AN UPDATE ON ALLOYS 690/52/152 PWSCC INITIATION TESTING

AN UPDATE ON ALLOYS 690/52/152 PWSCC INITIATION TESTING 17th International Conference on Environmental Degradation of Materials in Nuclear Power Systems – Water Reactors August, 2015

Kimihisa SAKIMA, Takaharu MAEGUCHI, Kenji SATO, Koji FUJIMOTO, Yasuto NAGOSHI (Mitsubishi Heavy Industries, Ltd.) Morihito NAKANO (The Kansai Electric Power Co.Inc)

© 2015 MITSUBISHI HEAVY INDUSTRIES, LTD. All Rights Reserved.

Introduction

It is well-known that Alloy 690 has high PWSCC resistance than that of Alloy 600 and selected as a replacement material for PWSCC.

PWSCC initiation data to verify long-term reliability for Alloy 690 is required.

The Japanese PWR Utilities & MHI have been conducting uni-axial constant load PWSCC tests for Alloy 690 (base and weld metals).

1


Test Materials

2

Chemical Compositions of Test Materials (Alloys 600 MA, 690 TT, 152 and 52)

0.03 9.00 29.70 60.15 0.001 0.008 0.28 0.32 0.021 BMI Nozzle

0.01 8.65 30.10 60.10 0.001 0.010 0.32 0.35 0.020 CRDM Nozzle

690 TT

0.02 8.51 15.90 74.50 0.001 0.008 0.30 0.35 0.027 SG Tube (Reference)

600 MA

Cu Fe Cr Ni S P Mn Si C

Chemical Composition (mass%) Base Metals

0.63 0.01 0.56 <0.01 28.95 60.41 <0.001 0.005 0.24 0.17 0.030 Weld Joint (TIG) 52

0.16 1.62 0.12 <0.01 28.93 55.9 0.007 0.007 3.37 0.46 0.030 Weld Joint (SMAW) 152

Al Nb Ti Cu Cr Ni S P Mn Si C

Chemical Composition (mass%) Weld Metals


Test Materials

3

Heat Treatment Condition and Mechanical Properties of Test Materials

(Alloys 600 MA, 690 TT)

5.9 51 661 284 1075ºC +TT

BMI Nozzle (bar)

4.0 50 650 286 1075ºC +TT

CRDM Nozzle (pipe)

690 TT

－ 42 680 346 975ºC MA

SG Tube (Reference) 600 MA

(％) (MPa) (MPa)

Elongation Tensile Strength

Yield Strength

Grain Size

Mechanical Properties (R.T.) Heat

Treatment Alloys


Experimental

4

(1) For Pipe and Bar (Plate Type)

(2) For Weld Joints

Detail of A

Weld Metal A

Weld Metal (SMAW, TIG)

Specimen thickness : 1mm


Experimental

5

Simulated PWR primary water

pH (at 25ºC) 6 ~ 8

Conductivity (mS/cm at 25ºC) 5 ~ 30

H3BO3 (ppm as B) 400 ~ 600 (target 500)

LiOH (ppm as Li at 25ºC) 0.2 ~ 2.2 (target 2.0)

Dissolved Hydrogen (cc・STP/kg・H2O) 25 ~ 35

Dissolved Oxygen (ppb) <5

Cl-(ppm) <0.05

Temperature(ºC) 360

Test parameters for PWSCC initiation test


Experimental

6

Air CylinderAir Inlet

Water Outlet

Water InletTest Specimen

Test Chamber

Test Chamber (I)

Pump PumpHeater

Thermocouple

Thermocouple

Thermo-couple

Thermo-couple

Thermo-couple

Thermo-couple

H2RCS water

TankWater

Test Chamber (II) Test Chamber (III)

Air pressure loading Rupture time measured by pressure detector


100

1000

Stre

ss（M

Pa）

Time（hour）

Alloy 690 TT CRDM NozzleAlloy 600 MA SG Tube

102 103 104 105 106

Temperature: 360 ºCEnvironment: Simulated Primary Water

(B: 500 ppm, Li: 2 ppm)

Result of constant load PWSCC tests

Comparison of PWSCC Initiation Data of Alloy 690 TT CRDM Nozzle with those of Alloy 600 MA SG tube No PWSCC initiation for more than 110,925 hr

Max. 110,925hr

Alloy 690 TT for CRDM Nozzle

7


100

1000

Stre

ss（M

Pa）

Time （hour）

Alloy 690 TT BMI NozzleAlloy 600 MA SG Tube


(B: 500 ppm, Li: 2 ppm)

102 103 104 105 106


Comparison of PWSCC Initiation Data of 690 TT BMI Nozzle with those of Alloy 600 MA SG tube No PWSCC initiation for more than 95,965 hr

