ASTM ISO/ASTM51607-22

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: ISO/ASTM 51607 − 2013(E) 51607 − 22
Standard Practice for
Use of an Alanine-EPR Dosimetry System
This standard is issued under the fixed designation ISO/ASTM 51607; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers dosimeter materials, instrumentation, and procedures for using the alanine-EPR dosimetry system for
measuringto measure the absorbed dose in the photon andor electron radiation processing of materials. The alanine system is based
on electron paramagnetic resonance (EPR) spectroscopy of free radicals derived from the amino acid alanine.
1.2 The alanine dosimeter is classified as a type I dosimeter as it is affected by individual influence quantities in a well-defined
way that can be expressed in terms of independent correction factors (see ASTMISO/ASTM Practice E262852628). The alanine
dosimeter may be used in either a reference standard dosimetry system or in a routine dosimetry system.
1.3 This document is one of a set of standards that provides recommendations for properly implementing dosimetry in radiation
processing, and describes a means of achieving compliance with the requirements of ASTMISO/ASTM E262852628 “Practice for
Dosimetry in Radiation Processing” for alanine dosimetry system. It should be read in conjunction with ASTMISO/ASTM
E262852628.
1.4 This practice covers the use of alanine-EPR dosimetry systems for dose measurements under the following conditions:
1.4.1 The absorbed dose range is between 1 and 1.5 × 100.001 kGy and 150 kGy. Gy.
2 -1 10 -1
1.4.2 The absorbed dose rate is up to 101 × 10 Gy s for continuous radiation fields and up to 3 × 10 Gy s for pulsed radiation
fields (1-4).
1.4.3 The radiation energy for photons and electrons is between 0.10.1 MeV and 30 MeV (1, 2, 5-8).
1.4.4 The irradiation temperature is between –78 °C and + 70 +70 °C (2, 9-12).
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
This practice is under the jurisdiction of ASTM Committee E61 on Radiation Processing and is the direct responsibility of Subcommittee E61.02 on Dosimetry Systems,
and is also under the jurisdiction of . Originally developed as a joint ASTM/ISO standard in conjunction with ISO/TC 85/WG 3.
Current edition approved April 9, 2013Jan. 1, 2022. Published June 2013May 2024. Originally published as ASTM E 1607 – 94. Last previous ASTM edition
ε1
E 1607 – 96approved in 1994. Last previous edition approved . ASTM E 1607 – 94 was adopted by ISO in 1998 with the intermediate designation ISO 15566:1998(E). The
present International Standard ISO/ASTM 51607:2013(E) replaces ISO 15566 and is a major revision of the last previous edition ISO/ASTM 51607–2004(E). in 2013 as
ISO/ASTM 51607:2013(E). DOI: 10.1520/51607-22.
The term “electron spin resonance” (ESR) is used interchangeably with electron paramagnetic resonance (EPR).
The boldface numbers in parentheses refer to the bibliography at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
51607 − 22
2. Referenced documents
2.1 ASTM Standards:
E170E3083 Terminology Relating to Radiation Measurements and DosimetryProcessing: Dosimetry and Applications
E2628 Practice for Dosimetry in Radiation Processing
E2701 Guide for Performance Characterization of Dosimeters and Dosimetry Systems for Use in Radiation Processing
2.2 ISO/ASTM Standards:
51261 Practice for Calibration of Routine Dosimetry Systems for Radiation Processing
51707 Guide for Estimating Uncertainties Estimation of Measurement Uncertainty in Dosimetry for Radiation Processing
52628 Practice for Dosimetry in Radiation Processing
52701 Guide for Performance Characterization of Dosimeters and Dosimetry Systems for Use in Radiation Processing
2.3 ICRU International Commission on Radiation Units and Measurements (ICRU) Reports:
ICRU Report 85a Fundamental Quantities and Units for Ionizing Radiation
ICRU Report 80 Dosimetry Systems for Use in Radiation Processing
ICRU Report 85a Fundamental Quantities and Units for Ionizing Radiation
2.4 ISO Standard:
12749-4 Nuclear energy – Vocabulary – Part 4: Dosimetry for radiation processing
2.5 Joint Committee for Guides in Metrology (JCGM) Reports:
JCGM 100:2008, GUM 1995, with minor corrections, Evaluation of measurement data – Guide to the Expression of Uncertainty
in Measurement
JCGM 100:2008, 200:2012 (JCGM 200:2008 with minor revisions), VIM , International vocabulary of metrology – Basis and
general concepts and associated termsVocabulary of Metrology – Basic and General Concepts and Associated Terms
3. Terminology
3.1 Definitions:
3.1.1 alanine dosimeter—specified quantity and physical form of the radiation-sensitive material alanine and any added inert
substance such as a binder.
