1、ISO/ASTM 51026:2015(E)An American National StandardStandard Practice forUsing the Fricke Dosimetry System1This standard is issued under the fixed designation ISO/ASTM 51026; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the year
2、of last revision.1. Scope1.1 This practice covers the procedures for preparation,testing and using the acidic aqueous ferrous ammonium sulfatesolution dosimetry system to measure absorbed dose to waterwhen exposed to ionizing radiation. The system consists of adosimeter and appropriate analytical in
3、strumentation. Thesystem will be referred to as the Fricke dosimetry system. TheFricke dosimetry system may be used as either a referencestandard dosimetry system or a routine dosimetry system.1.2 This practice is one of a set of standards that providesrecommendations for properly implementing dosim
4、etry inradiation processing, and describes a means of achievingcompliance with the requirements of ISO/ASTM Practice52628 for the Fricke dosimetry system. It is intended to be readin conjunction with ISO/ASTM Practice 52628.1.3 The practice describes the spectrophotometric analysisprocedures for the
5、 Fricke dosimetry 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 are satis-fied:1.5.1 The absorbed dose range shall be from 20 to 400 Gy(1).21.5.2 The absorbed-dose rate does not exceed
6、 106Gys1(2).1.5.3 For radioisotope gamma sources, the initial photonenergy is greater than 0.6 MeV. For X-radiation(bremsstrahlung), the initial energy of the electrons used toproduce the photons is equal to or greater than 2 MeV. Forelectron beams, the initial electron energy is greater than 8MeV.N
7、OTE 1The lower energy limits given are appropriate for a cylindricaldosimeter ampoule of 12 mm diameter. Corrections for displacementeffects and dose gradient across the ampoule may be required for electronbeams (3). The Fricke dosimetry system may be used at lower energies byemploying thinner (in t
8、he beam direction) dosimeter containers (see ICRUReport 35).1.5.4 The irradiation temperature of the dosimeter should bewithin the range of 10 to 60C.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this
9、standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced documents2.1 ASTM Standards:3C912 Practice for Designing a Process for Cleaning Techni-cal GlassesE170 Terminology Relating to Radiation Measurements a
10、ndDosimetryE178 Practice for Dealing With Outlying ObservationsE275 Practice for Describing and Measuring Performance ofUltraviolet and Visible SpectrophotometersE666 Practice for Calculating Absorbed Dose From Gammaor X RadiationE668 Practice for Application of Thermoluminescence-Dosimetry (TLD) Sy
11、stems 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 Practice for Estimation of the Spectral Bandwidth ofUltraviolet-Visible Spectr
12、ophotometers2.2 ISO/ASTM Standards:351261 Practice for Calibration of Routine Dosimetry Sys-tems for Radiation Processing51707 Guide for Estimating Uncertainties in Dosimetry forRadiation Processing52628 Practice for Dosimetry in Radiation Processing2.3 ISO/IEC Standard:ISO/IEC 17025 General require
13、ments for the competence oftesting and calibration laboratories41This 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 appro
14、ved Feb. 9, 2015. Published June 2015. Originallypublished as ASTM E102684. Last previous ASTM edition E1026 13. Thepresent International Standard ISO/ASTM 510262015(E) replaces ASTME1026 13.2The boldface numbers that appear in parentheses refer to a bibliography at theend of this practice.3For refe
15、renced ASTM and ISO/ASTM standards, visit the ASTM webiste,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.4Available from American National Standards Institute (AN
16、SI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org. ISO/ASTM International 2015 All rights reserved12.4 International Commission on Radiation Units and Mea-surements (ICRU) Reports:5ICRU Report 14 Radiation Dosimetry: X Rays and GammaRays with Maximum Photon Energies Between 0.6 a
17、nd 50MeVICRU Report 35 Radiation Dosimetry: Electrons with InitialEnergies Between 1 and 50 MeVICRU Report 64 Dosimetry of High-Energy Photon Beamsbased on Standards of Absorbed Dose to WaterICRU Report 80 Dosimetry Systems for Use in RadiationProcessingICRU Report 85a Fundamental Quantities and Uni
18、ts forIonizing Radiation2.5 Joint Committee for Guides in Metrology (JCGM)Reports:6JCGM 100:2008 GUM 1995 , with minor corrections,Evaluation of measurement data Guide to the expressionof uncertainty in measurement2.6 National Research Council Canada (NRCC):PIRS-0815 The IRS Fricke Dosimetry System7
