Standard Historical Last Updated: Apr 28, 2017 Track Document
ASTM E693-12

Standard Practice for Characterizing Neutron Exposures in Iron and Low Alloy Steels in Terms of Displacements Per Atom (DPA), E 706(ID)

Standard Practice for Characterizing Neutron Exposures in Iron and Low Alloy Steels in Terms of Displacements Per Atom (DPA), E 706(ID) E0693-12 ASTM|E0693-12|en-US Standard Practice for Characterizing Neutron Exposures in Iron and Low Alloy Steels in Terms of Displacements Per Atom (DPA), E 706(ID) Standard new BOS Vol. 12.02 Committee E10
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Significance and Use

A pressure vessel surveillance program requires a methodology for relating radiation-induced changes in materials exposed in accelerated surveillance locations to the condition of the pressure vessel (see Practice E853). An important consideration is that the irradiation exposures be expressed in a unit that is physically related to the damage mechanisms.

A major source of neutron radiation damage in metals is the displacement of atoms from their normal lattice sites. Hence, an appropriate damage exposure index is the number of times, on the average, that an atom has been displaced during an irradiation. This can be expressed as the total number of displaced atoms per unit volume, per unit mass, or per atom of the material. Displacements per atom is the most common way of expressing this quantity. The number of dpa associated with a particular irradiation depends on the amount of energy deposited in the material by the neutrons, and hence, depends on the neutron spectrum. (For a more extended discussion, see Practice E521.)

No simple correspondence exists in general between dpa and a particular change in a material property. A reasonable starting point, however, for relative correlations of property changes produced in different neutron spectra is the dpa value associated with each environment. That is, the dpa values themselves provide a spectrum-sensitive index that may be a useful correlation parameter, or some function of the dpa values may affect correlation.

