1、ISO/ASTM 51401:2013(E)Standard Practice forUse of a Dichromate Dosimetry System1This standard is issued under the fixed designation ISO/ASTM 51401; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year of last revision.1. Scope1
2、.1 This practice covers the preparation, testing, and proce-dure for using the acidic aqueous silver dichromate dosimetrysystem to measure absorbed dose to water when exposed toionizing radiation. The system consists of a dosimeter andappropriate analytical instrumentation. For simplicity, the sys-t
3、em will be referred to as the dichromate system. The dichro-mate dosimeter is classified as a type I dosimeter on the basisof the effect of influence quantities. The dichromate systemmay be used as either a reference standard dosimetry system ora routine dosimetry system.1.2 This document is one of
4、a set of standards that providesrecommendations for properly implementing dosimetry inradiation processing, and describes a means of achievingcompliance with the requirements of ISO/ASTM Practice52628 for the dichromate dosimetry system. It is intended to beread in conjunction with ISO/ASTM Practice
5、 52628.1.3 This practice describes the spectrophotometric analysisprocedures 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 conditionsare satisfied:1.5.1 The absorbed d
6、ose range is from 2 103to5104Gy.1.5.2 The absorbed dose rate does not exceed 600 Gy/pulse(12.5 pulses per second), or does not exceed an equivalent doserate of 7.5 kGy/s from continuous sources (1).21.5.3 For radionuclide gamma sources, the initial photonenergy shall be greater than 0.6 MeV. For bre
7、msstrahlungphotons, the initial energy of the electrons used to produce thebremsstrahlung photons shall be equal to or greater than 2MeV. For electron beams, the initial electron energy shall begreater than 8 MeV.NOTE 1The lower energy limits given are appropriate for a cylindricaldosimeter ampoule
8、of 12 mm diameter. Corrections for displacementeffects and dose gradient across the ampoule may be required for electronbeams (2). The dichromate system may be used at lower energies byemploying thinner (in the beam direction) dosimeter containers (see ICRUReport 35).1.5.4 The irradiation temperatur
9、e of the dosimeter shall beabove 0C and should be below 80C.NOTE 2The temperature coefficient of dosimeter response is knownonly in the range of 5 to 50C (see 5.2). Use outside this range requiresdetermination of the temperature coefficient.1.6 This standard does not purport to address all of thesaf
10、ety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific precau-tionary statements are given in 9.3.2. Referenced documen
11、ts2.1 ASTM Standards:3E170 Terminology Relating to Radiation Measurements andDosimetryE178 Practice for Dealing With Outlying ObservationsE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible SpectrophotometersE666 Practice for Calculating Absorbed Dose From Gammaor X Radi
12、ationE668 Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for Determining AbsorbedDose in Radiation-Hardness Testing of Electronic DevicesE925 Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Bandwidthdoes not Exceed 2 nmE958 Pra
13、ctice for Estimation of the Spectral Bandwidth ofUltraviolet-Visible Spectrophotometers2.2 ISO/ASTM Standards:351261 Practice for Calibration of Routine Dosimetry Sys-tems for Radiation Processing51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Processing1This practice is under the
14、 jurisdiction of ASTM Committee E61 on RadiationProcessing and is the direct responsibility of Subcommittee E61.02 on DosimetrySystems, and is also under the jurisdiction of ISO/TC 85/WG 3.Current edition approved Sept. 14, 2013. Published November 2013. Originallypublished asASTM E 1401 91.ASTM E 1
15、401 961was adopted by ISO in 1998with the intermediate designation ISO 15561:1998(E). The present InternationalStandard ISO/ASTM 51401:2013(E) replaces ISO 15561 and is a major revision ofthe last previous edition ISO/ASTM 51401:2003(E).2The boldface numbers in parentheses refer to the bibliography
16、at the end of thispractice.3For referenced ASTM and ISO/ASTM standards, visit the ASTM website,www.astm.org, or contact ASTM Customer Service at serviceastm.org. ForAnnual Book of ASTM Standards volume information, refer to the standardsDocument Summary page on the ASTM website. ISO/ASTM Internation
17、al 2017 All rights reservedThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization
18、Technical Barriers to Trade (TBT) Committee.152628 Practice for Dosimetry in Radiation Processing52701 Guide for Performance Characterization of Dosim-eters and Dosimetry Systems for Use in Radiation Pro-cessing2.3 ISO/IEC Standards:417025 General Requirements for the Competence of Testingand Calibr
