Structural Materials in Nuclear Power Systems

In recent years the effort devoted to assuring both the safety and reliability of commercial nuclear fission power reactors has markedly increased. The incentives for performing this work are large since the resulting im­ provement in plant productivity translates into lower fuel costs and, more importantly, reduced reliance on imported oil. Reliability and availability of nuclear power plants, whether fission or fusion, demand that more attention be focused on the behavior of materials. Recent experiences with fission power indicate that the basic properties of materials, which categorize their reliable behavior under specified conditions, need reinforcement to assure trouble-free operation for the expected service life. The pursuit of additional information con­ tinues to demand a better understanding of some of the observed anom­ alous behavior, and of the margin of resistance of materials to unpre­ dictable service conditions. It is also apparent that, next to plasma heating and confinement, materials selection represents the most serious chal­ lenge to the introduction of fusion power. The recognition of the importance of materials performance to nu­ clear plant performance has sustained a multimillion dollar worldwide research and development effort that has yielded significant results, both in quantification of the performance limits of materials in current use and the development and qualification of new materials. Most of this infor­ mation appears in the open literature in the form of research reports, journal articles, and conference proceedings.

1. Introduction and Overview.- 1.1. Reactor Systems and Materials.- 1.1.1. Boiling Water Reactor.- 1.1.2. Pressurized Water Reactor.- 1.1.3. Liquid Metal Fast Breeder Reactor.- 1.1.4. Fusion Reactor Systems.- 1.1.4.1. Magnetic Confinement Concepts.- 1.1.4.2. Inertial Confinement Concepts.- 1.2. Past Performance of Nuclear Plants.- 1.3. Materials and Design Considerations.- 1.3.1. Traditional Design Approach.- 1.3.2. Structural Integrity Analysis.- 1.3.3. Methods of Analysis.- 1.3.3.1. Stress Analysis.- 1.3.3.2. Fracture Mechanics.- 1.3.4. Materials Properties and Phenomena.- 1.3.4.1. Plastic Flow Properties.- 1.3.4.2. Fracture Toughness.- 1.3.4.3. Fatigue.- 1.3.4.4. Environmental Fatigue.- 1.3.4.5. Radiation Effects.- 1.3.4.6. Corrosion.- References.- 2. LWR Core Materials.- 2.1. Fuel and Core Designs.- 2.2. Fuel Performance.- 2.2.1. Fuel Reliability.- 2.2.1.1. Pellet-Cladding Interaction.- 2.2.1.1a. Results of Experimental and Theoretical Studies.- 2.2.1.1b. PCI Failure Models and Criteria.- 2.2.1.1c. PCI Remedies.- 2.2.1.2. Waterside Corrosion of Zircaloys.- 2.2.1.2a. Corrosion in BWRs.- 2.2.1.2b. Corrosion in PWRs.- 2.2.2. Fuel Operating Margins (or Fuel Safety Considerations).- 2.2.2.1. LOCA Criteria.- 2.2.2.1a. Zircaloy Embrittlement Criteria.- 2.2.2.1b. Fuel Pellet Densifïcation.- 2.2.2.1c. Fission Gas Release.- 2.2.2.2. Heat Flux Limits.- 2.2.2.2a. Departure from Nucleate Boiling.- 2.2.2.2b. Fuel Rod Bow.- 2.2.2.3. Core Damage Assessment in Three Mile Island Accident.- 2.3. Plutonium Recycle Fuel Performance.- 2.4. Stainless Steel-UO2 Fuel Experience.- 2.5. Control Materials.- 2.5.1. Control Rod Materials.- 2.5.2. Burnable Poisons.- 2.6. Uranium Conservation Measures.- References.- 3. LMFBR Core Materials.- 3.1. Fuel and Core Designs.- 3.2. Performance of Current Mixed Oxide Fuel Designs.- 3.2.1. Mixed Oxide Fuel Behavior.- 3.2.2. Cladding and Duct Mechanical Behavior.- 3.2.3. Fuel-Cladding Interactions.- 3.2.4. External Cladding Corrosion.- 3.3. Advanced Oxide Fuel Development.- 3.3.1. Optimization of Mixed Oxide Fuels.- 3.3.2. Optimization of Cladding and Duct Materials.- 3.4. Advanced Fuel Development.- 3.4.1. Carbide Fuel Development.- 3.4.2. Nitride Fuel Development.- 3.5. Control Rod Material Development.- 3.6. Proliferation-Resistant Fuel Cycles.- 3.6.1. Modified Mixed Oxide Fuel Cycles.- 3.6.2. Alternative Fuel Cycles.- 3.6.2.1. Thorium-Based Ceramic Fuels.