ISO/ASTM 51276:2002
(Main)Practice for use of a polymethylmethacrylate dosimetry system
Practice for use of a polymethylmethacrylate dosimetry system
ISO/ASTM 51276 covers procedures for using hermetically-sealed polymethylmethacrylate (PMMA) dosimeters for measuring absorbed doses in materials irradiated by photons or electrons in terms of absorbed dose in water. It also covers systems that permit absorbed dose measurements under the following conditions: the absorbed dose range is 0,1 kGy to 100 kGy. the absorbed dose rate is 1 times 10-2 Gy·s -1 to 1 times 107 Gy·s -1. the radiation energy range for photons is 0,1 MeV to 50 MeV and for electrons 3 MeV to 50 MeV. the irradiation temperature is -78 °C to + 50 °C.
Pratique de l'utilisation d'un système dosimétrique au polyméthylméthacrylate
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Standards Content (Sample)
INTERNATIONAL ISO/ASTM
STANDARD 51276
First edition
2002-03-15
Practice for use of a
polymethylmethacrylate dosimetry
system
Pratique de l’utilisation d’un système dosimétrique au
polyméthylméthacrylate
Reference number
ISO/ASTM 51276:2002(E)
© ISO/ASTM International 2002
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ISO/ASTM 51276:2002(E)
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ii © ISO/ASTM International 2002 – All rights reserved
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ISO/ASTM 51276:2002(E)
Contents Page
1 Scope . 1
2 Referenced documents . 1
3 Terminology . 1
4 Significance and use . 3
5 Apparatus . 3
6 Performance check of instrumentation . 3
7 Calibration of dosimeters . 3
8 Procedures . 5
9 Characterization of each stock of dosimeters . 5
10 Application of dosimetry system . 5
11 Documentation requirements . 5
12 Measurement uncertainty . 6
13 Keywords . 6
ANNEX . 6
Bibliography . 7
Table A1.1 Basic properties of available dosimeters . 6
Table A1.2 Some suppliers of polymethylmethacrylate (pmma) dosimeters . 6
© ISO/ASTM International 2002 – All rights reserved iii
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ISO/ASTM 51276:2002(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 pilot project between ISO and ASTM International has been formed to develop and maintain a group of
ISO/ASTM radiation processing dosimetry standards. Under this pilot 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 International Standard 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 51276 was developed by ASTM Committee E10, Nuclear Technology and
Applications, through Subcommittee E10.01, and by Technical Committee ISO/TC 85, Nuclear Energy.
Annex A1 of this International Standard is for information only.
iv © ISO/ASTM International 2002 – All rights reserved
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ISO/ASTM 51276:2002(E)
Standard Practice for
1
Use of a Polymethylmethacrylate Dosimetry System
This standard is issued under the fixed designation ISO/ASTM 51276; 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 ties for Food Processing
51205 Practice for Use of a Ceric-Cerous Sulfate Dosimetry
1.1 This practice covers procedures for using hermetically-
2
System
sealed polymethylmethacrylate (PMMA) dosimeters for mea-
51261 Guide for Selection and Calibration of Dosimetry
suring absorbed dose in materials irradiated by photons or
2
Systems for Radiation Processing
electrons in terms of absorbed dose in water.
51400 Practice for Characterization and Performance of a
1.2 This practice covers systems that permit absorbed dose
2
High-Dose Radiation Dosimetry Calibration Laboratory
measurements under the following conditions:
51401 Practice for Use of a Dichromate Dosimetry System
1.2.1 The absorbed dose range is 0.1 to 100 kGy.
−2 7 −1
51607 Practice for Use of the Alanine-EPR Dosimetry
1.2.2 The absorbed dose rate is 1 3 10 to 1 3 10 Gy·s .
2
System
1.2.3 The radiation energy range for photons is 0.1 to 50
51631 Practice for Use of Calorimetric Dosimetry Systems
MeV, and for electrons 3 to 50 MeV.
for Electron Beam Dose Measurements and Dosimeter
1.2.4 The irradiation temperature is −78 to +50°C.
2
Calibrations
1.3 This standard does not purport to address all of the
51707 Guide for Estimating Uncertainties in Dosimetry for
safety concerns, if any, associated with its use. It is the
2
Radiation Processing
responsibility of the user of this standard to establish appro-
2.3 International Commission on Radiation Units and
priate safety and health practices and determine the applica-
Measurements (ICRU) Reports:
bility of regulatory limitations prior to use.
