ISO 10647:1996
(Main)Procedures for calibrating and determining the response of neutron-measuring devices used for radiation protection purposes
Procedures for calibrating and determining the response of neutron-measuring devices used for radiation protection purposes
Specifies procedures for the calibration of neutron-measuring devices used for radiation protection purposes, and for determining their response as a function of energy, angle of incidence and dose equivalent rate, using the neutron reference radiations according to ISO 8529.
Méthodes d'étalonnage et de détermination de la réponse des instruments de mesure des neutrons utilisés en radioprotection
General Information
Standards Content (Sample)
INTERNATIONAL
STANDARD 10647
First edition
1996-12-15
Procedures for calibrating and determining
the response of neutron-measuring devices
used for radiation protection purposes
Methodes d ‘6 talonnage et de dktermina tion de Ia r6ponse des
ins trumen ts de mesut-e des neutrons utilisb en radioprotection
Reference number
ISO 10647:1996(E)
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ISO 10647:1996(E)
Page
Contents
1
Scope .
1
1
2 Normative references. . .
........................... 2
3 Devices covered in this International Standard
2
3.1 Individual dosemeters . .
........................ 2
3.2 Devices for surveying and area monitoring.
........... 2
4 Definitions . .
......................... 3
4.1 Metrological terms .
............................... 3
4.1.1 Reading .
................................... 3
4.1.2 Response .
.................................................... 3
4.1.3 Calibration factor
4.1.4 Energy dependence of response. . 3
4.1.5 Angular dependence of response . 3
3
4.1.6 Gamma-ray sensitivity .
3
4.1.7 Free-field quantities . .
3
4.2 Reference and monitoring instruments .
instrument . 3
4.2.1 Primary Standard
............................. 3
4.2.2 Secondary Standard instrument
............................ ................... 3
4.2.3 Transfer instrument
........................................... 3
4.2.4 Monitoring instrument
4
.......................................... ..................
4.3 Devices to be tested
4
Neutron dosemeter .
4.3.1
4
4.3.2 Neutron dose-ratemeter .
4
4.3.3 Neutron detector .
4
Symbols (sec annex G) .
5
...... 4
6 Traceability of the calibration of the reference radiation field
..................... 4
6.1 Traceability for radionuclide neutron sources.
0 ISO 1996
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hternational Organization for Standardization
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Printed in Switzerland
ii
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@ ISO ISO 10647:1996(E)
............ 5
6.2 Traceability for neutron produced by an accelerator
................................. 5
6.3 Traceability for reactor neutron beams
7 Calibration principles for radionuclide neutron sources . 5
7.1 General principles . 5
............. 6
7.2 Important features of a neutron calibration facility.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.2.1 Source
Irradiation set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.2.2
7.2.3 Irradiation room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.3 Sources of scattered neutrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.3.1 Room-scatter . . . . . . .0. 7
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.3.2 Air-attenuation (air-outscatter)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.3.3 Room-inscatter
Stattering from support structures . . . . . . . . . . . . . . . . . . . . . . . . 7
7.3.4
7.3.5 Spectral effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.4 Effective Point of measurement and effective calibration
distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.1 Spherical devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.2 Cylindrical devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.4.3 Irradiation of individual dosemeters upon a
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Phantom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.5 Effect of Photon radiation
8 Correcting for stattering effects for radionuclide neutron
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8.1 Initial measurements
.............................................. ..............
8.2 Geometry correction
......................................................... ........... 9
8.3 Analysis of data
8.3.1 Semi-empirical method . 9
9
8.3.2 Shadow-cone technique .
...... IO
8.3.3 Polynomial fit method .
IO
8.4 Choice of methods . .
............................ .............. IO
8.4.1 Semi-empirical method
............................................ IO
8.4.2 Shadow-cone method
Polynomial fit method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.4.3
11
............
9 Routine calibrations with radionuclide neutron sources.
11
9.1 Linearitiy determination .
....... 12
9.2 Determination of the angular dependence of response
................... 12
IO Estimated uncertainties .
