ISO/ASTM 51631:2003
(Main)Practice for use of calorimetric dosimetry systems for electron beam dose measurements and dosimeter calibrations
Practice for use of calorimetric dosimetry systems for electron beam dose measurements and dosimeter calibrations
ISO/ASTM 51631:2003 covers the preparation and use of semi-adiabatic calorimeters for measurement of absorbed dose and routine dosimeter calibration when irradiated with electrons for radiation processing applications. The calorimeters are either transported by a conveyor past a scanned electron beam or are stationary in a broadened beam. ISO/ASTM 51631:2003 applies to electron beams in the energy range from 1,5 to 12 MeV.
Pratique de l'utilisation des systèmes dosimétriques calorimétriques pour des mesures de dose délivrée par un faisceau d'électrons et pour l'étalonnage de dosimètres
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INTERNATIONAL ISO/ASTM
STANDARD 51631
Second edition
2003-07-15
Practice for use of calorimetric dosimetry
systems for electron beam dose
measurements and dosimeter
calibrations
Pratique de l’utilisation des systèmes dosimétriques
calorimétriques pour des mesures de dose délivrée par un
faisceau d’électrons et pour l’étalonnage de dosimètres
Reference number
ISO/ASTM 51631:2003(E)
© ISO/ASTM International 2003
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ISO/ASTM 51631:2003(E)
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ii © ISO/ASTM International 2003 – All rights reserved
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ISO/ASTM 51631:2003(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 1
4 Significance and use . 2
5 Interferences . 2
6 Apparatus . 2
7 Calibration Procedures . 4
8 Dose measurement procedures . 4
9 Calibration of other dosimeters . 6
10 Documentation . 6
11 Measurement uncertainty . 6
12 Keywords . 7
ANNEX . 7
Bibliography . 7
Figure 1 Example of a graphite calorimeter used at a 10-MeV industrial electron accelerator . 3
Figure 2 Example of a polystyrene calorimeter used for routine measurements at a 10-MeV
industrial electron accelerator . 3
Figure 3 Example of a polystyrene calorimeter for use at 1.5 to 4 MeV industrial electron
accelerators . 4
Figure 4 Absorber for irradiation of routine and transfer-standard dosimeters . 5
Figure 5 Example of measurements of temperature of a graphite calorimeter before and after
irradiation only . 5
Figure 6 Example of on-line measurements of a graphite calorimeter . 6
Table 1 Thickness and size of several graphite calorimetric bodies designed at NIST for use at
specific electron energies . 3
Table 2 Measurement uncertainties of routine polystyrene calorimeters from Risø High Dose
Reference Laboratory (in percent, atk=2) . 7
© ISO/ASTM International 2003 – All rights reserved iii
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ISO/ASTM 51631:2003(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
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.
ASTM International is one of the world’s largest voluntary standards development organizations with global
participation from affected stakeholders. ASTM technical committees follow rigorous due process balloting
procedures.
A project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this project, ASTM Subcommittee E10.01,
Dosimetry for Radiation Processing, is responsible for the development and maintenance of these dosimetry
standards with unrestricted participation and input from appropriate ISO member bodies.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. Neither ISO nor ASTM International shall be held responsible for identifying any or all such patent
rights.
International Standard ISO/ASTM 51631 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear Energy.
Annexes A1 and A2 of this International Standard are for information only.
iv © ISO/ASTM International 2003 – All rights reserved
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ISO/ASTM 51631 – 2003(E)
Standard Practice for
Use of Calorimetric Dosimetry Systems for Electron Beam
1
Dose Measurements and Routine Dosimeter Calibration
This standard is issued under the fixed designation ISO/ASTM 51631; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision.
2
1. Scope Systems for Radiation Processing
51431 Practice for Dosimetry in Electron and Bremsstrahl-
1.1 This practice covers the preparation and use of semi-
2
ung Irradiation Facilities for Food Processing
adiabatic calorimeters for measurement of absorbed dose and
51649 Practice for Dosimetry in an Electron Beam Facility
routine dosimeter calibration when irradiated with electrons for
for Radiation Processing at Energies Between 300 keV
radiation processing applications. The calorimeters are either
2
and 25 MeV
transported by a conveyor past a scanned electron beam or are
51707 Guide for Estimating Uncertainties in Dosimetry for
stationary in a broadened beam.
2
Radiation Processing
1.2 This practice applies to electron beams in the energy
2.3 International Commission on Radiation Units and
range from 1.5 to 12 MeV.
3
Measurements (ICRU) Reports:
1.3 The absorbed dose range depends on the absorbing
ICRU Report 34 The Dosimetry of Pulsed Radiation
material and the irradiation and measurement conditions.
ICRU Report 35 Radiation Dosimetry: Electron Beams with
Minimum dose is approximately 100 Gy and maximum dose is
Energies Between 1 and 50 MeV
approximately 50 kGy.
ICRU Report 37 Stopping Powers for Electrons and
1.4 The average absorbed–dose rate range shall generally be
-1
Positrons
greater than 10 Gy·s .
