Значение и использование

4.1 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.

4.2 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.)

4.3 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

Bin

Eng^A (MeV)

σ_d (barns)

Bin

Eng^A (MeV)

σ_d (barns)

Bin

Eng^A (MeV)

σ_d (barns)

1

0.100E-09

158.3543

2

0.1050E-09

154.6209

3

0.110E-09

151.1395

4

0.1150E-09

147.8895

5

0.120E-09

144.1054

6

0.1275E-09

139.9202

7

0.1350E-09

136.0860

8

0.1425E-09

132.5445

9

0.150E-09

128.7502

10

0.160E-09

124.7860

11

0.170E-09

121.1728

12

0.180E-09

117.8527

13

0.190E-09

114.8137

14

0.200E-09

111.9561

15

0.210E-09

109.3199

16

0.220E-09

106.8646

17

0.230E-09

104.5694

18

0.240E-09

101.8930

19

0.2550E-09

98.93331

20

0.270E-09

96.65981

21

0.280E-09

94.12717

22

0.300E-09

91.05218

23

0.320E-09

88.24872

24

0.340E-09

85.68787

25

0.360E-09

83.33912

26

0.380E-09

81.17265

27

0.400E-09

78.92472

28

0.4250E-09

76.63646

29

0.450E-09

74.53734

30

0.4750E-09

72.59930

31

0.500E-09

70.81827

32

0.5250E-09

69.14790

33

0.550E-09

67.59222

34

0.5750E-09

66.13822

35

0.600E-09

64.64189

36

0.630E-09

63.12039

37

0.660E-09

61.70157

38

0.690E-09

60.37332

39

0.720E-09

58.92732

40

0.760E-09

57.39681

41

0.800E-09

55.97892

42

0.840E-09

54.65984

43

0.880E-09

53.43220

44

0.920E-09

52.28703

45

0.960E-09

51.21545

46

0.100E-08

50.07727

47

0.1050E-08

48.89598

48

0.110E-08

47.79609

49

0.1150E-08

46.76870

50

0.120E-08

45.57125

51

0.1275E-08

44.25006

52

0.1350E-08

43.03653

53

0.1425E-08

41.91761

54

0.150E-08

40.71708

55

0.160E-08

39.46333

56

0.170E-08

38.32018

57

0.180E-08

37.26968

58

0.190E-08

36.30967

59

0.200E-08

35.40710

60

0.210E-08

34.57391

61

0.220E-08

33.79705

62

0.230E-08

33.06956

63

0.240E-08

32.22424

64

0.2550E-08

31.28942

65

0.270E-08

30.57002

66

0.280E-08

29.76999

67

0.300E-08

28.79791

68

0.320E-08

27.91048

69

0.340E-08

27.10139

70

0.360E-08

26.35879

71

0.380E-08

25.67357

72

0.400E-08

24.96309

73

0.4250E-08

24.23960

74

0.450E-08

23.57548

75

0.4750E-08

22.96268

76

0.500E-08

22.39920

77

0.5250E-08

21.87094

78

0.550E-08

21.37982

79

0.5750E-08

20.91994

80

0.600E-08

20.44705

81

0.630E-08

19.96509

82

0.660E-08

19.51724

83

0.690E-08

19.09670

84

0.720E-08

18.63984

85

0.760E-08

18.15581

86

0.800E-08

17.70708

87

0.840E-08

17.29049

88

0.880E-08

16.90205

89

0.920E-08

16.54074

90

0.960E-08

16.20166

91

0.100E-07

15.84242

92

0.1050E-07

15.46908

93

0.110E-07

15.12094

94

0.1150E-07

14.79594

95

0.120E-07

14.41855

96

0.1275E-07

14.00095

97

0.13050E-07

13.61661

98

0.1425E-07

13.26338

99

0.150E-07

12.88403

100

0.160E-07

12.48759

101

0.170E-07

12.12633

102

0.180E-07

11.79428

103

0.190E-07

11.49039

104

0.200E-07

11.20760

105

0.210E-07

10.94298

106

0.220E-07

10.69745

107

0.230E-07

10.46804

108

0.240E-07

10.20132

109

0.2550E-07

