ASTM ISO/ASTM51401-21

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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 51401 − 2013(E) 51401 − 21
Standard Practice for
Use of a Dichromate Dosimetry System
This standard is issued under the fixed designation ISO/ASTM 51401; 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 the preparation, testing, and procedure for using the acidic aqueous silver dichromate dosimetry system
to measure absorbed dose to water when exposed to ionizing radiation. The system consists of a dosimeter and appropriate
analytical instrumentation. For simplicity, the system will be referred to as the dichromate system. The dichromate dosimeter is
classified as a type I dosimeter on the basis of the effect of influence quantities. The dichromate system may be used as either a
reference standard dosimetry system or a routine dosimetry system.
1.2 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 ISO/ASTM Practice 52628 for the dichromate
dosimetry system. It is intended to be read in conjunction with ISO/ASTM Practice 52628.
1.3 This practice describes the spectrophotometric analysis procedures for the dichromate system.
1.4 This practice applies only to gamma radiation, X-radiation/bremsstrahlung, and high energy electrons.
1.5 This practice applies provided the following conditions are satisfied:
3 4
1.5.1 The absorbed dose range is from 2 × 10 to 5 × 10 Gy.
1.5.2 The absorbed dose rate does not exceed 600 Gy/pulse (12.5 pulses per second), or does not exceed an equivalent dose rate
of 7.5 kGy/s from continuous sources (1).
1.5.3 For radionuclide gamma sources, the initial photon energy shall be greater than 0.6 MeV. For bremsstrahlung photons, the
initial energy of the electrons used to produce the bremsstrahlung photons shall be equal to or greater than 2 MeV. For electron
beams, the initial electron energy shall be greater than 8 MeV.
NOTE 1—The lower energy limits given are appropriate for a cylindrical dosimeter ampoule of 12 mm diameter. Corrections for displacement effects and
dose gradient across the ampoule may be required for electron beams (2). The dichromate system may be used at lower energies by employing thinner
(in the beam direction) dosimeter containers (see ICRU Report 35).
1.5.4 The irradiation temperature of the dosimeter shall be above 0°C 0 °C and should be below 80°C. 80 °C.
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.
ε1
Current edition approved Sept. 14, 2013Oct. 1, 2021. Published November 2013May 2024. Originally published as ASTM E 1401 – 91. ASTM E 1401 – 96approved
was adopted by ISO in 1998 with the intermediate designation ISO 15561:1998(E). The present International Standard ISO/ASTM 51401:2013(E) replaces ISO 15561 and
is a major revision of the last previous edition ISO/ASTM 51401:2003(E).in 1991. Last previous edition approved in 2013 as ISO/ASTM 51401:2013(E). DOI:
10.1520/51401-21.
The boldface numbers in parentheses refer to the bibliography at the end of this practice.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
51401 − 21
NOTE 2—The temperature coefficient of dosimeter response is known only in the range of 5 to 50°C 50 °C (see 5.2). Use outside this range requires
determination of the temperature coefficient.
1.6 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. Specific precautionary statements are given in 9.3.
1.7 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.
2. Referenced documents
2.1 ASTM Standards:
E170 Terminology Relating to Radiation Measurements and Dosimetry
E178 Practice for Dealing With Outlying Observations
E275 Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E666 Practice for Calculating Absorbed Dose From Gamma or X Radiation
E668 Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining Absorbed Dose in
Radiation-Hardness Testing of Electronic Devices
E925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidth does not
Exceed 2 nm
E958 Practice for Estimation of the Spectral Bandwidth of Ultraviolet-Visible Spectrophotometers
E3083 Terminology Relating to Radiation Processing: Dosimetry and Applications
2.2 ISO/ASTM Standards:
51261 Practice for Calibration of Routine Dosimetry Systems for Radiation Processing
51707 Guide for Estimating Uncertainties 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 ISO/IEC Standards:
17025 General Requirements for the Competence of Testing and Calibration Laboratories
12749-4 Nuclear energy — Vocabulary — Part 4: Dosimetry for radiation processing
2.4 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 200:2012, VIM International Vocabulary of Metrology - Basic and General Concepts and Associated Terms
2.5 International Commission on Radiation Units and Measurements (ICRU) Reports:
ICRU Report 35 Radiation Dosimetry: Electrons With Initial Energies Between 1 and 50 MeV
ICRU Report 80 Dosimetry Systems for Use in Radiation Processing
ICRU Report 85a Fundamental Quantities and Units for Ionizing Radiation
3. Terminology
3.1 Definitions:
3.1.1 approved laboratory—laboratory that is a recognized national metrology institute; or has been formally accredited to
ISO/IEC 17025; or has a quality system consistent with the requirements of ISO/IEC 17025.