19、3. Terminology3.1 Definitions:3.1.1 approved laboratorylaboratory that is a 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 o
20、r other calibration laboratory accredited to ISO/IEC17025 should be used in 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
21、or international standard.3.1.2 molar linear absorption coeffcient (m)a constantrelating the spectrophotometric absorbance (A) of an opticallyabsorbing molecular species at a given wavelength () per unitpathlength (d) to the molar concentration (c) of that species insolution:m5Ad 3c!(1)Unit: m2mol-1
22、3.1.3 radiation chemical yield (G(x)quotient of n(x)by,where n(x) is the mean amount of a specified entity, x,produced, destroyed, or changed by the mean energy, ,imparted to the matter.Gx! 5Snx!HD(2)Unit: molJ-13.1.4 reference standard dosimetry systemdosimetrysystem, generally having the highest m
23、etrological qualityavailable at a given location or in a given organization, fromwhich measurements made there are derived.3.1.5 type I dosimeterdosimeter of high metrologicalquality, the response of which is affected by individual influ-ence quantities in a well-defined way that can be expressed in
24、terms of independent correction factors.3.2 Definitions of other terms used in this standard thatpertain to radiation measurement and dosimetry may be foundin Terminology E170. Definitions in E170 are compatible withICRU 85a; that document, therefore, may be used as analternative reference.4. Signif
25、icance and use4.1 The Fricke dosimetry system provides a reliable meansfor measurement of absorbed dose to water, based on a processof oxidation of ferrous ions to ferric ions in acidic aqueoussolution by ionizing radiation (ICRU 80, PIRS-0815,(4). Insituations not requiring traceability to national
26、 standards, thissystem can be used for absolute determination of absorbeddose without calibration, as the radiation chemical yield offerric ions is well characterized (see Appendix X3).4.2 The dosimeter is an air-saturated solution of ferroussulfate or ferrous ammonium sulfate that indicates absorbe
27、ddose by an increase in optical absorbance at a specifiedwavelength. A temperature-controlled calibrated spectropho-tometer is used to measure the absorbance.5. Effect of influence quantities5.1 The Fricke dosimeter response (change in optical absor-bance) to a given radiation dose is dependent on i
28、rradiationtemperature and measurement temperature. Thus, correctionsmay have to be applied for changes to the radiation chemicalyield (G) for irradiation temperature and to the molar linearabsorption coefficient () for measurement temperatures. Both(Fe3+) and G(Fe3+) increase with increase in temper
29、ature. Thesubscripts indicate the temperature of irradiation andmeasurement, as applicable. Both of the temperatures are inC.Tmeas5 25110.0069 Tmeas2 25!# (3)GTirrad5 G25110.0012 Tirrad2 25!# (4)5.2 The radiation chemical yield depends on the type andenergy of the radiation employed and, in particul
30、ar, changessignificantly at low photon energies (5).6. Interferences6.1 The Fricke dosimeter response is extremely sensitive toimpurities in the solution, particularly organic impurities. Evenin trace quantities, impurities can cause a detectable change inthe observed response. For high accuracy, or
31、ganic materialsshall not be used for any component in contact with thesolution, unless it has been demonstrated that the materials donot affect the dosimeter response.5Available from International Commission on Radiation Units and Measure-ments (ICRU), 7910 Woodmont Ave., Suite 400, Bethesda, MD 208
32、41-3095,http:/www.icru.org.6Document produced by Working Group 1 of the Joint Committee for Guides inMetrology (JCGM/WG1). Available free of charge at the BIPM website (http:/www.bipm.org).7Available from the National Research Council, Ionizing Radiation Standards,Ottawa, Ontario. K1A 0R6.ISO/ASTM 5
33、1026:2015(E)2 ISO/ASTM International 2015 All rights reserved6.2 Traces of metal ions in the irradiated and unirradiateddosimetric solutions can also affect dosimeter response.Therefore, do not use metal in any component in contact withthe solutions.6.3 If flame sealed ampoules are used as the dosim
34、eters,exercise care in filling ampoules to avoid depositing solution inthe ampoule neck. Subsequent heating during sealing of theampoule may cause undesirable chemical change in the dosi-metric solution remaining inside the ampoule neck. For thesame reason, exercise care to avoid heating the body of
