ISO 15556:1998

INTERNATIONAL Is0
STANDARD
First edition
1998-12-15
Guide for selection and calibration of
dosimetry systems for radiation processing
Guide de choix et d ’ktalonnage des appareils de mesure dosimktrique pour
le traitemen t par irradiation
Reference number
IS0 15556:1998(E)
IS0 15556:1998(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies
(IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 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 IS0 15556 was prepared by the American Society for Testing and Materials (ASTM)
Subcommittee E1O.O1 (as E 1261-94) and was adopted, under a special “fast-track procedure ”, by Technical
Committee lSO/TC 85, Nuclear energy, in parallel with its approval by the IS0 member bodies.
A new ISOfTC 85 Working Group WG 3, High-level dosimetry for radiation processing, was formed to review the
voting comments from the IS0 “Fast-track procedure” and to maintain these standards. The USA holds the
convenership of this working group.
International Standard IS0 15556 is one of 20 standards developed and published by ASTM. The 20 fast-tracked
standards and their associated ASTM designations are listed below:
IS0 Designation ASTM Designation Title
Practice for dosimetry in gamma irradiation facilities for food
15554 E 1204-93
processing
Practice for use of a ceric-cerous sulfate dosimetry system
15555 E 1205-93
15556 E 1261-94 Guide for selection and calibration of dosimetry systems for
radiation processing
15557 E 1275-93 Practice for use of a radiochromic film dosimetry system
15558 E 1276-96 Practice for use of a polymethylmethacrylate dosimetry system
E 1310-94 Practice for use of a radiochromic optical waveguide dosimetry
system
E 1400-95a Practice for characterization and performance of a high-dose
radiation dosimetry calibration laboratory
15561 E 1401-96 Practice for use of a dichromate dosimetry system
0 IS0 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet iso @ isoch
Printed in Switzerland
ii
0 IS0 IS0 15556:1998(E)
Practice for dosimetry in electron and bremss tra hlung irradiation
15562 E 1431-w
facilities for food processing
15563 E 1538-93 Practice for use of the ethanol-chlorobenzene dosimetry system
Guide for use of radiation-sensitive indicators
15564 E 1539-93
15565 E 1540-93 Practice for use of a radiochromic liquid dosimetry system
Practice for use of the alanine-EPR dosimetry system
15566 E 1607-94
15567 E 1608-94 Practice for dosimetry in an X-ray (bremsstrahlung) facility for
radiation processing
for electron
Practice for use of calorimetric dosimetry systems
15568 E 1631-96
beam dose measurements and dosimeter calibrations
Practice for dosimetry in an electron-beam facility for radiation
15569 E 1649-94
processing at energies between 300 keV and 25 MeV
Practice for use of cellulose acetate dosimetry system
15570 E1650-94
15571 E 1702-95 Practice for dosimetry in a gamma irradiation facility for radiation
processing
15572 E 1707-95 Guide for estimating uncertainties in dosimetry for radiation
processing
15573 E 1818-96 Practice for dosimetry in an electron-beam facility for radiation
processing at energies between 80 keV and 300 keV
. . .
III
0 IS0 IS0 15556: 1998(E)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
Designation: E 1261 - 94
1916 Race St. Philadelphia, Pa 19103
ASTM
Reprinted from the Annual Book of ASTM Standards. Copyright
edition.
If not listed in the current combined index, will appear in the next
Standard Guide for
Selection and Calibration of Dosimetry Systems for
Radiation Processing’
This standard is issued under the fixed designation E 126 1; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope E 1205 Practice for Use of a Ceric-Cerous Sulfate
Dosimetry System2
1.1 This guide provides the basis for selecting and cali-
E
1275 Practice for Use of a Radiochromic Film
brating dosimetry systems used to measure absorbed dose in
Dosimetry System2
gamma-ray or X-ray fields and in electron beams used for
E 1276 Practice for Use of a Polymethylmethacrylate
radiation processing. It discusses the types of dosimetry
Dosimetry System2
systems that may be employed during calibration or on a
E 13 10 Practice for Use of a Radiochromic Optical
routine basis as part of quality assurance in commercial
Waveguide Dosimetry System2
radiation processing of products. This guide also discusses
E
1400 Practice for Characterization and Performance of a
interpretation of absorbed dose and briefly outlines the
High-Dose Radiation Dosimetry Calibration Labo-
uncertainties associated with the dosimetry measurements.
ratory2
The details of the calibration of the analytical instrumenta-
E 140 1 Practice for Use of a Dichromate Dosimetry
tion are addressed in individual dosimetry system standard
System2
practices.
E 143 1 Practice for Dosimetry in Electron and Brems-
1.2 The absorbed-dose range covered is from about 1 Gy
strahlung Irradiation Facilities for Food Processing2
(100 rad) to 1 MGy (100 Mrad). Source energies covered are
E 1538 Practice for Use of the Ethanol-Chlorobenzene
from 0.1 to 50 MeV photons and electrons.