9.906717

110

0.270E-07

9.679449

111

0.280E-07

9.427035

112

0.300E-07

9.118745

113

0.320E-07

8.838819

114

0.340E-07

8.582926

115

0.360E-07

8.347962

116

0.380E-07

8.131618

117

0.400E-07

7.907534

118

0.4250E-07

7.678809

119

0.450E-07

7.468805

120

0.4750E-07

7.276812

121

0.500E-07

7.097598

122

0.5250E-07

6.930767

123

0.550E-07

6.775607

124

0.5750E-07

6.630701

125

0.600E-07

6.482083

126

0.630E-07

6.330435

127

0.660E-07

6.188963

128

0.690E-07

6.056631

129

0.720E-07

5.913148

130

0.760E-07

5.760298

131

0.800E-07

5.618617

132

0.840E-07

5.486900

133

0.880E-07

5.364337

134

0.920E-07

5.250029

135

0.960E-07

5.143171

136

0.100E-06

5.029254

137

0.1050E-06

4.911427

138

0.110E-06

4.801945

139

0.1150E-06

4.699714

140

0.120E-06

4.581585

141

0.1275E-06

4.450361

142

0.1350E-06

4.329614

143

0.1425E-06

4.218222

144

0.150E-06

4.099185

145

0.160E-06

3.974304

146

0.170E-06

3.860402

147

0.180E-06

3.756055

148

0.190E-06

3.660761

149

0.200E-06

3.571313

150

0.210E-06

3.488699

151

0.220E-06

3.411616

152

0.230E-06

3.339466

153

0.240E-06

3.256051

154

0.2550E-06

3.163276

155

0.270E-06

3.091628

156

0.280E-06

3.013147

157

0.300E-06

2.916945

158

0.320E-06

2.829403

159

0.340E-06

2.749808

160

0.360E-06

2.676750

161

0.380E-06

2.608835

162

0.400E-06

2.527930

163

0.4250E-06

2.440897

164

0.450E-06

2.374384

165

0.4750E-06

2.313606

166

0.500E-06

2.257462

167

0.5250E-06

2.205331

168

0.550E-06

2.154114

169

0.5750E-06

2.108733

170

0.600E-06

2.060134

171

0.630E-06

2.011735

172

0.660E-06

1.966045

173

0.690E-06

1.923586

174

0.720E-06

1.877395

175

0.760E-06

1.828596

176

0.800E-06

1.783008

177

0.840E-06

1.741254

178

0.880E-06

1.703417

179

0.920E-06

1.667792

180

0.960E-06

1.632082

181

0.100E-05

1.595754

182

0.1050E-05

1.558720

183

0.110E-05

1.522295

184

0.1150E-05

1.490200

185

0.120E-05

1.451554

186

0.1275E-05

1.409592

187

0.1350E-05

1.370247

188

0.1425E-05

1.334635

189

0.150E-05

1.296298

190

0.160E-05

1.256143

191

0.170E-05

1.219824

192

0.180E-05

1.187621

193

0.190E-05

1.156028

194

0.200E-05

1.126746

195

0.210E-05

1.099981

196

0.220E-05

1.075226

197

0.230E-05

1.051885

198

0.240E-05

1.026221

199

0.2550E-05

0.9965719

200

0.270E-05

0.9722222

201

0.280E-05

0.9476671

202

0.300E-05

0.9157118

203

0.320E-05

0.8876799

204

0.340E-05

0.8611951

205

0.360E-05

0.8377314

206

0.380E-05

0.8153836

207

0.400E-05

0.7928756

208

0.4250E-05

0.7695923

209

0.450E-05

0.7481711

210

0.4750E-05

0.7286609

211

0.500E-05

0.7107515

212

0.5250E-05

0.6941600

213

0.550E-05

0.6778895

214

0.5750E-05

0.6635014

215

0.600E-05

0.6480775

216

0.630E-05

0.6327240

217

0.660E-05

0.6182052

218

0.690E-05

0.6047435

219

0.720E-05

0.5900444

220

0.760E-05

0.5745604

221

0.800E-05

0.5600318

222

0.840E-05

0.5467011

223

0.880E-05

0.5345984

224

0.920E-05

0.5232391

