09/25/2007 - 09/26/2007 Meeting Presentation on Task 1 ...
Transcript of 09/25/2007 - 09/26/2007 Meeting Presentation on Task 1 ...
Work sponsored by the US Nuclear Regulatory Commission
Task 1: Evaluation of the Causes &Mechanisms of IASCC in BWRs -IASCC Susceptibility of Austenitic SSs& Alloy 690
September 25-26, 2007
Nuclear Engineering Division
Argonne National Laboratory, Argonne, IL 60439
Investigators: Yiren Chen, Omesh Chopra, Bill Shack, Bill Soppet,
and Nancy Dietz Rago1
Experimental Effort: Loren Knoblich and Ed Listwan
1Chemical Engineering Division
2Work sponsored by theUS Nuclear Regulatory Commission
Objectives and Approach
Objectives:
– Evaluate the influence of GBE treatment;
– Evaluate the influence of alloy composition;
– Evaluate the effect of irradiation dose.
Approach:
SSRT tests in high-DO water at 289ºC, complemented with
Fractography on:
– specimens with different proportions of special boundaries
– specimens with various chemical compositions
– specimens irradiated to a range of doses.
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Alloys
Fe 10.26, Al 0.22, Ti 0.2929.10-0.0100.420.0030.0260.4259.40GBE Alloy 690GBE690
Fe 9.02, Co 0.007, Cu 0.0129.24-0.0300.150.001-0.0561.49Alloy 690690
Mo 2.39, Ti 0.027, Cu 0.2117.250.0640.0120.920.0020.0070.7212.30Type 316LN SS, Ti-doped625
Mo 2.38, Cu 0.2117.230.1030.0190.970.0020.0070.712.20Type 316LN SS623
Mo 2.07, Cu 0.37, Co 0.0916.340.0500.0411.590.0250.0290.3511.16GBE Type 316 SSGBE316
Mo <0.005, O 0.04719.210.0030.0051.110.005<0.0050.039.03High-purity Type 304L SS
with high O945
Mo 0.02, O 0.00819.71<0.0010.0061.120.0020.0010.019.54High-purity Type 304L SS
with low O327
Mo 0.37, Cu 0.3518.350.0900.0201.740.0070.0280.458.33GBE Type 304L SSGBE304L
Mo 0.37, Co 0.13, Cu 0.3518.350.0900.0231.740.0070.0280.458.33Type 304L SS.304L
Mo 0.23, Co 0.10, Cu 0.3118.280.0520.0541.730.0060.0290.418.19GBE Type 304 SSGBE304
Mo 0.3718.540.0680.041.380.0190.0270.688.45Type 304 SS from ABBa333
OthersCrNCMnSPSiNi
Composition (wt.%)
DescriptionHeat ID
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! Flat dog-bone specimen
! Dry irradiation in He-sealed capsules in Halden boiling heavy water reactor
– Dose: 0.45, 1.34 and 3 dpa (phase-I); 1.96 and 2.44 dpa (phase-II)
– Irradiation temperature (phase-II): ~290-305°C
– Radioactivity: ~ 200 R/hr on contact, 0.3 Ci.
SSRT specimens and Irradiation condition
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SSRT test condition
1
5
6
v6 v7
v8
v10
9
8
32
14 15
16
17 18
19
20
21
22
23
25 26
28 31
V11
V12
V13
V17
11
24
34
2 v1
3 v2
v3
4 v5 v4
7
10
13
27
29
30
12 33
35
36
v9
V14
V15V16
V18
Low pressure High pressure
In Cell
29B
v1937
38
Temperature - 289°C DO - 8 ppm
Pressure - 9.31 MPa (1350 psig) Conductivity - 0.06~0.1 µS/cm
pH - 6.4 ~ 7.2 ECP – 150~200 mV (ss)
Flow rate – 15~30 ml /min 270~310 mV (Pt)
Strain rate ~ 3.31x10-7 s-1
Stabilize test condition by soaking the specimen in high-DO water >24 hr
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Influence of irradiation and high-DO water on SSRT curve
- The yield strength for irradiated material is similar in air and in water.
- The reduction in ductility is attributed to both neutron irradiation and
high-DO water environment.
Strain rate:
~ 3.31x10-7 s-1
0
100
200
300
400
500
600
700
800
0 5 10 15 20 25 30 35 40
Str
ess (
MP
a)
Strain (%)
GBE Type 304L SS
non-irr., in water
1.96 dpa, in water
1.96 dpa, in air
in air test - 287 ~292 oC
in water test - 289 oC
Pressure ~ 9.3 MPa pH ~ 6.8 DO ~ 8 ppm
Conductivity ~ 0.067 µSv/cm
Flow ~ 20 ml/min
Strain rate:
8.15 x 10 -7
s-1
Strain rate:
3.31 x 10 -7
s-1
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SSRT tests in high-DO water environment
0
200
400
600
800
1000
0 2 4 6 8 10
Str
ess (
MP
a)
Strain (%)
GBE304 (1.96 dpa)
Strain rate = 3.31 x 10-7
s-1
Type 304 SS
333 (2.44 dpa)
(a)
0
200
400
600
800
1000
0 2 4 6 8 10
Str
ess (
MP
a)
Strain (%)
GBE304L (1.96 dpa)
Strain rate = 3.31 x 10-7
s-1
304L (1.96 dpa)
Type 304L SS
327 (2.44 dpa)
945 (2.44 dpa)
(b)
0
200
400
600
800
1000
0 2 4 6 8 10
Str
ess (
MP
a)
Strain (%)
GBE316 (1.96 dpa)
Strain rate = 3.31 x 10-7
s-1
623 (2.44 dpa)
Type 316 and 316L SSs
625 (2.44 dpa)
(c)
0
200
400
600
800
1000
0 5 10 15 20 25 30
Str
ess (
MP
a)
Strain (%)
690 (1.96 dpa)
Strain rate = 3.31 x 10-7
s-1
Alloy 690
GBE690 (1.96 dpa)
(d)
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Dose dependence of yield strength and ultimate tensile strength
Rate of increase of yield strength
decreases significantly at 3 dpa.