1.3 Standard practices and guides for specific dosimetry Dosimetry System2
systems and applications are covered in other standards. E 1540 Practice for Use of a Radiochromic Liquid
Dosimetry for radiation processing with neutrons or heavy Dosimetry System2
charged particles is not covered in this guide. E 1607 Practice for Use of the Alanine-EPR Dosimetry
1.4 This standard does not purport to address all of the System2
safity concerns, zj’ any, associated with its use. It is the E 163 1 Practice for Use of Calorimetric Dosimetry Sys-
responsibility of the user ofthis standard to establish appro- tems for Electron Beam Dose Measurements and Do-
priate safety and health practices and determine the applica- simeter Calibrations2
bility of regulatory limitations prior to use. 2.2 International Commission on Radiation Units and
Measurements Reports:
ICRU Report 14 Radiation Dosimetry: X-rays and
2. Referenced Documents
Gamma rays with Maximum Photon Energies Between
0.6 and 50 MeV4
2.1 ASTM Standards:
ICRU Report 17 Radiation Dosimetry: X-rays Generated
170 Terminology Relating to Radiation Measurements
at Potentials of 5 to 150 kV4
and Dosimetry2
ICRU Report 33 Radiation Quantities and Units4
178 Practice for Dealing with Outlying Observations3
ICRU Report 34 The Dosimetry of Pulsed Radiation4
666 Practice for Calculating Absorbed Dose from
ICRU Report 35 Radiation Dosimetry: Electron Beams
Gamma or X Radiation2
with Energies between 1 and 50 MeV4
668 Practice for the Application of Thermolumi-
ICRU Report 37 Stopping Powers for Electrons and
nescence-Dosimetry (TLD) Systems for Determining
Positrons4
Absorbed Dose in Radiation-Hardness Testing of Elec-
tronic Devices2
1026 Practice for Using the Fricke Reference Standard
3. Terminology
Dosimetry System2
3.1 Descriptions of Terms Specific to This Standard:
1204 Practice for Dosimetry in Gamma Irradiation
3.1.1 accredited dosimetry calibration laboratory-a labo-
Facilities for Food Processing2
ratory that meets specific performance criteria and has been
tested and approved by a recognized accrediting organiza-
I This guide is under the jurisdiction of ASTM Committee E- 10 on Nuclear
tion.
Technology and Applications and is the direct responsibility of Subcommittee
3.1.2 calibration curve-graphical or mathematical rela-
E1O.O 1 on Dosimetry for Radiation Processing.
Current edition approved Sept. 15, 1994. Published November 1994. Originally
published as E 126 1 - 88% Last previous edition E 1261 - 88?
2 Annual Book of ASTM Standurds, Vol 12.02.
* Available from International Commission on Radiation Units and Measure-
3 Annual Book of ASTM Standards, Vol 14.02. ments, 79 10 Woodmont Ave., Suite 800, Bethesda, MD 208
14.
IS0 15556:1998(E) @ IS0
3.2 Other terms used in this guide may be found in
tionship between dosimeter response and absorbed dose for a
Terminology E 170, ICRU Report 33, and Ref (l)?
given dosimetry system.
DIscussroN-This term is also referred to as the response function.
4. Significance and Use
4.1 Ionizing radiation is used to produce various desired
3.1.3 calibration facility-combination of an ionizing ra-
effects in products. Examples include the sterilization of
diation source and its associated instrumentation that pro-
medical products, processing of food, modification of poly-
vides uniform and reproducible absorbed-dose rates at spe-
mers, irradiation of electronic devices, and curing of inks,
cific locations in a specific material traceable to national
coatings, and adhesives (2,3). The absorbed doses employed
standards, and therefore, may be used to calibrate the
vary according to the application. The doses cover a range
absorbed-dose response of routine or other types of dosime-
from about 10 Gy to more than 100 kGy.
ters.
4.2 Regulations for sterilization of medical products and
3.1.4 dosimeter batch--quantity of dosimeters made from
radiation processing of food exist in many countries. These
a specific mass of material with uniform composition,
regulations may require that the response of the dosimetry
fabricated in a single production run under controlled,
system be calibrated and traceable to national standards (4,
consistent conditions, and having a unique identification
5, 6). Adequate dosimetry, with proper statistical controls
code.
and documentation, is necessary to ensure that the products
3.15 dosimetry system- system used to determine ab-
are properly processed. ’
sorbed dose, consisting of dosimeters, measurement instru-
4.3 Proper dosimetric measurements must be employed
ments and their associated reference standards, and proce-
to ensure that the product receives the desired absorbed dose.
dures for the system ’s use.