TABLE 1 ENDF/B-VI-based Iron Displacement Cross Section

BinEngA (MeV)σd (barns)BinEngA (MeV)σd (barns)BinEngA (MeV)σd (barns)
10.100E-09158.354320.1050E-09154.620930.110E-09151.1395
40.1150E-09147.889550.120E-09144.105460.1275E-09139.9202
70.1350E-09136.086080.1425E-09132.544590.150E-09128.7502
100.160E-09124.7860110.170E-09121.1728120.180E-09117.8527
130.190E-09114.8137140.200E-09111.9561150.210E-09109.3199
160.220E-09106.8646170.230E-09104.5694180.240E-09101.8930
190.2550E-0998.93331200.270E-0996.65981210.280E-0994.12717
220.300E-0991.05218230.320E-0988.24872240.340E-0985.68787
250.360E-0983.33912260.380E-0981.17265270.400E-0978.92472
280.4250E-0976.63646290.450E-0974.53734300.4750E-0972.59930
310.500E-0970.81827320.5250E-0969.14790330.550E-0967.59222
340.5750E-0966.13822350.600E-0964.64189360.630E-0963.12039
370.660E-0961.70157380.690E-0960.37332390.720E-0958.92732
400.760E-0957.39681410.800E-0955.97892420.840E-0954.65984
430.880E-0953.43220440.920E-0952.28703450.960E-0951.21545
460.100E-0850.07727470.1050E-0848.89598480.110E-0847.79609
490.1150E-0846.76870500.120E-0845.57125510.1275E-0844.25006
520.1350E-0843.03653530.1425E-0841.91761540.150E-0840.71708
550.160E-0839.46333560.170E-0838.32018570.180E-0837.26968
580.190E-0836.30967590.200E-0835.40710600.210E-0834.57391
610.220E-0833.79705620.230E-0833.06956630.240E-0832.22424
640.2550E-0831.28942650.270E-0830.57002660.280E-0829.76999
670.300E-0828.79791680.320E-0827.91048690.340E-0827.10139
700.360E-0826.35879710.380E-0825.67357720.400E-0824.96309
730.4250E-0824.23960740.450E-0823.57548750.4750E-0822.96268
760.500E-0822.39920770.5250E-0821.87094780.550E-0821.37982
790.5750E-0820.91994800.600E-0820.44705810.630E-0819.96509
820.660E-0819.51724830.690E-0819.09670840.720E-0818.63984
850.760E-0818.15581860.800E-0817.70708870.840E-0817.29049
880.880E-0816.90205890.920E-0816.54074900.960E-0816.20166
910.100E-0715.84242920.1050E-0715.46908930.110E-0715.12094
940.1150E-0714.79594950.120E-0714.41855960.1275E-0714.00095
970.13050E-0713.61661980.1425E-0713.26338990.150E-0712.88403
1000.160E-0712.487591010.170E-0712.126331020.180E-0711.79428
1030.190E-0711.490391040.200E-0711.207601050.210E-0710.94298
1060.220E-0710.697451070.230E-0710.468041080.240E-0710.20132
1090.2550E-079.9067171100.270E-079.6794491110.280E-079.427035
1120.300E-079.1187451130.320E-078.8388191140.340E-078.582926
1150.360E-078.3479621160.380E-078.1316181170.400E-077.907534
1180.4250E-077.6788091190.450E-077.4688051200.4750E-077.276812
1210.500E-077.0975981220.5250E-076.9307671230.550E-076.775607
1240.5750E-076.6307011250.600E-076.4820831260.630E-076.330435
1270.660E-076.1889631280.690E-076.0566311290.720E-075.913148
1300.760E-075.7602981310.800E-075.6186171320.840E-075.486900
1330.880E-075.3643371340.920E-075.2500291350.960E-075.143171
1360.100E-065.0292541370.1050E-064.9114271380.110E-064.801945
1390.1150E-064.6997141400.120E-064.5815851410.1275E-064.450361
1420.1350E-064.3296141430.1425E-064.2182221440.150E-064.099185
1450.160E-063.9743041460.170E-063.8604021470.180E-063.756055
1480.190E-063.6607611490.200E-063.5713131500.210E-063.488699
1510.220E-063.4116161520.230E-063.3394661530.240E-063.256051
1540.2550E-063.1632761550.270E-063.0916281560.280E-063.013147
1570.300E-062.9169451580.320E-062.8294031590.340E-062.749808
1600.360E-062.6767501610.380E-062.6088351620.400E-062.527930
1630.4250E-062.4408971640.450E-062.3743841650.4750E-062.313606
1660.500E-062.2574621670.5250E-062.2053311680.550E-062.154114
1690.5750E-062.1087331700.600E-062.0601341710.630E-062.011735
1720.660E-061.9660451730.690E-061.9235861740.720E-061.877395
1750.760E-061.8285961760.800E-061.7830081770.840E-061.741254
1780.880E-061.7034171790.920E-061.6677921800.960E-061.632082
1810.100E-051.5957541820.1050E-051.5587201830.110E-051.522295
1840.1150E-051.4902001850.120E-051.4515541860.1275E-051.409592
1870.1350E-051.3702471880.1425E-051.3346351890.150E-051.296298
1900.160E-051.2561431910.170E-051.2198241920.180E-051.187621
1930.190E-051.1560281940.200E-051.1267461950.210E-051.099981
1960.220E-051.0752261970.230E-051.0518851980.240E-051.026221