35、 theampoule during sealing.6.4 Thermal oxidation (as indicated by an increase in opticalabsorbance), in the absence of radiation, is a function ofambient temperature.At normal laboratory temperatures (about20 to 25C), this effect may be significant if there is a longperiod of time between solution p
36、reparation and photometricmeasurement. This interference is discussed further in 9.3.6.5 The dosimetric solution is somewhat sensitive to ultra-violet light and should be kept in the dark for long-termstorage. No special precautions are required during routinehandling under normal laboratory lightin
37、g conditions, butstrong UV sources such as sunlight should be avoided.7. Apparatus7.1 For the analysis of the dosimetric solution, use ahigh-precision spectrophotometer capable of measuring absor-bance values up to 2 with an uncertainty of no more than 61%in the region of 300 nm. Use a quartz cuvett
38、e with 5- or 10-mmpathlength for spectrophotometric measurement of the solu-tion. The cuvette capacity must be small enough to allow it tobe thoroughly rinsed by the dosimeter solution and still leavean adequate amount of that solution to fill the cuvette to theappropriate level for the absorbance m
39、easurement. For dosim-eter ampoules of less than 2 mL, this may require the use ofsemi-microcapacity cuvettes. Other solution handlingtechniques, such as the use of micro-capacity flow cells, maybe employed provided precautions are taken to avoid cross-contamination. Either control the temperature o
40、f the dosimetricsolution during measurement at 25 6 0.5C, or determine thesolution temperature during the spectrophotometric analysisand correct the measured absorbance to 25C using Eq 3.7.2 Use borosilicate glass or equivalent chemically-resistantglass to store the reagents and the prepared dosimet
41、ric solution.Clean all apparatus thoroughly before use (see Practice C912).7.2.1 Store the cleaned glassware in a clean, dust-freeenvironment. For extreme accuracy, bake the glassware invacuum at 550C for at least 1 h (6).7.2.2 As an alternative method to baking the glassware, thedosimeter container
42、s (for example, ampoules) may be filledwith the dosimetric solution and irradiated to a dose of at least500 Gy. When a container is needed, pour out the irradiatedsolution, rinse the container at least three times with unirradi-ated solution and then refill with the dosimetric solution to beirradiat
43、ed. The time between filling, irradiation and measure-ment should be as short as practical, preferably no more than afew hours. Refer to Note 2.7.3 Use a sealed glass ampoule or other appropriate glasscontainer to hold the dosimetric solution during irradiation.NOTE 2To minimize errors due to differ
44、ences in radiation absorptionproperties between the container material and the Fricke solution, it ispossible to use plastic containers (for example, PMMA or polystyrene) tohold Fricke solution. However, the interferences discussed in Section 6may result in a reduction in accuracy.To reduce these pr
45、oblems, the plasticcontainers may be conditioned by irradiating them filled with dosimetricsolution to approximately 500 Gy. The containers should then bethoroughly rinsed with unirradiated solution before use.8. Reagents8.1 Purity of ReagentsReagent grade chemicals shall beused. Unless otherwise in
46、dicated, all reagents shall conform tothe specifications of the Committee on Analytical Reagents ofthe American Chemical Society (or equivalent) where suchspecifications are available.8Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficient highpurity to permit
47、its use without lessening the accuracy of themeasurements. Methods of obtaining higher purity of chemi-cals exist (for example, crystallization or distillation), but arenot discussed here.8.2 Purity of WaterWater purity is very important sincewater is the major constituent of the dosimetric solution
48、, andtherefore, may be the prime source of contamination. The useof double-distilled water from coupled all-glass and silica stillsor water from a high-quality commercial purification unitcapable of achieving Total Oxidizable Carbon (T.O.C.) contentbelow 5 ppb is recommended. Use of deionized water
49、is notrecommended.NOTE 3Double-distilled water distilled from an alkaline permangan-ate (KMnO4) solution (2 g KMnO4plus 5 g sodium hydroxide (NaOH) in2 L of distilled water) has been found to be adequate for routinepreparation of the dosimetric solution. High purity water is commerciallyavailable from some suppliers. Water labelled HPLC (high pressure liquidchromatography) grade is usually sufficiently free of organic impurities tobe used in this practice.8.3 Reagents:8.3.1 Ferrous Ammonium Sulfate(NH4)2Fe(SO4)26H2O.8.3.2 Sodium
