141
150
90
9
Journal of Chinese Corrosion Engineering, Vol.15 No.3, PP.1411~150(2001)
The Influence of Hydrogen Water Chemistry and Platinum-coating
on Stress Corrosion Cracking of Sensitized Type 304 Stainless Steels
K. L. Lee, T. K. Yeh, and C. H. Tsai
Boiling Water Reactor, BWR
Intergranular Stress Corrosion Cracking, IGSCC
Hydrogen Water Chemistry, HWC
Noble
Metal Chemical addition, NMCA
BWR
IGSCC
M H/O
2
Electrochemical Corrosion Potential,
ECP
M H/O
2
ECP
M H/O
Slow Strain Rate Tensile, SSRT
ECP
ECP
HWC
IGSCC
Abstract
The reactor internal structural components in boiling water reactors BWRs are composed
of stainless steel SS materials due to their good corrosion resistant properties. However,
vessel internal cracking VIC problems due to intergranular stress corrosion cracking
IGSCC were still found. Two technologies, hydrogen water chemistry HWC and noble
metal chemical addition NMCA , have been proposed to mitigate VIC problems. In theory, the
*
Department of Engineering and system science, National Tsing Hua University
**
Nuclear Science and Technology Development Center, National Tsing Hua University
-141-
90
9
electrochemical corrosion potential ECP on surface of component material is reduced when the molar ratio of
hydrogen to oxygen M H/O
in H2O recombination reactions is greater than 2. It was also found that even ECP
would be reduced with the catalysis of noble metals when M H/O is smaller than 2. In this study, the specimens of
different coating condition were tested in the water chemistry of various M H/O by slow strain rate tensile SSRT
and continuous monitoring of ECP. The result came out that ECP reduction was more profound under the condition of
higher dissolved hydrogen. In HWC environment, no IGSCC occurred regardless of specimens with or without noble
metal coating.
Key words hydrogen water chemistry, noble metal chemical addition, intergranular stress corrosion cracking,
electrochemical corrosion potential, slow strain rate tensile
Normal Water Chemistry, NWC
NMT
Stoichiometric Ratio
M H/O
Boiling Water Reactor, BWR
M H/O
Hydrogen Water Chemistry, HWC
2
ECP
HWC
(1)
M H/O
(8)
Radiolysis
IGSCC
Slow Strain Rate Tensile, SSRT
ECP
Noble Metal Chemical Addition, NMCA
304
Electrochemical Corrosion
(9)
Potential, ECP
HWC
(5)
SSRT
Noble Metal Treatment,
NMT
2
HWC
(10)
(14)
ECP
304
NMT
1
650
24
288
360
(15)
-142-
200 ppb
304
100 ppb
Na2Pt (OH) 6
150
NMCA-12
24
12
NMCA-24
1
Prefilm
2
IGSCC
Transgranular
Stress Corrosion Cracking, TGSCC
1
300 ppb
24
12
2
300 ppb
50 ppb
Prefilm
NMCA-12
NMCA-24
1.
Figure 1. Sample size of tensile test
1.
300 ppb
SSRT
Table 1. The SSRT results of different coating
SSRT
BWR
specimens at 300 ppb [O2]dis
3
288
-7
10 s
-1
IGSCC
8.3 MPa
(MPa)
300 ppb
10 ppb
50 ppb
(
)
(
TGSCC
)
(
)
Prefilm
109
20.6
9.8
15.9
NMCA-24 (1)
107
15.6
30.5
7.1
NMCA-24 (2)
147
20.0
27.4
6.5
2.
300 ppb
10 ppb
SSRT
Table 2. The SSRT results of different coating
0.1
S/cm
specimens at 300 ppb [O2]dis and 10 ppb [H2]dis
20mL/min
IGSCC
ECP
KCl
TGSCC
Ag/AgCl
(MPa)
Intergranular Stress Corrosion
Cracking, IGSCC
Scanning Electron Microscopy, SEM
-143-
(
)
(
)
(
)
Prefilm (1)
170
39
0
17
Prefilm (2)
174
39
0
0
NMCA-12 (1)
136
33
0
2
NMCA-12 (2)
162
22
0
10
NMCA-24 (1)
153
39
0
12
NMCA-24 (2)
179
39
0
2
90
9
Prefilm
Prefilm
NMCA-24 (1)
NMCA-24 (1)
2.
300 ppb
3.
