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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

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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

    • Pressure vessel

    • shielding

  • Fusion

    • Fuel

    • Structure

    • Tritium breeder

    • Coolant

    • insulators

    • shielding


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

  • Low thermal absorption cross section

    • Al

    • Mg

    • Zr

    • Be

  • High thermal absorption cross section

    • Nb

    • Mo

    • Ta

    • V

    • Ti

    • Steel


Some Numbers


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 hardening (increase in strength)

  • Embrittlement (decrease in ductility)

  • Swelling (volume increase due to voids)

  • Irradiation creep


Tests

  • Tensile tests (modulus, ductility, strength)

  • Tube burst tests (creep)

  • Impact tests (ductility, fracture toughness)


Tensile Tests


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 Tests

  • Engineering stress=eng=P/A0

  • True Stress=true=P/A

  • Before necking, A~A0

  • Engineering strain==(L-L0)/L0

  • True strain=


Stress-Strain Curve


True Stress – True Strain


Combined


When does necking start?

  • Plastic Instability (dP=0)

Volume is conserved


Plastic Instability

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


Plastic Instability

  • suppose


Hardening


Impact Testing

  • Test for ductility

  • Measure energy absorbed during fracture


Typical Results

  • DBTT=ductile to brittle transition temperature

Upper shelf

Lower shelf

E (J)

irradiated

40

T

DBTT


Creep Tests

  • Apply load and measure deformation as a function of time

primary

secondary

tertiary

Creep strain

time


Study creep rupture with a tube burst test

2R

L

p


Burst Test Analysis

Slice cylinder vertically

p


Burst Test Analysis

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


Burst Test Analysis

  • Uniaxial (1-D tensile test)

  • Constant stress


Burst Test Analysis


Burst Test Analysis


Burst Test Analysis


Burst Test Analysis


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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