The dosimeters must be calibrated. Calibration of a routine
3.1.6 electron equilibrium-a condition that exists in
dosimetry system can be carried out directly in a national or
material under irradiation when the energies, number, and
secondary standards laboratory by standardized irradiation
direction of electrons induced by the radiation are constant
of routine dosimeters. It may be carried out through the use
throughout the volume of interest; thus, within such a
of a local (in-house) calibration facility (7) or in a production
volume, the sum of the energies of the electrons entering it is
irradiator. All possible factors that may affect the response of
equal to the sum of the energies of all the electrons leaving it.
dosimeters, including environmental conditions and varia-
3.1.7 measurement quality assurance plan-a docu-
tions of such conditions within a processing facility, should
mented program for a measurement process that quantifies
be known and taken into account. The associated analytical
the total uncertainty of the measurement (both random and
instrumentation must also be calibrated.
non-random components); this plan shall demonstrate trace-
ability to national standards, and shall show that the total
5. Dosimeter Classes and Applications
uncertainty meets the requirements of the specific applica-
tion.
5.1 Dosimeters may be divided into four basic classes in
3.1.8 primary standard dosimeter-dosimeter, of the
accordance with their relative quality and areas of applica-
highest metrological quality, established and maintained as
tions (see Section 3).
an absorbed dose standard by a national or international
5.1.1 Primary Standard Dosimeter-Primary standard
standards organization.
dosimeters are established and maintained by national stan-
3.1.9 quality assurance- all systematic actions necessary
dards laboratories for calibration of radiation fields. The two
to provide adequate confidence that a measurement is
most commonly used primary standard dosimeters are
performed to a predefined level of quality.
ionization chambers and calorimeters (for details, see ICRU
3.1.10 reference standard dosimeter-dosimeter, of high
Reports 14, 17, 34, and 35).
metrological quality, used as a standard to provide measure-
5.1.2 Reference Standard Dosimeter-Reference standard
ments traceable to, and consistent with, measurements made
dosimeters are used to calibrate radiation fields and routine
using primary standard dosimeters.
dosimeters. A widely used reference dosimeter is the ferrous
3.1.11 routine dosimeter-dosimeter calibrated against a
sulfate (Fricke) aqueous solution (see Practice E 1026).
primary, reference, or transfer standard dosimeter and used
Examples of reference dosimeters are listed in Table 1; more
for routine dosimetry measurements.
details of the characteristics of several systems may be found
3.1.12 simulated product-mass of material with attenua-
in Appendix X3.
tion and scattering properties similar to those of a particular
5.1.3 Routine Dosimeters-Examples of routine dosime-
material or combination of materials.
ters are listed in Table 2; more details of the characteristics of
several of these systems may be found in Appendix X3.
DIscussroN-This term is sometimes referred to as dummy product.
5.1.4 Transfer Standard Dosimeters-Transfer standard
dosimeters are specially selected dosimeters used for transfer-
3.1.13 stock-part of a batch held by the user.
ring dose information from an accredited or national stan-
3.1.14 traceability-the ability to show that a measure-
dards laboratory to a local irradiation facility in order to
ment is consistent with appropriate national or international
establish traceability for the local calibration facility. Nor-
standards through an unbroken chain of comparisons.
mally, these dosimeters are used under conditions that are
3.1.15 transfer standard dosimeter-dosimeter, often a
reference standard dosimeter, intended for transport between
different locations for use as an intermediary to compare
s The boldface numbers in parentheses refer to the list of references at the end
absorbed dose measurements. of this guide.
0 IS0 IS0 15556: 1998(E)
E 1261
TABLE 1 Examples of Reference Standard Dosimeters dosimeter, or if correction factors can be applied to bring the dosimeter ’s
response into conformity within the necessary limits of uncertainty for
Useful Absorbed Refer-
Dosimeter Readout System
the application.
Dose, Gy encesA
102 to 105 0
Calorimeter Thermometer
EPR spectrometer 1 to 105
Alanine 6. Criteria for Selection of Routine Dosimetry Systems
Ceric-cerous sulfate W spectrophotometer or lo3 to 1 O5 10,ll
6.1 The selection of an appropriate dosimetry system
electrochemical
solution
potentiometer
requires matching its performance with the specific appiica-
10 to 2 x 1 O6 12,13
Ethanol-chlorobenzene Spectrophotometer, color
tion criteria. The following operational criteria should be
solution titration, high frequency
considered in selecting a suitable dosimetry system.
conductivity
Ferrous sulfate solution UV spectrophotometer 20 to 4 x lo2
NOTE 2-Availability of adequate information on the performance
103 to 105 15
Potassium/silver W/visible
characteristics of the dosimetry systems should be considered in
dichromate spectrophotometer
selecting a dosimetry system.
A These references are not exhaustive; others may be found in the literature.
