1、Designation: E 693 01 (Reapproved 2007)Standard Practice forCharacterizing Neutron Exposures in Iron and Low AlloySteels in Terms of Displacements Per Atom (DPA),E 706(ID)1This standard is issued under the fixed designation E 693; the number immediately following the designation indicates the year o
2、foriginal adoption or, in the case of revision, 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.1. Scope1.1 This practice describes a standard procedure for charac-t
3、erizing neutron irradiations of iron (and low alloy steels) interms of the exposure index displacements per atom (dpa) foriron.1.2 Although the general procedures of this practice applyto any material for which a displacement cross section sd(E)isknown (see Practice E 521), this practice is written
4、specificallyfor iron.1.3 It is assumed that the displacement cross section for ironis an adequate approximation for calculating displacements insteels that are mostly iron (95 to 100 %) in radiation fields forwhich secondary damage processes are not important.1.4 Procedures analogous to this one can
5、 be formulated forcalculating dpa in charged particle irradiations. (See PracticeE 521.)1.5 The application of this practice requires knowledge ofthe total neutron fluence and flux spectrum. Refer to PracticeE 521 for determining these quantities.1.6 The correlation of radiation effects data is beyo
6、nd thescope of this practice.1.7 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 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations
7、 prior to use.2. Referenced Documents2.1 ASTM Standards:2E 170 Terminology Relating to Radiation Measurementsand DosimetryE 521 Practice for Neutron Radiation Damage Simulationby Charged-Particle IrradiationE 560 Practice for Extrapolating Reactor Vessel Surveil-lance Dosimetry Results, E 706(IC)E 8
8、21 Practice for Measurement of Mechanical PropertiesDuring Charged-Particle IrradiationE 853 Practice for Analysis and Interpretation of Light-Water Reactor Surveillance Results, E706(IA)3. Terminology3.1 Definitions for terms used in this practice can be foundin Terminology E 170.4. Significance an
9、d Use4.1 Apressure vessel surveillance program requires a meth-odology for relating radiation-induced changes in materialsexposed in accelerated surveillance locations to the conditionof the pressure vessel (see Practices E 560 and E 853). Animportant consideration is that the irradiation exposures
10、beexpressed in a unit that is physically related to the damagemechanisms.4.2 Amajor source of neutron radiation damage in metals isthe displacement of atoms from their normal lattice sites.Hence, an appropriate damage exposure index is the number oftimes, on the average, that an atom has been displa
11、ced duringan irradiation. This can be expressed as the total number ofdisplaced atoms per unit volume, per unit mass, or per atom ofthe material. Displacements per atom is the most common wayof expresssing this quantity.The number of dpa associated witha particular irradiation depends on the amount
12、of energydeposited in the material by the neutrons, and hence, dependson the neutron spectrum. (For a more extended discussion, seePractice E 521.)4.3 No simple correspondence exists in general between dpaand a particular change in a material property. A reasonablestarting point, however, for relati
13、ve correlations of propertychanges produced in different neutron spectra is the dpa valueassociated with each environment. That is, the dpa valuesthemselves provide a spectrum-sensitive index that may be auseful correlation parameter, or some function of the dpavalues may affect correlation.1This pr
