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Transcript of Content of Boric Acid Corrosion Research Program · te c t ab l e V e r y t h i n f i lm for m e d...
United States Nuclear Regulatory Commission
Page 1NRC/EPRI Collaborative Presentation – March 22, 2004
Content of Boric Acid CorrosionResearch Program
Crack Growth Rates of Alloys 600 & 182 from Davis-Besse HeadDifficult to accomplish – small size of specimensMetallography, yield strength suggest relatively good quality alloys
Computational Model, Probabilistic Assessment of:Statistics of Initiation, Probability of Detection & Accuracy of SizingCrack Growth Rate Variations, Stress Intensity Factor Gradients
Measure Ecp and wastage rates for range of solution compositions, temperatures (Tasks 3 & 4)
Wastage (bulk corrosion) as function of temperature and solutionconcentration
Includes tests in molten boric acidElectrochemical Potential and Polarization Measurements of Low-Alloy Steel, Alloys 600 & 182 in Concentrated Boric Acid Solutions
United States Nuclear Regulatory Commission
Page 2NRC/EPRI Collaborative Presentation – March 22, 2004
Crack Initiation and Growth Non-destructive Inspection Structural Integrity Analysis
Initiation StudiesCrack Growth Studies
Corrosion StudiesCrack Growth Rate Modeling
Visual Techniques (Bare Metal Visuals)Eddy Current & Ultrasonic Techniques
Probabilities of DeectionInnovative Development
Stress Analysis – Crack Driving ForcesMaterials PropertiesWelding Processes
Probabilistic Risk Assessment ModelsCalculation of Inspection Intervals
Calculation Of Inspection Interval Is An Integrated Process
United States Nuclear Regulatory Commission
Page 3NRC/EPRI Collaborative Presentation – March 22, 2004
Integrated Inspection Model
Time
Flaw
Siz
e
a0
a + N•σa
af
af - N•σaf
da dt mean
dadt Nσa
Interval Between Inspections Margin to Accountfor Uncertainties
United States Nuclear Regulatory Commission
Page 4NRC/EPRI Collaborative Presentation – March 22, 2004
Corrosion Tests
Determine the wastage rates and electrochemical potentials for: A533 Gr B and Type 308 SS weld (diluted by A533Gr B).
- Flowing & quiescent, aerated and deaerated BA solutions - T = 100-316ºC (212-600ºF)- PWR (1000-wppm B + 2-wppm Li) - 3500-wppm B + 2-wppm Li
and
Molten H-B-O conditions
United States Nuclear Regulatory Commission
Page 5NRC/EPRI Collaborative Presentation – March 22, 2004
Wastage test apparatus for the aqueous solution and molten boric acid systems
United States Nuclear Regulatory Commission
Page 6NRC/EPRI Collaborative Presentation – March 22, 2004
Wastage test sample assembly
Bottom (BA solution) TopTeflon insulator rotate (50 rpm)
SS308 Weld A533Gr-B
Sample: 6.5 gram, OD (0.50”), ID (0.275”), length (0.5”)
United States Nuclear Regulatory Commission
Page 7NRC/EPRI Collaborative Presentation – March 22, 2004
CR for A533-Gr. B & SS 308 in sat’d BA sol’n(40,514 wppm-B) at 97.5ºC
1
1 0
1 0 0
A533
Gr B
-1
A53
3Gr B
-2
A533
Gr B
-3
A53
3Gr B
-4
A533
Gr B
-5
SS
308W
eld-
1
SS
308W
eld-
2
0 -2 4 -h0 -1 0 0 h2 4 -1 0 0
CR
(mm
/yr)
United States Nuclear Regulatory Commission
Page 8NRC/EPRI Collaborative Presentation – March 22, 2004
Corrosion rates for A533-Gr. B half-saturated BA solution (20,257 Wppm-B) at 97.5°C
0
1 0
2 0
3 0
4 0
5 0
6 0A5
33G
r B-2
0
A53
3Gr B
-21
A533
Gr B
-22
A53
3Gr B
-26
A533
Gr B
-23
A53
3Gr B
-24
A533
Gr B
-25
C R .H a lf .S a t.B A @ 9 7.5 C
0 -24h0 -24 h(use d s o l'n )2 4 -10 0h0 -76h0 -100 h
7 6 -31 1h0 -311 h
1 00 -4 11h0 -411 h
CR
(mm
/yr)
United States Nuclear Regulatory Commission
Page 9NRC/EPRI Collaborative Presentation – March 22, 2004
Sample stack view for A533Gr-B, A600, SS308 after exposure for 311 or 411 h in sat’d BA solution at 97.5ºC
A B C D E F G H I J K L M N OA: Screw tightening mechanism with flat O-ring a the bottomB: A600 (30%CW), C: A600-1, E: SS308 clad weldD,F,H,J, & M: O-rings, G, I, K, & L: A533Gr-B #1,2,4, &7.N & O: Alumina (N, in the sol’n & O, interface solution/vapor)
United States Nuclear Regulatory Commission
Page 10NRC/EPRI Collaborative Presentation – March 22, 2004
Corrosion Rates of A533Gr-B in various BA solutions at 97.5ºC
0.1
1.0
10.0
100.0
0 100 200 300 400 500All_A533Gr_B_CR
Sat'd sol'n
Sat'd sol'n (PD)
half sat'd sol'n
half sat'd (used)
PWR water
UHP water
CR
(mm
/yr)
Exposure t (h)
Note:CR determined for times between 24 and 411 h.