10.1 Components of the uncertainty applicable to radionuclide
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Source calibrations
12
10.1.1 Uncertainty in neutron Source strength, B . . . . . . . . . . . . .
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ISO 10647:1996(E) @ ISO
12
Uncertainty in anisotropy function, Fr(e) ~.~~~.O~.D.n
10.1.2
10.1.3 Uncertainty in calibration distance, k e . . . . . . . . . . . . . . . . . . . . . 12
10.1.4 Uncertainty in geometry-correction factor Fl(Z) . . . . . 12
10.1.5 Stattering correction uncertainty . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
10.1.6 Statistical uncertainty in readings, hil . . . . . . . . . . . . . . . . . . . . . 13
10.1.7 Timing uncertainty . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
10.1.8 Uncertainty in spectrum-averaged values of
fluence to-dose equivalent conversion . . . . . . . . . . . . . . . . . . 13
13
11 Calibrations using accelerators and reactors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.*
11.2 Accelerator-produced neutrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.2.1 Neutron f luence rate. . 14
14
11.2.2 Monitoring .
14
11.2.3 Energy dependence of response. .
11.2.4 Contaminant sources of neutrons . 14
11.2.5 Neutron energy and energy spread . 14
11.2.6 Variation of neutron spectrum with emission 14
angle . .
................................ 14
11.2.7 Target-scatter corrections.
............................. 15
11.2.8 Effects of neutron stattering
. . . . . . . . . . . . . . . . . . . 15
11.3 Reactor neutron beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
.................................... 15
11.3.1 Filtered neutron beams.
11.3.2 Thermal neutrons . . 15
11.4 Estimated uncertainties for accelerator and reactors . . . . . . 15
11.4.1 Neutron energy and energy spread . 16
11.4.2 Variation of neutron spectrum with emission 16
angle . .
11.4.3 Target-scatter corrections. . 16
11.4.4 Effects of neutron stattering . 16
11.4.5 Fluence determination . 16
16
11.5 Combining uncertainties . .
Annexes
17
A Scheme of physical characteristics to be tested . . . . . . . . . . . . . . . . . . . . . . . . .
18
B Recommendations on Phantoms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C Angular Source strength characteristics of two radionuclide
19
neutron sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
20
D Minimum room length for 40% room return . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
21
E Air-attenuation correction factors and total air-scatter correction
23
F Criteria for construction and use of shadow cones . . . . . . . . . . . . . . . . . . . . .
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ISO 10647:1996(E)
G List of Symbols used in ISO 8529
................................................
24
H Bibliography
.................................................................................
25
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ISO 10647:1996(E) 0 ISO
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. Esch 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.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 10647 was prepared by Technical Committee
ISOPC 85, Nuclear energy, Subcommittee SC 2, Radiation protection.
Annexes A to F form an integral part of this International Standard.
Annexes G and H are for information only.
vi
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INTERNATIONAL STANDARD 0 ISO
ISO 10647:1996(E)
Procedures for calibrating and determining the response of
neutron-measuring devices used for radiation protection
purposes
1 Scope
This International Standard specifies procedures for the calibration of neutron-measuring devices used for radiation
protection purposes, and for determining their response as a function 0% energy, angle of incidence and dose
equivalent rate, using the neutron reference radiations specified in ISO 8529.
Since, according to ICRU Report 39 and ICRU Report 43, neutrons of all energies are strongly penetrating, area
monitors should be calibrated in terms of ambient dose equivalent [H*(lO)], and individual dosemeters should be
calibrated to measure individual dose equivalent, penetrating [Hp(lO)]. The procedures given in this International
Standard are, however, quite general, and may be used with any System of dose equivalent quantities. A
diagrammatic scheme of the physical characteristics to be tested is given as annex A.
2 Normative references
The following Standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All Standards are subject to
revision, and Parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the Standards indicated below. Members of IEC and ISO maintain
registers of currently valid International Standards.
ISO 8529: 1989, Neutron reference radiations for calibrating neutron-measuring devices used for radiation
protection purposes and for determining their response as a function of neutron energy.
IEC 1005, 1990: Portable neutron ambient dose equivalent rate-meters for use in radiation protection.
ICRP Publication 21 (1973): Data for Protection Against lonizing Radiation from fxternal Sources. (Supplement to
ICRP Publication 15.)
ICRU Report 13 (1969): Neutron Fluence, Neutron Spectra and Kerma. International Commission on Radiation Units
and Measurements, Washington, D.C., USA.
ICRU Report 20 (1971): Radiation Protection lnstrumentation and its Application. International Commission an
Radiation Units and Measurements, Washington, D.C., USA.
ICRU Report 26 (1977): Neutron Dosimetry for Biology and Medicine. International Commission on Radiation Units
and Measurements, Washington, D.C., USA.