14、actice is under the jurisdiction of ASTM Committee E10 on NuclearTechnology and Applications and is the direct responsibility of SubcommitteeE10.05 on Nuclear Radiation Metrology.Current edition approved June 1, 2007. Published July 2007. Originally approvedin 1979. Last previous edition approved in
15、 2001 as E 693 01(2007).2For referenced ASTM standards, visit the ASTM website, www.astm.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.1Copyright ASTM International, 100 Ba
16、rr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.4 Since dpa is a construct that depends on a model of theneutron interaction processes in the material lattice, as well asthe cross section (probability) for each of these processes, thevalue of dpa would be different if
17、 improved models or crosssections are used. The calculated dpa cross section for ferriticiron, as given in this practice, is determined by the proceduregiven in 6.3. A considerable body of irradiated materials datahas been reported using dpa cross sections based on the ironENDF/B-IV (1, 2)3cross sec
18、tion. The recent changes in theiron cross section (3), the recommendation to use the updatediron cross sections in radiation transport calculations of pres-sure vessel spectra (4), and the recent availability of ENDF/B-VI iron dpa cross section calculations (1, 2, 5) have resultedin the update of th
19、e recommended dpa cross section to reflectthe ENDF/B-VI cross sections (1). Although the ENDF/B-VIbased dpa cross section differs from the previously recom-mended ENDF/B-IV dpa cross section (1) by about 60 % in theenergy region around 10 keV, by about 10 % for energiesbetween 100 keV and 2 MeV, and
20、 by a factor of 4 near 1 keVdue to the opening of reaction channels in the cross section, theintegral iron dpa values are much less sensitive to the changein cross sections. The update from ENDF/B-IV to ENDF/B-VIdpa rates when applied to the H. B. Robinson-2 pressurizedwater reactor results in “up t
21、o ;4 % higher dpa rates in theregion close to the pressure vessel outer surface” and in“slightly lower dpa rates . close to the pressure vessel innerwall” (6, 7).Thus the update of the recommended dpa exposureparameter to reflect an iron cross section consistent with thatused in the current radiatio
22、n transport calculations is “notexpected to introduce a bias in embrittlement data bases” (6)based on the change in the dpa cross section. Table 1 presentsa comparison of the previous edition (Practice E 693-94) andcurrently recommended dpa estimates for several neutronspectra.5. Procedure5.1 The di
23、splacement rate at time t is calculated as follows:dpa/s 5*0sdE!fE,t! dE (1)where:sd(E) = the displacement cross section for a particularmaterial, andf(E,t) dE = the fluence rate of neutrons in the energyinterval E to E + dE.5.2 The exposure index, dpa, is then the time integratedvalue of the displa
24、cement rate, calculated as follows:dpa 5*0trftott!*0sdE!cE,t! dE dt (2)where:ftot(t) = the time dependent fluence rate intensity, andc(E,t) = the fluence rate spectrum normalized to give unitintegral fluence rate at any time when integratedover energy.5.2.1 If the fluence rate spectrum is constant o
25、ver theduration, tr, of the irradiation, then:dpa 5ftottr*0sdE!cE! dE 5ftottrsd(3)where sd= the spectrum-average displacement cross sec-tion.5.3 It is assumed for purposes of this practice that thefluence ftottrand the spectrum c(E) are known.6. Calculation6.1 The integral can be evaluated by a simp
26、le numericalintegration as follows:*0sdE!fE! dE 5(i 5 1Nsd!ifiDEi(4)where (sd)iand fiare grouped-averaged values over theinterval EiEo) by the following equation:sdE . E0! 5*EosdE!fE!dE*EofE! dE(11)FIG. 1 ENDF/B-VI-based Iron Displacement Cross SectionE 693 01 (2007)3anddpa/s sdE . Eo! 3fE .Eo! (12)