United States Nuclear Regulatory Commission
Page 11NRC/EPRI Collaborative Presentation – March 22, 2004
Corrosion Rates vs. Wppm-B for A533Gr-Bin BA solutions at 97.5ºC
0.0
10.0
20.0
30.0
40.0
50.0
0 10000 20000 30000 40000 50000
CR411&311avg.
CR
(mm
/yr)
at 9
7.5o C
Concentration ( Wppm-B )
Note:Corrosion rates based on 311 & 411 h exposure
United States Nuclear Regulatory Commission
Page 12NRC/EPRI Collaborative Presentation – March 22, 2004
CRs of A533Gr-B in oxygenated PWR & UHP @97.5ºC
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
28 29 37 38
PW R (rinsed)
UHP (w/o rinsed)UHP (rinse)
CR
(mm
/yr)
Sample # (A533Gr-B)
PW R sim ulated water (1000-W ppm -B,2-W ppm-Li)
UHP waterNegative CR, Form ation of scale
PW R (w/o rinsed)
Error bar (+/- 0.03 mm/yr)
United States Nuclear Regulatory Commission
Page 13NRC/EPRI Collaborative Presentation – March 22, 2004
A533-Gr. B, A 600, and SS 308 at 150°C &170ºC with H2O additions in molten H-B-O
0
5 0
1 0 0
1 5 0
2 0 0
A53
3GrB
(#9)
A533
GrB
(#10
)
A60
0CW
-2
A53
3GrB
(#11
)
A533
GrB
(#12
)
SS3
08
CR
(mm
/yr)
T = 1 5 0 o C T = 1 7 0 o C
A60
0 no
t det
ecta
ble
Very
thin
film
form
ed
SS30
8 no
t det
ecta
ble
Very
thin
film
form
ed
United States Nuclear Regulatory Commission
Page 14NRC/EPRI Collaborative Presentation – March 22, 2004
Molten H-B-O wastage tests: A600 and A533-Gr. B with and without H2O additions
3.0
4.0
5.0
6.0
7.0
8.0
A533Gr-B#9 A533Gr-B#10 A600 (HT)-2
As Rec'd24 h 300C
26 h 260C
24 h 150C45 h 150 C (add-H
2O)
Sam
ple
Wt (
g)
United States Nuclear Regulatory Commission
Page 15NRC/EPRI Collaborative Presentation – March 22, 2004
Summary - (TASK #3)Wastage tests for the A533Gr B in the BA solution at 97.5ºC were completed. -CR value of 2-in/yr in the saturated solution was highest -CRs shown to have a linear relationship with the concentration of BA
Note: CRs for A600 & SS308 were negligible when compared with those of A533Gr-B.
Wastage tests in the molten H-B-O at 150-290ºC were performed.-Without water addition, none of the metallic samples showed corrosion, except thin oxide scale formed on A600 & SS308. -With water addition, A533Gr B at 150ºC showed the highest CR value, and higher the T the lower the CR.