3.1.2 alanine-EPR dosimetry system—system used for determining absorbed dose, consisting of alanine dosimeters, an EPR
spectrometer and its associated reference materials, and procedures for the system’s use.
3.1.3 alanine-EPR dosimeter response—value resulting from applied adjustments to the EPR signal amplitude.
3.1.4 check standard—a standard prepared independently of the calibration standards that is measured to verify the performance
of a dosimetry system.
3.1.5 EPR intensity reference material—a stable paramagnetic material whose measurement by EPR is applied to the dosimeter
EPR signal amplitude as part of the dosimeter response determination.
3.1.6 EPR signal amplitude—peak-to-peak amplitude of the central signal of the EPR spectrum.
3.1.6.1 Discussion—
This signal is proportional to the alanine-derived free radical concentration in the alanine dosimeter.
3.1.7 EPR spectroscopy—measurement of resonant absorption of electromagnetic energy resulting from the transition of unpaired
electrons between different energy levels, upon application of radio frequencies to a paramagnetic substance in the presence of a
magnetic field.
For referenced ASTM and ISO/ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book
of ASTM Standards volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from International Commission on Radiation Units and Measurements, Measurements (ICRU), 7910 Woodmont Ave., Suite 800,400, Bethesda, MD 20814,
U.S.A.20814-3095, U.S.A., https://www.icru.org/.
Available from International Organization for Standardization (ISO), ISO Central Secretariat, Chemin de Blandonnet 8, CP 401, 1214 Vernier, Geneva, Switzerland,
https://www.iso.org.
Document produced by Working Group 1 of the Joint Committee for Guides in Metrology (JCGM/WG 1). Available free of charge at the BIPM website
(http://www.bipm.org).
Document produced by Working Group 2 of the Joint Committee for Guides in Metrology (JCGM/WG 2). Available free of charge at the BIPM website
(http://www.bipm.org).
51607 − 22
3.1.8 EPR spectrum—first derivative of the electron paramagnetic absorption spectrum measured as a function of the magnetic
field.
3.1.9 zero dose amplitude—EPR signal amplitude of an unirradiated alanine dosimeter with the same EPR spectrometer
parameters used for the lowest measurable absorbed dose value.
3.2 Definitions of other terms used in this standard that pertain to radiation measurement and dosimetry may be found in ASTM
Terminology E170E3083. Definitions in Terminology E170E3083 are compatible with ICRU Report 85a; that document, therefore,
may be used as an alternative reference.
4. Significance and use
4.1 The alanine-EPR dosimetry system provides a means for measuring absorbed dose. It is based on the measurement of specific
stable free radicals in crystalline alanine generated by ionizing radiation.
4.2 Alanine-EPR dosimetry systems are used in reference- or transfer-standard or routine dosimetry systems in radiation
applications that include: sterilization of medical devices and pharmaceuticals, food irradiation, polymer modifications, medical
therapy and radiation damage studies in materials (1, 13-15).
5. Overview
5.1 The dosimeter is prepared using α-alanine, CH -CH(NH )-COOH, in the form of polycrystalline powder.
3 2
5.2 All stereoisomers of α-alanine are suitable for dosimetry; L-alanine is used most commonly.
5.3 Usual physical shapes are films or pellets (cylinders).(cylinders), and pellets with a packaged form.
NOTE 1—Additives, capsules, or film support materials used in the preparation of dosimeters should not add any significant intrinsic or radiation-induced
EPR signal. Examples of suitable binders are ethylene-propylene rubber, gelatin, paraffin, polyethylene, polyethylene vinyl acetate, polystyrene,
polyvinylpyrrolidone, polyvinyl propylene, and stearin. Lubricants added in the dosimeter manufacturing process are optional. An example of a suitable
lubricant is stearic acid (16-21).