27、Areasonable value for Eois 0.01 MeV. The quantity sd(E 0.01 MeV) is then a good index of spectrum hardness irrespec-tive of the thermal-to-fast ratio.7. Precision and Accuracy7.1 PrecisionThe energy group structure selected to per-form the integral in 6.1 should be selected such that the integralof
28、the dpa exposure parameter over the neutron spectrum iswithin 1 % of that obtained when the complete 640-groupSAND-II energy structure is used to represent the energydependence of the dpa exposure parameter and the energy-dependent structure of the neutron spectrum. The precision inthe spectrum-aver
29、aged dpa is dominated by the precision in theneutron spectrum characterization, including its representationof the fine energy structure.7.2 Accuracy:7.2.1 Absolute AccuracyThe absolute accuracy of the dpacalculation is not important when dpa is used as an exposureunit or correlation parameter for n
30、eutron irradiations, so longas a standard practice is used by all laboratories in calculatingdpa. The absolute uncertainty is estimated to be 40 % or morewhen applied to a light water reactor spectrum (less in a softerspectrum). The major sources of error are the fluence spectrum,the reaction cross
31、sections used in calculating sd(E), theLindhard model for the partition of energy between atoms andelectrons, and the conversion of deposited energy to displace-ments.7.2.2 Relative AccuracyThe relative accuracy of dpa cal-culations for different environments depends on the energydependence of sd(E)
32、 and on the relative accuracy of fluence-spectrum determinations. The covariance matrix for the irondpa cross section is not available at present, although covari-ance matrices for the individual File 3 nuclear reaction crosssections which contribute to the dpa can be found in File 33 ofthe ENDF/B-V
33、I cross section evaluations (1). For a discussionof the effect of the energy dependence of sd(E) on the relativeaccuracy of the dpa calculation see Ref 23 and Practice E 521.Losses in the relative accuracy of the dpa calculation due tothis effect are estimated to be less than 10 % for most reactorsp
34、ectra (23). The relative accuracy of the fluence-spectrumdetermination depends on the method of determination. (Forrecommended methods see E 706, Matrix Standard.) Anyuncertainty in the total fluence is, of course, reflected directlyin the dpa calculation (see 5.2.1).NOTE 4Measurement uncertainty is
35、 described by a precision-and-biasstatement in this standard. Another acceptable approach is to use Type Aand B uncertainty components (24, 25). This Type A/B uncertaintyspecification is now used in International Organization for Standardization(ISO) standards and this approach can be expected to pl
36、ay a moreprominent role in future uncertainty analyses.8. Damage Correlation8.1 This practice is concerned with standardizing a radiationexposure unit. It is concerned only secondarily with thecorrelation of damage produced in different environments. Asstated in 4.1, the dpa is a logical first step
37、in attempting tocorrelate displacement damage. Active research programs onimproving the damage correlation methodology are inprogress, and recent results (26) indicate that dpa can, in somecases, produce improved damage correlation when comparedto fast neutron fluence. Because many past data correla
38、tionshave been based on “fast fluence” (E 1 MeV), this quantityshould also be given, along with the dpa value, when express-ing irradiation exposures. (For a general discussion of thedamage correlation problem, see Ref 27.)9. Keywords9.1 atomic displacements; cross section; irradiation; mate-rials d
