Tutorial Irradiation Embrittlement and Life Management of RPVs
Enclosure 4: Irradiation Embrittlement - Mechanical Properties … · 2012-12-01 · Irradiation...
Transcript of Enclosure 4: Irradiation Embrittlement - Mechanical Properties … · 2012-12-01 · Irradiation...
Irradiation Embrittlement Mechanical Properties and Irradiated Assisted Stress Corrosion Cracking
Dr. Appajosula S. Rao, Darrell Dunn U.S. Nuclear Regulatory Commission
Y. Chen, O. K. Chopra and W. J. Shack Nuclear Engineering Division
Argonne National Laboratory, Argonne, IL 60439
NRC Research
NRC IASCC research focused on the following areasEvaluate effectiveness of SCC mitigations• Hydrogen Water Chemistry• Grain Boundary Engineering
Evaluate CGR models for BWRs and PWRsEvaluate the causes, mechanisms and effects of EAC on BWR internalsEffect of cold work on crack growth ratesReview and evaluation of EAC in vessel internal components and emerging aging degradation issuesRadiation embrittlement at relevant to PWR conditionsRadiation and thermal embrittlement of cast austenitic stainlesssteels
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Alloys for SSRT
304-like alloy with high Ni and CrL5Low S, Type 304 SSC12
Effect of SHigh S, Type 304 SSC9Type 304L SSC3 (SA, CW)Low S, Type 304 SS, high PC1 (SA, CW)High-purity Type 304L SS with high O945
Effect of O High-purity Type 304L SS with low O327Type 316LN SS, Ti-doped625
Effect of Ti Type 316LN SS623GBE Alloy 690GBE690Alloy 690690GBE Type 316 SSGBE316
Effect of GBEGBE Type 304L SSGBE304LType 304L SS.304LGBE Type 304 SSGBE304Type 304 SS from ABB333
ObjectivesDescriptionHeat ID
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Common Materials in Halden & BOR-60Irr.
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SSRT Specimens
Halden
BOR-60
Ratio(Halden / BOR-60)
Thickness (t) 1
Gauge cross-section (A) 2
Gauge length (l) 2.5
Elongations are expected to be different between the Halden and BOR-60 specimens (l/A0.5 ≈ 1.8)
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Experimental – Irradiation
Halden reactor – a boiling heavy water reactorDry irradiation in He-sealed capsulesIrradiation temperature ~ 290°CDose rate ~ 10-7 dpa/sHe/dpa ratio for a Typical LWR: ~2-5 appm/dpa.
BOR-60 reactor – a sodium cooled fast breeder reactorSamples exposed to sodiumIrradiation temperature ~ 320°CDose rate ~ 9x10-7 dpa/sHe/dpa ratio for a Typical fast reactor: < 0.5 appm/dpa
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SSRT Testing
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 v13 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 ppmPressure - 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: Halden ~ 3.3x10-7 s-1; BOR-60: ~ 7.4x10-7 s-1
Loading grip for BOR-60 specimen
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~ 2 mm
0.7 mm 3.15 mm
Fractography – SSRT Specimens
TG
Ductile fracture
IG
IG
d1
TGl1
l2
d2
Characterize fracture surfaceIG or TG area fractionsNumber of IG or TG areas
~ 1.5 mm
~ 0.7
mm
Sectioned Halden specimen
BOR-60 specimen
Fracture Toughness Testing
Weldments304L submerge arc (SA) weld -- a double-V butt weld on Type 304L hot-rolled plates (ASME SA240 ) using ER308L filler rods.304 shield metal arc (SMA) weld -- a single-V butt weld on Type 304 plates using E308 filler rods.Post-weld thermal treatment -- 500°C for 24 hours (to simulate the effect of low-temperature sensitization).