6.1.1 Suitability of the dosimeter for the absorbed-dose
range of interest and for use with a specific product,
TABLE 2 Examples of Routine Dosimeters
6.1.2 Stability and reproducibility of the system,
Useful Absorbed Refer-
6.1.3 Ease of system calibration,
Readout System
Dosimeter
Dose, Gy encesA
6.1.4 Traceability of system calibration to national stan-
Alanine EPR spectrometer 1 to 105 9
dards,
Dyed polymethylmeth- Visible spectropho- 103 to 5 x 10’ 16, 17, 10
6.1.5 Ability to control or correct system response for
acrylate tometer
Clear polymethylmeth- W spectrophotometer 103 to lo5 16,19 systematic errors, such as those caused by temperature and
acrylate
humidity,
Cellulose triacetate Spectrophotometer 10’ to 4 x lo5 20
6.1.6 Ease and simplicity of use,
Lithium borate, lithium Thermoluminescence lo- ‘to 103 21
6.1.7 Availability of dosimeters in reasonably large quan-
reader
fluoride
Lithium fluoride (optical W/Visible spectropho- 102 to 106 22
tities,
grade) tometer
6.1.8 Overall initial and operational cost of the system,
Visible spectropho- 1 to 105 23,24, 25
Radiochromic dye films,
including dosimeters, readout equipment, and labor,
solutions, papers, tometer
optical wave guide
6.1.9 Time required for dosimeter response development,
1p to 105 10
Ceric-cerous sulfate Potentiometer or UV
and labor required for dosimeter readout and interpretation,
solution spectrophotometer
6.1.10 Ruggedness of the system-resistance to damage
Ferrous-cupric sulfate 103 to 5 x 103 26
UV spectrophotometer
during routine handling and use in a processing environ-
solution
Ethanol-chlorobenzene Spectrophotometer, color 102 to 105 13
ment,
titration, high-fre-
solution
6.1.11 Variance of the dosimetry system response data
quency conductivity
within established limits about a fitted calibration curve over
Amino acids 10-5 to 10’ 27
Lyoluminescence reader
the absorbed-dose range of interest. Suitable regression
A These references are not exhaustive; others may be found in the literature.
analysis methods should be used to fit the curve, and could
include linear, polynomial, or exponential functions,
carefully controlled by the issuing laboratory. They are
6.1.12 Dependence of dosimeter response on environ-
selected from the list of available reference standard dosime-
mental conditions (such as temperature, humidity, and light)
ters (Table 1) or routine dosimeters (Table 2) that have
before, during, and after calibration and production irradia-
characteristics listed in Table 3 that meet the required
tion. Effects of environmental conditions on the dosimeter
application requirements. In addition to the references given
readout equipment shall also be considered,
in Tables 1 and 2, relevant information on some other types
6.1.13 Dependence of dosimeter response on absorbed-
of dosimeters may be found in Practices E 668, E 1275, and
dose rate or incremental delivery of absorbed dose, or both,
E 1276.
6.1.14 Stability of dosimeter response both before and
NOTE l-None of the reference standard dosimeters or routine after irradiation,
dosimeter listed have all of the desirable characteristics given in Table 3
6.1.15 Variation of dosimeter response within a batch or
for an “ideal” transfer standard dosimeter. However, such dosimeters
between batches,
may be used as transfer standard dosimeters if the absence of one or
6.1.16 Effects of size, location, and composition of the
more desirable characteristics has negligible effect on the response of the
dosimeter on the radiation field or the interpretation of the
absorbed-dose measurement. In cases where it is desirable to
TABLE 3 Characteristics of Transfer Standard Dosimeters
measure absorbed dose at the interface of different materials
Long shelf life
(for example, at a bone-tissue interface or the surface of a
Easily calibrated
product), dosimeters should be used that are thin compared
Stable
Portable to distances over which the absorbed-dose gradient is signif-
Mailable
icant, and
Broad absorbed-dose range
6.1.17 Effects of differences in radiation energy spectra
Radiation absorption properties similar to those of irradiated product
between calibration and product irradiation fields.
Relatively insensitive to extremes of environmental conditions
Correctable systematic errors (for example, temperature, humidity, etc.)