1990.2550E-050.99657192000.270E-050.97222222010.280E-050.9476671
2020.300E-050.91571182030.320E-050.88767992040.340E-050.8611951
2050.360E-050.83773142060.380E-050.81538362070.400E-050.7928756
2080.4250E-050.76959232090.450E-050.74817112100.4750E-050.7286609
2110.500E-050.71075152120.5250E-050.69416002130.550E-050.6778895
2140.5750E-050.66350142150.600E-050.64807752160.630E-050.6327240
2170.660E-050.61820522180.690E-050.60474352190.720E-050.5900444
2200.760E-050.57456042210.800E-050.56003182220.840E-050.5467011
2230.880E-050.53459842240.920E-050.52323912250.960E-050.5118709
2260.100E-040.50029172270.1050E-040.48849022280.110E-040.4769112
2290.1150E-040.46668982300.120E-040.45435602310.1275E-040.4409762
2320.1350E-040.42842232330.1425E-040.41706482340.150E-040.4048129
2350.160E-040.39194772360.170E-040.38029932370.180E-040.3699498
2380.190E-040.35982112390.200E-040.35044752400.210E-040.3418580
2410.220E-040.33390292420.230E-040.32638102430.240E-040.3181047
2440.2550E-040.30854132450.270E-040.30068802460.280E-040.2927655
2470.300E-040.28245932480.320E-040.27339162490.340E-040.2648267
2500.360E-040.25721752510.380E-040.24997032520.400E-040.2426542
2530.4250E-040.23507712540.450E-040.22809362550.4750E-040.2217044
2560.500E-040.21584712570.5250E-040.21040362580.550E-040.2050605
2590.5750E-040.20034032600.600E-040.19527002610.630E-040.1902102
2620.660E-040.18542212630.690E-040.18097562640.720E-040.1761094
2650.760E-040.17097262660.800E-040.16614742670.840E-040.1616956
2680.880E-040.15765492690.920E-040.15384602700.960E-040.1500470
2710.100E-030.14616012720.1050E-030.14219332730.110E-030.1382971
2740.1150E-030.13485282750.120E-030.13067992760.1275E-030.1261477
2770.1350E-030.12188732780.1425E-030.11801862790.150E-030.1138330
2800.160E-030.10942872810.170E-030.10542792820.180E-030.1018602
2830.190E-030.9837523E-012840.200E-030.9515446E-012850.210E-030.9224781E-01
2860.220E-030.10484592870.230E-030.10282882880.240E-030.8397242E-01
2890.2550E-030.8057346E-012900.270E-030.7782596E-012910.280E-030.7506079E-01
2920.300E-030.7147984E-012930.320E-030.6842791E-012940.340E-030.1581741
2950.360E-030.7452445E-012960.380E-030.6020231E-012970.400E-030.5752645E-01
2980.4250E-030.5484677E-012990.450E-030.5239946E-013000.4750E-030.5017326E-01
3010.500E-030.4855164E-013020.5250E-030.4750492E-013030.550E-030.8634498E-01
3040.5750E-030.36845673050.600E-030.72306623060.630E-031.085166
3070.660E-031.4330573080.690E-031.7537643090.720E-032.100540
3100.760E-032.4288953110.800E-032.7227883120.840E-032.998771
3130.880E-033.2584613140.920E-033.4653723150.960E-033.618973
3160.100E-023.7870813170.1050E-023.9642713180.110E-0213.13789
3190.1150E-0210.693823200.120E-024.2626933210.1275E-024.338387
3220.1350E-024.4353673230.1425E-024.5342253240.150E-024.592575
3250.160E-024.7831803260.170E-024.7016233270.180E-024.841220
3280.190E-024.9990093290.200E-025.1113353300.201E-025.183993
3310.220E-025.2790693320.230E-025.4089103330.240E-025.523736
3340.2550E-025.6954423350.270E-025.8268533360.280E-025.975410
3370.300E-026.1735233380.320E-026.3954153390.340E-026.658582
3400.360E-027.1839393410.380E-0210.011683420.400E-029.194485
3430.4250E-028.1782663440.450E-028.2296573450.4750E-028.508525
3460.500E-028.9108763470.5250E-029.5253953480.550E-0210.59739
3490.5750E-0213.204113500.600E-0221.174663510.630E-0219.67340
3520.660E-0218.592033530.690E-0224.366273540.720E-0239.42936
3550.760E-0256.386213560.800E-0248.661023570.840E-0235.11790
3580.880E-0227.248923590.920E-0223.521593600.960E-0220.66808
3610.100E-0119.983923620.1050E-0118.418693630.110E-0118.51923
3640.1150E-0116.803653650.120E-0116.409453660.1275E-0116.00651
3670.1350E-0116.067923680.1425E-0115.558763690.150E-0115.08970
3700.160E-0114.618093710.170E-0113.995113720.180E-0113.21823
3730.190E-0112.019593740.200E-0110.615303750.210E-018.888706
3760.220E-016.8576863770.230E-014.4352993780.240E-014.034283
3790.2550E-0151.588563800.270E-01462.42043810.280E-01374.2036
3820.300E-01138.85823830.320E-0191.992423840.340E-0175.21491
3850.360E-0166.928963860.380E-0162.406113870.400E-0165.56062