225

0.960E-05

0.5118709

226

0.100E-04

0.5002917

227

0.1050E-04

0.4884902

228

0.110E-04

0.4769112

229

0.1150E-04

0.4666898

230

0.120E-04

0.4543560

231

0.1275E-04

0.4409762

232

0.1350E-04

0.4284223

233

0.1425E-04

0.4170648

234

0.150E-04

0.4048129

235

0.160E-04

0.3919477

236

0.170E-04

0.3802993

237

0.180E-04

0.3699498

238

0.190E-04

0.3598211

239

0.200E-04

0.3504475

240

0.210E-04

0.3418580

241

0.220E-04

0.3339029

242

0.230E-04

0.3263810

243

0.240E-04

0.3181047

244

0.2550E-04

0.3085413

245

0.270E-04

0.3006880

246

0.280E-04

0.2927655

247

0.300E-04

0.2824593

248

0.320E-04

0.2733916

249

0.340E-04

0.2648267

250

0.360E-04

0.2572175

251

0.380E-04

0.2499703

252

0.400E-04

0.2426542

253

0.4250E-04

0.2350771

254

0.450E-04

0.2280936

255

0.4750E-04

0.2217044

256

0.500E-04

0.2158471

257

0.5250E-04

0.2104036

258

0.550E-04

0.2050605

259

0.5750E-04

0.2003403

260

0.600E-04

0.1952700

261

0.630E-04

0.1902102

262

0.660E-04

0.1854221

263

0.690E-04

0.1809756

264

0.720E-04

0.1761094

265

0.760E-04

0.1709726

266

0.800E-04

0.1661474

267

0.840E-04

0.1616956

268

0.880E-04

0.1576549

269

0.920E-04

0.1538460

270

0.960E-04

0.1500470

271

0.100E-03

0.1461601

272

0.1050E-03

0.1421933

273

0.110E-03

0.1382971

274

0.1150E-03

0.1348528

275

0.120E-03

0.1306799

276

0.1275E-03

0.1261477

277

0.1350E-03

0.1218873

278

0.1425E-03

0.1180186

279

0.150E-03

0.1138330

280

0.160E-03

0.1094287

281

0.170E-03

0.1054279

282

0.180E-03

0.1018602

283

0.190E-03

0.9837523E-01

284

0.200E-03

0.9515446E-01

285

0.210E-03

0.9224781E-01

286

0.220E-03

0.1048459

287

0.230E-03

0.1028288

288

0.240E-03

0.8397242E-01

289

0.2550E-03

0.8057346E-01

290

0.270E-03

0.7782596E-01

291

0.280E-03

0.7506079E-01

292

0.300E-03

0.7147984E-01

293

0.320E-03

0.6842791E-01

294

0.340E-03

0.1581741

295

0.360E-03

0.7452445E-01

296

0.380E-03

0.6020231E-01

297

0.400E-03

0.5752645E-01

298

0.4250E-03

0.5484677E-01

299

0.450E-03

0.5239946E-01

300

0.4750E-03

0.5017326E-01

301

0.500E-03

0.4855164E-01

302

0.5250E-03

0.4750492E-01

303

0.550E-03

0.8634498E-01

304

0.5750E-03

0.3684567

305

0.600E-03

0.7230662

306

0.630E-03

1.085166

307

0.660E-03

1.433057

308

0.690E-03

1.753764

309

0.720E-03

2.100540

310

0.760E-03

2.428895

311

0.800E-03

2.722788

312

0.840E-03

2.998771

313

0.880E-03

3.258461

314

0.920E-03

3.465372

315

0.960E-03

3.618973

316

0.100E-02

3.787081

317

0.1050E-02

3.964271

318

0.110E-02

13.13789

319

0.1150E-02

10.69382

320

0.120E-02

4.262693

321

0.1275E-02

4.338387

322

0.1350E-02

4.435367

323

0.1425E-02

4.534225

324

0.150E-02

4.592575

325

0.160E-02

4.783180

326

0.170E-02

4.701623

327

0.180E-02

4.841220

328

0.190E-02

4.999009

329

0.200E-02

5.111335

330

0.201E-02

5.183993

331

0.220E-02

5.279069

332

0.230E-02

5.408910

333

0.240E-02

5.523736

334

0.2550E-02

5.695442

335