- 3.6.2.2. Metal Alloy Fuels.- References.- 4. Fission Reactor Pressure Boundary Materials.- 4.1. Design and Materials of Construction.- 4.1.1. LWR Vessel and Piping.- 4.1.2. LMFBR Vessel and Piping.- 4.2. Developments in Fracture Mechanics.- 4.2.1. Elastic Fracture.- 4.2.2. Elastic-Plastic and Fully Plastic Fracture.- 4.3. Material Characteristics.- 4.3.1. LWR Materials.- 4.3.1.1. Fracture Toughness.- 4.3.1.2. Radiation Embrittlement.- 4.3.1.3. Fatigue Crack Growth.- 4.3.1.4. Stress-Corrosion Cracking.- 4.3.1.4a. Stress-Corrosion Cracking of Piping.- 4.3.1.4b. Stress-Corrosion Cracking in Nozzle Safe-Ends.- 4.3.1.5. Closing Remarks.- 4.3.2. LMFBR Materials.- 4.3.2.1. Elevated-Temperature Low-Cycle Fatigue.- 4.3.2.2. Fatigue Crack Growth.- 4.3.2.3. Closing Remarks.- 4.4. Materials Improvements.- 4.4.1. Improvements to Vessel Steels.- 4.4.2. Remedies for BWR Pipe Cracking.- 4.4.2.1. Modifications to Type 304 Stainless Steel.- 4.4.2.2. Alternative Materials.- 4.4.3. Improvements to Castings.- References.- 5. Fusion First-Wall/Blanket Materials.- 5.1. First-Wall/Blanket Designs.- 5.1.1. Magnetic Fusion.- 5.1.2. Inertial Confinement Fusion.- 5.2. Materials and Structural Integrity Considerations.- 5.2.1. Candidate Metals and Alloys.- 5.2.1.1. Helium Embrittlement.- 5.2.1.2. Swelling Behavior.- 5.2.1.3. Fatigue Behavior.- 5.2.1.4. Closing Remarks.- 5.2.2. Candidate Ceramics.- 5.2.2.1. Brittle Fracture Characteristics.- 5.2.2.2. Erosion Characteristics.- 5.2.2.3. Irradiation Effects.- 5.2.2.4. Closing Remarks.- References.- 6. Heat Exchanger Materials.- 6.1. Design and Materials of Construction.- 6.1.1. PWR Steam Generator.- 6.1.2. LMFBR Heat Exchangers.- 6.1.2.1. Steam Generator.- 6.1.2.2. Intermediate Heat Exchanger.- 6.1.3. CTR Steam Generator.- 6.1.4. Condenser.- 6.2. PWR Steam Generator Experience.- 6.2.1. Corrosion Damage Processes.- 6.2.1.1. Denting.- 6.2.1.2. Stress-Corrosion Cracking.- 6.2.1.3. “Phosphate Thinning”.- 6.2.2. Vibration and Mechanical Problems.- 6.2.2.1. Fretting and Wear.- 6.2.2.2. Fatigue Cracking.- 6.2.3. Avoidance or Mitigation of Steam Generator Damage.- 6.2.3.1. Chemical Control.- 6.2.3.2. Design and Fabrication Changes.- 6.2.3.3. Modified or Alternative Materials.- 6.2.3.3a. Inconel 600.- 6.2.3.3b. Alloy 800.- 6.2.3.3c. Inconel 690.- 6.2.3.3d. SCR-3 Alloy.- 6.2.3.3e. Ferritic (Martensitic) Stainless Steels.- 6.3. LMFBR Steam Generator and IHX Development.- 6.3.1. Steam Generator Materials Properties.- 6.3.1.1. Sodium Corrosion.- 6.3.1.2. Water-Steam Corrosion Performance.- 6.3.1.3. Tube Wastage by Sodium-Water Reactions.- 6.3.2. IHX Materials Properties.- 6.3.3. Closing Remarks.- 6.4. Condenser Experience.- 6.4.1. Copper-Base Alloys.- 6.4.1.1. Admiralty Brass.- 6.4.1.2. 90-10 Copper-Nickel (CL and CA7O6).- 6.4.1.3. 70-30 Copper-Nickel (CN and CA715).- 6.4.1.4. Aluminum Brass and Bronze.- 6.4.1.5. Chromium-Modified Copper-Nickel Alloys (IN-838 or CA-722).- 6.4.2. Iron-Chromium Base Alloys.- 6.4.3. Titanium-Base Alloys.- 6.4.4. Closing Remarks.- References.- 7. Steam Turbine Materials.- 7.1. Design and Materials of Construction.- 7.1.1. Major Components.- 7.1.1.1. Rotors.- 7.1.1.2. (Shrunk-on) Discs.- 7.1.1.3. Blades.- 7.1.2. Material Characteristics.- 7.2. Turbine Damage Mechanisms.- 7.2.1. Stress-Corrosion Cracking.- 7.2.2. Thermal-Mechanical Crack Growth.- 7.2.3. Moisture Erosion.- 7.3. Improvements in Turbine Materials.- 7.3.1. Low-Alloy Ferritic Steels.- 7.3.1.1. Impurity Reductions.- 7.3.1.2. Elimination of Temper Embrittlement.- 7.3.2. Alternative Blade Materials.- References.- 8. Future Trends in Nuclear Materials.- 8.1. Overview of the Materials Problems.- 8.2. Specific Materials Developments.- 8.2.1. Clean (Low-Alloy) Steels.- 8.2.2. “Stainless” Steels.- 8.2.3. Nickel-Base Alloys.- 8.2.4. New Materials—Titanium.- 8.2.5. Barriers and Coatings.- 8.2.5.1. Fuel Rod Cladding Barriers.- 8.2.5.2. Fusion First-Wall Coatings.- 8.2.5.3. Tritium Barriers.- 8.3. Related Technologies.- 8.4. Closing Remarks.- References.- Appendixes.- Appendix A.- Appendix B.- Appendix C.