19、ation Laboratories2.4 Joint Committee for Guides in Metrology (JCGM)Reports:5JCGM 100:2008, GUM 1995, with minor corrections,Evaluation of measurement data Guide to the Expres-sion of Uncertainty in Measurement2.5 International Commission on Radiation Units and Mea-surements (ICRU) Reports:6ICRU Rep
20、ort 35 Radiation Dosimetry: Electrons With InitialEnergies Between 1 and 50 MeVICRU Report 80 Dosimetry Systems for Use in RadiationProcessingICRU Report 85a Fundamental Quantities and Units forIonizing Radiation3. Terminology3.1 Definitions:3.1.1 approved laboratorylaboratory that is a recognizedna
21、tional metrology institute; or has been formally accredited toISO/IEC 17025; or has a quality system consistent with therequirements of ISO/IEC 17025.3.1.1.1 DiscussionA recognized national metrology insti-tute or other calibration laboratory accredited to ISO/IEC17025 should be used in order to ens
22、ure traceability to anational or international standard. A calibration certificateprovided by a laboratory not having formal recognition oraccreditation will not necessarily be proof of traceability to anational or international standard.3.1.2 reference standard dosimetry systemdosimetrysystem, gene
23、rally having the highest metrological qualityavailable at a given location or in a given organization, fromwhich measurements made there are derived.3.1.3 type I dosimeterdosimeter of high metrologicalquality, the response of which is affected by individual influ-ence quantities in a well-defined wa
24、y that can be expressed interms of independent correction factors.3.2 Definitions of other terms used in this practice thatpertain to radiation measurement and dosimetry may be foundin ASTM Terminology E170. Definitions in E170 are compat-ible with ICRU Report 85a; that document, therefore, may beus
25、ed as an alternative reference.4. Significance and use4.1 The dichromate system provides a reliable means formeasuring absorbed dose to water. It is based on a process ofreduction of dichromate ions to chromic ions in acidic aqueoussolution by ionizing radiation.4.2 The dosimeter is a solution conta
26、ining silver and dichro-mate ions in perchloric acid in an appropriate container such asa sealed glass ampoule. The solution indicates absorbed doseby a change (decrease) in optical absorbance at a specifiedwavelength(s) (3), ICRU Report 80).Acalibrated spectropho-tometer is used to measure the abso
27、rbance.5. Effect of influence quantities5.1 Guidance on the determination of the performancecharacteristics of dosimeters and dosimetry systems can befound inASTM Guide 52701. The relevant influence quantitiesthat need to be considered when using the dichromate dosim-etry system are given below.5.2
28、The dosimeter response has a temperature dependenceduring irradiation that is approximately equal to 0.2 % perdegree Celsius between 25 and 50C. At temperatures below25C, the dependence is smaller. The dosimeter responsebetween 5 and 50C is shown in Table 1, where the response ata given temperature
29、is tabulated relative to the response at25C (4,5).5.2.1 The data in Table 1 may be fitted with an appropriateformula for convenience of interpolation as follows:Rt5 b01 b1tb2(1)where:Rt= dosimeter response at temperature t relative to that at25C.The curve generated from the fitted data is shown in F
30、ig. 1.5.3 No effect of ambient light (even direct sunlight) hasbeen observed on dichromate solutions in glass ampoules (6).5.4 The dosimeter response is dependent on the type andenergy of the radiation employed. For example, the response inhigh energy (10 MeV) electron beams is reported to beapproxi
31、mately 3 % lower than the response in cobalt-60radiation (2).5.5 Provided the dosimeter solution is prepared as describedin this document, and steps are taken to avoid contamination,the dosimeter solution stored, or sealed, in glass vessels (forexample, ampoules) is stable for several years before a
32、nd afterirradiation.6. Interferences6.1 The dichromate dosimetric solution response is sensitiveto impurities, particularly organic impurities. Even in tracequantities, impurities can cause a detectable change in theobserved response (6). For high accuracy results, organic4Available from Internation
33、al Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, CP 56, CH-1211 Geneva 20, Switzerland, http:/www.iso.org.5Document produced by Working Group 1 of the Joint Committee for Guides inMetrology (JCGM/WG 1). Available free of charge at the BIPM website (http:/www.bipm.org).6Available f
34、rom the International Commission on Radiation Units and Measure-ments (ICRU), 7910 Woodmont Ave., Bethesda, MD 20814, U.S.A.TABLE 1 Effect of irradiation temperature on dosimeter responseTemperature, C Relative Response Temperature, C Relative Response5 1.020 30 0.99210 1.017 35 0.98315 1.013 40 0.9