0
500
1000
1500
0 0.5 1 1.5 2 2.5 3 3.5
Yie
ld S
tre
ng
th (
MP
a)
Dose (dpa)
0
500
1000
1500
0 0.5 1 1.5 2 2.5 3 3.5
Ultim
ate
Te
nsile
Str
en
gth
(M
Pa
)
Dose (dpa)
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Dose dependence of uniform elongation and total elongation
Loss of elongation reaches
minimum at less than 2 dpa
in high-DO water.
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3 3.5
Un
ifo
rm E
lon
ga
tio
n (
%)
Dose (dpa)
0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3 3.5
Tota
l E
longation (
%)
Dose (dpa)
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Correlation between C content and UE of SSRT tests
No other correlation found between other elements & SSRT elongation
0
1
2
3
4
5
6
7
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Type 304 SS, with GBE
Type 304 SS, w/o GBE
Type 316 SS, with GBE
Type 316 SS, w/o GBE
Uniform
Elo
ngation (
%)
Carbon Content (wt.%)
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~ 2 mm
0
.
7
m
m
3.15 mm
Fractographic analyses
! Cut fracture tip to reduce radioactivity: <100 mR/hr @ 30 cm; <7mCi.
! Clean off loose contamination: < 200 dpm
! Hitachi S-3000N SEM, secondary electron image at 30-kV acceleration
voltage with a 25-mm work distance.
TG
Ductile fracture
IG
IG
d1
TGl1
l2
d2
! Characterize fracture surface
– IG or TG area fractions
– Number of IG or TG cracks
…
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Type 304L SS with high O content (Heat 945)
Dose = 2.44 dpa
YS = 666 MPa
UTS = 666 MPa
UE = 1.22%
TE = 2.20%
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Susceptibility to cracking – IG and TG area fractions
- Type 304 and 304L SSs are more vulnerable to IG cracking in high-DO water;
- Large TG cracking was observed in GBE Type 316;
- High-O content stimulates IG cracking in HP Type 304L SS;
- Low-C Type 304 SSs show more IG cracking.
0
10
20
30
40
50
IG %
TG %
Are
a F
ractio
n (
%)
333
GBE304
304L
GBE304L
327
945
GBE316
623
625
690
GBE690
Type 304 Type 304L Type 316 Alloy 690
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Likelihood of IG crack initiation
-The highest IG initiation is found in Type 304L SS with high-O content.
- No IG initiation in high-purity Type 316 SSs, and GBE 690.
0
1
2
3
4
Num
ber
of IG
Cra
cks / u
niform
elo
ngation
333
GBE304
304L
GBE304L
327
945
GBE316
623 625690
GBE690
Type 304 Type 304L Type 316 Alloy 690
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Effect of GBE! Treatment
! GBE treatment does not appear to improve IG cracking in Type 304 and 304L SSs
! The effectiveness of GBE treatment is inconclusive for Type 316 SS (no base tested)
! GBE treatment appears to suppress IG cracking in Alloy 690 at !2 dpa
! GBE CSL (""29) fractions:
–67% Type 304 SS;
–66% Type 304L SS;
–66% Type 316 SS;
–71% Alloy 690.
0
5
10
15
20
25
30
35
nonGBE
GBE
IG A
rea
Fra
ctio
n (
%)
333
GBE304
304L
GBE304L
GBE316
690
GBE690
Type 304 Type 304L Type 316 Alloy 690
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Effect of Alloying Elements
! Type 304 SSs cracked more
than Type 316 SSs (Mo
addition is helpful to reduce
cracking)
! Type 304L SS cracked more
than Type 304 SS (blue vs.
orange)
! Low-O Type 304 SS cracked
less (light blue vs. dark blue)
Appear to be significant differences within alloy types; such heat-to-heat variability
may be dependent on differences in microstructure & minor impurity levels
0
5
10
15
20
25
30
35
Type 304 SS
Type 304L SS
Low-O Type 304L SS
Type 316 SS
IG A
rea fra
ction (
%)
333
GBE304
304L
GBE304L
327
945
GBE316
623 625
Type 304 Type 316
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Effect of Irradiation-Dose Threshold
IG cracking does not occur below 0.45 dpa (3 x 1020 n/cm2) for the
commercial heats of austenitic SSs in the Halden irradiations.
Halden-I data
is included.
0
20
40
60
80
100
0 0.5 1 1.5 2 2.5 3 3.5
333
GBE304
304L
GBE304L
327
945
GBE316
623
625
690
GBE690
C1
C3
C9
C10
C12
C16
C19
C21
IG a
rea
fra
ctio
n (
%)
Dose (dpa)
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Conclusions
! GBE process used in this study shows no beneficial effect for Types 304 or
304L SS. However, the GBE treatment results in a smaller reduction in UE
for Alloy 690 at 2 dpa, & reduces its IASCC susceptibility in high-DO water.
! Type 316 SSs are generally more resistant to IG cracking than Type 304 SSs.
The presence of Mo or the higher Ni concentrations in Type 316 SSs may be
responsible.
! The O content of the material is critical for IASCC susceptibility; high O
content contributes to IASCC susceptibility by enhancing IG crack initiation.
! The UE obtained from SSRT tests in high-DO water increases linearly with C
content below 0.06 wt.%. Also, the low-C SSs are more susceptible to
IGSCC (results consistent with data from Halden-I irradiations).