Table of Contents

1 Introduction and Overview 1

1.1 Industrial Innovation 1

1.2 Evolution of Boilers 1

1.3 Overview of the Super LWR and Super FR 6

1.3.1 Concept and Features 6

1.3.2 Improvement of Thermal Design Criterion 10

1.3.3 Core Design Criteria 12

1.3.4 Improvement of Core Design and Analysis 13

1.3.5 Fuel Design 16

1.3.6 Plant Control 19

1.3.7 Startup Schemes 22

1.3.8 Stability 28

1.3.9 Safety 37

1.3.10 Super FR 54

1.3.11 Computer Codes and Database 61

1.4 Past Concepts of High Temperature Water and Steam Cooled Reactors 62

1.5 Research and Development 63

1.5.1 Japan 63

1.5.2 Europe 68

1.5.3 GIF and SCWR 68

1.5.4 Korea, China, US, Russia and IAEA 68

References 69

2 Core Design 79

2.1 Introduction 79

2.1.1 Supercritical Water Thermophysical Properties 80

2.1.2 Heat Transfer Deterioration in Supercritical Water 82

2.1.3 Design Considerations with Heat Transfer Deterioration 90

2.2 Core Design Scope 92

2.2.1 Design Margins 92

2.2.2 Design Criteria 96

2.2.3 Design Boundary Conditions 98

2.2.4 Design Targets 100

2.3 Core Calculations 102

2.3.1 Neutronic Calculations 102

2.3.2 Thermal-Hydraulic Calculations 112

2.3.3 Equilibrium Core Calculations 120

2.4 Core Designs 122

2.4.1 Fuel Rod Designs 122

2.4.2 Fuel Assembly Designs 128

2.4.3 Coolant Flow Scheme 137

2.4.4 Low Temperature Core Design with R-Z Two-Dimensional Core Calculations 140

2.4.5 High Temperature Core Design with Three-Dimensional Core Calculations 145

2.4.6 Design Improvements 161

2.4.7 Summary 170

2.5 Subchannel Analysis 173

2.5.1 Subchannel Analysis Code 173

2.5.2 Subchannel Analysis of the Super LWR 177

2.6 Statistical Thermal Design 181

2.6.1 Comparison of Thermal Design Methods 182

2.6.2 Description of MCSTDP 184

2.6.3 Application of MCSTDP 190

2.6.4 Comparison with RTDP 198

2.6.5 Summary 200

2.7 Fuel Rod Behaviors During Normal Operations 200

2.7.1 Evaluation of the Maximum Peak Cladding Temperature 200

2.7.2 Fuel Rod Analysis 201

2.7.3 Fuel Rod Design 205

2.8 Development of Transient Criteria 208

2.8.1 Selection of Fuel Rods for Analyses 209

2.8.2 Principle of Rationalizing the Criteria for Abnormal Transients 210

2.9 Summary 217

References 218

3 Plant System Design 221

3.1 Introduction 221

3.2 System Components and Configuration 222

3.3 Main Components Characteristics 223

3.3.1 Containment 224

3.3.2 Reactor Pressure Vessel 226

3.3.3 Internals 227

3.3.4 Turbine 228

3.3.5 Steam Lines and Candidate Materials 230

3.4 Plant Heat Balance 230

3.4.1 Super LWR Steam Cycle Characteristics 230

3.4.2 Thermal Efficiency Evaluation 232

3.4.3 Factors Influencing Thermal Efficiency 235

3.5 Summary 238

References 239

4 Plant Dynamics and Control 241

4.1 Introduction 241

4.2 Analysis Method for Plant Dynamics 241

4.3 Plant Dynamics without a Control System 246

4.3.1 Withdrawal of a Control Rod Cluster 248

4.3.2 Decrease in Feedwater Flow Rate 248

4.3.3 Decrease in Turbine Control Valve Opening 250

4.4 Control System Design 252

4.4.1 Pressure Control System 253

4.4.2 Main Steam Temperature Control System 255

4.4.3 Reactor Power Control System 256

4.5 Plant Dynamics with Control System 258

4.5.1 Stepwise Increase in Pressure Setpoint 259

4.5.2 Stepwise Increase in Temperature Setpoint 261

4.5.3 Stepwise Decrease in Power Setpoint 262

4.5.4 Impulsive Decrease in Feedwater Flow Rate 262

4.5.5 Decrease in Feedwater Temperature 264

4.5.6 Discussion 265

4.6 Summary 266

References 266

5 Plant Startup and Stability 269

5.1 Introduction 269

5.2 Design of Startup Systems 270

5.2.1 Introduction to Startup Schemes of FPPs 270

5.2.2 Constant Pressure Startup System of the Super LWR 273

5.2.3 Sliding Pressure Startup System of the Super LWR 279

5.3 Thermal Considerations 282

5.3.1 Startup Thermal Analysis Code 282

5.3.2 Thermal Criteria for Plant Startup 288

5.3.3 Thermal Analyses 289

5.4 Thermal-Hydraulic Stability Considerations 295

5.4.1 Mechanism of Thermal-Hydraulic Instability 295

5.4.2 Selection of Analysis Method 297

5.4.3 Thermal-Hydraulic Stability Analysis Method 298

5.4.4 Thermal-Hydraulic Stability Analyses 304

5.5 Coupled Neutronic Thermal-Hydraulic Stability Considerations 316

5.5.1 Mechanism of Coupled Neutronic Thermal-Hydraulic Instability 316

5.5.2 Coupled Neutronic Thermal-Hydraulic Stability Analysis Method 318

5.5.3 Coupled Neutronic Thermal-Hydraulic Stability Analyses 324

5.6 Design of Startup Procedures with Both Thermal and Stability Considerations 335

5.7 Design and Analysis of Procedures for System Pressurization and Line Switching in Sliding Pressure Startup Scheme 338