5.4 The dosimeter contains crystalline alanine and registers the absorbed dose by the formation of alanine-derived free radicals
(22). Identification and measurement of alanine-derived free radicals are performed by EPR spectroscopy. ICRU Report 80
provides information on the scientific basis and historical development of this dosimetry system.
5.5 The measurement of free radicals by EPR spectroscopy is nondestructive. This can be repeated and hence can be used for
archival purposes (23-25).
6. Influence quantities
6.1 Factors other than absorbed dose which influence the dosimeter response are referred to as influence quantities, and are
discussed in the following sections (see also ASTMISO/ASTM Guide E270152701). Examples of such influence quantities are
temperature and dose rate.
6.2 Pre-Irradiation Conditions:
6.2.1 Dosimeter Conditioning and Packaging—Alanine dosimeter conditioning and packaging may be important under certain
conditions (see 6.2.4).
NOTE 2—The sorting of alanine pellet dosimeters by mass into sub-lots will improve the measurement uncertainty.
6.2.2 Time Since Manufacture—There is no known influence of time since manufacture on alanine dosimeters when stored under
recommended conditions.
51607 − 22
6.2.3 Temperature—There is no known influence of pre-irradiation temperature. However, it is recommended that alanine
dosimeters be stored at manufacturer recommended temperatures. Exposure to temperatures outside the manufacturer’s
recommended range should be avoided to reduce the potential for adverse effects on dosimeter response.
6.2.4 Relative Humidity—The humidity during pre-irradiation storage may influence the EPR signal amplitude of alanine
dosimeters (24, 25). The effect of humidity may be reduced by sealing dosimeters in a material impervious to water.
6.2.5 Exposure to Light—There is no known influence of ambient light.
6.3 Conditions During Irradiation:
6.3.1 Irradiation Temperature—The irradiation temperature influences the EPR signal amplitude of alanine dosimeters.
NOTE 3—The effect of irradiation temperature on the dosimeter EPR signal amplitude may be dependent on the dosimeter type. The temperature
-1
coefficient, R (K ) is described by the relationship, (Δm/m)/ΔT, where m is the EPR signal amplitude (in arbitrary units) and T is the irradiation
t
-1
temperature (in K). For dosimeters with L-alanine, a positive temperature coefficient, expressed in percent, in the range of +0.1 to +0.2 % °C is typical
for irradiation temperatures from –10 °C to +70 °C (10, 11, 26-28); refer to Ref (9, 12) for irradiation temperatures below –10 °C. The temperature
coefficient for dosimeters prepared with the DL stereoisomer of alanine is more than 50 % higher than one prepared with L-alanine (29). A summary of
published temperature coefficients is tabulated in Ref (26, 29).
6.3.2 Absorbed-Dose Rate—Under normal radiation processing conditions there is no measurable effect of absorbed dose rate;
however, a dose dependent effect has been characterized for alanine dosimeters irradiated to high doses at low dose rates (30).
NOTE 4—The dose-rate effect is absorbed-dose dependent. Alanine dosimeters irradiated with gamma radiation to absorbed doses > 5 kGy at low dose
rates (< 2 Gy/s) show a progressive decrease in EPR signal amplitudes relative to that found at dose rates greater than 2 Gy/s (30). This combined
dose/dose rate effect may reach several percent and is irradiation temperature dependent; though relatively constant above 0 °C, no rate effect was
measured at –10 °C and –40 °C (31).
6.3.3 Dose Fractionation—There is no known influence of dose fractionation.
NOTE 5—In some instances the fractionation of dose to alanine dosimeters may not be straightforward. Certain influence quantities that contribute to the
dosimeter response may not be equivalent for the fractionated and non-fractionated irradiations. For example, the fractionation of dose imposes multiple
temperature changes to the dosimeter that may not be equivalent to the irradiation temperature experienced by a dosimeter irradiated to a single dose
(equal to the sum of the fractionated doses). An accurate comparison of fractionated and non-fractionated doses will depend greatly on an accurate
knowledge of the irradiation temperature for the irradiations (see 6.3.1).