0.270E-02

5.826853

336

0.280E-02

5.975410

337

0.300E-02

6.173523

338

0.320E-02

6.395415

339

0.340E-02

6.658582

340

0.360E-02

7.183939

341

0.380E-02

10.01168

342

0.400E-02

9.194485

343

0.4250E-02

8.178266

344

0.450E-02

8.229657

345

0.4750E-02

8.508525

346

0.500E-02

8.910876

347

0.5250E-02

9.525395

348

0.550E-02

10.59739

349

0.5750E-02

13.20411

350

0.600E-02

21.17466

351

0.630E-02

19.67340

352

0.660E-02

18.59203

353

0.690E-02

24.36627

354

0.720E-02

39.42936

355

0.760E-02

56.38621

356

0.800E-02

48.66102

357

0.840E-02

35.11790

358

0.880E-02

27.24892

359

0.920E-02

23.52159

360

0.960E-02

20.66808

361

0.100E-01

19.98392

362

0.1050E-01

18.41869

363

0.110E-01

18.51923

364

0.1150E-01

16.80365

365

0.120E-01

16.40945

366

0.1275E-01

16.00651

367

0.1350E-01

16.06792

368

0.1425E-01

15.55876

369

0.150E-01

15.08970

370

0.160E-01

14.61809

371

0.170E-01

13.99511

372

0.180E-01

13.21823

373

0.190E-01

12.01959

374

0.200E-01

10.61530

375

0.210E-01

8.888706

376

0.220E-01

6.857686

377

0.230E-01

4.435299

378

0.240E-01

4.034283

379

0.2550E-01

51.58856

380

0.270E-01

462.4204

381

0.280E-01

374.2036

382

0.300E-01

138.8582

383

0.320E-01

91.99242

384

0.340E-01

75.21491

385

0.360E-01

66.92896

386

0.380E-01

62.40611

387

0.400E-01

65.56062

388

0.4250E-01

59.51893

389

0.450E-01

61.42897

390

0.4750E-01

55.61853

391

0.500E-01

80.54994

392

0.5250E-01

84.93746

393

0.550E-01

61.63473

394

0.5750E-01

61.83547

395

0.600E-01

61.39486

396

0.630E-01

51.44463

397

0.660E-01

41.05520

398

0.690E-01

35.18787

399

0.720E-01

195.2115

400

0.760E-01

72.97270

401

0.800E-01

139.3801

402

0.840E-01

276.0543

403

0.880E-01

138.4568

404

0.920E-01

104.0743

405

0.960E-01

113.7160

406

0.100

105.5489

407

0.1050

78.43095

408

0.110

78.06753

409

0.1150

60.44543

410

0.120

70.47430

411

0.1275

134.1587

412

0.1350

255.3630

413

0.1425

293.0161

414

0.150

133.0900

415

0.160

122.7596

416

0.170

156.0143

417

0.180

244.4100

418

0.190

370.7627

419

0.200

205.3339

420

0.210

101.0349

421

0.220

307.5111

422

0.230

146.9613

423

0.240

171.8077

424

0.2550

135.3387

425

0.270

282.5501

426

0.280

187.6945

427

0.300

142.0391

428

0.320

315.5791

429

0.340

166.5530

430

0.360

302.1184

431

0.380

545.7117

432

0.400

528.4010

433

0.4250

400.4412

434

0.450

309.7825

435

0.4750

351.4453

436

0.500

381.0001

437

0.5250

327.4008

438

0.550

316.9469

439

0.5750

264.2091

440

0.600

190.8042

441

0.630

255.5292

442

0.660

529.8745

443

0.690

389.0167

444

0.720

680.4310

445

0.760

627.3019

446

0.800

427.2328

447

0.840

461.2467

448

0.880

327.1398

449

0.920

278.1719

450

0.960

479.7678

451

1.00

498.4922

452

1.10

477.6893

453

1.20

707.1735

454

1.30

616.4640

455

1.40

716.4101

456

1.50

734.1659

457

1.60

758.8353

458

1.70

784.5580

459

1.80

819.3325