5.7.1 Motivation and Purpose 338

5.7.2 Redesign of Sliding Pressure Startup System 339

5.7.3 Redesign of Sliding Pressure Startup Procedures 340

5.7.4 System Transient Analysis 343

5.8 Summary 345

References 347

6 Safety 349

6.1 Introduction 349

6.2 Safety Principle 349

6.3 Safety System Design 350

6.3.1 Equipment 350

6.3.2 Actuation Conditions of the Safety System 355

6.4 Selection and Classification of Abnormal Events 357

6.4.1 Reactor Coolant Flow Abnormality 358

6.4.2 Other Abnormalities 360

6.4.3 Event Selection for Safety Analysis 361

6.4.4 Uniqueness in the LOCA of the Super LWR 362

6.5 Safety Criteria 363

6.5.1 Criteria for Fuel Rod Integrity 364

6.5.2 Criteria for Pressure Boundary Integrity 365

6.5.3 Criteria for ATWS 365

6.6 Safety Analysis Methods 366

6.6.1 Safety Analysis Code for Supercritical Pressure Condition 366

6.6.2 Safely Analysis Code for Subcritical Pressure Condition 371

6.6.3 Blowdown Analysis Code 372

6.6.4 Reflooding Analysis Code 377

6.7 Safety Analyses 380

6.7.1 Abnormal Transient Analyses at Supercritical Pressure 382

6.7.2 Accident Analyses at Supercritical Pressure 391

6.7.3 Loss of Coolant Accident Analyses 395

6.7.4 ATWS Analysis 401

6.7.5 Abnormal Transient and Accident Analyses at Subcritical Pressure 412

6.8 Development of a Transient Subchannel Analysis Code and Application to Flow Decreasing Events 415

6.8.1 A Transient Subchannel Analysis Code 415

6.8.2 Analyses of Flow Decreasing Events 417

6.8.3 Summary 423

6.9 Simplified Level-1 Probabilistic Safety Assessment 423

6.9.1 Preparation of Event Trees 423

6.9.2 Initiating Event Frequency and Mitigation System Unavailability 431

6.9.3 Results and Considerations 432

6.9.4 Summary 435

6.10 Summary 436

References 437

7 Fast Reactor Design 441

7.1 Introduction 441

7.2 Design Goals, Criteria, and Overall Procedure 441

7.2.1 Design Goals and Criteria 441

7.2.2 Overall Design Procedure 443

7.3 Concept of Blanket Assembly with Zirconium Hydride Layer 445

7.3.1 Effect of Zirconium Hydride Layer on Void Reactivity 445

7.3.2 Effect of Zirconium Hydride Layer on Breeding Capability 450

7.3.3 Effect of Hydrogen Loss from Zirconium Hydride Layers on Void Reactivity 451

7.4 Fuel Rod Design 453

7.4.1 Introduction 453

7.4.2 Failure Modes of Fuel Cladding 454

7.4.3 Fuel Rod Design Criteria 456

7.4.4 Fuel Rod Design Method 459

7.4.5 Fuel Rod Design and Analysis 462

7.4.6 Summary of Fuel Rod Design 465

7.5 Core Design Method and 1,000 MWe Class Core Design 467