ICRU Report 14 Radiation Dosimetry: X Rays and Gamma
2. Referenced Documents
Rays with Maximum Photon Energies Between 0.6 and 50
5
MeV
2.1 ASTM Standards:
ICRU Report 17 Radiation Dosimetry: X Rays Generated at
E 170 Terminology Relating to Radiation Measurements
5
2
Potentials of 5 to 150 kV
and Dosimetry
5
ICRU Report 34 The Dosimetry of Pulsed Radiation
E 177 Practice for Use of the Terms Precision and Bias in
3
ICRU Report 35 Radiation Dosimetry: Electron Beams with
ASTM Test Methods
5
3
Energies Between 1 and 50 MeV
E 178 Practice for Dealing with Outlying Observations
5
ICRU Report 60 Radiation Quantities and Units
E 275 Practice for Describing and Measuring Performance
of Ultraviolet, Visible, and Near Infrared Spectrophotom-
3. Terminology
4
eters
3
3.1 Definitions:
E 456 Terminology Relating to Quality and Statistics
3.1.1 absorbed dose (D)—quantity of ionizing radiation
E 668 Practice for Application of Thermoluminescence-
energy imparted per unit mass of a specified material. The SI
Dosimetry (TLD) Systems for Determining Absorbed Dose
2
unit of absorbed dose is the gray (Gy), where 1 gray is
in Radiation-Hardness Testing of Electronic Devices
equivalent to the absorption of 1 joule per kilogram of the
E 1026 Practice for Using the Fricke Reference Standard
2
specified material (1 Gy = 1 J/kg). The mathematical relation-
Dosimetry System
ship is the quotient of d e¯by dm, where d e¯ is the mean
2.2 ISO/ASTM Standards:
incremental energy imparted by ionizing radiation to matter of
51204 Practice for Dosimetry in Gamma Irradiation Facili-
incremental mass dm (see ICRU Report 60).
de¯
1
This practice is under the jurisdiction of ASTM Committee E10 on Nuclear D 5 (1)
dm
Technology and Applications and is the direct responsibility of Subcommittee
E10.01 on Dosimetry for Radiation Processing, and is also under the jurisdiction of
3.1.1.1 Discussion—The discontinued unit for absorbed
ISO/TC 85/WG 3.
dose is the rad (1 rad = 100 erg per gram = 0.01 Gy). Absorbed
Current edition approved Jan. 22, 2002. Published March 15, 2002. Originally
e1 dose is sometimes referred to simply as dose.
published as E 1276 – 88. Last previous ASTM edition E 1276 – 96 . ASTM
e1
˙
E1276-96 was adopted by ISO in 1998 with the intermediate designation ISO
3.1.2 absorbed-dose rate (D)—the absorbed dose in a
15558:1998(E). The present International Standard ISO/ASTM 51276:2002(E) is a
material per incremental time interval, that is, the quotient of
revision of ISO 15558.
2
Annual Book of ASTM Standards, Vol 12.02.
3 5
Annual Book of ASTM Standards, Vol 14.02. Available from International Commission on Radiation Units and Measure-
4
Annual Book of ASTM Standards, Vol 03.06. ments, 7910 Woodmont Ave., Suite 800, Bethesda, MD 20814, U.S.A.
© ISO/ASTM International 2002 – All rights reserved
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ISO/ASTM 51276:2002(E)
dD by dt (see ICRU Report 60).
where:
n = number of dosimeters, and
dD
˙
D 5 (2)
k = individual dosimeter specific absorbance.
dt i
3.1.14 polymethylmethacrylate (PMMA) dosimeter—piece
−1
Unit: Gy·s .
of specially selected or specially developed PMMA material
that exhibits characterizable ionizing radiation-induced
3.1.2.1 Discussion—The absorbed-dose rate is often speci-
˙ changes in specific optical absorbance as a function of ab-
fied in terms of average value of D over long-time intervals, for
−1 −1
sorbed doses, individually sealed by the manufacturer in a
example, in units of Gy · min or Gy · h .
hermetically sealed pouch.
