lec20_rb

Materials Issues Related

to Reactor Design, Operation & Safety

Professor R. G. Ballinger Department of Nuclear Engineering

Department of Materials Science & Engineering

22.39 Le cture 1-1

Objective

• To Develop an Understanding of Materials Issues and Their Implications for Design, Operation & Safety

22.39 Le cture 1-2

Outline

Lecture #1: Materials Selection

Lecture #2: Radiation Damage/Effects & Implications for Design

Lecture #3: Environmental Degradation & Implications for Design

Lecture #4: Applications to PWR Design (Steam Generator Design, Penetrations)

Lecture #5: Applications to GFR Design

22.39 Le cture 1-3

Materials Selection Considerations

• A pplicability

• Suitability

• Fabricability

• A vailability

• E conomics

• Compromise

22.39 Le cture 1-4

Assessment of Applicability

1. Mechanical Environment

• S tress (Load) History

• S train History

• Normal, Transient, Accident

2. Chemical (Electrochemical) Environment

• N ormal, Faulted

3. Thermal Environment

4. Nuclear Environment

5. Mechanical-Chemical-Thermal-Nuclear

22.39 Le cture 1-5

General Material Failure Modes

1. Overload

2. Creep Rupture

3. Fatigue

4. Brittle Fracture

5. Wastage

6. Environmentally Enhanced

7. Radiation Effects Related

22.39 Le cture 1-6

Environmentally Enhanced Failure Modes

1. Stress Corrosion Cracking

2. Hydrogen Embrittlement

3. Corrosion Fatigue

4. Intergranular Attack

5. Erosion-Corrosion

6. Creep-Fatigue Interaction

22.39 Le cture 1-7

Key Point

• Big Difference Between General & Localized Corrosion

– General Corrosion

» Predictable

» Slow (Normally)

– Localized Corrosion

» “Unpredictable

» Potentially Ve ry Rapid

» Ca n be Multi-Pheno m ena (P itting leading to Crack Initiation)

– Sign ificant Design Implication s

» Example-PWR Steam Generators

22.39 Le cture 1-8

Radiation Effects Related

• Radiation Embrittlement

• Radiation Enhanced Creep

• Swelling

• Radiation Induced Growth

• Fuel/Clad Interaction

22.39 Le cture 1-9

Mechanical Environment

1. Load-Time History (Operational)

• S t a t i c

• C yclic (Fatigue)

• E lastic vs. Plastic

2. Fabrication Related Loads

• W elding

• M achining

3. Environment Related Loads

• T hermal (Static, Cyclic)

• Nuclear (Distortion due to swelling)

4. Time Dependent vs. Time Independent

• C reep

• C reep-Fatigue

22.39 Le cture 1-10

Chemical Environment

1. Electrochemical Compatibility

2. Bulk vs. Local

3. Normal vs. Faulted

4. Nominal vs. Actual

22.39 Le cture 1-11

Thermal Environment

1. Steady State

2. Startup/Shutdown

3. Transient

4. Accident

22.39 Le cture 1-12

Nuclear Environment

1. Effects on Mechanical Properties

• D uctility

• Toughness

• S trength

2. Dynamic Effects

• Radiation Induced Segregation (RIS)

• Growth

• Fission Gas Release & Fuel Swelling

3. Effects on Chemical Environment

• F uel Rod Chemistry

• Coolant Chemistry

4. Effects on Corrosion Products

• A ctivation Products

22.39 Le cture 1-13

Mechanical/Chemical/Thermal/ Nuclear Environment Interactions

• Stress Corrosion Cracking

• Corrosion Fatigue

• Hydrogen Embrittlement

• Creep-Fatigue Interaction

• Pellet Clad Mechanical Interaction (PCMI)

• Fretting

• Corrosion Product Transport

• Flow Assisted Corrosion

• Radiation Induced Segregation

22.39 Le cture 1-14

Interactions

Thermal

Mechanical

Chemical

Nuclear

Compromise

22.39 Le cture 1-15

Assessment of Suitability

1. Is the material qualified for use in the environment?

2. Is there an existing data base?

Is The Material In The ASME Code

3. If not, what information will be required?

4. Can the information be obtained in time?

22.39 Le cture 1-16

Assessment of Fabricability

1. Thermomechanical Processing

2. Can the component be fabricated from the material?

3. Quality Control

4. Quality Assurance

22.39 Le cture 1-17

Thermomechanical Processing

1. Can the desired mechanical properties be obtained?

2. Mechanical properties variability? How much can be allowed?

3. Can the desired properties be obtained?

4. Can the desired properties be maintained?

22.39 Le cture 1-18

Component Fabrication

1. Fabrication techniques

• W elding

Effects on Chemistry

Effects on Mechanical Properties

Effects on Chemical/Electrochem. Props. Effects on Mechanical Environment

• Residual Stress•

• M achining

Stress Concentrators

2. Assembly

Crevices Couples

22.39 Le cture 1-19

Assessment of Availability

1. Is the Material Available?

2. Is the Source Reliable?

3. Is there Enough of it?

4. At What Cost?

22.39 Le cture 1-20

Assessment of Economics

1. How Much Does it Cost Now?

2. How Much Could it Cost?

22.39 Le cture 1-21

Compromise

Th e Grea t Traged y o f Engineering:

The slaying of a great hypothesis by an ugly fact

Corollary

Don’t Do Stupid Things- a .k.a. Davis Besse

22.39 Le cture 1-22

Material Degradation Prevention Options

1. Design:

Proper Materials Selection at the Initial Design Phase Material “Friendly” Design

2. Remediation

Alteration of Chemical Environment Alteration of Mechanical Environment Alteration of Operating Conditions

3. Replacement

22.39 Le cture 1-23

Materials Selection

1. Select The Right Material in the First Place

2. Change the Material Properties

3. Replace the Material

22.39 Le cture 1-24

Alteration of Environment

1. Changing System Conditions

• Lower Temperature

• Change Chemistry

22.39 Le cture 1-25

Material “Friendly” Design

1. Avoid Stress/ Stress Concentrations

2. Avoid Galvanic Couples

3. Avoid Sharp Bends of Velocity Changes in Piping Systems

4. Design Tanks for Complete Draining

5. To Weld or Not to Weld?

6. Design to Exclude Air

7. Avoid Heterogeneity

8. Design for Replacement

22.39 Le cture 1-26