3880.4250E-0159.518933890.450E-0161.428973900.4750E-0155.61853
3910.500E-0180.549943920.5250E-0184.937463930.550E-0161.63473
3940.5750E-0161.835473950.600E-0161.394863960.630E-0151.44463
3970.660E-0141.055203980.690E-0135.187873990.720E-01195.2115
4000.760E-0172.972704010.800E-01139.38014020.840E-01276.0543
4030.880E-01138.45684040.920E-01104.07434050.960E-01113.7160
4060.100105.54894070.105078.430954080.11078.06753
4090.115060.445434100.12070.474304110.1275134.1587
4120.1350255.36304130.1425293.01614140.150133.0900
4150.160122.75964160.170156.01434170.180244.4100
4180.190370.76274190.200205.33394200.210101.0349
4210.220307.51114220.230146.96134230.240171.8077
4240.2550135.33874250.270282.55014260.280187.6945
4270.300142.03914280.320315.57914290.340166.5530
4300.360302.11844310.380545.71174320.400528.4010
4330.4250400.44124340.450309.78254350.4750351.4453
4360.500381.00014370.5250327.40084380.550316.9469
4390.5750264.20914400.600190.80424410.630255.5292
4420.660529.87454430.690389.01674440.720680.4310
4450.760627.30194460.800427.23284470.840461.2467
4480.880327.13984490.920278.17194500.960479.7678
4511.00498.49224521.10477.68934531.20707.1735
4541.30616.46404551.40716.41014561.50734.1659
4571.60758.83534581.70784.55804591.80819.3325
4601.90989.32654612.00928.76814622.10923.3754
4632.20969.48004642.301079.7164652.401143.224
4662.501348.9544672.601192.1054682.701263.538
4692.801277.8014702.901271.5784713.001364.006
4723.101387.7244733.201358.4664743.301346.851
4753.401398.0344763.501334.7434773.601424.447
4783.701440.7084793.801483.8804803.901464.868
4814.001526.3714824.101560.4434834.201530.309
4844.301582.9164854.401523.3404864.501626.724
4874.601600.8634884.701617.4554894.801653.609
4904.901642.8334915.001600.0754925.101682.554
4935.201687.2864945.301716.4694955.401731.089
4965.501729.7854975.601760.8524985.701760.538
4995.801768.6565005.901792.1055016.001811.511
5026.101800.9405036.201811.5475046.301859.081
5056.401859.1255066.501879.2375076.601890.037
5086.701891.7625096.801909.4855106.901909.076
5117.001914.4425127.101936.4145137.201941.750
5147.301966.6635157.401963.3065167.501986.044
5177.601976.2135187.701989.2435197.802003.646
5207.902006.7715218.002009.0935228.102013.259
5238.202032.5885248.302064.7555258.402063.837
5268.502061.3655278.602059.5075288.702072.344
5298.802089.9765308.902107.5255319.002122.580
5329.102135.0775339.202147.5775349.302160.074
5359.402172.4825369.502185.8925379.602199.950
5389.702213.9185399.802226.6985409.902238.281
54110.02250.48254210.102263.39254310.202276.220
54410.302288.97154510.402301.72554610.502313.910
54710.602325.62854810.702337.34254910.802348.869
55010.902360.30155111.02371.74455211.102383.112
55311.202395.21255411.302407.95255511.402421.344
55611.502434.32555711.602446.24355811.702458.956
55911.802471.20556011.902482.24756112.02493.659
56212.102506.01656312.202519.59856412.302534.971
56512.402549.08656612.502562.97756712.602576.115
56812.702586.93656912.802600.01157012.902615.468
57113.02630.34357213.102644.45557313.202658.475
57413.302672.21857513.402685.52057613.502698.683
57713.602711.99057813.702725.31357913.802738.112
58013.902750.41858114.02763.16458214.102775.980
58314.202788.33158414.302800.21458514.402811.915
58614.502824.20858714.602837.18358814.702849.781
58914.802862.18459014.902874.42159115.02877.552
59215.102871.08459315.202864.61759415.302858.147
59515.402851.58159615.502844.83959715.602837.641
59815.702830.53859915.802823.42760015.902816.329
60116.02813.38660216.102814.81960316.202816.344
60416.302817.78260516.402819.12460616.502819.920
60716.602819.88360816.702819.84660916.802819.725
61016.902819.63161117.02823.43761217.102831.455
61317.202839.47561417.302847.22061517.402855.056
61617.502862.95661717.602870.91361817.702878.960
61917.802886.82662017.902894.59462118.02903.983
62218.102914.91362318.202925.79162418.302936.340
62518.402946.71262618.502956.44862718.602965.448
62818.702974.45062918.802983.45363018.902992.455
63119.02999.56163219.103004.58363319.203009.698
63419.303014.72163519.403019.74163619.503025.406
63719.603031.52663819.703037.73763919.803043.950
64019.903050.161641

