1. NEEP 541 – Material Properties Fall 2003 Jake Blanchard

2. Outline Materials in Reactors Fission Fusion Material Properties Tensile tests Impact tests Creep tests

3. Materials in Reactors Fission Fuel Cladding Moderator Core structure Reflector Control rods Coolant Pressure vessel shielding Fusion Fuel Structure Tritium breeder Coolant insulators shielding

4. Fission Primary radiation damage is in fuel and cladding Cladding: Adequate strength (T, fluence) Corrosion resistance Thermal conductivity Neutronics (low absorption) Available resources Fabricability Inexpensive

5. Cladding Materials Low thermal absorption cross section Al Mg Zr Be High thermal absorption cross section Nb Mo Ta V Ti Steel

6. Some Numbers MaterialThermal - ZrFast - steel Tmax (C)380660 CoolantWaterSodium Pressure (atm)130<1 Clad thickness (mm) 0.60.4 Clad OD (mm)10.86.3 Life (dpa)20150

7. Fusion Structure Requirements Same as fission plus… Low swelling Low embrittlement Typical Materials Austenitic steel (316 SS) Ferritic steel (lately ODS FS) Refractory alloys composites

8. Radiation Effects Radiation hardening (increase in strength) Embrittlement (decrease in ductility) Swelling (volume increase due to voids) Irradiation creep

9. Tests Tensile tests (modulus, ductility, strength) Tube burst tests (creep) Impact tests (ductility, fracture toughness)

10. Tensile Tests

11. Understanding the Tensile Test A 0 =cross sectional area before test (in test section) A=cross sectional area during test (load=P) L 0 =section length before test L=section length during test

12. Tensile Tests Engineering stress=  eng =P/A 0 True Stress=  true =P/A Before necking, A~ A 0 Engineering strain=  =(L-L 0 )/L 0 True strain=

13. Stress-Strain Curve

14. True Stress – True Strain

15. Combined

16. When does necking start? Plastic Instability (dP=0) Volume is conserved

17. Plastic Instability Necking occurs when slope of true stress-true strain curve=true stress

18. Plastic Instability suppose

19. Hardening

20. Impact Testing Test for ductility Measure energy absorbed during fracture

21. Typical Results DBTT=ductile to brittle transition temperature T E (J) Upper shelf Lower shelf irradiated DBTT 40

22. Creep Tests Apply load and measure deformation as a function of time time Creep strain primarysecondarytertiary

23. Study creep rupture with a tube burst test p 2R L

24. Burst Test Analysis p Slice cylinder vertically

25. Burst Test Analysis Slice cylinder horizontally (picture is shown cut away vertically as well)

26. Burst Test Analysis Uniaxial (1-D tensile test) Constant stress

27. Burst Test Analysis

31. Negative radial strain means that wall gets thinner Zero axial strain means length doesn’t change Positive hoop strain means radius increases Analysis assumes small strain, constant stress For large strain, wall thins and stress increases, leading to rupture