Produced in reproducible lots
7. Analytical Instrument Performance
Small dimensions compared to distances over which absorbed-dose gradients
become significant
7.1 Check the performance of the analytical instrumenta-
IS0 15556:1998(E)
0 IS0
#) ‘l E 1261
NOTE 5-The response of some routine dosimeters may be affected
tion prior to the reading of dosimeters irradiated for a
by the combined effect of several environmental factors such as
dosimetry system calibration.
temperature, absorbed-dose rate, energy spectrum, and relative hu-
7.1.1 Check the analytical instrumentation in accordance
midity, including possible seasonal variations of some of these factors.
with documented procedures (for example, the operating
For these cases, it may not be possible to take these combined effects
manual) to ensure that the instrument is functioning in
into account by applying a correction factor. To ensure that the
accordance with appropriate performance specifications.
calibration curve is valid for the conditions of use, the calibration of
routine dosimeters should be performed using irradiation conditions
7.1.1.1 For optical absorbance measurements using a
similar to those in the actual production irradiator and verified prior to
spectrophotometer, check and document that the wavelength
use.
and absorbance scales are within the documented specifica-
tions at or near the analysis wavelength using optical density
8.1.3.1 The calibration of routine dosimeters using a
filters and wavelength standards traceable to national stan-
gamma, electron beam, or X-ray calibration facility meeting
dards.
the requirements of Practice E 1400 has the advantage that
7.1.1.2 For thickness measurements using a thickness
the dosimeters are irradiated to accurately known absorbed
gage, check and document that the instrument is within
doses under well-controlled and documented conditions.
documented specifications using gage blocks traceable to
However, use of these routine dosimeters under different
national standards.
environmental conditions in a production irradiator may
7.2 For some analytical instrumentation, correct perfor-
introduce uncertainties that are difficult to quantify. Trans-
mance can be demonstrated by showing that the readings of
porting of the dosimeters to and from the calibration facility
dosimeters given known absorbed doses are in agreement
may also introduce uncertainties from pre- and post-irradi-
with the expected readings within the limits of the dosimetry
ation storage effects.
system uncertainty.
8.1.3.2 The calibration of routine dosimeters using an
in-house calibration facility has the advantage that the pre-
8. Dosimetry System Calibration
and post-irradiation storage conditions of the dosimeters can
be controlled so that they are similar to those encountered
8.1 General:
during routine production. However, it may not be possible
8.1.1 The calibration of a dosimetry system consists of the
for the in-house calibration facility to meet all the irradiation
irradiation of dosimeters to a number of known absorbed
requirements of Practice E 1400. In addition, use of transfer
doses over the range of use, analysis of the dosimeters using
standard dosimeters is required to provide traceability to
calibrated analytical equipment, and the generation of a
national standards.
calibration curve. Calibration verification is performed peri-
8.1.3.3 The calibration of routine dosimeters by irradia-
odically to confirm the continued validity of the calibration
tion of the dosimeters together with reference or transfer
curve.
standard dosimeters in the production irradiator has the
8.1.2 The calibration of reference or transfer standard
advantage that the environmetal conditions are similar to
dosimeters shall be performed using a calibration facility that
those encountered during routine production, reducing the
has an absorbed-dose rate traceable to national standards.
requirement to make corrections for the routine dosimeter
Gamma calibration facilities shall meet the requirements
for environmental effects. However, great care must be taken
specified in Practice E 1400. Electron beam and X-ray
to ensure that the routine and reference or transfer standard
(bremsstrahlung) calibration facilities should meet similar
dosimeters irradiated together receive the same absorbed
requirements.
dose (23).
NOTE 3-In several countries, the national standard is realized
8.2 Analytical Instrument Calibration:
indirectly through a calibrated radiation field. For example, the ab-
8.2.1 Analytical instrumentation shall be calibrated annu-
sorbed-dose rate in the center of a 6oCo source array at the U.S. National
ally in accordance with written procedures by qualified
Institute of Standards and Technology (NIST) has been well character-
individuals.
ized by calorimetry and is one of the national standards used by NIST to
irradiate reference standard, transfer standard, and routine dosimeters to 8.2.2 Calibration should provide traceability and consis-
known absorbed-dose levels.
tency to national standards if available.
NOTE 4-The response of reference and transfer standard dosimeters
8.2.3 Verification of the calibration curve shall be per-
to environmental effects such as temperature and relative humidity,
formed if any maintenance or modification of the analytical
absorbed-dose rate, and energy spectrum, should be documented.
instrumentation occurs that may affect its performance. In
Differences in the dosimeter response between calibration and use
this case, it shall be demonstrated that the measurements of
conditions should be taken into account using known correction factors.
dosimeter response are within specified limits over the full
8.1.3 The calibration of routine dosimeters can be per- dose range.
formed in three different ways. One way (described in 8.3) 8.3 Irradiation of Dosimeters Using a Calibration Fa-
calls for routine dosimeters to be irradiated in a gamma, cilit y:
electron beam, or X-ray (bremsstrahlung) calibration facility 8.3.1 Irradiate reference standard, transfer standard, or
meeting the requirements of Practice E 1400. The second routine dosimeters to known absorbed doses in a national
way (described in 8.4) calls for routine dosimeters to be calibration facility or a calibration facility that has an
irradiated in an in-house calibration facility that has an absorbed-dose rate traceable to national standards. Gamma,
absorbed-dose rate measured by reference or transfer stan- electron beam, or X-ray calibration facilities shall meet the
dard dosimeters. The third way (described in 8.5) calls for requirements specified in Practice E 1400,
routine dosimeters to be irradiated together with reference or 8.3.2 Calibrate routine dosimeters using irradiation condi-
tions similar to those in the actual production irradiator.
transfer standard dosimeters in the production irradiator.