ICRU Report 44 Tissue Substitutes in Radiation Dosimetry
1.5 The temperature range for use of these calorimeters
and Measurements
depends on the thermal resistance of the materials, on the
ICRU Report 60 Fundamental Quantities and Units for
calibrated range of the temperature sensor, and on the sensi-
Ionizing Radiation
tivity of the measurement device.
1.6 This standard does not purport to address all of the
3. Terminology
safety concerns, if any, associated with its use. It is the
3.1 Definitions:
responsibility of the user of this standard to establish appro-
3.1.1 adiabatic—no heat exchange with the surroundings.
priate safety and health practices and determine the applica-
3.1.2 calorimeter—assembly consisting of calorimetric
bility of regulatory limitations prior to use.
body (absorber), thermal insulation, and temperature sensor
2. Referenced documents with wiring.
3.1.3 calorimetric body— mass of material absorbing radia-
2.1 ASTM Standards:
tion energy and whose temperature is measured.
E 170 Terminology Relating to Radiation Measurements
2
3.1.4 endothermic reaction—chemical reaction that con-
and Dosimetry
sumes energy.
E 666 Practice for Calculating Absorbed Dose from Gamma
2
3.1.5 exothermic reaction—chemical reaction that releases
or X Radiation
energy.
E 668 Practice for Application of Thermoluminescence-
3.1.6 heat defect (thermal defect)—amount of energy re-
Dosimetry (TLD) Systems for Determining Absorbed Dose
2
leased or consumed by chemical reactions caused by the
in Radiation-Hardness Testing of Electronic Devices
absorption of radiation energy.
2.2 ISO/ASTM Standards:
3.1.7 primary-standard dosimeter—dosimeter of the high-
51261 Guide for Selection and Calibration of Dosimetry
est metrological quality, established and maintained as an
absorbed-dose standard by a national or international standards
1
organization.
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear
Technology and Applications and is the direct responsibility of Subcommittee 3.1.8 specific heat capacity—amount of energy required to
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
raise 1 kg of material by the temperature of 1 K.
ISO/TC 85/WG 3.
3.1.9 thermistor—electrical resistor with a well-defined re-
Current edition approved May 28, 2003. Published July 15, 2003. Originally
e1
lationship between resistance and temperature.
published as E 1631 – 94. ASTM E 1631 – 96 was adopted by ISO in 1998 with
the intermediate designation ISO 15568:1998(E). The present International Standard
ISO/ASTM 51631:2003(E) replaces ISO 15568 and is a major revision of the last
3
previous edition ISO/ASTM 51631–2002(E). Available from the Commission on Radiation Units and Measurements, 7910
2
Annual Book of ASTM Standards, Vol 12.02. Woodmont Ave., Suite 800, Bethesda, MD 20814, U.S.A.
© ISO/ASTM International 2003 – All rights reserved
1
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ISO/ASTM 51631 – 2003(E)
3.1.10 thermocouple—junction of two metals producing an cause it is known to be resistant to radiation (11) and because
electrical voltage with a well-defined relationship to junction no exo- or endothermic reactions take place (12).
temperature.
5. Interferences
3.1.11 transfer-standard dosimeter—dosimeter, often a
5.1 Extrapolation—The calorimeters described in this prac-
reference-standard dosimeter suitable for transport between
tice are not adiabatic, because of the exchange of heat with the
different locations, used to compare absorbed-dose measure-
surroundings or within the calorimeter assembly. The maxi-
ments.
mum temperature reached by the calorimetric body is different
3.2 Definitions of other terms used in this standard that
from the temperature that would have been reached in the
pertain to radiation measurement and dosimetry may be found
absence of that heat exchange. The temperature drifts before
in ASTM Terminology E 170. Definitions in E 170 are com-
and after irradiation are extrapolated to the midpoint of the
patible with ICRU 60; that document, therefore, may be used
irradiation period in order to determine the true temperature
as an alternative reference.
increase due to the absorbed dose.
4. Significance and use
5.2 Heat Defect—Chemical reactions in irradiated material
4.1 This practice is applicable to the use of a calorimeter for (resulting in what is called the heat defect or thermal defect)
the measurement of absorbed dose in electron beams, the may be endo- or exothermic and may lead to measurable
qualification of electron irradiation facilities, periodic checks temperature changes. In water, for example, these are respec-
of operating parameters of electron irradiation facilities, and tively deficient or excessive with respect to the temperature
calibration of other dosimeters in electron beams. increase due solely to the absorption of radiation energy in the
water. The extent of these effects depends on the purity or the
NOTE 1—For additional information of the use of dosimetry in electron
gas content of the water and on any chemical effects arising
accelerator facilities, see ISO/ASTM Practices 51431 and 51649, and
4
from the container of the water. At the absorbed doses and dose
ICRU Reports 34 and 35, and Refs (1-3).
rates usually encountered by these calorimeters, these effects
4.2 The calorimeters described in this practice are not
are not significant (3).
primary-standard dosimeters. They may be used as transfer-
5.3 Temperature Effects from Accelerator Structure—The
standard dosimeters or as internal standards at an electron
calorimeters are often irradiated on a conveyor used for passing
beam irradiation facility, or may be routine dosimeters used for
products and samples through the irradiation zone. Radiated
routine dose measurements. The calorimeters are calibrated by
heat from the mechanical structures of the irradiation facility
comparison with transfer-standard dosimeters.
and from the conveyor may contribute to the measured
4.3 The dose measurement is based on the measurement of
temperature increase in the calorimeters.
the temperature rise in an absorber (calorimetric body) irradi-
5.4 Thermal Equilibrium—The most reproducible results
ated by an electron beam. Different absorbing materials are
are obtained when the calorimeters are in thermal equilibrium
used, but the response is usually defined in terms of dose to
before irradiation.
water.