3.1.3 analysis wavelength—wavelength used in a spectro-
3.1.14.1 Discussion—The PMMA piece, when removed
photometric instrument for the measurement of optical absor-
from the pouch, is still referred to as the dosimeter.
bance.
3.1.15 reference–standard dosimeter—a dosimeter of high
3.1.4 calibration curve—graphical representation of the
metrological quality, used as a standard to provide measure-
dosimetry system’s response function.
ments traceable to and consistent with measurements made
3.1.5 calibration facility—combination of an ionizing radia-
using primary–standard dosimeters (see ISO/ASTM Guide
tion source and its associated instrumentation that provides a
51261).
uniform and reproducible absorbed dose or absorbed-dose rate
3.1.16 response—see dosimeter response.
traceable to national or international standards, at a specified
3.1.17 response function—mathematical representation of
location and within a specific material, and that may be used to
the relationship between dosimeter response and absorbed dose
derive the dosimetry system’s response function or calibration
for a given dosimetry system.
curve.
3.1.18 routine dosimeter—dosimeter calibrated against a
3.1.6 dosimeter—a device that, when irradiated, exhibits a
primary-, reference-, or transfer-standard dosimeter and used
quantifiable change in some property of the device which can
for routine absorbed-dose measurement (see ISO/ASTM Guide
be related to absorbed dose in a given material using appro-
51261).
priate analytical instrumentation and techniques.
3.1.19 simulated product—a mass of material with attenu-
3.1.7 dosimeter batch—quantity of dosimeters made from a
ation and scattering properties similar to those of the product,
specific mass of material with uniform composition, fabricated
material, or substance to be irradiated.
in a single production run under controlled, consistent condi-
3.1.19.1 Discussion—Simulated product is used during ir-
tions, and having a unique identification code.
radiator characterization as a substitute for the actual product,
3.1.8 dosimeter response—the reproducible, quantifiable ra-
material, or substance to be irradiated. When used in routine
diation effect produced by a given absorbed dose.
production runs, it is sometimes referred to as compensating
3.1.9 dosimeter stock—part of a dosimeter batch held by the
dummy. When used for absorbed-dose mapping, simulated
user.
product is sometimes referred to as phantom material.
3.1.10 dosimetry system—a system used for determining
3.1.20 specific absorbance (k)—absorbance, A, at a selected
absorbed dose, consisting of dosimeters, measurement instru-
wavelength divided by the optical path length, d, through the
ments and their associated reference standards, and procedures
dosimeter, as follows:
for the system’s use.
3.1.11 electron equilibrium—a condition that exists in ma- k 5 A/d (4)
terial under irradiation if the kinetic energies, number, and
3.1.20.1 Discussion—In this practice (ISO/ASTM 51276),
direction of electrons induced by the radiation are uniform
d is equated to dosimeter thickness (t). If t is virtually constant
throughout the measurement volume of interest. Thus, the sum
(within 61 %), calculation of specific absorbance is unneces-
of the kinetic energies of the electrons entering the volume
sary, and absorbance A may be taken as the dose-related
equals the sum of the kinetic energies of the electrons leaving
quantity.
the volume (see ICRU Report 60).
3.1.21 traceability—the documentation demonstrating by
3.1.11.1 Discussion—Electron equilibrium is often referred
means of an unbroken chain of comparisons that a measure-
to as charged particle equilibrium (see ASTM Terminology
ment is in agreement within acceptable limits of uncertainty
E 170 and ICRU Report 60).
with comparable nationally or internationally recognized stan-
3.1.12 measurement quality assurance plan—a documented
dards.
program for the measurement process that assures on a
3.1.22 transfer–standard dosimeter—a dosimeter, often a
continuing basis that the overall uncertainty meets the require-
reference–standard dosimeter, suitable for transport between
ments of the specific application. This plan requires traceability
different locations, used to compare absorbed-dose measure-
to, and consistency with, nationally or internationally recog-
ments (see ISO/ASTM Guide 51261).
nized standards.
