ML18267A090

1030-1045 Hold Time and Chemistry Effects

ML18267A090
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Issue date:	09/24/2018
From:	Robert Tregoning NRC/RES/DE
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Water Chemistry Effects on EAF, EAF Under Plant-Like Conditions (Hold Time Effects), and EAF Short Crack Growth 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

© 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) 2

© 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 3

© 2018 Electric Power Research Institute, Inc. All rights reserved.

Zn Effect on EAF - Test Matrix Objective Test Material 316 Austenitic Stainless Steel Establish a PWR environmental Test condition Reference PWR Air PWR fatigue database of Type 316 SS Number of test specimen (ea) 4 4 16 for Zn addition combined with Test Environment Air PWR environment dissolved hydrogen condition Temperature RT / 325°C 325°C Control type Strain control (ASTM E606)

Test program includes reference Strain amplitude (%) 0.4 tests in air and PWR water Strain rate (%/s) 0.004 (0.04)

PWR water tests include Hold time (sec) 0 / 400 DO < 5 ppb

- Hold time (0 or 400 sec) DH (cc/kg) 25 25 / 50 Water

- Zinc addition (0 or 30 ppb) Chemistry Zinc (ppb) - 0 / 30 Conductivity (RT)

- DH control (25 or 50 cc/kg) pH (RT) 6.3 4

© 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) 5

© 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 PWR + 30 ppb Zn with 400 with 400 second second hold hold 6

© 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 7

© 2018 Electric Power Research Institute, Inc. All rights reserved.

Zn Effect on EAF - Upcoming Plans Next steps for this program Future project ideas KAIST Facility Strain Rate Effect

- Zn & High DH condition test - Very low strain rate vs. hold time effect KHNP Facility 0.001%/s strain rate

- Reference tests Confirm strain rate dependency of Zn effect

- High DH condition test Hold time variation Further Analysis - Fatigue life variation as a function of hold time

- Oxide identification: diffraction pattern analysis (100s, 400s, 800s) to confirm Zn incorporation into oxide Zinc effect in carbon and low-alloy steel 8

© 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 Type 316 Austenitic Stainless Steel Test Material Air/PWR Mixed Wave (reference)

Specimens 6 total 6 total 6 total Case 2 each at 3 2 each at 3 2 each at 3 conditions different strain different strain rates with 60 rates with 300 second hold second hold time 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 DO < 5 ppb DH 25 cc/Kg Water Conductivity < 20-25 S/cm Solid specimen Chemistry (RT) (1200 ppm H3BO3 + 2.2 ppm LiOH) with gauge section pH (RT) 6-7 19.05 mm long x 9.63 mm dia 9

© 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

© 2018 Electric Power Research Institute, Inc. All rights reserved.

10

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 11

© 2018 Electric Power Research Institute, Inc. All rights reserved.

EAF Short Crack Growth Commissioning tests in air and in PWR Test Matrix water complete Test Broach Depth (mm) Environment Loading

- Proved ability to grow cracks using 0.228 mm Trial 1 0.228 Air (RT) R=0.05, f=0.5Hz (1s 1s )

broaches at R = 0.05. Trial 2 0.228 Air (RT) R=0.05, f=0.5Hz (1s 1s )

- Demonstrated ability to generate DCPD data Trial 3 0.228 Air (300 °C) R=0.05, f=0.25Hz (3s 1s )

in RT, 300 ºC Air and 300 ºC water Trial 4 0.228 Water (300 °C) R=0.05, f=0.5Hz (1s 1s )

(simulated primary coolant chemistry) 1 0.228 Air (300 °C) R=0.05, f=0.5Hz (1s 1s )

- Improved predictions between DCPD 2 0.228 Water (300 °C) R=0.05, f=0.5Hz (1s 1s )

readings and fractographic measurements 3 0.228 Water (300 °C) R=0.05, f=0.25Hz (3s 1s )

achieved during trial program 4 0.1-0.15* Air (300 °C) R=0.05, f=0.5Hz (1s 1s )

- Noted that FEA needed to be undertaken to 5 0.1-0.15* Water (300 °C) R=0.05, f=0.25Hz (3s 1s )

provide material specific K values. 6 TBD 2018 test matrix * *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

- Compare CGRs in air and PWR environment

• Simulated PWR primary water: 300ºC, 2 ppm Li, 500 ppm B as boric acid, 30 - 40 cc/kg H2 (1,2,3)

- Study rise time effects for environmental enhancement (2,3)

- Compare broach depths (4,5) 12

© 2018 Electric Power Research Institute, Inc. All rights reserved.

TogetherShaping the Future of Electricity 13

© 2018 Electric Power Research Institute, Inc. All rights reserved.