1、Designation: E 1026 04e1An American National StandardStandard Practice forUsing the Fricke Reference-Standard Dosimetry System1This standard is issued under the fixed designation E 1026; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.e1NOTEEquations 3 and 4 were corrected editorially in August 2005.1. Scope1.1 This practice covers the procedures
3、 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 instrumentation. Thesystem will be referred to as the Fricke syste
4、m. It is classifiedas a reference-standard dosimetry system (see ISO/ASTM51261).1.2 The practice describes the spectrophotometric analysisprocedures for the Fricke dosimeter.1.3 This practice applies only to gamma rays, x-rays(bremsstrahlung), and high-energy electrons.1.4 This practice applies prov
5、ided the following are satis-fied:1.4.1 The absorbed dose range shall be from 20 to 400 Gy(1).21.4.2 The absorbed-dose rate does not exceed 106Gys1(2).1.4.3 For radioisotope gamma-ray sources, the initial pho-ton energy is greater than 0.6 MeV. For x-rays (bremsstrahl-ung), the initial energy of the
6、 electrons used to produce thephotons is equal to or greater than 2 MeV. For electron beams,the initial electron energy is greater than 8 MeV (see ICRUReports 34 and 35).NOTE 1The lower energy limits given are appropriate for a cylindri-cal dosimeter ampoule of 12-mm outside diameter. Corrections fo
7、r dosegradients across an ampoule of that diameter or less are not required.1.4.4 The irradiation temperature of the dosimeter should bewithin the range of 10 to 60C.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of t
8、he user of this 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:3C 912 Practice for Designing a Process for Cleaning Tech-nical GlassesD 1193 Specification for Reagent Wat
9、erE 170 Terminology Relating to Radiation Measurementsand DosimetryE 178 Practice for Dealing with Outlying ObservationsE 275 Practice for Describing and Measuring Performanceof Ultraviolet, Visible, and Near Infrared Spectrophotom-etersE 666 Practice for CalculatingAbsorbed Dose from Gammaor X-Radi
10、ationE 668 Practice for Application of Thermoluminescence-Dosimetry (TLD) Systems for DeterminingAbsorbed Dosein Radiation-Hardness Testing of Electronic DevicesE 925 Practice for the Periodic Calibration of Narrow Band-Pass SpectrophotometersE 958 Practice for Measuring Practical Spectral Bandwidth
11、of Ultraviolet-Visible Spectrophotometers2.2 ISO/ASTM Standards:ISO/ASTM 51205 Method for Using the Ceric-Cerous Sul-fate Dosimetry SystemISO/ASTM 51261 Guide for Selection and Calibration ofDosimetry Systems for Radiation ProcessingISO/ASTM 51707 Estimating Uncertainties in Dosimetryfor Radiation P
12、rocessing2.3 International Commission on Radiation Units andMeasurements (ICRU) Reports:ICRU Report 34 The Dosimetry of Pulsed Radiation4ICRU Report 35 Radiation Dosimetry: Electrons with Ini-tial Energies Between 1 and 50 MeV4ICRU Report 60 Fundamental Quantities and Units forIonizing Radiation4ICR
13、U Report 64 Dosimetry of High-Energy Photon Beamsbased on Standards of Absorbed Dose to Water41This practice is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.01 on Dosimetry for Radiation Processing.Current edit
14、ion approved Jan. 1, 2004. Published February 2004. Originallyapproved in 1984. Last previous edition approved in 2003 as E 1026 03.2The boldface numbers that appear in parentheses refer to a list of references atthe end of this practice.3For referenced ASTM standards, visit the ASTM webiste, www.as
15、tm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from the International Commission on Radiation Units and Measure-ments (ICRU), 7910 Woodmont Ave., Suite 800, Be
16、thesda, MD 20814.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.2.4 National Research Council Canada (NRCC):PIRS-0815 The IRS Fricke Dosimetry System53. Terminology3.1 Definitions:3.1.1 Fricke Dosimetry Systemconsists of a liquid ch
17、emi-cal dosimeter (composed of ferrous sulfate or ferrous ammo-nium sulfate in aqueous sulfuric acid solution), a spectropho-tometer (to measure optical absorbance) and its associatedreference standards, and procedures for its use.3.1.1.1 DiscussionThe Fricke dosimetry system is consid-ered a refere
