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1015 Ni EAF Testing
	ML18267A097
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Issue date:	09/24/2018
From:	Robert Tregoning; NRC/RES/DE
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Seiji Asada Mitsubishi Heavy Industries, Ltd.

Gary Stevens Technical Executive, EPRI EAF Research and Related ASME Activities, NRC Public Meeting September 25, 2018 Non-Isothermal EAF Testing for 316 Stainless Steel in Simulated PWR Environment

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Outlines Objectives Experimental Procedure Test Condition Test Matrix Comparison of Experimental Fatigue Lives and Predictions Measurement of Crack Growth Rate Beachmark Observation Extended WKR Method to Non-Isothermal Condition Conclusions

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Objectives In November 2012, EPRI gap report, Environmentally Assisted Fatigue Gap Analysis and Roadmap for Future Research, Roadmap, 1026724, Final Report was issued.

Gap 15 Non-Isothermal S-N Testing

- Limited data available on the influence of variable temperature and variable strain rate within test cycles and of the influence of out-of-phase variations of temperature and strain rate

- Influence of in-phase and out-of-phase temperature and strain variations to be identified by comparison with isothermal tests.

- Austenitic stainless steels in PWR environmental are highest priority Non-isothermal & isothermal testing has been performed to address Gap 15.

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R20 GL(24mm) 30 160 12 20 6

17 26 Experimental Procedure Specimen T/C Extensometer (GL : 24mm)

Induction heater Water Environment

Simulates PWR primary water

500 ppm H3BO3 as B

2 ppm LiOH as Li.

Dissolved oxygen (DO)

< 0.005 ppm

Dissolved hydrogen (DH) : 30 cc/kg H2O Material

Type 316 Stainless Steel C

Si Mn P

S Ni Cr Mo Min

10.00 16.00 2.00 Max 0.08 1.00 2.00 0.045 0.030 14.00 18.00 3.00 Heat 0.04 0.61 0.92 0.038 0.001 10.22 16.86 2.06 (Note) Average grain size: 30 m (Aqua regia liquid for 10 s)

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Test Condition Isothermal fatigue test & Non-isothermal fatigue test Temperature:

100325 ºC.

Strain amplitude (a):

0.6 %

The period t1, t3, t3 and strain rate 1, 2, 3 are parameters.

- I1-1~4 Isothermal(I) tests with strain change patterns of Slow-Fast and Fast -Fast

[addressed to positive strain rate changes]

- NI2-1~4 Non-Isothermal(NI) tests with strain change patterns of Slow-Fast and Fast -Fast

- NI3-1 Non-isothermal test with very high strain rate in compression (Very Fast-Fast)

- NI4-1 Non-isothermal test with the same condition of NI2-1 adding beach marking Measure crack shape for fatigue life Fast Fast Out of phase (NI2-1)

Strain Rate: Slow-Fast

[Out-of-Phase]

100 Temp.(ºC) 325 a

1 3

2 a

Time Fast Slow Strain (%)

0.6 0.6 1

3 2

t1=600 sec t2=480 sec t3=1000 sec 2

1 2

1 3

3 Out of phase (NI2-4)

Strain Rate: Fast-Fast

[In-Phase]

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Test Matrix No Temp.

()

Strain amp.

(%)

Temp.

change Pattern Strain rate change Pattern Period (sec)

Strain rate (%/sec t1 t2 t3

I1-1 100 0.60 Constant Slow-fast 600 480 1000 0.001 0.0025 0.0006 I1-2 325 0.60 Constant Slow-fast 600 480 1000 0.001 0.0025 0.0006 I1-3 100 0.60 Constant Fast-fast 600 480 1000 0.001 0.0025 0.0006 I1-4 325 0.60 Constant Fast-fast 600 480 1000 0.001 0.0025 0.0006 NI2-1 100-325 0.60 Out of phase Slow-fast 600 480 1000 0.001 0.0025 0.0006 NI2-2 100-325 0.60 In-phase Slow-fast 600 480 1000 0.001 0.0025 0.0006 NI2-3 100-325 0.60 In-phase Fast-fast 600 480 1000 0.001 0.0025 0.0006 NI2-4 100-325 0.60 Out of phase Fast-fast 600 480 1000 0.001 0.0025 0.0006 NI3-1 100-325 0.60 Out of phase Very fast-fast 600 480 30 0.001 0.0025 0.02 NI4-1 100-325 0.60 Out of phase Slow-fast 600 480 1000 0.001 0.0025 0.0006