6.3.4 Relative Humidity—The humidity during irradiation may influence the EPR signal amplitude of alanine dosimeters. The
effect of humidity may be reduced by sealing dosimeters in a material impervious to water.
6.3.5 Exposure to Light—There is no known influence of ambient light.
6.3.6 Radiation Energy—For most radiation processing applications there is no influence of radiation energy for photons and
electrons.
NOTE 6—Differences have been reported between the absorbed dose to water response of alanine dosimeters irradiated by photons and electrons over a
range of energies (4, 6-8). The response in electron beams has been reported to be 1–2 % lower than in Co-60 beams (8) and the response in 150 kV
X-ray beams has been reported to be ~15 % lower (7). The response to ~100 keV electrons was found to be equivalent to the response to high energy
electrons (32, 33).
6.4 Post-Irradiation Conditions:
6.4.1 Time—The interval between irradiation and dosimeter reading shall be standardized and should conform to the
manufacturer’s recommendations (see 6.4.4). Alanine dosimeters are commonly regarded as stable over time periods as long as
weeks or months. However, the degree of stability may be influenced by, but not limited to, absorbed dose, relative humidity,
dosimeter composition and this should be characterized by the end user.
51607 − 22
6.4.2 Temperature—There is no known influence of storage temperature on alanine dosimeters. However, it is recommended that
alanine dosimeters be stored according to in accordance with manufacturer’s recommendations.
6.4.3 Conditioning Treatment—Post-irradiation treatment is not applicable.
6.4.4 Storage Relative Humidity—The humidity during post-irradiation storage can influence the EPR signal amplitude of alanine
dosimeters. Sufficient time should be allowed for dosimeters to equilibrate with ambient conditions before measurement (25).
6.4.5 Exposure to Light—There is no significant influence of ambient light.
6.5 Response Measurement Conditions:
6.5.1 Exposure to Light—There is no significant influence of ambient light.
6.5.2 Temperature—Controlled temperatures are recommended for measuring alanine dosimeters. Avoid exposure to temperatures
outside the manufacturer’s recommended range.
6.5.3 Relative Humidity—The humidity during measurement can influence the EPR signal amplitude of alanine dosimeters.
During measurement, the effects of humidity can be compensated by measuring the ratio of the alanine signal to that of a humidity
insensitive EPR intensity reference material (see 7.3.1). If a humidity sensitive EPR reference material is used (e.g. (for example,
an irradiation-calibrated alanine dosimeter) compensate for changes in humidity by standardizing the time of measurement (see
6.4.4) between the reference and dosimeter reading (see Note 8).
NOTE 7—Some commercial EPR instrumentation may automatically compensate for nominal changes in temperature and ambient humidity.
NOTE 8—The historical data for humidity effects on alanine dosimeters and quantitative EPR measurements have been compiled (25, 34-36).
7. Dosimetry system and its verification
7.1 The following are components of the Alanine-EPR Dosimetry System:
7.1.1 Alanine Dosimeters.
7.1.2 EPR Spectrometer.
7.1.2.1 An X-band EPR spectrometer is used to measure the EPR signal amplitude of an alanine dosimeter. To obtain the expanded
uncertainty cited in 12.3, an EPR spectrometer should be capable of the following settings:
(1) microwave frequency 99 GHz to 10 GHz with automatic frequency locking (AFC);
(2) corresponding magnetic field to set a g-factor of 2.0 (at 9.8 GHz, this equals 350 mT) with a field scan range of 20 mT
about the center field;
(3) magnetic field modulation amplitude 0.10.1 mT to 1.5 mT;
(4) microwave power 0.10.1 mW to 10 mW (leveled);
(5) adjustable sweep time, time constant, and receiver gain according to in accordance with absorbed dose.
7.1.2.2 The sensitivity of the spectrometer should be at least 2 × 10 spins for EPR line width of 0.1 mT (37).
7.1.3 Dosimeter Holder.
7.1.3.1 There shall be some mechanical means of positioning the dosimeter accurately and reproducibly, in terms of both vertical
position and centricity in the EPR spectrometer cavity. The dosimeter holder is usually made of fused quartz or suitable polymer
and should be of such quality and cleanliness to contribute no interfering EPR signal.
