45A standards are consistent with those used by the IAEA.

60951-2 © IEC:2009 – 7 –
NUCLEAR POWER PLANTS –
INSTRUMENTATION IMPORTANT TO SAFETY –
RADIATION MONITORING FOR ACCIDENT
AND POST-ACCIDENT CONDITIONS –

Part 2: Equipment for continuous off-line monitoring of
radioactivity in gaseous effluents and ventilation air

1 Scope
This part of IEC 60951 provides general guidance on the design principles and performance
criteria for equipment for continuous off-line monitoring of radioactivity in gaseous effluents
and ventilation air used in nuclear power plants for accident and post-accident conditions.
General requirements for technical characteristics, test procedures, radiation characteristics,
electrical, mechanical, and environmental characteristics are given in IEC 60951-1. These
requirements are applicable in this part unless otherwise stated.
This standard is applicable to:
• noble gas activity monitors intended to measure the volumetric activity of radioactive noble
gases in gaseous effluents at the discharge point and the variation of volumetric activity
with time during accident and post-accident conditions. The monitor may also be used for
the determination of the total discharge of noble gas activity over a given period;
• noble gas, aerosol and specific nuclide (commonly iodine, in its different forms: inorganic
iodine, organic iodine and iodine sticking on dust) monitors intended to measure the
volumetric activity in air or gas systems (control room ventilation, reactor leakage
collection, drywell ventilation exhaust, fuel handling building ventilation exhaust, reactor
building ventilation purge exhaust) and detect any significant increase of radioactivity
during or after an accident.
This standard is only applicable to continuous off-line measurement, i.e. monitors whose
detector measures a representative proportion of the main effluent or ventilation stream at
some remote location (sampling assembly). It does not apply to monitors with the detector
positioned in or adjacent to the effluent or ventilation stream, which are within the scope of
IEC 60951-4.
Sample extraction and laboratory analysis, which are essential to a complete programme of
effluent monitoring, are not within the scope of this standard.
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 60951-1:2009, Nuclear power plants – Instrumentation important to safety – Radiation
monitoring for accident and post-accident conditions – Part 1: General requirements
IEC 61226, Nuclear power plants – Instrumentation and control systems important to safety –
Classification of instrumentation and control functions