IS0 15556:1998(E)
@ IS0
Employ an energy spectrum, absorbed-dose rate, and irradi- conversion factors for calculating the absorbed dose in
ation temperature as close as practical to those encountered different materials.
during routine use. 8.3.14 Consider the possibility of combined environ-
.
8.3.3 Adverse environmental conditions (such as high or
mental effects (see Note 5).
low temperature and humidity) during transport of the
* 8.4 Irradiation ofDosimeters Using an In-House Calibra-
dosimeters to and from the calibration facility may affect the
t ion Facility:
dosimeter response.
8.4.1 Routine dosimetry systems may be calibrated by
8.3.4 Package dosimeters to minimize the effects of envi-
irradiating dosimeters in an in-house calibration facility.
ronmental conditions during transport.
8.4.2 The absorbed-dose rate in the in-house calibration
8.3.5 Environmental monitors such as maximum temper-
facility shall be demonstrated to be traceable to appropriate
ature indicators may be included in the dosimeter package
national standards by direct measurement intercomparisons
during transport to document environmental extremes.
or calibrations using transfer standard dosimeters supplied
8.3.6 Confirm that the environmental conditions during
by a nationally recognized radiation dosimetry calibration
transfer have not changed the response of the dosimeter.
laboratory.
This may be achieved by sending dosimeters irradiated to
8.4.3 Measurement intercomparisons or calibrations of
known absorbed doses along with the dosimeters sent for
absorbed-dose rates of the in-house calibration facility shall
calibration. The readings of the two sets of dosimeters should
be performed at least once every three years and after any
be compared when they are returned with readings from
change in source activity or geometry.
additional dosimeters given the same absorbed dose and
8.4.4 Procedures, protocols, and training of personnel
stored under controlled conditions.
shall be provided to ensure that the correct absorbed dose is
8.3.7 Position the dosimeters in the calibration radiation
given to dosimeters.
field in a defined, reproducible location. The variation in
8.4.5 All criteria given in 8.3.2 to 8.3.14 shall be met.
absorbed-dose rate within the volume occupied by the
8.4.6 Calibration of routine dosimeters in an in-house
dosimeters should be within tl %.
calibration facility reduces the possibility of changes in the
8.3.8 When using a gamma-ray source or X-ray beam for
response due to adverse storage conditions during transport
calibration, surround the dosimeter with a sufficient amount
of dosimeters. After irradiation, dosimeters should be stored
of material to achieve approximate electron equilibrium
under similar conditions to those encountered in the produc-
conditions (28).
tion irradiator and read at approximately the same time after
NOTE 6-The appropriate thickness of such material depends on the
irradiation as the dosimeters used in routine dosimetry.
energy of the radiation (see Practices E 666 and E 668). For measure-
8.5 Irradiation of Dosimeters Using a Production Irradi-
ment of absorbed dose in water, use materials that have radiation-
ator:
absorption properties essentially equivalent to water. For example, for a
8.5.1 Calibration of routine dosimeters in the production
6oCo source, 3 to 5 mm of polystyrene (or equivalent polymeric
material) should surround the dosimeter in all directions.
irradiator using reference or transfer standard dosimeters
provides a calibration curve valid for the actual production
8.3.9 Control or monitor the temperature during gamma
irradiation conditions existing during the calibration. This
irradiation of the dosimeters.
method takes combined environmental factors into account
NOTE 7-It may be diflicult to control or monitor the temperature of
to the extent that the reference or transfer dosimeter re-
the dosimeter during electron or X-ray irradiation.
sponse can be corrected for differences in environmental
factors between the calibration facility and production irra-
8.3.10 If the response of the dosimeters is affected by
diator.
humidity and they are not sealed, control or monitor the
8.5.2 Use reference or transfer standard dosimeters sup-
relative humidity during irradiation.
plied and analyzed by a nationally recognized radiation
8.3.11 For each absorbed dose point, use the number of
dosimetry calibration laboratory to demonstrate traceability
dosimeters required to achieve the desired confidence level
to national standards.
(see Section 9 of Practice E 668).