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Comparison of Experimental Fatigue Lives and Predictions Strain Temp I1-2 Strain Temp I1-1 Isothermal Isothermal Isothermal Isothermal Non-Isothermal Out-of-Phase Non-Isothermal Out-of-Phase Non-Isothermal Out-of-Phase Non-Isothermal In-Phase Non-Isothermal In-Phase I1-3 Strain Temp I1-4 Strain Temp Strain Temp NI2-1&NI4-1 NI2-2 Strain Temp NI2-3 Strain Temp NI2-4 Strain Temp NI3-1 Strain Temp 100 1000 10000 I1-1 I1-2 I1-3 I1-4 NI2-1 NI2-2 NI2-3 NI2-4 NI3-1 NI4-1 Isothermal Condition Non-Isothermal Condition Fatigue Life in PWR environment Prediction by Draft NUREG/CR-6909 Rev.1 Prediction by JSME S NF1-2009 Experimental Fatigue life Factor of 2 with respect to NUREG

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Comparison of Experimental Fatigue Lives and Predictions (continued)

Considering the characteristic of the used material The experimental fatigue lives of non-isothermal conditions showed longer fatigue lives than the predictions.

1.E+02 1.E+03 1.E+04 1.E+02 1.E+03 1.E+04 Experimental Life (cycles) mean factor of 2 factor of 2

[I1-1] 100 ºC Constant Slow-fast

[I1-2] 325 ºC Constant Slow-fast

[I1-3] 100 ºC Constant Fast-fast

[I1-4] 325 ºC Constant Fast-fast

[NI2-1] 100-325 ºC Out of phase Slow-fast

[NI2-2] 100-325 ºC In-phase Slow-fast

[NI2-3] 100-325 ºC In-phase Fast-fast

[NI2-4] 100-325 ºC Out of phase Fast-fast

[NI3-1] 100-325 ºC Out of phase Slow-fast

[NI4-1] 100-325 ºC Out of phase Slow-fast Austenitic SS Draft NUREG CR6909 Rev.1 Expressions Predicted Life with factor (x0.52) (cycles) 0 0.2 0.4 0.6 0.8 1

1.2 I1-1 I1-2 I1-3 I1-4 Nleak/Nwp Prediction by Draft NUREG/CR-6909 Rev.1 Prediction by JSME S NF1-2009 0.77 for JSME 0.52 for Draft NUREG

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Measurement of Crack Growth Rate Typical striation widths were measured and da/dN data were obtained.

da/dN of the isothermal tests show the dependency on temperature da/dN of the non-isothermal tests are close to that of 100 ºC isothermal tests.

Striation width

1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 0.01 0.1 1

da/dN (mm/cycle)

Crack Depth, a (mm)

I1-1 Constant Slow-fast 100 I1-2 Constant Slow-fast 325 I1-3 Constant Fast-fast 100 I1-4 Constant Fast-fast 325 NI2-1 Out of phase Slow-fast 325100 NI2-2 In phase Slow-fast 100325 NI2-3 In phase Fase-fast 325100 NI2-4 Out of phase Fast-fast 100325 NI3-1 Out of phase Slow-fast 325100 NI4-1 Out of phase Slow-fast 325100 1

1.125

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The 4th beachmark was identified, but the 1st beachmark could not be found.

The 2nd and 3rd beachmarks could be identified only a few portion, and so the crack depths are estimated.

Multiple crack coalescence may have been occurred around the 2nd to 3rd beachmarks.

0 1

2 3

0 0.2 0.4 0.6 0.8 1

Crack depth, a [mm]

Fatigue life ratio, N /Nleak (No.2)

(No.4) 0.2 (No.1)

(No.3)

Calculated by Best Fitting Beachmark Observation of NI4-1

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Kamaya et al.(*1)proposed stress intensity factor

()

=

The stress intensity factor range (K) is transformed into the apparent effective strain intensity factor range (K(eff))

by the following equation. By using K(eff), da/dN can be predicted.

()

=

Next, the relations between measured da/dN and K(eff) from the Japanese project data(*2) and I1-1~4 for isothermal testing by hollow specimens, of which material, strain rate and temperature condition are identified, are compared with the above correlation between da/dN and K(eff).