– 8 – 60951-2 © IEC:2009
ISO 2889:2009, Sampling airborne radioactive materials from the stacks and ducts of nuclear
facilities
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60951-1 apply.
4 Design principles
4.1 General
The general requirements of IEC 60951-1 are applicable to all types of monitors within the
scope of the present standard, unless otherwise stated.
4.2 Basic requirements related to functions
The equipment will typically measure levels of activity in engineered gaseous discharge
routes, such as reactor or fuel handling buildings, and ventilation ducts and stacks. It is
intended to provide, depending on the required function, a measure of activity discharged to
the environment or detection and quantification of leakage in containment barriers, and any
useful information on the behaviour of the plant, which causes or allows the activity release.
The measurement of activity discharge to the environment should ideally be comprehensive,
but since measurement of halogen and particulate activity released in effluents during an
accident is more complex, it is often judged that monitoring only noble gases will be sufficient.
Therefore, monitors should be capable of detecting and measuring gaseous effluent
radioactivity with compositions ranging from fresh equilibrium noble gas fission product
mixtures to 10 days old mixtures. Multiple instruments may be needed to cover the effective
range of measurements required.
Since the measurement is continuously carried out on a sample of effluent or ventilation
transferred to a remote location, the detection and measurement assembly shall be installed
in an accessible location and in an environment which is compatible with the equipment
design limits specified in this standard. This shall be also applicable to the active parts of the
sampling assembly (pumps, flow control instruments) requiring maintenance.
The other part of the sampling assembly (sampling probe, pipework) may be designed for and
located in a harsh environment. In this case, if the monitor is classified according to the
guidance of IEC 61226, it should be classified at the same level as the monitor. If qualification
is needed, the part of the sampling assembly located in the harsh environment should be
environmentally qualified to these specific ambient conditions.
If necessary, the system shall indicate a value related to the measured volumetric activity
under the conditions of temperature and pressure at the sampling location, agreed upon
between the manufacturer and purchaser. They shall also agree on how to correct the
expression of measurement if the conditions inside the measuring assembly are different from
the calibration conditions.
4.3 Sampling assembly
4.3.1 General
The design of the sampling assembly shall take into account the guidance of ISO 2889 and
shall comply with the general requirements of IEC 60951-1.
The sampling assembly typically includes one or more of the following assemblies and
functional units:
60951-2 © IEC:2009 – 9 –
• Sampling and exhaust pipes.
• Gas conditioning device (e.g. gas cooling device with condensate removing device or gas
reheating device to prevent condensation inside the measuring chamber, inlet and outlet
connection for an external purging system to remove the remaining gas in the collecting
device, etc).
• Measuring chamber.
• Airborne particles collecting devices:
• aerosol filter unit (filter tape or fixed filter) for aerosol monitors;
• inlet dust filter only for iodine and noble gas monitors;
• iodine molecular filter unit or charcoal filter or cartridge unit (filter changing device or
fixed filter) for iodine monitors.
• Ambient gamma radiation protection device and/or compensation device.
• Individual air pump or centralized pumping station.
• Air flow-rate measurement and/or control devices.
• When appropriate (depending on sampling conditions): pressure, temperature or humidity
measurement and/or control device.
4.3.2 Measurement technique requirements
Depending on the radionuclides to be monitored, the air or gas shall be filtered to remove
radioactive particulates and iodine or passed in a container of known constant volume; in the
latter case, the measuring cell shall be of the flow-through type, its volume and operating
pressure shall be specified, and the detector shall be easily removable for service or
replacement with a detector mounting ensuring a repeatable geometrical location.
Where the measurement technique is sensitive to pressure, a pressure measurement shall be
provided. The calibration shall take into account the actual conditions of service by
appropriate corrections; the acceptable pressure and variation of pressure in the sampling
assembly shall be specified by the manufacturer. Care shall be taken to ensure that the
pressure in the measuring volume is only slightly affected by the variation of pressure drop
across the inlet filter.
Where the measurement technique is sensitive to flow rate, a flow-rate measuring device shall
be provided. The calibration shall take into account the actual pressure and temperature of
service by appropriate corrections. The influence of gas stream conditioning devices upon the
volume measurement shall be considered. A flow-rate control device should also be provided
which has a flow-rate adjustment range sufficient to allow for variation in the intrinsic
characteristics of the air pump and any filters used. A correction of the measurement for the
effects of different flow-rates should also be provided.
If necessary, a humidity measurement of the atmosphere to be monitored may be provided to
control the conditioning device in order to avoid any condensation in the pipes and the
monitors; alarms should be provided to signal when the relative humidity exceeds a value
specified by the manufacturer.
If necessary, a temperature measurement of the sample in front of and close to the measuring
device may be provided. In this case, alarms should be provided to signal when the
temperature is close to the maximum allowed temperature for the detector.
4.3.3 Requirements on filters and collecting devices
If required, filters or other trapping devices shall be placed in holders at the sampling
assembly inlet to remove any dust, aerosols or volatiles from the air or gas. They shall
therefore be designed not to trap or retain noble gases or iodine (except iodine sticking onto