39、amage; neutron; steelTABLE 2 ENDF/B-VI-based Iron Displacement Cross SectionBin EngA(MeV) sd(barns) Bin EngA(MeV) sd(barns) Bin EngA(MeV) sd(barns)1 0.100E-09 158.3543 2 0.1050E-09 154.6209 3 0.110E-09 151.13954 0.1150E-09 147.8895 5 0.120E-09 144.1054 6 0.1275E-09 139.92027 0.1350E-09 136.0860 8 0.
40、1425E-09 132.5445 9 0.150E-09 128.750210 0.160E-09 124.7860 11 0.170E-09 121.1728 12 0.180E-09 117.852713 0.190E-09 114.8137 14 0.200E-09 111.9561 15 0.210E-09 109.319916 0.220E-09 106.8646 17 0.230E-09 104.5694 18 0.240E-09 101.893019 0.2550E-09 98.93331 20 0.270E-09 96.65981 21 0.280E-09 94.127172
41、2 0.300E-09 91.05218 23 0.320E-09 88.24872 24 0.340E-09 85.6878725 0.360E-09 83.33912 26 0.380E-09 81.17265 27 0.400E-09 78.9247228 0.4250E-09 76.63646 29 0.450E-09 74.53734 30 0.4750E-09 72.5993031 0.500E-09 70.81827 32 0.5250E-09 69.14790 33 0.550E-09 67.5922234 0.5750E-09 66.13822 35 0.600E-09 64
42、.64189 36 0.630E-09 63.1203937 0.660E-09 61.70157 38 0.690E-09 60.37332 39 0.720E-09 58.9273240 0.760E-09 57.39681 41 0.800E-09 55.97892 42 0.840E-09 54.6598443 0.880E-09 53.43220 44 0.920E-09 52.28703 45 0.960E-09 51.2154546 0.100E-08 50.07727 47 0.1050E-08 48.89598 48 0.110E-08 47.7960949 0.1150E-
43、08 46.76870 50 0.120E-08 45.57125 51 0.1275E-08 44.2500652 0.1350E-08 43.03653 53 0.1425E-08 41.91761 54 0.150E-08 40.7170855 0.160E-08 39.46333 56 0.170E-08 38.32018 57 0.180E-08 37.2696858 0.190E-08 36.30967 59 0.200E-08 35.40710 60 0.210E-08 34.5739161 0.220E-08 33.79705 62 0.230E-08 33.06956 63
44、0.240E-08 32.2242464 0.2550E-08 31.28942 65 0.270E-08 30.57002 66 0.280E-08 29.7699967 0.300E-08 28.79791 68 0.320E-08 27.91048 69 0.340E-08 27.1013970 0.360E-08 26.35879 71 0.380E-08 25.67357 72 0.400E-08 24.9630973 0.4250E-08 24.23960 74 0.450E-08 23.57548 75 0.4750E-08 22.96268E 693 01 (2007)4TAB
45、LE 2 ContinuedBin EngA(MeV) sd(barns) Bin EngA(MeV) sd(barns) Bin EngA(MeV) sd(barns)76 0.500E-08 22.39920 77 0.5250E-08 21.87094 78 0.550E-08 21.3798279 0.5750E-08 20.91994 80 0.600E-08 20.44705 81 0.630E-08 19.9650982 0.660E-08 19.51724 83 0.690E-08 19.09670 84 0.720E-08 18.6398485 0.760E-08 18.15
46、581 86 0.800E-08 17.70708 87 0.840E-08 17.2904988 0.880E-08 16.90205 89 0.920E-08 16.54074 90 0.960E-08 16.2016691 0.100E-07 15.84242 92 0.1050E-07 15.46908 93 0.110E-07 15.1209494 0.1150E-07 14.79594 95 0.120E-07 14.41855 96 0.1275E-07 14.0009597 0.13050E-07 13.61661 98 0.1425E-07 13.26338 99 0.150
47、E-07 12.88403100 0.160E-07 12.48759 101 0.170E-07 12.12633 102 0.180E-07 11.79428103 0.190E-07 11.49039 104 0.200E-07 11.20760 105 0.210E-07 10.94298106 0.220E-07 10.69745 107 0.230E-07 10.46804 108 0.240E-07 10.20132109 0.2550E-07 9.906717 110 0.270E-07 9.679449 111 0.280E-07 9.427035112 0.300E-07
48、9.118745 113 0.320E-07 8.838819 114 0.340E-07 8.582926115 0.360E-07 8.347962 116 0.380E-07 8.131618 117 0.400E-07 7.907534118 0.4250E-07 7.678809 119 0.450E-07 7.468805 120 0.4750E-07 7.276812121 0.500E-07 7.097598 122 0.5250E-07 6.930767 123 0.550E-07 6.775607124 0.5750E-07 6.630701 125 0.600E-07 6
49、.482083 126 0.630E-07 6.330435127 0.660E-07 6.188963 128 0.690E-07 6.056631 129 0.720E-07 5.913148130 0.760E-07 5.760298 131 0.800E-07 5.618617 132 0.840E-07 5.486900133 0.880E-07 5.364337 134 0.920E-07 5.250029 135 0.960E-07 5.143171136 0.100E-06 5.029254 137 0.1050E-06 4.911427 138 0.110E-06 4.801945139 0.1150E-06 4.699714 140 0.120E-06 4.581585 141 0.1275E-06 4.450361142 0.1350E-06 4.329614 143 0.1425E-06 4.218222 144 0.150E-06 4.099185145 0.160E-06 3.974304 146 0.170E-06 3.860402 147 0.180E-06 3.756055148 0.190E-06 3.660761 149 0.200E-06 3.571313 15