Because of plastic region, specimen shape, aspect ratio and so on, these prediction was not consist with measured da/dN and should be corrected.

Dcp is defined as the plastic correction factor. Then K(eff) can be converted to K(eff)

() = ()

=

Extended WKR Method to Non-Isothermal Condition 1.E-04 1.E-03 1.E-02 1.E-01 1.E-04 1.E-03 1.E-02 1.E-01 Measured da/dN (mm/cycles)

Analysis da/dN (mm/cycles)

JPN Project 100°C 0.6% 0.004%/s.

325°C 0.6% 0.004%/s 100°C 0.6% 0.4%/s 325°C 0.6% 0.4%/s Isothermal Tests I1-1(100°C)

I1-2(325°C)

I1-3(100°C)

I1-4(325°C)

+2 2

1: Kamay, M., PVP2016-63434, ASME, 2016.

2: JNES, Report on Environmental Fatigue Tests of Nuclear Power Plant Materials for Reliability Verification [General Version] 2006FY Dcp=0.628 JPN PJ (*2)

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-1

-0.8

-0.6

-0.4

-0.2 0

0.2 0.4 0.6 0.8 1

0 50 100 150 200 250 300 350 400 450 500 0

500 1000 1500 2000 2500 Strain (%)

Temperature ()

Elapsed time per cycle (s)

Water temperature Strain NI2-1 Out-of-phase Slow-Fast 100-325 N=1 The WKR method is extended to non-isothermal condition.

ST was modified to reflect the effect of temperature change; STi

.Youngs modulus, E, was modified to reflect the effect of temperature change; Ei.

Proposed expanded WKR methodfor NI evaluation

da dN = Cx

=0 1

12 2.25 x x K()i+1 K()0 2.55 K()i K()0 2.55 x

K()i+1K()i ti+1ti 0.3 Extended WKR Method to Non-Isothermal Condition (continued)

Temp.

ST(Tc) exp

2516

+273 150343 3.39 x 105 x exp

2516

+273 0.0301(+273) ; 20< 150

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Extended WKR Method to Non-Isothermal Condition (continued) 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 Measured da/dN (mm/cycle)

Extended WKR da/dN (mm/cycle)

I1-1 I1-2 I1-3 I1-4 NI2-1 NI2-2 NI2-3 NI2-4 NI3-1 NI4-1

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The comparison between the experimental fatigue lives and the predicted fatigue lives with the factor that considered the material variability showed that the experimental fatigue lives of non-isothermal condition were greater than the predicted fatigue lives.

The da/dN curves of the non-isothermal tests do not show great difference while those of the isothermal tests depended on the temperature and the strain history.

It is suggested that the effect of EAF on fatigue crack growth for non-isothermal condition is different from isothermal condition and/or the relation between microstructurally small crack (MSC) stage (Stage I) and crack growth stage (Stage II) for non-isothermal condition is different from isothermal condition.

The WKR method was modified to apply to non-isothermal condition by incorporating K and plastic correction. This extended WKR method was applied to the isothermal and non-isothermal tests and could estimate the test data with the factor of 2.

Conclusions

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Backup Slides

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Test Facility Water temp.

Outer surface temp.

Loop control panel Fatigue test control unit Electric power Flow Load Disp.

Strain Time synchronization Specimen T/C Extensometer GL : 24mm Induction heater Flow Fatigue test section Heater Induction heater output Electric power output Input output Test control unit.

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Observation of Crack Surfaces Crack surface of NI2-1 has relatively large arc-like sub cracks The axial distance between the main crack and the sub crack of NI2-1 was larger than those of NI3-1 and NI4-1.

Main crack growth could be effected by interference by sub cracks About 4mm Main Crack Sub Crack About 1.5mm Main Crack Sub Crack About 0.5mm Main Crack Sub Crack NI2-1 NI3-1 NI4-1

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Proposal to incorporate the effect of non-isothermal condition into UFen;

= x,x

=,+,

,+,

If the crack growth is dominant, NI can be expressed by only crack growth life.

=

If the extended WKR method is improved and an appropriate initial crack is assumed, then Stage II fatigue life can be calculated and NI can be obtained.

Proposal of a New Method Correction factor for NI condition Stage I fatigue life under NI condition Stage I fatigue life under isothermal condition Stage II fatigue life under NI condition Stage II fatigue life under isothermal condition

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ML18267A097

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