7.5.1 Discussion of Neutronic Calculation Methods 467

7.5.2 Core Design Method 468

7.5.3 Materials Used in Core Design 479

7.5.4 Fuel Assembly Design 480

7.5.5 Core Arrangement 481

7.5.6 Design of 1,000 MWe Class Core 483

7.6 Subchannel Analysis 491

7.6.1 Introduction 491

7.6.2 Temperature Difference Arising from Subchannel Heterogeneity 493

7.6.3 Evaluation of MCST over Equilibrium Cycle 495

7.7 Evaluation of Maximum Cladding Surface Temperature with Engineering Uncertainties 499

7.7.1 Treatment of Downward Flow 499

7.7.2 Nominal Conditions and Uncertainties 501

7.7.3 Statistical Thermal Design of the Super FR 505

7.7.4 Comprehensive Evaluation of Maximum Cladding Surface Temperature at Normal Operation 506

Design and Improvements of 700 MWe Class Core 508

7.8.1 Design of Reference Fuel Rod and Core 509

7.8.2 Core Design Improvement for Negative Local Void Reactivity 509

7.8.3 Core Design Improvement for Higher Power Density 518

7.9 Plant Control 522

7.9.1 Plant Transient Analysis Code for the Super FR 523

7.9.2 Basic Plant Dynamics of the Super FR 523

7.9.3 Design of Reference Control System 525

7.9.4 Improvement of Feedwater Controller 527

7.9.5 Plant Stability Analyses 530

7.9.6 Comparison of Improved Feedwater Controllers 534

7.9.7 Summary of Improvement of Feedwater Controller 535

7.10 Thermal and Stability Considerations During Power Raising Phase of Plant Startup 536

7.10.1 Introduction 536

7.10.2 Calculation of Flow Distribution 537

7.10.3 Thermal and Thermal-Hydraulic Stability Considerations 539

7.10.4 Sensitivity Analyses 547

7.11 Safety 550

7.11.1 Introduction 550

7.11.2 Analyses of Abnormal Transients and Accidents at Supercritical Pressure 551

7.11.3 Analyses of Loss of Coolant Accidents 556

7.11.4 Analyses of Anticipated Transient without Scram Events 563

7.12 Summary 564

References 567

8 Research and Development 571

8.1 Japan 571

8.1.1 Concept Development 571

8.1.2 Thermal Hydraulics 575

8.1.3 Materials and Water Chemistry 577

8.2 Other Countries 581

8.2.1 Europe 581

8.2.2 Canada 583

8.2.3 Korea 584

8.2.4 China 584

8.2.5 USA 585

8.3 International Activities 587

8.3.1 Generation-IV International Forum 587

8.3.2 IAEA-Coordinated Research Program 587

8.3.3 International Symposiums 588

References 590

Appendix A Supercritical Fossil Fired Power Plants - Design and Developments 599

Appendix B Review of High Temperature Water and Steam Cooled Reactor Concepts 619

Index 645