3.1.23 uncertainty—a parameter associated with the result
3.1.13 mean specific absorbance (k¯)—average value of k for
of a measurement, that characterizes the dispersion of the
a set of dosimeters irradiated to the same absorbed dose, under
values that could reasonably be attributed to the measurand or
the same conditions.
derived quantity.
n
1
3.1.23.1 Discussion—The parameter may be, for example, a
¯
k 5 k (3)
(
i
n
i21 standard deviation (or a given multiple of it), or the half-width
© ISO/ASTM International 2002 – All rights reserved
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ISO/ASTM 51276:2002(E)
of an interval having a stated confidence. 5. Apparatus
3.1.23.2 Discussion—Uncertainty of measurement com-
5.1 Components of the PMMA Dosimetry System—The
prises, in general, many components. Some of these compo-
following shall be used to determine absorbed dose with
nents may be evaluated from the statistical distribution of the
PMMA dosimetry systems:
results of series of measurements and can be characterized by
5.1.1 Polymethylmethacrylate Dosimeters.
experimental standard deviations. The other components,
5.1.2 Spectrophotometer (or an equivalent instrument), ca-
which also can be characterized by standard deviations, are
pable of determining optical absorbance at the analysis wave-
evaluated from assumed probability distributions based on
length and having documentation covering analysis wave-
experience or other information.
length range, accuracy of wavelength selection and absorbance
3.1.23.3 Discussion—It is understood that the result of the
determination, spectral bandwidth, and stray light rejection.
measurement is the best estimate of the value of the measur-
5.1.3 Holder, to position the dosimeter reproducibly in, and
and, and that all components of uncertainty, including those
perpendicular to, the analyzing light beam.
arising from systematic effects, such as components associated
5.1.4 Calibrated Thickness Gage.
with corrections and reference standards, contribute to the
5.1.5 Calibrated thickness gage blocks covering the range of
dispersion.
thicknesses encountered.
3.2 Other appropriate terms may be found in ASTM Termi-
nology E 170.
NOTE 2—For constant thickness dosimeters (see 3.1.20.1) documenta-
tion provided by the manufacturer of the PMMA dosimeter with regard to
4. Significance and Use
the thickness and its uniformity must first be verified by the user for a
representative sample, and may then be substituted for direct measurement
4.1 Polymethylmethacrylate dosimetry systems are com-
by the user.
monly applied in industrial radiation processing, for example,
in the sterilization of medical devices and the processing of
5.1.6 Calibration curve or response function (see 7.5.6).
foods. In these applications, doses fall mostly within the 0.1 to
100 kGy working range of the family of PMMA dosimeters.
6. Performance Check of Instrumentation
4.2 Properly selected PMMA dosimeter materials provide a
6.1 Check and document the uncertainties of the wavelength
means of directly estimating absorbed doses in near water-
and absorbance scales of the spectrophotometer at or near the
equivalent substances, such as plastics, cotton, paper, gut, and
analysis wavelength at documented time intervals during
rubber. The doses are normally expressed in terms of dose in
periods of use, or whenever there are indications of poor
water (see 4.7). Under the influence of ionizing radiation,
performance. Compare and document this information with the
chemical reactions take place in the material, creating and/or
original instrument specifications to verify adequate perfor-
enhancing absorption bands in the visible and/or ultraviolet
mance. (See ASTM Practices E 275 and E 1026.)
regions of the spectrum. Absorbance is determined at selected
6.2 Check the thickness gage before, during, and after use to
wavelengths within these radiation-induced absorption bands.
assure reproducibility and lack of zero drift. Check and
Examples of appropriate wavelengths used for analysis of
document the calibration of the gage at documented time
specific dosimeters are provided in Table A1.1.
intervals. Use gage blocks traceable to national standards for
4.3 In the application of a specific dosimetry system,
this purpose.