8.5.3 Reference or transfer standard dosimeters obtained
8.3.12 The number of sets of dosimeters required to
determine the calibration curve of the dosimetry system commercially or prepared in accordance with published
depends on the absorbed-dose range of utilization. Use at standards and analyzed on site may be used provided that
least five sets for each factor of ten span of absorbed dose, or the reference or transfer standard dosimetry systems have
at least four sets if the range of utilization is less than a factor been calibrated in accordance with 8.1.
of ten. 8.5.4 Calibrate routine dosimeters by irradiating them
together with reference or transfer standard dosimeters under
NOTE ~-TO determine mathematically the minimum number of
actual production irradiation conditions over the entire
sets to be used, divide the maximum dose in the range of utilization
range of normal use. Ensure that the routine and reference or
(D,,,) by the minimum dose (Dmin), then, calculate log(base 10) of this
ratio: Q = lOg(D,,,/D,i ”), If Q is less than 1, use a minimum of four transfer standard dosimeters receive the same absorbed dose.
sets. If Q is equal to or greater than 1, calculate the multiple 5 X Q, and
8.5.5 Design a calibration package to ensure that the
round this to the nearest integer value. This value represents the
dosimeters do not shield each other significantly during
minimum number of sets to be used.
irradiation. The calibration package shall contain the
8.3.13 Specify the calibration dose in terms of the mate- number of routine dosimeters required to achieve the desired
rial of interest. The calibration dose is usually specified in confidence level and one or more reference or transfer
terms of absorbed dose in water. See Appendix X 1 for standard dosimeter (see Section 9 of Practice E 668).
0 IS0
IS0 15556:1998(E)
NOTE g-This absorbed dose variation can be confirmed by irradi- 8.7.5 Repeat this calibration procedure to the extent
ating calibration packages containing one type of dosimeter in all
necessary if any response value exceeds accepted statistical
dosimeter positions within the calibration package.
limits of the determined curve, and if discarding this value
would result in there being insufficient data to adequately
8.5.5.1 For gamma or X-ray sources, the calibration
define the curve (see Practice E 178 for guidance on dealing
package should provide a sufficient thickness of water-
with outliers).
equivalent material to achieve approximate electron equilib-
8.8 Calibration Verification.
rium conditions (see Note 6).
8.8.1 Verify that calibration curves for routine dosimetry
8.5.5.2 When thick and thin dosimeters are irradiated
together, surround the thin dosimeters by sufficient poly- systems obtained by irradiating dosimeters in a dosimetry
calibration facility or in an in-house calibration facility are
meric material to ensure that the attenuation characteristics
valid for the actual conditions of use in the production
are similar and to ensure that the dosimeters receive the
facility.
same dose.
8.5.6 To calibrate the dosimeters under conditions similar 8.8.2 Calibration verification may be performed by irradi-
to those used for processing, place the calibration packages ating the routine dosimeters together with reference standard
or transfer standard dosimeters to three different absorbed
with product or simulated product in volumes where the
doses in the production irradiator. The reference standard or
absorbed-dose variation over the area containing dosimeters
is within specified limits.
transfer standard dosimeters should be of a different type
8.5.7 Use a sufficient number of routine and reference or than the routine dosimeters, to reduce the probability that
transfer standard dosimeters to give statistically significant both types of dosimeters are influenced by the same com-
results. Irradiate at least five calibration packages to different bined environmental effects. Ensure that the routine and
absorbed doses covering the absorbed-dose range of utiliza- reference standard or transfer standard dosimeters receive
tion for each factor of ten span of absorbed dose (see Note 8).
the same absorbed dose (see 8.5.5 for guidance).
8.8.3 Compare absorbed-dose values obtained from the
NOTE lo-The absorbed-dose rate, temperature, and energy spec-
calibration curve with the absorbed doses measured by the
trum may vary depending on the location of the dosimeter on or in the
irradiation unit. These factors may have to be considered when reference standard or transfer standard dosimeters.
evaluating overall dosimeter uncertainties during routine use.
8.8.3.1 If the difference between the transfer standard and
routine dosimeter measurement of absorbed dose exceeds
8.6 Dosimeter Analysis.
the estimated combined uncertainty in the two systems
8.6.1 Analyze dosimeters using analytical instrumentation
exclusive of environmental effects, the calibration curve may
with calibration traceable to national standards.
be adjusted by a constant factor to give agreement with the
8.6.2 Check the performance of the analytical instrumen-
reference or transfer standard dosimeters.
tation (see 7.1).
8.8.3.2 If the difference varies significantly at different
8.6.3 If the dosimeter response changes with time after
absorbed doses, recalibration using the method described in
irradiation, analyze dosimeters at approximately the time
8.5 may be necessary.
after irradiation when dosimeters will be analyzed during
8.8.4 Calibration curves supplied by a manufacturer shall
routine production.
not be used.
