ML18267A090
| ML18267A090 | |
| Person / Time | |
|---|---|
| Issue date: | 09/24/2018 |
| From: | Robert Tregoning NRC/RES/DE |
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| ML18267A083 | List: |
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| Download: ML18267A090 (13) | |
Text
© 2018 Electric Power Research Institute, Inc. All rights reserved.
Jean Smith, Ph.D., P.E.
Principal Technical Leader U.S. Nuclear Regulatory Commission Public Meeting on Environmentally Assisted Fatigue Research September 25, 2018 Rockville, Maryland Water Chemistry Effects on EAF, EAF Under Plant-Like Conditions (Hold Time Effects), and EAF Short Crack Growth
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Content Water Chemistry Effects on EAF (KHNP)
- Effect of Zn addition on EAF of Type 316SS in PWR water EAF Under Plant-Like Conditions (KHNP)
- Hold Time Effects on EAF of Type 316SS in PWR water EAF Short Crack Growth (Wood)
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Zn Effect on EAF - Background Zinc additions to PWR primary water is known to stabilize the oxide structure and increase PWSCC resistance of nickel-base alloys In Alloy 182:
- Zn addition reduced PWSCC initiation for all levels of dissolved hydrogen (DH)
- Zn addition modified the oxide morphology and composition more strongly in normal and high DH conditions In Type 316 stainless steel an iron-nickel-chromium (Fe-Ni-Cr) spinel forms at the EAF crack tip Hypothesis: Zinc addition in PWR primary water will result in crack tip oxide modification in Type 316 SS and mitigate EAF
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Zn Effect on EAF - Test Matrix Objective Establish a PWR environmental fatigue database of Type 316 SS for Zn addition combined with dissolved hydrogen condition Test program includes reference tests in air and PWR water PWR water tests include
- Hold time (0 or 400 sec)
- Zinc addition (0 or 30 ppb)
- DH control (25 or 50 cc/kg)
Test Material 316 Austenitic Stainless Steel Test condition Reference PWR Air PWR Number of test specimen (ea) 4 4
16 Test Environment Air PWR environment Temperature RT / 325°C 325°C Control type Strain control (ASTM E606)
Strain amplitude (%)
0.4 Strain rate (%/s) 0.004 (0.04)
Hold time (sec) 0 / 400 Water Chemistry DO
< 5 ppb DH (cc/kg) 25 25 / 50 Zinc (ppb) 0 / 30 Conductivity (RT) pH (RT) 6.3
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Zn Effect on EAF - Fatigue Life Fatigue life comparison
- With no hold: Fatigue life increased but within the data scatter
- With 400 s hold: Fatigue life increased significantly and is comparable to Ni-base alloy (w/out hold)
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Zn Effect on EAF - Crack Tip Crack tip behavior
- Analysis by several methods (TEM, ToF-SIMS, AED, XPS) shows Zn is incorporated into crack tip oxide
- Less metal dissolution occurs -> relative sharp crack tip PWR with 400 second hold PWR + 30 ppb Zn with 400 second hold
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Zn Effect on EAF - Oxides Oxide stability enhancement
- Film resistance increased
- Defect density decreased
- Resulting oxide film is more stable and protective
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
Zn Effect on EAF - Upcoming Plans Next steps for this program KAIST Facility
- Zn & High DH condition test KHNP Facility
- Reference tests
- High DH condition test Further Analysis
- Oxide identification: diffraction pattern analysis to confirm Zn incorporation into oxide Future project ideas Strain Rate Effect
- Very low strain rate vs. hold time effect 0.001%/s strain rate Confirm strain rate dependency of Zn effect Hold time variation
- Fatigue life variation as a function of hold time (100s, 400s, 800s)
Zinc effect in carbon and low-alloy steel
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
EAF Under Plant-Like Conditions (Hold Time Effects -- KHNP)
Objective Characterize the influence of complex loading conditions on fatigue life of austenitic stainless steels in PWR environments Test Material Type 316 Austenitic Stainless Steel Air/PWR (reference)
Mixed Wave Specimens 6 total 6 total 6 total Case 2 each at 3 conditions 2 each at 3 different strain rates with 60 second hold time 2 each at 3 different strain rates with 300 second hold time Environment PWR Environment Temperature 310 C Control Strain Control Strain Rate (%/s) 0.4/0.04/0.004 0.4/0.04/0.004 0.4/0.04/0.004 Strain Amplitude (%)
0.4 0.4 0.4 Water Chemistry DO
< 5 ppb DH 25 cc/Kg Conductivity (RT)
< 20-25 S/cm (1200 ppm H3BO3 + 2.2 ppm LiOH) pH (RT) 6 - 7 Solid specimen with gauge section 19.05 mm long x 9.63 mm dia
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
EAF Under Plant-Like Conditions (Hold Time Effects -- KHNP)
Effect of hold-time on EAF life is inconclusive in this test 10
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
EAF Short Crack Growth Objectives Further the mechanistic understanding of EAF behavior in the short crack regime.
Develop an understanding intended to bridge the gap between fatigue endurance and Paris Law crack growth to better enable prediction of total (Stage I + Stage II) life 12x12mm specimen with a corner crack at each corner Crack depth is 0.228mm Specimen loaded to 50kN Model half crack (uses symmetry) and 1/8th of specimen
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
EAF Short Crack Growth Commissioning tests in air and in PWR water complete
- Proved ability to grow cracks using 0.228 mm broaches at R = 0.05.
- Demonstrated ability to generate DCPD data in RT, 300 ºC Air and 300 ºC water (simulated primary coolant chemistry)
- Improved predictions between DCPD readings and fractographic measurements achieved during trial program
- Noted that FEA needed to be undertaken to provide material specific K values.
2018 test matrix
- Compare CGRs in air and PWR environment (1,2,3)
- Study rise time effects for environmental enhancement (2,3)
- Compare broach depths (4,5)
Test Matrix Test Broach Depth (mm)
Environment Loading Trial 1 0.228 Air (RT)
R=0.05, f=0.5Hz (1s 1s )
Trial 2 0.228 Air (RT)
R=0.05, f=0.5Hz (1s 1s )
Trial 3 0.228 Air (300 °C)
R=0.05, f=0.25Hz (3s 1s )
Trial 4 0.228 Water (300 °C)
R=0.05, f=0.5Hz (1s 1s )
1 0.228 Air (300 °C)
R=0.05, f=0.5Hz (1s 1s )
2 0.228 Water (300 °C)
R=0.05, f=0.5Hz (1s 1s )
3 0.228 Water (300 °C)
R=0.05, f=0.25Hz (3s 1s )
4 0.1-0.15*
Air (300 °C)
R=0.05, f=0.5Hz (1s 1s )
5 0.1-0.15*
Water (300 °C)
R=0.05, f=0.25Hz (3s 1s )
6 TBD
- *Broach depth to be determined by FEA calculations of K/K
- Beach marks to be inserted after 6 to 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />; R=0.3 or 0.5
- Simulated PWR primary water: 300ºC, 2 ppm Li, 500 ppm B as boric acid, 30 - 40 cc/kg H2
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© 2018 Electric Power Research Institute, Inc. All rights reserved.
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