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NEEP 541 – Material Properties
Fall 2003Jake 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
Material Thermal - Zr Fast - steel
Tmax (C) 380 660
Coolant Water Sodium
Pressure (atm)
130 <1
Clad thickness
(mm)
0.6 0.4
Clad OD (mm)
10.8 6.3
Life (dpa) 20 150
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=
1lnln
00L
L
L
dLL
L
true
Stress-Strain Curve
True Stress – True Strain
Combined
When does necking start? Plastic Instability (dP=0)
20
0
0
0
00
0
A
dAA
L
dL
A
A
L
L
LAALA
dAd
AddAAddP
Volume is conserve
d
Plastic Instability
true
true
d
d
dL
dL
A
dAd
A
dA
A
dAA
L
L
L
dL
L
L
L
dL
A
LAL
200
0
0
00
Necking occurs when slope of true stress-true strain curve=true
stress
Plastic Instability suppose
n
CCCn
CCnd
d
C
C
nn
n
n
n
1
1
1
111
11
1
Hardening
Impact Testing Test for ductility Measure energy absorbed during
fracture
Typical Results DBTT=ductile to brittle transition
temperature
T
E (J)
Upper shelfLower
shelf
irradiated
DBTT
40
Creep Tests Apply load and measure
deformation as a function of time
time
Creep strain
primary secondary
tertiary
Study creep rupture with a tube burst test
p
2R
L
Burst Test Analysis
t
pR
pRLRLdptL
h
h
2)sin(20
p
hh
Slice cylinder vertically
Burst Test Analysis
t
pR
pRRt
axial
axial
2
2 2
axialaxial
Slice cylinder horizontally (picture is shown cut away vertically as well)
Burst Test Analysis Uniaxial (1-D tensile test) Constant stress
tK
Kdt
d
n
n
Burst Test Analysis
zrijij
ijij
zzrr
zzrr
n
S
S
dt
d
dt
d
Kdt
d
;3
12
3
2
12
1
*
*
21
222*
21
222*
**
Burst Test Analysis
023
12
23
1
223
1
3
1
zz
z
zr
S
t
pRS
t
pR
t
pR
t
pRS
Burst Test Analysis
t
pR
zzrr
2
3
222
1
2
1
*
21
222*
21
222*
Burst Test Analysis
0
2
3
4
3
2
3
4
3
22
3
2
3
2
3
1
1
11*
dt
d
t
pRK
dt
d
t
pRK
dt
d
t
pR
t
pRKSK
dt
d
z
nn
nn
r
n
r
nr
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