8.6.4 Document and retain all analysis data.
8.8.5 Calibration curves generated by one analytical in-
8.7 Calibration Curve:
strument shall not be used for another instrument unless it
8.7.1 Calculate and document the mean response, E, and
has been demonstrated that the measurements of the dosim-
the sample standard deviation (&-- J for each set of dosime-
eters’ response is within specified limits over the full ab-
ters at each absorbed-dose value. The sample standard
is calculated from the sample data set of n sorbed dose range.
deviation, S,,- ],
8.9 Absorbed-Dose Rate EfSects.
values as follows:
8.9.1 For some routine dosimetry systems, the dosimeter
response at different absorbed-dose rates for the same given
sn-, = JT
(1)
absorbed dose may differ over portions of the system ’s
working range. In these portions, the higher absorbed-dose
where ki = ith value of k.
rate response may diverge from the lower absorbed-dose rate
8.7.2 Calculate the coefficients of variation, CV, for each
response. This divergence may be dependent on several
absorbed dose value as follows:
factors, such as the absorbed dose and type of radiation
s-
(gamma, electron beam, or X ray). In these divergence tests,
CV= -y x lOO(%)
(2)
other factors that could influence dosimeter response, for
NOTE 1 l-In general, if any CV values are greater than 2 %, then a
example irradiation temperature, should be either fixed or
redetermination of the data should be considered, or the stock of
kept within a narrow range. The divergence may be checked
dosimeters should be rejected.
by several methods.
8.9.2 As appropriate for the intended application, irra-
8.7.3 Graphically plot dosimeter response versus absorbed
dose, or use a suitable computer code, or both, to derive this diate dosimeters using gamma, electron beam, or X-ray
relationship in mathematical form. Choose an analytical facilities with absorbed-dose rates that span the range ex-
form (for example, linear, polynomial, or exponential) that pected in the production facility. Irradiate the dosimeters to
provides an appropriate fit to the measured data. the same absorbed dose at two or more dose rates. Repeat
8.7.4 Examine the resulting calibration curve for goodness this process for several absorbed doses to the highest ab-
of fit within specified limits. sorbed dose of interest. Compare the resultant responses of
IS0 15556: 1998(E)
@ IS0
d&’ E 1261
dosimeters placed throughout the product under actual
the dosimeters. Divergence of the response curves provides
processing conditions. This particularly is the case near
an indication of the magnitude of the absorbed-dose rate
interfaces of different materials, for example, at bone-tissue
effect.
interfaces or on the surface of a product package. Absorbed-
NOTE 12-This effect may vary for each batch of routine dosimeters.
dose measured under non-equilibrium conditions is some-
8.9.3 For dosimetry systems known to have negligible
times used to monitor the absorbed dose within the product
absorbed-dose rate dependence in the low absorbed-dose using the procedures described in Practices E 1204 and
portion, irradiate the dosimeters in a gamma, electron beam,
E 1431.
or X-ray production facility to an absorbed dose in the low
absorbed-dose portion of the working range of the dosimetry
10. Minimum Documentation Requirements
system. Interpret the absorbed dose using the calibration
10.1 Record the routine dosimetry system used with each
curve obtained from dosimeters irradiated at a dosimetry
product irradiated. Identify the dosimeter manufacturer,
calibration facility. Change the production facility irradiation
type and batch number, and instruments used for analysis.
parameters (for example, conveyor speed, electron beam
10.2 Record the dosimeter calibration data, including
current, or dwell time) to increase the absorbed dose.
date, reference standard or transfer standard, and description
Compare the resultant dosimeter response curve to the
of the facility used.
original calibration curve. The resultant response curve may
10.3 Record or reference a description of the radiation
show divergence from the calibration curve as the absorbed
source used in processing, including the type, nominal
dose increases. The resultant response curve can be related to
activity or beam parameters, and any available information
the original calibration curve at low absorbed doses to
on the energy spectrum.
provide corrected response at higher absorbed doses.
10.4 Record the irradiation environmental conditions for
8.10 Frequency of Calibration:
the routine dosimeter, including temperature, pressure (if
8.10.1 Calibrate the dosimetry system for each new batch
other than atmospheric), relative humidity, and surrounding
of reference standard, transfer standard, or routine dosime-
atmosphere (if other than air).
ters prior to use.
10.5 Record or reference the method used to convert
8.10.1.1 At an interval not exceeding one year, re-cali-
dosimetry measurements to absorbed-dose values in water or
brate the dosimetry system for each batch of reference
the product (see Section 9).
standard, transfer standard, or routine dosimeters. This
10.6 Record the value and the assigned uncertainty of the
re-calibration shall include the analytical instrumentation.
absorbed dose to the product for each irradiation.
Depending on seasonal variations in ambient conditions (for
10.7 Record or reference the measurement quality assur-
example, temperature and relative humidity) the interval of
ance plan used for the routine dosimetry.
re-calibration may have to be decreased (see Note 5).
8.10.2 Check the calibration of the dosimetry system for
11. Precision and Bias
each new stock of reference standard or transfer standard
11.1 To be meanin
...