Wastage tests in the Hi-T & P conditions - ongoing
United States Nuclear Regulatory Commission
Page 16NRC/EPRI Collaborative Presentation – March 22, 2004
pH for BA & Sat’d BA (rt < T < 100°C)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
20 30 40 50 60 70 80 90 100
Sat'd BA sol'n @ rt(9,086-wppm B)
O2 purge
Ar purge
pH
T(C)
1.0
1.5
2.0
2.5
3.0
3.5 3.9
4.0
4.1
4.2
4.3
4.4
4.5
4.62.7 2.8 2.9 3.0 3.1 3.2 3.3 3.4
Ar purgeO
2 purge
Solubility of Boric AcidpH
Log Wppm
-B
1000/T(K)
1.0
1.5
2.0
2.5
3.0
3.5
4.0
20 30 40 50 60 70 80 90 100
H3BO
3 Sat'd Solution @ T
Ar purgeAr purgeO
2 purge
pH
T(C)
United States Nuclear Regulatory Commission
Page 17NRC/EPRI Collaborative Presentation – March 22, 2004
E(V) vs. t in the Sat’d BA sol’n @97.5°C
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
30
40
50
60
70
80
90
100
0 2 4 6 8 10 12 14 16
90401%
E (V
) vs.
SH
E T(C)
t (h)
A533Gr-B
A600
T(C)
SS308
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
1.0
30
40
50
60
70
80
90
100
0 20 40 60 80 100 120
90201%
E(V)
vs.
SH
E
T (C)
t (h)
T (C)
SS308
A600
A533Gr-B
United States Nuclear Regulatory Commission
Page 18NRC/EPRI Collaborative Presentation – March 22, 2004
PD-test of A533Gr B in Sat’d BA solution at 97.5°C
10-4
10-3
10-2
10-1
-0.50 -0.45 -0.40 -0.35 -0.30 -0.25 -0.20 -0.15
Cur
rent
den
sity
, J (a
mp/
cm2 )
E(V) vs. SHE
JCorr
= 4 mA/cm2
CR = 46 mm/yrE
Corr = -0.342 V vs. SHE
A533Gr-B at 94oC Sat'd-Areated BALSV.30.dta t = 240 h
3.0
4.0
5.0
6.0
7.0
8.0
40
50
60
70
80
90
100
0 100 200 300 400 500
Cor
rosi
on C
urre
nt, J
Cor
r (m
A/cm
2)
CR
(mm
/yr)
Exposure t (h)
Wastage-test
PD-test
42,000-ppm B (Sat’d BA)
United States Nuclear Regulatory Commission
Page 19NRC/EPRI Collaborative Presentation – March 22, 2004
Electrochemical Corrosion Products for the A533Gr B in Sat’d BA at 95°C
Darker brown color precipitates bottom of the test chamber: X-ray analysis shows iron borate (FeBO3)
Brown color slurry deposited around the A533B: X-ray diffraction shows boric acid (H3BO3)
United States Nuclear Regulatory Commission
Page 20NRC/EPRI Collaborative Presentation – March 22, 2004
5 0 .0
6 0 .0
7 0 .0
8 0 .0
9 0 .0
1 0 0 .0
1 1 0 .0
0 .5
0 .6
0 .7
0 .8
0 .9
1 .0
1 .1
0 .0 5 .0 1 0 .0 1 5 .0 2 0 .0 2 5 .0
Wt (
g)
Wt. Fraction (w
t/wt,i)
t (h )
B (O H )3 P h a s e
H B O2 P h a s e
B2O
3 P h a s e
T = 2 8 0 o C in a ir 1 a tm
Boric acid turned to snow-ball shape and then glass like transparent boric oxide
Note:100-g Boric acid heated in air (pH2O = 3%) at 280°C
United States Nuclear Regulatory Commission
Page 21NRC/EPRI Collaborative Presentation – March 22, 2004
ECP for A533Gr-B, A600, SS308, and Pt in hydrogen covered UHP-water at 288 & 316ºC
-0.600
-0.550
-0.500
-0.450
-0.400
250
255
260
265
270
275
280
285
290
10 15 20 25
91701 9 31 17 AM 9/16/2003
E(V
) vs.
SH
E
T(C)
t(h) 91701
Pt
T(C)
A600
SS308
A533Gr-B -0.700
-0.650
-0.600
-0.550
-0.500
288
292
296
300
304
308
312
316
320
0 5 10 15 20 25 30
E(V
) vs.
SH
E
T(C)
t (h)
P =1800psig. T = 316oCHydrogen cover UHP-water
T(C)
A600PtSS308A533Gr-B