SSRT
300 ppb
SEM
SSRT
SEM
Figure 2. Fractured surface of the prefilmed and
Figure 3. Side surface if the prefilmed and platinum
platinum treated specimens after the SSRT
treated specimens after the SSRT tests under
tests under 300 ppb [O2]dis
300 ppb [O2]dis
300 ppb
NMCA-24 (2)
30.5
NMCA-24 (1)
27.4
9.8
NMCA-24 (2)
2
NMCA-24 (1)
Prefilm
NMCA-24 (1)
IGSCC
NMCA-24 (2)
1
IGSCC
NMCA-24 (1)
3
-144-
304
3
300 ppb
50 ppb
SSRT
Table 3.
The SSRT results of different coating
specimens at 300 ppb [O 2] dis and 50 ppb
[H2]dis.
TGSCC
IGSCC
(MPa)
Prefilm
(
(
)
)
)
Prefilm
162
27.8
0
27
NMCA-12
213
50.0
0
0
NMCA-24
221
47.2
0
0
Prefilm
NMCA-24 (1)
2
300 ppb
(M H/O
1)
10 ppb
SSRT
NMCA-12
NMCA-24
NMCA-24
NMCA-12 (1)
(
NMCA-12
33
39
22
170
MPa
174 MPa
39
Prefilm
SSRT
4
HWC
IGSCC
Prefilm (1)
Prefilm (2)
NMCA-12 (2)
NMCA-24 (1)
TGSCC
10
NMCA-12 (1)
17
NMCA-24 (2)
TGSCC
HWC
NMCA-24 (1)
M H/O
Prefilm
4.
NMCA-24
300 ppb
10 ppb
SSRT
Figure 4. Fracture surfaces of three kinds of coating
specimens after the SSRT tests under 300 ppb
[O2]dis and 10 ppb [H2]dis
NMCA-24
Prefilm
-145-
0.5
SSRT
90
9
IGSCC
IGSCC
3.3
3
50 ppb
300 ppb
M H/O
2
SSRT
5
SEM
M H/O
HWC
IGSCC
NMCA-12
NMCA-24
NMCA-12
NMCA-24
213 MPa
221 MPa
Prefilm
NMCA12
NMCA-24
50
48
Prefilm
162 MPa
28
SCC
IGSCC
5
IGSCC
TGSCC
Prefilm
27
NMCA-12
NMCA-12
TGSCC
NMCA-24
HWC
TGSCC
M H/O
SSRT
12
2
NMCA-
NMCA-24
Prefilm
IGSCC
Prefilm
TGSCC
IGSCC
NMCA-24
5.
Prefilm
300 ppb
NMCA-12
50 ppb
SSRT
Fracture 5. Surfaces of three kinds of coating
specimens after the SSRT tests under 300
ppb [O2]dis and 50 ppb [H2]dis
NMCA-24
ECP
200 ppb
-146-
1500 ppb
50 ppb
304
6.
288
7.
Pt
ECP
10 ppb
ECP
Figure 6. ECP Variations as a function of dissolved
Figure 7. ECP Variations as a function of dissolved
oxygen concentration for the three different
oxygen concentration for the three different
specimens in 288
specimens in 288
water.
water with a fixed
dissolved hydrogen level of 10 ppb.
IGSCC
ECP
mVSHE
-230
Ecrit
3
BWR
304
initiation
ECP
IGSCC
6
13
200 ppb
1500 ppb
14
304
ECP
ECP
-230 mVSHE
200 ppb
mVSHE
ECP
NMCA-12
ECP
NMCA-24
-165
1000
1500 ppb
129 mVSHE
ECP
200 ppb
7
500 ppb
ppb
200
SSRT
1
IGSCC
IGSCC
ppb
1500 ppb
10 ppb
1500 ppb
100
ECP
Pt
300 ppb
300 ppb
1500 ppb
ECP
Pt
ECP
100 mVSHE
NMCA-24
ECP
300
Pt
SSRT
500 ppb
ECP
Prefilm
-147-
ECP
NMCA
90
9
8
50 ppb
ECP
5
ECP
ECP
ECP
-400 mVSHE
1500 ppb
200 ppb
-190 mV SHE
250 mV
ECP
-600 mV SHE
ECP
ECP
8.
288
50ppb
200 ppb
1000 ppb
250
mV
ECP
M H/O
2
1500 ppb
M H/O
Figure 8. ECP Variations as a function of dissolved
170 mV
oxygen concentration for the three different
specimens in 288
1
8
water with a fixed
50 ppb
dissolved hydrogen level of 50 ppb.
-600 mV SHE
ECP
ECP
100 mV SHE
ppb
Pt
200
ECP
ECP
Prefilm
NMCA
mV SHE
Pt
ECP
mVSHE
1500 ppb
1
50 ppb
M H/O
-250
ECP
1
-230 mVSHE
1000 ppb
Pt
1
M H/O
-400
ECP
Ecrit
500 ppb
0.5
ECP
100 ppb
M H/O
M H/O
M H/O
1
ECP
ECP
ECP
mV
300 ppb
Prefilm
10 ppb
SSRT
ECP
Prefilm
NMCA
Y.J.
