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NEEP 541 – Material Properties. Fall 2003 Jake Blanchard. Outline. Materials in Reactors Fission Fusion Material Properties Tensile tests Impact tests Creep tests. Materials in Reactors. Fission Fuel Cladding Moderator Core structure Reflector Control rods Coolant

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Neep 541 material properties

NEEP 541 – Material Properties

Fall 2003

Jake Blanchard


Outline
Outline

  • Materials in Reactors

    • Fission

    • Fusion

  • Material Properties

    • Tensile tests

    • Impact tests

    • Creep tests


Materials in reactors
Materials in Reactors

  • Fission

    • Fuel

    • Cladding

    • Moderator

    • Core structure

    • Reflector

    • Control rods

    • Coolant

    • Pressure vessel

    • shielding

  • Fusion

    • Fuel

    • Structure

    • Tritium breeder

    • Coolant

    • insulators

    • shielding


Fission
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


Cladding materials
Cladding Materials

  • Low thermal absorption cross section

    • Al

    • Mg

    • Zr

    • Be

  • High thermal absorption cross section

    • Nb

    • Mo

    • Ta

    • V

    • Ti

    • Steel



Fusion structure requirements
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


Radiation effects
Radiation Effects

  • Radiation hardening (increase in strength)

  • Embrittlement (decrease in ductility)

  • Swelling (volume increase due to voids)

  • Irradiation creep


Tests
Tests

  • Tensile tests (modulus, ductility, strength)

  • Tube burst tests (creep)

  • Impact tests (ductility, fracture toughness)



Understanding the tensile test
Understanding the Tensile Test

  • 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


Tensile tests1
Tensile Tests

  • Engineering stress=eng=P/A0

  • True Stress=true=P/A

  • Before necking, A~A0

  • Engineering strain==(L-L0)/L0

  • True strain=





When does necking start
When does necking start?

  • Plastic Instability (dP=0)

Volume is conserved


Plastic instability
Plastic Instability

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




Impact testing
Impact Testing

  • Test for ductility

  • Measure energy absorbed during fracture


Typical results
Typical Results

  • DBTT=ductile to brittle transition temperature

Upper shelf

Lower shelf

E (J)

irradiated

40

T

DBTT


Creep tests
Creep Tests

  • Apply load and measure deformation as a function of time

primary

secondary

tertiary

Creep strain

time



Burst test analysis
Burst Test Analysis

Slice cylinder vertically

p


Burst test analysis1
Burst Test Analysis

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


Burst test analysis2
Burst Test Analysis

  • Uniaxial (1-D tensile test)

  • Constant stress






Burst test analysis7
Burst Test Analysis

  • 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


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