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NEEP 541 – Material Properties

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NEEP 541 – Material Properties

Fall 2003

Jake Blanchard

- Materials in Reactors
- Fission
- Fusion

- Material Properties
- Tensile tests
- Impact tests
- Creep tests

- Fission
- Fuel
- Cladding
- Moderator
- Core structure
- Reflector
- Control rods
- Coolant
- Pressure vessel
- shielding

- Fusion
- Fuel
- Structure
- Tritium breeder
- Coolant
- insulators
- shielding

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

- Low thermal absorption cross section
- Al
- Mg
- Zr
- Be

- High thermal absorption cross section
- Nb
- Mo
- Ta
- V
- Ti
- Steel

- Same as fission plus…
- Low swelling
- Low embrittlement

- Typical Materials
- Austenitic steel (316 SS)
- Ferritic steel (lately ODS FS)
- Refractory alloys
- composites

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

- Tensile tests (modulus, ductility, strength)
- Tube burst tests (creep)
- Impact tests (ductility, fracture toughness)

- A0=cross sectional area before test (in test section)
- A=cross sectional area during test (load=P)
- L0=section length before test
- L=section length during test

- Engineering stress=eng=P/A0
- True Stress=true=P/A
- Before necking, A~A0
- Engineering strain==(L-L0)/L0
- True strain=

- Plastic Instability (dP=0)

Volume is conserved

Necking occurs when slope of true stress-true strain curve=true stress

- suppose

- Test for ductility
- Measure energy absorbed during fracture

- DBTT=ductile to brittle transition temperature

Upper shelf

Lower shelf

E (J)

irradiated

40

T

DBTT

- Apply load and measure deformation as a function of time

primary

secondary

tertiary

Creep strain

time

2R

L

p

Slice cylinder vertically

p

Slice cylinder horizontally (picture is shown cut away vertically as well)

- Uniaxial (1-D tensile test)
- Constant stress

- 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