35、7220 1.007 45 0.96025 1.000 50 0.948ISO/ASTM 51401:2013(E)2 ISO/ASTM International 2017 All rights reserved materials shall not be used for any component in contact withthe solution, unless it has been demonstrated that the materialsdo not affect dosimeter response. The effect of trace impuritiesmay
36、 be minimized by pre-irradiation of the bulk dichromatesolution (see Ref (6) and 9.4).6.2 Undesirable chemical changes in the dosimetric solutioncan occur if care is not taken during sealing of ampoules (see9.6).7. Apparatus7.1 High-Precision SpectrophotometerFor the analysis ofthe dosimetric soluti
37、on, use a high-precision spectrophotom-eter capable of measuring absorbance values up to 2 with anuncertainty of no more than 61 % in the region of 350 to440 nm. Use a quartz cuvette with 5 or 10 mm path length forspectrophotometric measurements of the solution. The cuvettecapacity must be small eno
38、ugh to allow it to be thoroughlyrinsed by the dosimeter solution and still leave an adequateamount of that solution to fill the cuvette to the appropriatelevel for the absorbance measurement. For dosimeter ampoulesof less than 2 mL, this may require the use of micro-capacitycuvettes. Other solution
39、handling techniques, such as the use ofmicro-capacity flow cells, may be employed provided precau-tions are taken to avoid cross-contamination. Either control thetemperature of the dosimetric solution during measurement at25 6 1C, or determine the solution temperature during thespectrophotometric an
40、alysis and correct the measured absor-bance to 25C. The temperature coefficient during measure-ment is 0.1 % per degree Celsius within the range of 20 to30C (6).NOTE 3The dosimetric ampoule commonly used has a capacity ofabout 2 mL.7.2 GlasswareUse borosilicate glass or equivalent chemi-cally resist
41、ant glass to store the reagents and the prepareddosimetric solution. Clean all apparatus used in the preparationof the solution, as well as the glass ampoules or otherirradiation containers using chromic acid solution or an equiva-lent cleaning agent. Rinse at least three times with double-distilled
42、 water. Dry thoroughly and store in a dust-free envi-ronment.8. Reagents8.1 Analytical reagent grade (or better) chemicals shall beused in this practice for preparing all solutions.8.2 Use of double-distilled water from coupled all-glass andsilica stills is recommended. Alternatively, water from a h
43、ighquality commercial purification unit capable of achieving TotalOxidisable Carbon (T.O.C.) content below 5 ppb may be used.Water purity is very important since it is the major constituentof the dosimetric solutions, and therefore may be the primesource of contamination. Use of deionized water is n
44、ot recom-mended.NOTE 4Double-distilled water distilled from an alkaline permangan-ate (KMnO4) solution (2 g KMnO4plus 5 g sodium hydroxide (NaOH)pellets in 2 dm3of distilled water) has been found to be adequate forpreparation of the dichromate dosimetric solution. High purity water iscommercially av
45、ailable from some suppliers. Such water labelled HPLC(high pressure liquid chromatography) grade is usually sufficiently free oforganic impurities to be used in this practice.9. Preparation of dosimeters9.1 The recommended concentrations for the dichromatedosimeter to measure absorbed doses from abo
46、ut 2 to 10 kGy(hereafter called the low-range dosimeter) are0.5103mol dm3silver dichromate (Ag2Cr2O7)in0.1 mol dm3aqueous perchloric acid (7). For measurement ofabsorbed doses from about 5 to 50 kGy (hereafter called thehigh-range dosimeter), the recommended concentrations are0.5103mol dm3silver dic
47、hromate and 2.0 103mol dm3potassium dichromate (K2Cr2O7) in 0.1 mol dm3aqueous perchloric acid (6).9.2 Air saturate both solutions before use. Shaking of thesolution is normally sufficient to achieve this.9.3 Silver dichromate dissolves slowly and normally re-quires at least 18 h to dissolve complet
48、ely. For the high-rangedosimeter, it is preferable to dissolve the silver dichromatebefore adding the potassium dichromate. (WarningConcentrated perchloric acid is a strong oxidizer and dichro-mate salts are skin irritants. Appropriate precautions should beexercised in handling these materials.)NOTE
49、 5Dichromate dosimeters of other formulations have beendescribed (8, 9).9.4 If appropriate, irradiate the bulk solution to minimizethe effects of impurities.9.4.1 The exact dose is not critical, but a dose of approxi-mately 1.0 kGy is recommended (6). The size of the containerfor this bulk solution irradiation should be such that the dosevariation to the solution is less than 610 %. Mix the solutionthoroughly after irradiation.9.5 Rinse the dosimeter ampoul