18、nce-standard dosimetry system. Sodium chlorideis usually added to dosimetric solution to minimize the effectsof organic impurities.3.1.2 molar linear absorption coeffcient (em)a constantrelating the spectrophotometric absorbance (Al) of an opticallyabsorbing molecular species at a given wavelength (
19、l) per unitpathlength (d) to the molar concentration (c) of that species insolution:em5Ald 3 c!Unit: m2mol-13.1.3 net absorbance (DA)change in measured opticalabsorbance at a selected wavelength determined as the absolutedifference between the pre-irradiation absorbance, Ao, and thepost-irradiation
20、absorbance, A as follows: DA =|A Ao|3.1.4 radiation chemical yield (G(x)the quotient of n (x)by e, where n (x) is the mean amount of a specified entity, x,produced, destroyed, or changed by the mean energy, e,imparted to the matter.Gx! 5Snx!e DUnit: molJ-13.2 Definitions of other terms used in this
21、standard thatpertain to radiation measurement and dosimetry may be foundin Terminology E 170. Definitions in E 170 are compatiblewith ICRU 60; that document, therefore, may be used as analternative reference.4. Significance and Use4.1 The Fricke dosimetry system provides a reliable meansfor measurem
22、ent of absorbed dose to water, based on a processof oxidation of ferrous ions to ferric ions in acidic aqueoussolution by ionizing radiation (3). In situations not requiringtraceability to national standards, this system can be used forabsolute determination of absorbed dose, as the radiationchemica
23、l yield of ferric ions is well characterized.4.1.1 In situations requiring traceability to national stan-dards, response of the Fricke system shall be verified by meansof comparison of expected and measured dose values. Thisverification process requires irradiation of dosimeters in acalibration faci
24、lity having measurement traceability to nation-ally or internationally recognized standards.4.2 The dosimeter is an air-saturated solution of ferroussulfate or ferrous ammonium sulfate that indicates absorbeddose by an increase in absorbance at a specified wavelength. Atemperature-controlled calibra
25、ted spectrophotometer is used tomeasure the absorbance.4.3 The Fricke dosimeter response is dependent on irradia-tion temperature and measurement temperature. Thus, correc-tions may have to be applied to the radiation chemical yield (G)for irradiation temperature and to the molar linear absorptionco
26、efficient (e) for measurement temperatures.4.4 The absorbed dose in materials other than water may becalculated using procedures given in Practices E 666 andE 668, and ISO/ASTM 51261, if the material is irradiatedunder equivalent conditions.4.5 There are two factors associated with use of the Fricke
27、system at energies below those specified in 1.4.3:4.5.1 The radiation chemical yield changes significantly atlow photon energies (4), and4.5.2 For electron energy below 8 MeV, dosimeter responserequires correction for dose gradients across the dosimeter witha dimension in the beam direction of 12 mm
28、 (see ICRU Report35).4.6 The lower energy limits given (refer to 1.4.3) areappropriate for a cylindrical dosimeter ampoule of 12-mmoutside diameter. With some difficulty, the Fricke system maybe used at lower energies by employing thinner (in the beamdirection) dosimeters (see ICRU Report 35). Below
29、 the lowerlimits for energy, there will be significant dose gradients acrossthe ampoule wall. In addition, it is difficult to perform accuratecalculations for a cylindrical ampoule.5. Interferences5.1 The Fricke dosimetric solution response is extremelysensitive to impurities, particularly organic i
30、mpurities. Even intrace quantities, impurities can cause a detectable change in theobserved response. For high accuracy, organic materials shallnot be used for any component in contact with the solution,unless it has been demonstrated that the materials do not affectthe dosimeter response.5.2 Traces
31、 of metal ions in the irradiated and unirradiateddosimetric solutions can also affect dosimeter response. There-fore, do not use metal in any component in contact with thesolutions.5.3 If flame sealing the dosimeters, exercise care in fillingampoules to avoid depositing solution in the ampoule neck.