absorbed dose is determined by using an experimentally
derived calibration curve. The calibration curve is determined
7. Calibration of Dosimeters
by measuring sets of dosimeters irradiated to known absorbed
7.1 Calibration of PMMA dosimeters can be accomplished
doses that adequately span the range of utilization of the
by irradiating the dosimeters in a calibration facility, or by
system (see 7.5.2).
irradiating the dosimeters, along with reference or transfer-
4.4 Polymethylmethacrylate dosimetry systems require cali-
–standard dosimeters in a production irradiator (see ISO/
bration traceable to national or international standards. See
ASTM Guide 51261).
ISO/ASTM Guide 51261.
4.5 During calibration and use, possible effects of condi- 7.2 The gamma- or electron-beam facility used may be an
accredited calibration facility that provides an absorbed-dose
tions such as temperature, light exposure, energy spectrum, and
absorbed dose rate are taken into account. rate measured by reference or transfer–standard dosimeters, or
it may be a production irradiator. If a production irradiator is
4.6 Unprotected PMMA dosimeter material is sensitive to
changes in humidity, and cut pieces are therefore individually used, the absorbed doses delivered to the calibration dosim-
eters shall be determined by means of reference or transfer-
sealed in water impermeable pouches at the manufacturing
stage. They must be kept in these sealed pouches during –standard dosimeters irradiated together with the dosimeters to
be calibrated, under conditions that ensure that the calibration-
irradiation.
4.7 Absorbed dose in materials other than water may be and corresponding reference- or transfer-standard dosimeter
sets receive the same dose, under the same environmental
determined by applying conversion factors in accordance with
conditions.
ISO/ASTM Guide 51261.
NOTE 1—For a comprehensive discussion of various dosimetry meth- NOTE 3—The radiation response of PMMA dosimeters may be affected
by extremes of environmental or seasonal conditions, such as absorbed
ods applicable to the radiation types and energies discussed in this
dose rate and temperature found in some production irradiators (see Refs
practice, see ICRU Reports 14, 17, 34, and 35.
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ISO/ASTM 51276:2002(E)
6
1-10, 17-19, and 25). In these circumstances the use of dosimeter calibration curve (any slight deviations being statistically insignificant),
calibrations performed at fixed dose rates and fixed temperatures could then the calibration is verified.
result in unacceptably large increases in dosimetric uncertainty. If prior
7.5.1 Use a set of at least four dosimeters for each absorbed
experience, manufacturer’s recommendations, or scientific literature sug-
dose point (see ASTM Practice E 668 for guidance on deter-
gest that the range of environmental conditions met by the dosimeters in
mining sample size).
the production facility are likely to significantly increase the uncertainties,
then the PMMA dosimeters should be calibrated in an environment that
7.5.2 The number of sets of PMMA dosimeters required to
encompasses these conditions. This type of calibration may, for example,
determine the calibration curve of the dosimetry system
be carried out using the production irradiator, under the conditions
depends on the dose-range of utilization. Use at least five sets
identified, using reference- or transfer-standard dosimeters to determine
for each factor of ten span of absorbed dose, or at least four sets
the calibration doses given.
if the range of utilization is less than a factor of ten. For
7.3 Absorbed doses shall be specified in terms of absorbed
example, a range of use from 0.2 to 45 kGy would require at
dose in water, or in another specified material appropriate for
least twelve sets.
the particular application.
NOTE 6—To determine mathematically the minimum number of sets to
7.4 Provide the following conditions for the calibration of
be used, divide the maximum dose in the range of utilization (D )bythe
max
dosimeters:
minimum dose (D ), then, calculate log(base 10) of this ratio:
min
7.4.1 Ensure that the shelf-life of the dosimeters, as stated
Q 5 log ~D /D ! (5)
by the manufacturer, has not been exceeded.
max min
7.4.2 Select a well defined and reproducible position for the
If Q is less than 1, use a minimum of four sets, If Q is greater than 1,
dosimeters during irradiation in the calibration field. In the case calculate the multiple 5 3 Q, and round this to the nearest integer value.