7.1.4 Analytical Balance (Optional).
7.1.4.1 For certain types of dosimeters, the measurement reproducibility may be improved by normalizing the EPR signal
51607 − 22
amplitude to the dosimeter mass. To attain the uncertainty cited in 12.3, an analytical balance capable of measuring masses to
within 60.1 mg should be used. The analytical balance shall be calibrated according to the manufacturer’sin accordance with the
manufacturer’s guidelines.
7.2 Measurement Management System:
7.2.1 The measurement management system includes the dosimeter system calibration curve resulting from calibration according
to in accordance with ISO/ASTM 51261 and the procedures for use.
7.3 Performance Verification of Instrumentation:
7.3.1 EPR spectrometer performance can be verified by routinely measuring a suitable EPR intensity reference material; examples
of these include Cr(III) in Al O (ruby), or Mn(II) in CaO or MgO (34, 37). If the EPR intensity reference material does not agree
2 3
with its established value within an acceptable range, ascertain any obvious faults, for example, an EPR intensity reference material
position error.
NOTE 9—EPR intensity reference materials traceable to National Metrology Institutes are currently unavailable. The suitability of an EPR intensity
reference material to verify and compensate for EPR spectrometer performance variation should be established either based on publication,
manufacturer-supplied data, or measurement. The acceptable range for the EPR intensity reference material measurements is dependent on the
measurement precision of the equipment used. Typically this is about 60.5 % (1 σ). Compensation for the specific performance changes may be applied
if the changes are greater than the measurement uncertainty requirements.
7.4 Dosimetry System Verification:
7.4.1 Calibrated alanine dosimeters are suitable check standards for dosimetry system verification. At prescribed time intervals,
and whenever there are indications of poor performance during periods of use, the performance of the dosimetry system shall be
checked through the measurement of check standards, and the results documented. This information should be compared with the
prescribed acceptance limits to verify adequate performance, and the result documented. Check standard measurements that
measure outside of set limits must be resolved through check-standard measurement repetition, the acquisition of new check
standards if necessary, or reconfiguration of spectrometer settings or dosimeter holder, or both (this reconfiguration may require
a total recalibration of the dosimetry system).
NOTE 10—Drift of the dosimetry system performance that exceeds prescribed acceptance limits may result from two primary causes, a change in the check
standard (e.g., signal fade) or a change in the spectrometer measurement system that includes the spectrometer electronics or its associated components,
or both (e.g., dosimeter holder). The source of the system drift may be determined through the procurement of new calibrated dosimeters or the
measurement of in-house check standards. In-house check standards may be prepared from dosimeters irradiated in a reproducible well-characterized
irradiation geometry with a stated uncertainty. The in-house check standards should be compared to the calibrated dosimeters upon initial calibration of
the dosimetry system so as to provide a reference for future comparisons.
7.4.2 Drift of the dosimetry system performance that exceeds prescribed acceptance limits may result from two primary causes,
a change in the check standard (for example, signal fade) or a change in the spectrometer measurement system that includes the
spectrometer electronics or its associated components, or both (for example, dosimeter holder). The source of the system drift may
be determined through the procurement of new calibrated dosimeters or the measurement of in-house check standards. In-house
check standards may be prepared from dosimeters irradiated in a reproducible well-characterized irradiation geometry with a stated
uncertainty. The in-house check standards should be compared to the calibrated dosimeters upon initial calibration of the dosimetry
system so as to provide a reference for future comparisons.
NOTE 11—Normalizing the EPR signal amplitude to the value of the EPR intensity reference material can compensate for performance changes. The
effectiveness of compensation for these changes depends on the choice of EPR intensity reference material ranging from in situ materials (e.g., ruby)
measured with the test alanine dosimeter in place, to ex situ materials (e.g., reference alanine dosimeter) measured in series with substitution of the test
alanine dosimeter. An in situ EPR intensity reference material can be used to compensate for electronic instabilities internal to the EPR spectrometer that
negatively affect measurement repeatability and its associated uncertainty (23, 34, 38). If the alanine dosimeters are susceptible to humidity, significant
errors can be introduced when the alanine dosimeter storage humidity differs significantly from the measurement humidity (25). An in situ EPR intensity
reference material can also be used to compensate for environmental humidity effects during the measurement of alanine dosimeters as well as the related
effect that results from alanine-dosimete
...