3.1.1.1 Discussion—
A recognized national metrology institute or other calibration laboratory accredited to ISO/IEC 17025 should be used in order to
ensure traceability to a national or international standard. A calibration certificate provided by a laboratory not having formal
recognition or accreditation will not necessarily be proof of traceability to a national or international standard.
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 Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http://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 1). Available free of charge at the BIPM website
(http://www.bipm.org).
Available from the International Commission on Radiation Units and Measurements (ICRU), 7910 Woodmont Ave., Bethesda, MD 20814, U.S.A.
51401 − 21
3.1.1 reference standard dosimetry system—dosimetry system, generally having the highest metrological quality available at a
given location or in a given organization, from which measurements made there are derived.
3.1.2 type I dosimeter—dosimeter of high metrological quality, the response of which is affected by individual influence quantities
in a well-defined way that can be expressed way that is well-defined and capable of expression in terms of independent correction
factors.
3.2 Definitions of other terms used in this practicestandard that pertain to radiation measurement and dosimetry may be found in
ISO/ASTM Practice 52628. Other terms that pertain to radiation measurement and dosimetry may be found in ASTM Terminology
E170E3083. Definitions and ISO Terminology 12749-4. Where appropriate, definitions used in E170 are compatible with ICRU
Report 85a; that document, therefore, may be used as an alternative reference.these standards have been derived from, and are
consistent with definitions in ICRU Report 85a, and general metrological definitions given in the VIM.
4. Significance and use
4.1 The dichromate system provides a reliable means for measuring absorbed dose to water. It is based on a process of reduction
of dichromate ions to chromic ions in acidic aqueous solution by ionizing radiation.
4.2 The dosimeter is a solution containing silver and dichromate ions in perchloric acid in an appropriate container such as a sealed
glass ampoule. The solution indicates absorbed dose by a change (decrease) in optical absorbance at a specified wavelength(s) ((3),
ICRU Report 80). A calibrated spectrophotometer is used to measure the absorbance.
5. Effect of influence quantities
5.1 Guidance on the determination of the performance characteristics of dosimeters and dosimetry systems can be found in ASTM
Guide 52701. The relevant influence quantities that need to be considered when using the dichromate dosimetry system are given
below.
5.2 The dosimeter response has a temperature dependence during irradiation that is approximately equal to −0.2 % per degree
Celsius between 25 and 50°C. 50 °C. At temperatures below 25°C, 25 °C, the dependence is smaller. The dosimeter response
between 5 and 50°C 50 °C is shown in Table 1, where the response at a given temperature is tabulated relative to the response
at 25°C 25 °C (4, 5).
5.2.1 The data in Table 1 may be fitted with an appropriate formula for convenience of interpolation as follows:
b
R 5 b 1b t (1)
t 0 1
where:
R = dosimeter response at temperature t relative to that at 25°C.
t
R = dosimeter response at temperature t relative to that at 25 °C.
t
The curve generated from the fitted data is shown in Fig. 1.
5.3 No effect of ambient light (even direct sunlight) has been observed on dichromate solutions in glass ampoules (6).
5.4 The dosimeter response is dependent on the type and energy of the radiation employed. For example, the response in high
energy (10 MeV) electron beams is reported to be approximately 3 % lower than the response in cobalt-60 radiation (2).
TABLE 1 Effect of irradiation temperature on dosimeter response
Temperature, °C Relative Response Temperature, °C Relative Response
5 1.020 30 0.992
10 1.017 35 0.983
15 1.013 40 0.972
20 1.007 45 0.960
25 1.000 50 0.948
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FIG. 1 Relative response of dichromate dosimeter as a function of irradiation temperature. A fit of the data using Eq 1 yields fit param-
−5
eters as follows: b = 1.021;b = −6.259 × 10 ;b = 1.806.
0 1 2
5.5 Provided the dosimeter solution is prepared as described in this document, and steps are taken to avoid contamination, the
dosimeter solution stored, or sealed, in glass vessels (for example, ampoules) is stable for several years before and after irradiation.
6. Interferences
6.1 The dichromate dosimetric solution response is sensitive to impurities, particularly organic impurities. Even in trace quantities,
impurities can cause a detectable change in the observed response (6). For high accuracy results, organic materials shall not be used
for any component in contact with the solution, unless it has been demonstrated that the materials do not affect dosimeter response.
The effect of trace impurities may be minimized by pre-irradiation of the bulk dichromate solution (see Ref (6) and 9.4).