A Energies represent the lower bin boundary. The upper bin limit is 20.0 MeV

Since dpa is a construct that depends on a model of the neutron interaction processes in the material lattice, as well as the cross section (probability) for each of these processes, the value of dpa would be different if improved models or cross sections are used. The calculated dpa cross section for ferritic iron, as given in this practice, is determined by the procedure given in 6.3. The currently recommended dpa cross sections in this practice (Table 1) were generated using the iron ENDF/B-VI iron cross section (1). A recent calculation using ENDF/B-VII produced identical results.(2,3) Although the ENDF/B-VI based dpa cross section differs from the previously recommended ENDF/B-IV dpa cross section (1) by about 60 % in the energy region around 10 keV, by about 10 % for energies between 100 keV and 2 MeV, and by a factor of 4 near 1 keV due to the opening of reaction channels in the cross section, the integral iron dpa values are much less sensitive to the change in cross sections. The update from ENDF/B-IV to ENDF/B-VI dpa rates when applied to the H. B. Robinson-2 pressurized water reactor resulted in up to 4 % higher dpa rates in the region close to the pressure vessel outer surface and in slightly lower dpa rates ... close to the pressure vessel inner wall (5, 6). Table 2 presents a comparison of a previous edition (Practice E693-94) and currently recommended dpa estimates for several neutron spectra.

TABLE 2 Changes in Spectrum-Integrated dpa for Benchmark Neutron Spectra

Neutron SpectrumSpectrum-averaged dpa cross section (barns)A
Old ENDF/B-IV-based E693 responseCurrent ENDF/B-VI-based E693 responseDifference ([Current - Old]/Old) (%)
ENDF/B-VI 235U Thermal Fission (1, 4)875.55858.541.9
Materials Dosimetry Reference Facility (MDRF) (7)345.03343.580.42
CFRMF (8, 9)382.94387.081.08
Intermediate-energy Standard Neutron Field (ISNF) (9, 10)483.63480.000.75
Arkansas Nuclear ONE-1 (ANO) Cavity (11, 12)134.40139.443.75
ORNL Poolside Facility (PSF) T/4 position (11, 13)242.14238.331.57
Oak Ridge Research Reactor (ORR) (9)291.68288.860.97
Yayoi (9)613.12609.030.67
BIGTEN (9, 14)334.98341.251.87
H.B. Robinson-2, in the vessel wall, close to the inner surface (5, 6)219.43218.810.28
H.B. Robinson-2, ¼ T vessel wall (5, 6)245.17249.241.66
H.B. Robinson-2, ¾ T vessel wall (5, 6)203.68211.233.71

A The spectrum-average dpa values in this table were computed using Eq 11 in a 640 SAND-II energy group representation and a lower integration bound of Eo = 1010 MeV.

Note—Table 2 is included to illustrate the effect on the dpa cross sections resulting from the change from the ENDF/B-IV to ENDF/B-VI cross sections. The spectrum-average cross section values given are not recommended for other uses because of their sensitivity to the assumed spectrum representations and the lower energy integration limit.

Scope

1.1 This practice describes a standard procedure for characterizing neutron irradiations of iron (and low alloy steels) in terms of the exposure index displacements per atom (dpa) for iron.

1.2 Although the methods of this practice apply to any material for which a displacement cross section σd(E) is known (see Practice E521), this practice is written specifically for iron.

1.3 It is assumed that the displacement cross section for iron is an adequate approximation for calculating displacements in steels that are mostly iron (95 to 100 %) in radiation fields for which secondary damage processes are not important.

1.4 Procedures analogous to this one can be formulated for calculating dpa in charged particle irradiations. (See Practice E521.)

1.5 The application of this practice requires knowledge of the total neutron fluence and flux spectrum. Refer to Practice E521 for determining these quantities.

1.6 The correlation of radiation effects data is beyond the scope of this practice.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

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Details
Book of Standards Volume: 12.02
Developed by Subcommittee: E10.05
Pages: 8
DOI: 10.1520/E0693-12
ICS Code: 77.080.20