32、Subsequent heating during sealing of the ampoule may causeundesirable chemical change in the dosimetric solution remain-ing inside the ampoules neck. For the same reason, exercisecare to avoid heating the body of the ampoule during sealing.5.4 Thermal oxidation (as indicated by an increase in optica
33、labsorbance), 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 preparation and photometricmeasurement. This interference is discussed further in 8.4.5.
34、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 routine5Available from the National Research Council, Ionizing Radiation Standards,Institute for National Measurement Standards, Ottaw
35、a, Ontario. K1A 0R6.E102604e12handling under normal laboratory lighting conditions, butstrong UV sources such as sunlight should be avoided.6. Apparatus6.1 For the analysis of the dosimetric solution, use ahigh-precision spectrophotometer capable of measuring absor-bance values up to 2 with an uncer
36、tainty of no more than 61%in the region of 300 nm. Use a quartz cuvette 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 sol
37、ution to fill the cuvette to theappropriate level for the absorbance measurement. For dosim-eter ampoules of less than 2 mL, this may require the use ofsemi-microcapacity cuvettes. Other solution handling tech-niques, such as the use of micro-capacity flow cells, may beemployed provided precautions
38、are taken to avoid cross-contamination. Control the temperature of the dosimetricsolution during measurement at 25 6 0.5C. If this is notpossible, determine the solution temperature during the spec-trophotometric analysis and correct the results using Eq 4 in10.4.5.6.2 Use borosilicate glass or equi
39、valent chemically-resistantglass to store the reagents and the prepared dosimetric solution.Clean all apparatus thoroughly before use (see Practice C 912).6.2.1 Store the cleaned glassware in a clean, dust-freeenvironment. For extreme accuracy, bake the glassware invacuum at 550C for at least one ho
40、ur (5).6.2.2 As an alternative method to baking the glassware, thedosimeter containers (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 w
41、ith unirradi-ated solution and then refill with the dosimetric solution to beirradiated. The time between filling, irradiation and measure-ment should be as short as practical, preferably no more than afew hours. Refer to Note 2.6.3 Use a sealed glass ampoule or other appropriate glasscontainer to h
42、old the dosimetric solution during irradiation.NOTE 2To minimize errors due to differences 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 interfe
43、rences discussed in Section 5may result in a reduction in accuracy.To reduce these problems, 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.7. Re
44、agents7.1 Purity of ReagentsReagent grade chemicals shall beused. Unless otherwise indicated, all reagents shall conform tothe specifications of the Committee on Analytical Reagents ofthe American Chemical Society where such specifications areavailable.6Other grades may be used, provided it is first
45、ascertained that the reagent is of sufficient high purity to permitits use without lessening the accuracy of the measurements.Methods of obtaining higher purity of chemicals exist (forexample, crystallization or distillation), but are not discussedhere7.2 Purity of WaterWater purity is very importan
46、t sincewater is the major constituent of the dosimetric solution, andtherefore, may be the prime source of contamination. The useof double-distilled water from coupled all-glass and silica stillsis recommended. Alternatively, water from a high-qualitycommercial purification unit capable of achieving
47、 Total Oxi-dizable Carbon (T.O.C.) content below 5 ppb may be used. Useof deionized water is not recommended.NOTE 3Double-distilled water distilled from an alkaline permangan-ate (KMnO4) solution (2 g KMnO4plus 5 g sodium hydroxide (NaOH) in2dm3of distilled water) has been found to be adequate for r
48、outinepreparation 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.7.3 Reagents:7.3.1 Ferrous Ammonium Sulfate(NH4)2
49、Fe(SO4)26H2O.7.3.2 Sodium Chloride (NaCl).7.3.3 Sulfuric Acid (H2SO4).8. Preparation of Dosimeters8.1 Prepare dosimetric solution:8.1.1 Dissolve 0.392 g of ferrous ammonium sulfate,(NH4)2Fe(SO4)26H2O, and 0.058 g of sodium chloride, NaCl,in 12.5 mL of 0.4 molL-1sulfuric acid, H2SO4. Dilute to 1 Lin a volumetric flask with air-saturated 0.4 molL-1sulfuric acidat 25C. To make 0.4 M solution, use 41.0 g of 96.7 % sulfuricacid plus water to make 1 L of solution.NOTE 4Sodium chloride is used to reduce any adverse effects on theresponse of the dosimeter d