460

1.90

989.3265

461

2.00

928.7681

462

2.10

923.3754

463

2.20

969.4800

464

2.30

1079.716

465

2.40

1143.224

466

2.50

1348.954

467

2.60

1192.105

468

2.70

1263.538

469

2.80

1277.801

470

2.90

1271.578

471

3.00

1364.006

472

3.10

1387.724

473

3.20

1358.466

474

3.30

1346.851

475

3.40

1398.034

476

3.50

1334.743

477

3.60

1424.447

478

3.70

1440.708

479

3.80

1483.880

480

3.90

1464.868

481

4.00

1526.371

482

4.10

1560.443

483

4.20

1530.309

484

4.30

1582.916

485

4.40

1523.340

486

4.50

1626.724

487

4.60

1600.863

488

4.70

1617.455

489

4.80

1653.609

490

4.90

1642.833

491

5.00

1600.075

492

5.10

1682.554

493

5.20

1687.286

494

5.30

1716.469

495

5.40

1731.089

496

5.50

1729.785

497

5.60

1760.852

498

5.70

1760.538

499

5.80

1768.656

500

5.90

1792.105

501

6.00

1811.511

502

6.10

1800.940

503

6.20

1811.547

504

6.30

1859.081

505

6.40

1859.125

506

6.50

1879.237

507

6.60

1890.037

508

6.70

1891.762

509

6.80

1909.485

510

6.90

1909.076

511

7.00

1914.442

512

7.10

1936.414

513

7.20

1941.750

514

7.30

1966.663

515

7.40

1963.306

516

7.50

1986.044

517

7.60

1976.213

518

7.70

1989.243

519

7.80

2003.646

520

7.90

2006.771

521

8.00

2009.093

522

8.10

2013.259

523

8.20

2032.588

524

8.30

2064.755

525

8.40

2063.837

526

8.50

2061.365

527

8.60

2059.507

528

8.70

2072.344

529

8.80

2089.976

530

8.90

2107.525

531

9.00

2122.580

532

9.10

2135.077

533

9.20

2147.577

534

9.30

2160.074

535

9.40

2172.482

536

9.50

2185.892

537

9.60

2199.950

538

9.70

2213.918

539

9.80

2226.698

540

9.90

2238.281

541

10.0

2250.482

542

10.10

2263.392

543

10.20

2276.220

544

10.30

2288.971

545

10.40

2301.725

546

10.50

2313.910

547

10.60

2325.628

548

10.70

2337.342

549

10.80

2348.869

550

10.90

2360.301

551

11.0

2371.744

552

11.10

2383.112

553

11.20

2395.212

554

11.30

2407.952

555

11.40

2421.344

556

11.50

2434.325

557

11.60

2446.243

558

11.70

2458.956

559

11.80

2471.205

560

11.90

2482.247

561

12.0

2493.659

562

12.10

2506.016

563

12.20

2519.598

564

12.30

2534.971

565

12.40

2549.086

566

12.50

2562.977

567

12.60

2576.115

568

12.70

2586.936

569

12.80

2600.011

570

12.90

2615.468

571

13.0

2630.343

572

13.10

2644.455

573

13.20

2658.475

574

13.30

2672.218

575

13.40

2685.520

576

13.50

2698.683

577

13.60

2711.990

578

13.70

2725.313

579

13.80

2738.112

580

13.90

2750.418

581

14.0

2763.164

582

14.10

2775.980

583

14.20

2788.331

584

14.30

2800.214

585

14.40

2811.915

586

14.50

2824.208

587

14.60

2837.183

588

14.70

2849.781

589

14.80

2862.184

590

14.90

2874.421

591

15.0

2877.552

592

15.10

2871.084

593

15.20

2864.617

594

15.30

2858.147

595

15.40

2851.581

596

15.50

2844.839

597

15.60

2837.641

598

15.70

2830.538

599

15.80

2823.427

600

15.90

2816.329

601

16.0

2813.386

602

16.10