6.2 Undesirable chemical changes in the dosimetric solution can occur if care is not taken during sealing of ampoules (see 9.6).
7. Apparatus
7.1 High-Precision Spectrophotometer—For the analysis of the dosimetric solution, use a high-precision spectrophotometer
capable of measuring absorbance values up to 2 with an uncertainty of no more than 61 % in the region of 350 to 440 nm. 440 nm
(see 10.3). Use a quartz cuvette with 5 or 10 mm path length for spectrophotometric measurements of the solution. The cuvette
capacity must be small enough to allow it to be thoroughly rinsed by the dosimeter solution and still leave an adequate amount
of that solution to fill the cuvette to the appropriate level for the absorbance measurement. For dosimeter ampoules of less than
2 mL, this may require the use of micro-capacity cuvettes. Other solution handling techniques, such as the use of micro-capacity
flow cells, may be employed provided precautions are taken to avoid cross-contamination. Either control the temperature of the
dosimetric solution during measurement at 25 6 1°C, 1 °C, or determine the solution temperature during the spectrophotometric
analysis and correct the measured absorbance to 25°C. The temperature coefficient during measurement is −0.1 % per degree
Celsius within the range of 20 to 30°C 30 °C (6).
NOTE 3—The dosimetric ampoule commonly used has a capacity of about 2 mL.
7.2 Glassware—Use borosilicate glass or equivalent chemically resistant glass to store the reagents and the prepared dosimetric
solution. Clean all apparatus used in the preparation of the solution, as well as the glass ampoules or other irradiation containers
using chromic acid solution or an equivalent cleaning agent. Rinse at least three times with double-distilled water. Dry thoroughly
and store in a dust-free environment.
NOTE 4—A validated process involving neutral liquid laboratory detergent in an ultrasonic bath, might be an alternative to chromic acid for cleaning
glassware.
8. Reagents
8.1 Analytical reagent grade (or better) chemicals shall be used in this practice for preparing all solutions.
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8.2 Use of double-distilled water from coupled all-glass and silica stills is recommended. Alternatively, water from a high quality
commercial purification unit capable of achieving Total Oxidisable Carbon (T.O.C.) content below 5 ppb may be used. Water purity
is very important since it is the major constituent of the dosimetric solutions, and therefore may be the prime source of
contamination. Use of deionized water is not recommended.
NOTE 5—Double-distilled water distilled from an alkaline permanganate (KMnO ) solution (2 g KMnO plus 5 g sodium hydroxide (NaOH) pellets in
4 4
2 dm of distilled water) has been found to be adequate for preparation of the dichromate dosimetric solution. High purity water is commercially available
from some suppliers. Such water labelled HPLC (high pressure liquid chromatography) grade is usually sufficiently free of organic impurities to be used
in this practice.
9. Preparation of dosimeters
9.1 The recommended concentrations for the dichromate dosimeter to measure absorbed doses from about 2 to 10 kGy (hereafter
−3 −3 −3
called the low-range dosimeter) are 0.5 × 10 mol dm silver dichromate (Ag Cr O ) in 0.1 mol dm aqueous perchloric acid
2 2 7
(7). For measurement of absorbed doses from about 5 to 50 kGy (hereafter called the high-range dosimeter), the recommended
−3 −3 −3 −3
concentrations are 0.5 × 10 mol dm silver dichromate and 2.0 × 10 mol dm potassium dichromate (K Cr O ) in 0.1 mol
2 2 7
−3
dm aqueous perchloric acid (6).
9.2 Air saturate both solutions before use. Shaking of the solution is normally sufficient to achieve this.
9.3 Silver dichromate dissolves slowly and normally requires at least 18 h to dissolve completely. For the high-range dosimeter,
it is preferable to dissolve the silver dichromate before adding the potassium dichromate. (Warning—Concentrated perchloric acid
is a strong oxidizer and dichromate salts are skin irritants. Appropriate precautions should be exercised in handling these materials.)
NOTE 6—Dichromate dosimeters of other formulations have been described (8, 9).
9.4 If appropriate, irradiate the bulk solution to minimize the effects of impurities.
9.4.1 The exact dose is not critical, but a dose of approximately 1.0 kGy is recommended (6). The size of the container for this
bulk solution irradiation should be such that the dose variation to the solution is less than 610 %. Mix the solution thoroughly after
irradiation.
9.5 Rinse the dosimeter ampoules or other containers as prepared in 7.2 at least once with the dosimeter solution before filling
them for irradiation.
9.6 Exercise care in filling ampoules to avoid depositing solution in the ampoule neck. neck, or
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