ICRU Report 33 (1980): Radiation Quantities and Units. International Commission on Radiation Units and
Measurements, Washington, D.C., USA.
1) ICRP: International Commission on Radiological Protection.
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@ ISO
ISO 10647:1996(E)
ICRU Report 39 (1985): Determination of Dose Equivaients ßesulting from fxternal ßadiat;on Sources. International
Commission on Radiation Units and Measurements, Bethesda, MD, USA.
ICRU Report 43 (1988): Determination of Dose Equivalents ßesulting from Extemal Radiation Sources - Part 2.
International Commission on Radiation Units and Measurements, Bethesda, MD, USA.
3 Devices covered in this International Standard
This International Standard applies to individual dosemeters and to portable devices for surveying and area
monitoring, some examples of which are given in 3.1 and 3.2. Some of these devices may also be used as
reference instruments.
3.1 ’ Individual dosemeters
Individual dosemeters include devices such as
nuclear emulsions;
- solid-state nuclear track detectors;
albedo dosemeters;
pocket ionization chambers;
bubble, or superheated drop, detectors;
semiconductor detectors.
These shall be calibrated on a suitable Phantom (see annex B). Reviews of the physical characteristics of individual
dosemeters are given by Griffith et al. [l]. Reviews of calibration procedures are given by Eisenhauer et ai. [Zl and
by Burger and Schwartz [3].
3.2 Devices for surveying and area monitoring
Dose equivalent meters, dose equivalent ratemeters or monitors for surveying and area monitoring of neutrons are
generally portable devices, calibrated free-in-air, rather than on a Phantom. These devices include
- moderating devices with thermal-neutron detectors for the measurement of neutrons over a wide range of
energies;
unters for the measu remen t of absorbed dose and dose
- low-pressu re tissue-equivalent proportional co
equivalent;
large ionization chambers for the measurement of tissue kerma;
BF3 and 3He proportional counters for the measurement of thermal neutrons;
bubble, or superheated drop, detectors;
recombination dose equivalent ratemeters.
More details concerning the characteristics of portable neutron dose-equivalent ratemeters, and of their calibration
requirements and procedures are given in references [3] and [4] in annex i-1, and in IEC 1005. Complete definitions
of radiation quantities and units tan be found in ICRP Publication 21, ICRU Report 13, ICRU Report 33, ICRU
Report 39, ICRU Report 43, and ISO 8529.
4 Definitions
For the purposes of this International Standard, the following definitions apply.
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ISO 10647:1996(E)
4.1 Metrological terms
4.1.1 reading, M: Value of the quantity indicated by an instrument.
4.1.2 response, R: Reading divided by the magnitude of the quantity causing it.
The type of response shall be specified, for example:
“fluence response”,
A4
Zr-
. . . (1)
R@
@
“dose equivalent response”,
h4
=-
. . .
(2)
RH H
or “Photon dose equivalent response”,
IM
=-
. . .
(3)
RHY
HY
If h4 is a measurement of a rate, the quant ities fluence, @, and dose equivalent, H, are replaced by fluence rate, @,
and dose equivalent rate, resp ectively.
M
The concept of dose equivalent, H, in this International Standard is intended to be general. For example, it may
apply to the dose equivalent calculated at the maximum of the depth-dose equivalent curve, i.e. MADE (ICRP
Publication 21) or the ambient dose equivalent (ICRU Report 39).
4.1.3 calibration fa ctor, C: Reciproca I of the response; factor by which the reading, M, is multiplied to obtain the
to be measured.
value of the quanti
tY
4.1.4 energy dependence of response, R@(E) or RH(E): Response, R, with respect to fluence, 0, or dose
equivalent, H, to monoenergetic neutrons as a function of neutron energy, E.
angular dependence of response: Response as a function of the direction of incidence of neutrons on the
4.1.5
device.
device when gamma-rays are added to a
4.1.6 gamm a-ray sensitivity: Change in the neutron reading of a
neutron field.
(Compare with “Photon dose equivalent response” in 4.1.2).
4.1.7 free-field quantities: Quantity which would exist if irradiations were performed in free space with no
scatter or background effects.
4.2 Reference and monitoring instruments
4.2.1 primary Standard instrument: Instrument that is capable of determining the required radiation quantity
from known physical data only.
Instrument whose radiation response characteristics have been
4.2.2 secondary Standard instrument:
determined by comparison with a primary Standard instrument.