2814.819

603

16.20

2816.344

604

16.30

2817.782

605

16.40

2819.124

606

16.50

2819.920

607

16.60

2819.883

608

16.70

2819.846

609

16.80

2819.725

610

16.90

2819.631

611

17.0

2823.437

612

17.10

2831.455

613

17.20

2839.475

614

17.30

2847.220

615

17.40

2855.056

616

17.50

2862.956

617

17.60

2870.913

618

17.70

2878.960

619

17.80

2886.826

620

17.90

2894.594

621

18.0

2903.983

622

18.10

2914.913

623

18.20

2925.791

624

18.30

2936.340

625

18.40

2946.712

626

18.50

2956.448

627

18.60

2965.448

628

18.70

2974.450

629

18.80

2983.453

630

18.90

2992.455

631

19.0

2999.561

632

19.10

3004.583

633

19.20

3009.698

634

19.30

3014.721

635

19.40

3019.741

636

19.50

3025.406

637

19.60

3031.526

638

19.70

3037.737

639

19.80

3043.950

640

19.90

3050.161

641

 

 

 

 

 

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

4.4 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 displacement cross section for ferritic iron, as given in this practice, is determined by the procedure given in 6.3. The currently recommended iron displacement cross section in this practice (Table 1) was generated using the ENDF/B-VI iron cross section (1).3 A recent calculation using ENDF/B-VII.0 produced identical results.(2, 3) The iron cross section data in ENDF/B-VII.1 does not differ from ENDF/B-VII.0. Although the ENDF/B-VI based iron displacement cross section differs from the previously recommended ENDF/B-IV iron displacement 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” (4, 5). 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 Spectrum

Spectrum-averaged iron displacment cross section (barns)^A

 

“Old” ENDF/B-IV-based E693 response

“Current” ENDF/B-VI-based E693 response

Difference ([Current - Old]/Old) (%)

ENDF/B-VI ²³⁵U Thermal Fission (1, 6)

875.55

858.54

–1.9

Materials Dosimetry Reference Facility (MDRF) (7)

345.03

343.58

–0.42

CFRMF (8, 9)

382.94

387.08

1.08

Intermediate-energy Standard Neutron Field (ISNF) (9, 10)

483.63

480.00

–0.75

Arkansas Nuclear ONE-1 (ANO) Cavity (11, 12)

134.40

139.44

3.75

ORNL Poolside Facility (PSF) T/4 position (11, 13)

242.14

238.33

–1.57

Oak Ridge Research Reactor (ORR) (9)

291.68

288.86

–0.97

Yayoi (9)

613.12

609.03

–0.67

BIGTEN (9, 14)

334.98

341.25

1.87

H.B. Robinson-2, in the vessel wall, close to the inner surface (4, 5)

219.43

218.81

–0.28

H.B. Robinson-2, ∼¹/₄ T vessel wall (4, 5)

245.17

249.24

1.66

H.B. Robinson-2, ∼³/₄ T vessel wall (4, 5)

203.68

211.23

3.71

(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 E_o = 10^–10 MeV.

Note 1: Table 2 is included to illustrate the effect on the iron displacment cross section 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.

Область применения

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 σ_d(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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.8 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.