– 10 – 60951-2 © IEC:2009
dust); if this is not possible, they shall be monitored separately. The manufacturer of such
filters shall specify their retention characteristics for several chemical forms of iodine.
Collecting filters (e.g. glass fibre filter plate, glass fibre filter tape, charcoal filter cartridges)
shall be designed to ensure an as uniform as possible deposition of particles. The
manufacturer of such filters shall state the retention characteristics of the filters for several
chemical forms of radioactive particles, their lifetime, and the collection efficiency of the
collecting filter for particles over a range of at least 0,1 μm to 10,0 μm aerodynamic
equivalent diameter or to values agreed upon by the manufacturer and the purchaser. The
efficiency of the filters should be more than 98 % for dust apart from iodine and more than
99 % for iodine.
41 85 133 222
The presence of radioactive gases (for example Ar, Kr, Xe or Rn) in the air being
monitored has an effect on the monitoring of particles; this is especially true for non-selective
detectors; to reduce the effects of these radionuclides, the air space in the vicinity of the
detector and inside the filters shall be kept to the minimum. If necessary, and if practicable, a
purging capability could be provided, to reduce unwanted and disturbing influence of
radioactive noble gasses on the measurement of the particle activity.
Collecting filters or trapping devices shall be accessible during normal and post-accident
conditions; the pressure drop in the filter as well as its contamination should be controlled,
and it should be possible to replace it by an easy and quick disconnection of the filter unit
from the pipes.
For the collecting filters introducing an important pressure drop, a differential pressure
measurement should be provided to indicate a clogged or pierced collector. In this case,
alarms shall be provided for warning of any excessive variation of this differential pressure.
4.3.4 Requirements on sampling circuit and materials
Where a pump is an integral part of any assembly, its nominal flow rate shall be stated by the
manufacturer. The sampling assembly design shall provide simple access to the pump and its
replaceable parts. Care shall be taken to prevent radioactive gases from leaking into the
breathing zone of workers. The acceptable leakage rate depends on the emergency
conditions and shall be agreed upon between the manufacturer and the purchaser.
Prevention against condensation in the pipe by variation of temperature or pressure shall be
taken. If a gas stream cooling device is used, the condensate flow of the cooling device shall
be removed automatically.
Leakage of air or gas in the sampling system (between inlet and outlet of the monitor) shall be
less than 5 %.
Losses of particulates and iodine shall be maintained as low as possible by taking into
account piping circuit and constructional material in order to estimate and minimize
electrostatic effects, adsorption, condensation and plate-out; the level of such losses, and the
ways to reduce it, shall be agreed upon between the manufacturer and the purchaser. In any
case, the roughness of the surfaces in contact with the gas stream should be less than
0,4 μm.
Delay time to detector shall be maintained as low as possible by optimising the pipe length
and diameter, flow rate, etc.
Where the measured sample may contain an explosive mixture of gases (e.g. H ), the
assembly shall be designed to prevent the possibility of ignition of the sample by the
instrumentation.
60951-2 © IEC:2009 – 11 –
Where the measured sample may contain noxious or corrosive chemical vapour, the assembly
shall be designed to protect the measuring system.
5 Functional testing
5.1 General
Except where otherwise specified, all the tests specified in Clause 5 of IEC 60951-1 shall be
carried out.
The tests described hereinafter are only additional tests dedicated to the type of monitors
within the scope of the present standard. As for tests stated in IEC 60951-1, these tests shall
be considered as type tests, although any or all may be considered as acceptance tests by
agreement between manufacturer and purchaser.
These tests shall be carried out under standard conditions or with variation of the influence
quantities. They are listed in Table 2.
5.2 Reference sources
In addition to 5.2.5 of IEC 60951-1, the following requirements shall apply:
A range of test gases may need to be used depending on the function and design of the
monitor. These gases shall be agreed upon between the purchaser and the manufacturer.
Depending on the design of the monitor, the test shall be to:
• either circulate air or gas filled with known activity through the assembly under test during
a sufficient time interval to reach measurement equilibrium and note the readings;
• or to immerse the detector in a sufficiently large volume of gas so as to be equivalent to
the volume in the actual operating position of the detector and note the readings under
equilibrium conditions for the monitor under test.
NOTE Circulation may not be required if the measurement is properly corrected for temperature and pressure.
If it is intended to use a reference instrument for tests, then it should be inserted in the gas
flow (or in a sufficiently large volume of gas) in the same way as the instrument under test
and, for both of them, the readings should be noted. In this case, to estimate the accuracy of
the instrument under test, the readings and the absolute measurement error of the reference
instrument should be used instead of the conventionally true value and its absolute
uncertainty of the reference source.
5.3 Performance characteristics : response to other radioactive gases or particles
5.3.1 Requirements
The designated radioactive gases and particles to which this requirement applies shall be the
subject of an agreement between the manufacturer and the purchaser. The manufacturer shall
specify the response to the radioactive gases or particles of interest present in the sample of
air or carrier-gas.
5.3.2 Test method
The test method is similar to the method used for determining the reference response, but
using the appropriate radioactive gas or gases.
Two methods may be used:
– 12 – 60951-2 © IEC:2009
133 85
– Continuously inject a known volume activity of noble gas for example Xe or Kr into
the monitor for the time necessary to reach equilibrium. Note the reading corresponding to
the equilibrium value. Express the result as the ratio of the indication to the volume
activity of the test gas.
– Connect the inlet air duct to the outlet air duct and measure the total air duct volume (for
example connecting the inlet air duct to a known volume under pressure and noting the
pressure change at equilibrium). Inject into the system a small volume (1 % of the air duct
133 85
volume) of gas, for example Xe or Kr, of known total activity. Operate the monitor in
the normal way. Note the reading corresponding to the equilibrium and to the highest
value attained. Express the result as the ratio of the indication to the volume activity of the
test gas.
5.4 Air circuit performance test
5.4.1 General
These tests shall be applied to all monitors for which the response is dependent upon a
known flow-rate through a sampling and detection assembly.
Where the equipment is insensitive to flow-rate, but nevertheless requires a sampling flow-
rate in order to function, a simple test of the flow-rate circuit and any flow-rate alarms shall be
agreed upon between the manufacturer and the purchaser.
When the equipment is sensitive to flow-rate, and the flow-rate varies in conjunction with the
effluent flow-rate, appropriate tests shall be agreed upon between the manufacturer and the
purchaser.
5.4.2 Monitor sampling efficiency
5.4.2.1 General
The collection efficiency, between the inlet of the monitor and the collecting filter, shall not
differ by more than 10 % from the value stated by the manufacturer for each given size of
particle.
If agreed upon between the manufacturer and the purchaser, a simulation could be also
performed, instead of real tests.
5.4.2.2 Particle size
The particle diameter and range of sizes used in the measurement of the collection efficiency
of the sampling system shall be agreed upon between the manufacturer and the purchaser,
for example depending upon the diameter of the aerosol to be monitored, collection efficiency
of the filter media versus particle size, etc.
5.4.2.3 Aerosol type
Various types of aerosols are suitable for use in the collection efficiency tests and include, for
example:
• non-radioactive aerosols with particles having a fluorescent tracer,
• non-radioactive aerosols composed of latex or polystyrene spheres,
• radioactive aerosols.
5.4.2.4 Test method
Collection efficiency shall be tested by introducing a sample of air containing particles of the
appropriate median aerodynamic diameter into the inlet sampling pipe. The distribution may
be polydispersed with a small geometric standard deviation. The sampling equipment shall be
operating under standard test conditions, e.g., flow-rate.