4.2.3 transfer instrument: Instrument whose radiation response characteristics, response precision and long-
term stability make it suitable for comparing the measurement of a radiation quantity in one laboratory with that in
another.
4.2.4 monitoring instrument: Instrument with suitable physical properties to monitor the radiation field
characteristics in a given laboratory over a long term.
More details concerning primary Standards, secondary Standards, and transfer instruments tan be found in ICRU
Report 20 and ICRU Report 26.
3
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ISO 10647:1996(E) @ ISO
4.3 Devices to be tested
4.3.1 neutron dosemeter: Device for the determination of neutron dose equivalent, kerma, or absorbed dose.
4.3.2 neutron dose-ratemeter: Device for the determination of neutron dose equivalent rate, kerma rate, or
absorbed dose rate.
4.3.3 neutron detector: Device sensitive to neutrons.
5 Symbols
For the purposes of this International Standard, the following Symbols, and certain Symbols Iisted in annex G, apply.
Symbol Meaning
k Characteristic constant for source-detector combination
r Detector radius
A Total air-scatter component
C Calibration factor
Geometry-correction factor
Fl
Air outscatter factor
FA
Anisotropy correction factor
Fl
Instrument reading under free-field conditions
4
Instrument reading due to inscattered neutrons alone, dunng a shadow-cone caiibration procedure
4
Total instrument reading during a calibration procedure
MT
S Room back-scatter component
6
Effectiveness factor
A
Lateral dosemeter distance on Phantom surface
2 Linear attenuation coefficient (energy averaged)
6 Traceability of the calibration of the reference radiation field
The neutron fluence rate of a radiation field established in a calibration laboratory in accordance with this
International Standard shall be traceable to a recognized national or international Standard. The method used to
provide this calibration link is dependent upon the type of reference radiation field, but measurement traceability is
usually achieved through the utilization of a transfer Standard. This may be, for example, a radionuclide Source (6.1)
or an approved transfer instrument (see 6.2). The calibration of the field is valid in exact terms only at the time of
the calibration, and thereafter shall be inferred, for example, from a knowledge of the half-life and isotopic
composition of the radionuclide Source, or knowledge of the properties of the transfer instrument.
The measurement technique used by the laboratory in the calibration of a neutron-measuring device shall also be
approved by a body or institution as required by national regulations. An instrument of the Same, or similar, type as
that routinely calibrated by the laboratory shall be calibrated by both the reference laboratory and the calibration
laboratory. These measurements shall be performed within each laboratory using its own approved calibration
methods. In Order to demonstrate that adequate traceability has been achieved, the calibration laboratory should
obtain the Same calibration factor, within agreed-upon limits, as that obtained by the reference laboratory.
The frequency of field calibrations shall be such that there is reasonable confidence that its value will not move
outside the limits of its specification between successive calibrations. The frequency of calibration of the
radionuclide neutron sources is given in ISO 8529. The calibration of the laboratory-approved transfer instrument,
and the check on the measurement techniques used by the calibration laboratory, shall be carried out at least every
five years, or whenever there are significant changes in the laboratory environment.
6.1 Traceability for radionuclide neutron sources
For calibrations using neutron fields produced by radionuclide neutron sources, traceability shall be provided either
by using a radionuclide Source whose angular Source strength has been determined by a reference laboratory
(see 7.2.1 for angular Source strength), or by determining the fluence rate at the instrument test Position using an
4
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ISO 10647:1996(E)
agreed-upon transfer instrument, calibrated in a reference laboratory. If the Source is encapsulated according to the
recommendations in ISO 8529:1989, 4.1.2, it may then be assumed that the spectral neutron fluence from the
Source is sufficiently similar to the appropriate spectral fluence given in ISO 8529 for the recommended fluence-to-
dose equivalent conversion factors to be used. The uncertainties in the conversion factors recommended in 10.1.8
of this International Standard reflect both uncertainties in the spectra given in ISO 8529, as well as variations in the
spectra caused by differentes in Source construction and encapsulation.
6.2 Traceability for neutrons produced by an accelerator
Traceability shall be provided by using a transfer instrument which has been agreed upon by the calibration and
reference laboratories. The transfer instrument shall be used in the same manner, for similar neutron fields, as
when it was calibrated, and the proper corrections shall be applied (see 7.2).
The laboratory transfer and monitorin g instrument s shall be checked at intervals as required by national regulations
(for example, by using an appropriate radionuclide neutro n Source), and the results shall be recorded.