ECP
Kim
M H/O
ECP
IGSCC
HWC
200 ppb(16)
304
Prefilm
ECP
Pt
150
50 ppb
-148-
/min
ECP
NMCA
304
15
Prefilm
20
Environmental Degradation of Materials in
/min
NMCA
ppb
Pt
ECP
300
150
200
Nuclear Power Plant - Water Reactors, NACE,
100
Myrtle Beach, South Carolina, Aug. 22-25,
(1983) p.69.
mVSHE
(3)
ECP
Internals with Hydrogen Water Chemistry," Water
10 ppb
ECP
ECP
200
R. L. Cowan, "The Mitigation of IGSCC of BWR
Chemistry of Nuclear Reactor Systems 7, BNES,
400 ppb
Bournemouth, England, Oct. 13-17, 1996, p.196.
E crit
ECP
(4)
300 ppb
10 ppb
J. C. Danko, "Recent Observations of Cracking in
Large Diameter BWR Piping," Proc. Intl.
SSRT
Symposium on Environmental Degradation of
IGSCC
Materials in Nuclear Power Plant - Water
Reactors, NACE, Myrtle Beach, South Carolina,
Aug. 22-25, 1983, p.209.
1.
NMCA
(5)
304
U.S.
Nuclear
Regulatory
Commission,
Intergranular Stress Corrosion of Core Shrouds in
Boiling Water Reactors, NRC Generic Letter 9403, July 25, 1994.
2.
(6)
IGSCC
U.S. Nuclear Regulatory Commission, Jet Pump
Hold-Down Beam Failure, NRC Information
3.
Notice 93-101, December 19, 1993.
IGSCC
HWC
4.
(7)
IGSCC
M H/O
of Lower Region of the Core Shroud in Boiling
ECP
Water Reactors, NRC Information Notice 94-42,
June 7, 1994 .
ECP
(8)
5.
U.S. Nuclear Regulatory Commission, Cracking
U.S. Nuclear Regulatory Commission, Reactor
Vessel Top Guide and Core Plate Cracking, NRC
304
Information Notice 95-17, March 10, 1995.
ECP
(9)
C. C. Lin, " Hydrogen Water Chemistry
Technology in BWRS", Proc. of the 1998 JAIF
Water Chemistry Conference, JAIF, Kashiwazaki,
Japan, Oct.11-16, 1998, p.211.
(10) S. Hettiarachchi et al., "The Concept of Noble
(1)
(2)
R. L. Cowan, Nuclear Engineering International,
Metal Chemical Addition Technology for IGSCC
January, (1986) p.26.
Mitigation of Structural Materials," Proc. 7th
R.W. Weeks, "Stress Corrosion Cracking in BWR
International Symposium on Environmental
and PWR Piping," Proc. Intl. Symposium on
Degradation of Material in Nuclear Power
-149-
90
Systems - Water Reactors, NACE, Breckenridge,
Colorado, Aug.6-10,1995,p.735.
(11) Y. J. Kim, L. W. Niedrach, M. E. Indig, P. L.
Andresen, "The Application of Noble Metals in
Light Water Reactors", JOM, April, (1992) p.14.
(12) P. L. Andresen, "Mitigation of Stress Corrosion
Cracking by Underwater Thermal Spray of Noble
Metals", CORROSION/95, paper no. 412,
Houston, TX, NACE International, (1995).
(13) Y. J. Kim, L. W. Niedrach, P. L. Andresen,
"Corrosion Potential Behavior of Noble Metal
Modified Alloys in High Temperature Water",
CORROSION/95, paper no.99. Houston, TX,
NACE International, (1995).
(14) S. Hettiarachchi, G. P. Wozadlo, "A Novel
Approach for Noble Metal Deposition on Surface
for IGSCC Mitigation of Boiling Water Reactor
Internals", CORROSION/95, paper no. 413,
Houston, TX, NACE International, (1995).
(15) T. K. Yeh et al.,"The Effect of Catalytic Coatings
on IGSCC Mitigation for Boiling Water Reactors
Operated Under Hydrogen Water Chemistry,"
Proceedings of the 8th International Symposium
on Environmental Degradation of Materials in
Nuclear Power Systems - Water Reactors, Amelia
Island, Floriga, August 10-14, 1997, American
Nuclear Society, p.559.
(16) Y. J. Kim, "Effect of Noble Metal Addition on
Electrochemical Polarization Behavior of
Hydrogen Oxidation and Oxygen Reduction on
Type 304 Stainless Steel in High-Temperature
Water", Corrosion, May, (1999) p.456.
-150-
9