1、ISO/ASTM 51401:2013(E)An American National StandardStandard 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 ye
2、ar of last revision.1. Scope1.1 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 instrumentati
3、on. For simplicity, the sys-tem 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
4、.1.2 This document is one of 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 conju
5、nction with ISO/ASTM Practice 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 s
6、atisfied:1.5.1 The absorbed dose 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
7、greater than 0.6 MeV. For bremsstrahlungphotons, 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
8、cylindricaldosimeter ampoule 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
9、.4 The irradiation temperature 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 pur
10、port to address all of thesafety 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
11、 in 9.3.2. Referenced documents2.1 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 Abso
12、rbed Dose From Gammaor X RadiationE668 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 Bandwidt
13、hdoes not Exceed 2 nmE958 Practice 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 Processi
14、ng52628 Practice for Dosimetry in Radiation Processing1This practice is under the 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.
15、 14, 2013. Published November 2013. Originallypublished asASTM E 1401 91.ASTM E 1401 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/A
16、STM 51401:2003(E).2The boldface numbers in parentheses refer to the bibliography 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, refe
17、r to the standardsDocument Summary page on the ASTM website. ISO/ASTM International 2013 All rights reserved152701 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 Testi
18、ngand Calibration 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) Repor
19、ts:6ICRU Report 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
20、recognizednational 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
21、order to ensure 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 systemdosimetry
22、system, generally 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 wel
23、l-defined way 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, therefo
24、re, may beused 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 so
25、lution containing 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 meas
26、ure the absorbance.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 give
27、n below.5.2 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
28、temperature 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 i
29、s shown in Fig. 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
30、to beapproximately 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 ye
31、ars before and 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
32、 International 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).
33、6Available from 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
34、1.013 40 0.97220 1.007 45 0.96025 1.000 50 0.948ISO/ASTM 51401:2013(E)2 ISO/ASTM International 2013 All rights reservedmaterials 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 im
35、puritiesmay 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 dosime
36、tric solution, 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 b
37、e small enough 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. Othe
38、r solution 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 thespectropho
39、tometric analysis 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-c
40、ally resistant 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 doubl
41、e-distilled 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, wat
42、er from a highquality 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
43、 water is not 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 iscomm
44、ercially available 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 dos
45、es from about 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 dm
46、3silver dichromate 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 disso
47、lve completely. 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 mate
48、rials.)NOTE 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 bul
49、k 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 ampoules or other containers asprepared in 7.2 at least once with the dosimeter solution beforefilling them for irradiation.9.6 Exercise care in filling ampoules to avoid depositingsolution in the ampoule neck. Subsequent heating duringsealing may cause an undesirable chemical change in theFIG. 1 Relative response of dichromate dosimeter as a functionof irradiation temper