6.3 Traceability for reactor neutron beams
The same general principle of traceability to a recognized Standard shall be applied to the calibration of these
specialized reference radiation fields (thermal or filtered neutron beams). For example, the thermal-neutron fluence
rate may be measured by the activation of gold foils, for which the measurement is traceable to a primary Standard.
7 Calibration principles for radionuclide neutron sources
7.1 General principles
The response or calibration factor of a device is a unique property of the type of device, and may depend on the
dose equivalent rate, the neutron Source spectrum or the angle of incidence of the neutrons, but should not be a
function of the characteristics of the calibration facility or experimental techniques employed. Hence, in this
International Standard, detailed procedures are given for the calibration of neutron-measuring devices which should
ensure that their calibration is independent of the technique, and of such factors as the source-to-device distance
and room size.
For simplicity, general principles are given for the calibration of devices such as dose equivalent ratemeters, but
most of the principles apply to other devices as weil. The instrument is placed in a radiation field of known free-field
fluence rate and the instrument reading is noted. In accordance with the above Paragraph, the reading must be
corrected for all extraneous neutron stattering effects, including neutron stattering by the air and by the Walls, floor
and ceiling of the calibration room (see 7.2). lt may also have to be corrected for effects due to Source or detector
size (see discussion of the geometry-correction factor Fl(Z) in 8.3).
The free-field fluence response, RQ, of the instrument is then given by
4
=-
. . .
(4)
Ra
0
where M, is the measured reading corrected for all extraneous effects.
The free-field fluence rate + to which the instrument has been exposed is calculated from
BL!
=-
. . .
(5)
e
l2
where 2 is the distance from the centre of the Source to the effective Point of measurement (see 7.4).
The neutron angular Source strength, Ba, (defined in ISO 8529) is calculated from
B x Fi(o)
BQ = . . .
6)
4n;
where
B is the neutron Source strength (i.e. the total neutron emission rate into 47~ sr);
Fl@) is the Source anisotropy correction (reference [5] in annex H).
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ISO 10647:1996(E)
@ ISO
Anisotropy functions for two types of sources are shown in annex C.
It is sometimes convenient to introduce the source-detector characteristic constant, k, which is just the instrument
reading at unit distance, fully corrected for all stattering effects (see 7.3). In general
k=M,l*
. . .
(71
Then, from equations (4) and (5) we obtain
k=R#Ba
. . .
(8)
The constant k is specific to each source-detector combination, since it depends on the quantities Ba and R@.
Finally, the dose equivalent response, RH, is obtained from
Ra
=-
. . .
RH (9)
hQz
where ha is the fluence-to-dose equivalent conversion factor. Recommended values of ha, in accordance with
ICRP Publication 21, are given in annex B of ISO 8529:1989 for ISO Standard sources. The value of ha and an
appropriate reference should always be given.
7.2 Important features of a neutron calibration facility
72.1 Source
The calibration field of the radionuclide Source shall be traceable to a reference laboratory (see clause 6). To
minimize anisotropic neutron emission, the Source shall be spherical or cylindrical. In the latter case, it is preferable
that the diameter and length be approximately the Same. For cylindrical sources, the detector shall be calibrated at
0 = 90” to the cylindrical axis (see ISO 8529:1989, 4.3). The anisotropy shall be measured for each Source used. The
encapsulation shall be as light as possible, consistent with relevant national and international Standards for the
integrity of sealed radioactive sources. For heavily encapsulated sources, there may be spectral changes
associated with the anisotropic emission. Eisenhauer and Hunt [5] used a long counter to determine the fluence
anisotropy. Examples of the anisotropy function are given in annex C of this International Standard, and 4.3 of
ISO 8529:1989 (see Eisenhauer et al. [21 for a more complete discussion.)
The Source shall be located at the centre of the room or, in th an open facility, as high as practical
e case of above
the ground. The sou rce shall be su pported by a non-hydroge no us structu re with as small a mass as possible.
In Order to perform a complete linearity check, a Variation in dose equivalent rate of more than three decades may
be required (e.g. from - 10 PSV- h-1 to - 40 mSv h-1). lt will usually be impractical to cover this range by varying
only the distance, 1. Rather, two (or more) sources, varying in Source strength by factors of 10 to 100, will generally
be required. The anisotropy factor, Fl(e), will not necessarily be the same for the different sources, even if they are
nominally identical in construction.
7.2.2 Irradiation set-up
A su
...
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