This value represents the minimum number of sets to be used.
of a fixed dose rate calibration, select a location in the
calibration field in which the variation in absorbed dose rate
7.5.3 Determine the specific absorbance of the dosimeters
within the volume occupied by the dosimeters has been
(see Section 8).
demonstrated to be within 61 %. For variable dose rate
7.5.4 Calculate and document the mean specific absorbance,
calibration in a production irradiator, use a location in the
k¯, and the sample standard deviation (S ) for each set of four
n−1
product, or simulated product, in which the variation of
(or more) dosimeters at each dose value.
absorbed dose delivered during production has been demon-
NOTE 7—The sample standard deviation, S , is calculated from the
n−1
strated to be within 61%.
sample data set of n values as follows:
7.4.3 If a calibration facility is used, the dose rate shall be
2
traceable to national or international standards. The tempera-
(~k 2 k¯!
i
S 5˛ (6)
n21
ture of the dosimeters, both during and after irradiation, and the
n 2 1
fixed dose rate used shall be arranged to be as close as
where:
practicable to the average irradiation temperature, average post
k = i’th value of k.
i
irradiation temperature/time, and average dose rate conditions
occurring in the actual production facility of interest.
7.5.5 For calibrations in a production irradiator, document
7.4.4 Whatever the irradiation conditions used, the dosim- the type, supplier, batch number, date of manufacture, and all
eters shall be surrounded with sufficient PMMA or equivalent
other relevant information for the reference- or transfer-
material to ensure electron equilibrium conditions. standard dosimeters used. Document the code number and title
of the measurement practice used, the correction factors used
NOTE 4—As an example, for cobalt-60 gamma irradiations, 3 to 5 mm
(if applicable), and correlate the measured reference- or
of PMMA (or equivalent polymeric material, such as solid polystyrene)
transfer-standard doses against the corresponding PMMA do-
surrounding the dosimeters on all sides effectively ensures electron
equilibrium conditions. In the case of calibrations in a production simeter specific absorbances.
irradiator, the material should take the form of a block having a minimum
7.5.6 Graphically plot mean specific absorbance versus
wall thickness of 3 mm and containing a cavity, or cavities, geometrically
absorbed dose, or use a suitable computer code, or both, to
located to ensure that the PMMA- and reference- or transfer-standard
derive this relationship in mathematical form. Choose an
dosimeters all receive the same dose.
analytical form (for example, linear, polynomial, or exponen-
7.5 Calibrate each stock or batch of dosimeters prior to
tial) that provides the best fit to the measured data.
routine use. If a new stock from the same batch is to be brought
7.5.7 Examine the resulting calibration curve or response
into use, recalibration may not be necessary. However, it must
function for goodness of fit (see ISO/ASTM Guide 51707).
be demonstrated that the existing calibration applies to the new
7.5.8 Repeat this calibration procedure if any value (or
stock, by means of a verification procedure (see Note 5).
values) deviates significantly from the determined curve, and if
discarding this value would result in there being insufficient
NOTE 5—To verify that an existing calibration still applies, irradiate
data to adequately define the curve (see ISO/ASTM Guide
sets of dosimeters at selected doses spanning the range of utilization. A
minimum effort is to irradiate dosimeters at the lower and upper limits of
51707).
this range, and the mid-point. If the resulting values fit the existing
NOTE 8—See ASTM Practice E 178 for guidance on dealing with
outlyers.
6
7.5.9 Repeat the calibration procedure at intervals not to
The boldface numbers in parentheses refer to the bibliography at the end of this
practice. exceed twelve months.
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ISO/ASTM 51276:2002(E)
8. Procedures tion (CV) for each absorbed dose value, as follows:
8.1 Examination and Storage Procedure: S
n21
CV 5 3 100 ~%! (7)
¯
8.1.1 Inspect each dosimeter pouch for imperfections, for
k
example, pouch seal violation. Discard any dosimeters that
9.1.3 Document these coefficients of variation and note any
show unacceptable imperfections that could give rise to erro-
that are unusually large.
neous readings.
NOTE 10—In gen
...
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