Four materials304L SA HAZ, as-welded304L SA HAZ, thermally-treated304 SMA HAZ, as welded304 SMA HAZ, thermally-treated
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Chemical composition of the weld HAZ materials
Weld Heat ID Ni Si P S Mn C N Cr Mo O
304 SMA 10285 8.45 0.60 0.015 0.007 1.90 0.070 0.084 18.56 0.51 0.013 304L SA GG Top Shell 9.05 0.53 0.027 0.016 1.84 0.013 0.064 18.23 0.44 0.010
Fracture Toughness Specimens - Irradiation
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Irradiation conditions for the weld HAZ compact tension specimens
Material Heat Treatment Fast Neutron Fluence
E >1 MeV (x1021 n/cm2)
Displacement Damage
(dpa)
Irradiation Temperature
(°C) 0.50 0.75 ~290 As-welded 1.44 2.15 290-296 GG 304L SA HAZ
24 h @ 500°C 1.63 2.43 ~290 0.50 0.75 ~290 As-welded 1.44 2.15 290-296 0.50 0.75 ~290
304 SS SMA HAZ 24 h @ 500°C
1.44 2.15 290-296
Irradiated in Halden reactor in helium-sealed capsules
Fracture Toughness Test Conditions
Temp: ≈290°CDO: ≈350 ppb with N2 + 1% O2 cover gas
<30 ppb with 4% H2 cover gasFlow rate: 15–25 mL/minConductivity: 0.08 - 0.12 μS/cmKmax: approximately constant by load sheddingK/size criterion: B and (W-a) ≥2.5*(K/σeff)2, where σeff = (σy + σu )/2 for
nonirradiated specimens, σeff = σy-irr for irradiated specimensJ-R curve tests: constant extension rate of 0.43 μm/s. Use a blunting line
given by Δa = J/(4σf).
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Effect of Irradiation Dose on Yield Strength
Irradiation hardening and embitterment start to appear at dose <0.5 dpa.
0
200
400
600
800
1000
0 10 20 30 40 50
Stre
ss (M
Pa)
Strain (%)
12 dpa
non-irr.
Test temp. = 320oC
Strain rate = 7.4 x 10 -7 s-1
5 dpa
316 SS BOR-60 Irradiation
0
500
1000
1500
0 0.5 1 1.5 2 2.5 3 3.5
Yie
ld S
treng
th (M
Pa)
Dose (dpa)
NUREG\CR-6965
Effect of Irradiation Dose on Total Elongation
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0
10
20
30
40
50
60
70
0 0.5 1 1.5 2 2.5 3 3.5
Tota
l Elo
ngat
ion
(%)
Dose (dpa)
Irradiation hardening starts to saturate around 3-5 dpa, and loss of elongation reaches a minimum around 2 dpa.
NUREG\CR-6965
Effect of Irradiation Dose on Intergranular Fracture
15
0
20
40
60
80
100
0 0.5 1 1.5 2 2.5 3 3.5
333GBE304304LGBE304L327945GBE316623625690
GBE690C1C3C9C10C12C16C19C21
IG a
rea
fract
ion
(%)
Dose (dpa)
IG cracking starts to occur at a dose lower than that elongationreaches minimum.
SSRT Testing
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0
20
40
60
80
100
0 5 10 15 20 25 30
Halden I, 0.4 dpaHalden I, 1.3 dpaHalden I, 3.0 dpaHalden II, ~2 dpa
Area
frac
tion
of IG
(%)
Uniform Elongation (%)
Resistant
NUREG/CR-6965, Halden Phase-II, Alloys 304, 304L, 316L, 690
Fracture Toughness Testing Results
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0
100
200
300
400
500
600
0 2 4
J-In
tegr
al (k
J/m
2 )
Neutron Exposure (dpa)
SA and SMA weld HAZTested at ~290oC in NWC BWR env.
304 SMA HAZ, Thermally-treated at 500OC for 24 h
304L SA HAZ, as welded
304 SMA HAZ, As-welded 304L SA HAZ, thermally-treated
at 500OC for 24 h
0
200
400
600
800
0 4 8 12
JAPEIC BBJapeic CTJAPEIC SRGE CTVTT CT CF-8M_airC19C16SA HAZSMA HAZ304 SensitizedIT+GBEJ-
Inte
gral
(kJ/
m2 )
Neutron Exposure (dpa)
Austenitic SSs
ANL dataScatter band for fast reactor irradiations
304L SA HAZ and304 SMA HAZ
Fracture toughness data of as-welded and thermally-treated HAZs are within the scatter band.Thermal treatment may have improved the fracture toughness of irradiated 304 SMA HAZ at 0.75 dpa
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Summary
While irradiation hardening and embattlement starts to appears at very low doses, the dose dependence of IG cracking shows a “threshold” behavior. IG cracking start to appear before the dose for that elongations reach minimum.
The post-irradiation strengths (YS and UTS) for the BOR-60 specimens were consistently lower than those of the corresponding Halden specimens. Likely related to Neutron spectrum and damage rate.
Fracture toughness data for irradiated SA and SMA HAZs are within the scatter band. Thermal treatment may have improved the fracture toughness of irradiated 304 SMA HAZ at 0.75 dpa