60951-2 © IEC:2009 – 13 –
After the shutdown of the sampling equipment, the amount of aerosol collected on the
sampling medium shall be determined. In addition, the total amount of aerosol available at the
monitor inlet shall be determined. This may be done by an independent measurement of the
sampled amount of aerosol, or by determining:
• the amount of aerosol collected on the internal surfaces of the inlet line and other surfaces
of the air circuit upstream from the collection medium,
• the amount of aerosol downstream from the collection medium.
5.4.2.5 Determination of collection efficiency
The collection efficiency (E ) of the monitor shall be calculated as:
m
C
M
E = ×100
m
C
T
where:
C is the amount deposited on the collection medium,
M
C is the total amount of aerosol.
T
It is recommended, if practical, that the total amount of aerosol (C ) be determined by an
T
alternative method as a means of verifying the values obtained. Such methods include the
measurement of the concentration of aerosols that enter into the instrument by various
instrumental techniques, for example spectrophotometer, particle analyzer, reference
sampling, etc.
If the total aerosol sampled is determined by the sum of the material collected within the
monitor, then the total amount of aerosol (C ) (activity, mass or number of particles) is given
T
by:
C = C + C + C
T M U D
where:
C is the amount recovered from the internal surfaces of the air circuit upstream of the
U
collection medium,
C is the amount collected downstream of the collection medium.
D
5.4.3 Susceptibility to gas or particles retention
5.4.3.1 General
The retention of noble gas or particles inside the air circuit may influence the measuring
results. Therefore the intention of the manufacturer’s air circuit design, selection of materials,
and construction shall be to prevent such a retention.
If agreed upon between the manufacturer and the purchaser, a simulation could be also
performed, instead of real tests.
5.4.3.2 Requirements
Noble gas with a volumetric activity greater than 10 times the decision threshold shall be
introduced into the monitor. The test for susceptibility to gaseous retention shall indicate less
than 1 % of the maximum resulting reading after clean air is introduced into the monitor.

– 14 – 60951-2 © IEC:2009
Particle concentration shall be introduced into the monitor. The test for susceptibility to
particle retention shall indicate less than 5 % of the maximum resulting reading after clean air
is introduced into the monitor.
5.4.3.3 Test method for noble gas
Introduce into the detection assembly, for a period of at least 10 times the response time of
the equipment, noble gas of the chemical form that the equipment is designed to measure
with a volumetric activity approximately equal to 10 times the decision threshold.
For assemblies not comprising a trapping system, make the gas system a closed loop and
introduce into this system sufficient noble gas for the volumetric activity to equal 1 000 times
the decision threshold. Operate until equilibrium of the gas concentration.
Verify that the indication of the measuring assembly stays at its maximum value for at least
10 times the response time of the equipment.
Then circulate fresh air at ambient temperature and pressure with the air circuit open at the
nominal flow-rate, for a time long enough to reach an equilibrium in indicated value. This
value shall be less than 1 % of the maximum indicated value during the test with noble gas
activity.
5.4.3.4 Test method for particles
Introduce into the detection assembly a well known quantity/mass of non-radioactive particles
by injecting the particles into the sampling pipe. The particles should be of the chemical form
that the equipment is designed to measure.
Then circulate fresh air at ambient temperature and pressure with the air circuit open at the
nominal flow-rate, for several minutes. Then measure the quantity/mass of the particles
collected on the filter unit of the monitor.
The total loss of particles shall be < 5 %.
5.4.4 Relative error of the volume and flow rate measurement
5.4.4.1 General
The relative error of the measured values of radioactive gas in air concentrations is directly
related to the relative error of the measured values of flow rate or volume for those samplers,
which concentrate or absorb the gas into the collection medium. An accurate volume and flow
rate measurement of counting gas mixed with the noble gas containing medium is also
important for an accura
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