5.5 Other Materials—The temperature sensors, wires, etc.
4.4 The absorbed dose in other materials irradiated under
of the calorimeter represent foreign materials, which may
equivalent conditions may be calculated. Procedures for mak-
influence the temperature rise of the calorimetric body. These
ing such calculations are given in ASTM Practices E 666 and
components should be as small as possible.
E 668, ISO/ASTM Guide 51261, and Ref (1).
5.6 Dose Gradients—Dose gradients will exist within the
4.5 The average absorbed dose in the volume of the calori-
calorimetric body when it is irradiated with electrons. These
metric body is measured. Dose gradients may occur in this
gradients must be taken into account, for example, when other
volume and may have to be considered when estimating dose
dosimeters are calibrated by comparison with calorimeters.
in other materials.
4.6 The calorimetric bodies of the calorimeters described in
6. Apparatus
this practice are made from low atomic number materials. The
6.1 A Typical Graphite Calorimeter is a disc of graphite
electron fluences within these calorimetric bodies will be
placed in a thermally-insulating material such as foamed
approximately equal when irradiated with electron beams of
plastic (4-6). A calibrated thermistor or thermocouple is em-
1.5 MeV or higher. Calibration in terms of dose to water is
bedded inside the disc. See Fig. 1 for an example of such a
possible for these calorimeters.
calorimeter. Some typical examples of graphite disc thick-
4.6.1 Calorimeters for use at industrial electron accelerators
nesses and masses are listed in Table 1 (2).
have been constructed using graphite, polystyrene or a Petri
6.2 A Typical Water Calorimeter is a sealed polystyrene
dish filled with water as the calorimetric body (4-10). The
Petri dish filled with water and placed in thermally-insulating
thickness of the calorimetric body shall be less than the range
foamed plastic (4). A calibrated temperature sensor (ther-
of the electrons for the specified material.
mistor) is placed through the side of the dish into the water.
4.6.2 Polymeric materials other than polystyrene may be
6.3 A Typical Polystyrene Calorimeter is a polystyrene disc
used for calorimetric measurements. Polystyrene is used be-
placed in thermally-insulating foamed plastic. A calibrated
thermistor or thermocouple is imbedded inside the disc. The
4 dimension of the polystyrene disc may be similar to that of the
The boldface numbers in parentheses refer to the bibliography at the end of this
practice. graphite and water calorimeters (9). See Fig. 2 as an example
© ISO/ASTM International 2003 – All rights reserved
2
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ISO/ASTM 51631 – 2003(E)
TABLE 1 Thickness and size of several graphite calorimetric bodies designed at NIST for use at specific electron energies
Electron Range
Calorimeter Disc (30 mm diameter)
A
Electron
in Graphite
B
-3
Energy
Thickness Mass, g
density: 1.7 g cm
MeV
-2 -2
gcm cm g cm cm
4 2.32 1.36 0.84 0.49 5.9
5 2.91 1.71 1.05 0.62 7.5
6 3.48 2.05 1.25 0.74 8.9
8 4.59 2.70 1.65 0.97 11.7
10 5.66 3.33 2.04 1.20 14.4
11 6.17 3.63 2.22 1.31 15.7
12 6.68 3.93 2.40 1.41 16.9
A
This is the continuous-slowing-down approximation (CSDA) range r of electrons for a broad beam incident on a semi-infinite absorber. It is calculated from:
o
E 0!
~
r 5 ~1/ ~S/r! ! dE
*
0 tot
0
where:
E = the primary electron energy, and
0
(S/r) = the total mass stopping power at a given electron energy (1).
tot
B
The thicknesses specified are equal to 0.36 r .
o
FIG. 1 Example of a graphite calorimeter used at a 10-MeV
industrial electron accelerator (5)
of a 10 MeV-calorimeter. Fig. 3 shows an example of a
polystyrene calorimeter designed for use at 1.5 to 4 MeV
electron accelerators.
6.4 The thickness of the calorimetric body should be less
than the range of the irradiating electrons, typically not
1
exceeding ⁄3 of the range of the electrons for the specified
material. That will limit the variation of the dose gradients
within the calorimetric body.
6.5 Radiation-resistant components should be used for the
parts of the calorimeter that are exposed to the electron beam.
This also applies to insulation of electrical wires.
6.6 Good thermal contact must exist between the tempera-
ture sensor and the calorimetric body. For graphite and
polystyrene calorimeters, this can be assured by adding a small
amount of heat-conducting compound when mounting the
te
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