Max. 95,965 hr

Alloy 690 TT bar for BMI Nozzle

8


100

1000

Stre

ss（M

Pa）

Time（hour）

Alloy 152 SMAW Weld Joint

Alloy 600 MA SG Tube


(B: 500 ppm, Li: 2 ppm)

102 103 104 105 106


Comparison of PWSCC Initiation Data of Alloy 152 (SMAW) weld joint with those of Alloy 600 MA SG tube No PWSCC initiation for more than 122,726 hr

Max. 122,726 hr

Weld Metal Alloy 152 (SMAW)

9


100

1000

Stre

ss（M

Pa）

Time（hour）

Alloy 52 TIG Weld JointAlloy 600 MA SG Tube


(B: 500 ppm, Li: 2 ppm)

102 103 104 105 106


Comparison of PWSCC Initiation Data of Alloy 52 (TIG) weld joint with those of Alloy 600 MA SG tube No PWSCC initiation for more than 122,535 hr

Max. 122,535 hr

10

Weld Metal Alloy 52 (TIG)


Latest SCC Test Results

11

Result of constant load PWSCC tests show NO PWSCC initiation for:

Over 110,925 hr (Alloy 690 TT CRDM Nozzle)

Over 95,965 hr (Alloy 690 TT BMI Nozzle)

Over 122,726 hr (Alloy 152/52 weld joint)


Additional Test of PWSCC Initiation

Long-term PWSCC initiation life time has been verified. However, following effects are not considered in the long term constant load PWSCC test.

Dilution zone Dissimilar weld joint (decreased Cr concentration)

Cold worke Cold worked surface layer Highest cold worked part of Alloy 690 TT

components

12


Alloy 52/316 SS dissimilar joints

13

• In order to evaluate the effects of decreased Cr concentration due to dilution of the weld, specimens were fabricated from dissimilar joint portion between Alloy 52 and 316 stainless steel.

• Cr concentration is decreased in the range of about 3 mm from the weld fusion line (the decrease was about 5%).


Alloy 690/52/152 with cold-worked surface layer

14

0

50

100

150

200

250

300

350

400

0 0.1 0.2 0.3 0.4 0.5 0.6表面からの距離（mm）

硬さ

(HV

0.0

1)

A690G(690母材部、溶接境界から0.5mm）

J52G(52合金部）

J152G(152合金部）

C52M(52合金部)

Har

dnes

s (H

V0.

01)

Distance from surface (mm)

A690G (690 HAZ with grinding)

J52G (52 with grinding)

J152G (152 with grinding)

C52 (52/316 dissimilar joint with machining)

Alloy 152

Welding direction

Dendrite growing direction

Welding direction

Grinding direction


Alloy 690 TT components with high cold work Investigation

• Components: Weld HAZ, Air ventilation nozzle, U bend area of SG tubes, SG mechanical plug

• Method: Hardness test Result

15

Cross-section of mechanical plug mockup (Without SCC test)

0

100

200

300

400

0 10 20 30 40 50 60Distance from corner(mm)

Hard

ness

(HV1

)

Hardness of cross-section near inner surface

Maximum hardness of mechanical plug is estimated to be approximately 330 HV

SG mechanical plug is considered to have largest cold work among various Alloy 690 TT components

330


Cold Worked Alloy 690 TT Specimen

16

Hardness: 330 HV PWSCC initiation specimen

1D Cold rolling ratio = 40%*1

OD 110, ID 59.6

In order to simulate the hardness of Alloy 690 TT mechanical plugs, １D cold rolling of CRDM nozzle material was conducted.

Alloy 690 TT CRDM Nozzle

*1: Highest cold rolling ratio without cracking.

Rolling Direction


Alloy 52/316 dissimilar joint

17

100

1000

100 1,000 10,000 100,000 1,000,000

Str

ess

(M

Pa)

Time (hr)

52/316 dissimilar joint

Alloy 600 MA SG tube

200

400

300

900

800

700

600

500

: Non Failure

Test Temp. : 360 ˚CTest Env. : Simulated primary water (B: 500 ppm, Li: 2 ppm)

Max. 30,166 hr

No PWSCC initiation for more than 30,166 hr (the same test environment as other tests)


Alloy 690 HAZ, 52, 152 with grinding

18

100

1000

100 1,000 10,000 100,000 1,000,000

Str

ess

(M

Pa)

Time (hr)

Alloy 690 TT HAZ with grinding

Alloy 52 weld metal with grinding

Alloy 152 weld metal with grinding

52/316 dissimilar joint with Machining


200

400

300

900

800

700

600

500

: Non Failure


Max. 26,796 hr



100

1000

100 1,000 10,000 100,000 1,000,000

Str

ess

(M

Pa)

Time (hr)

Alloy 690 TT mechanical plug mock-up


: Non Failure

200

400

300

900

800

700

600

500


Alloy 690 TT mechanical plug mock-up

19

Max. 8,958 hr



Time Extrapolation

20

Extrapolation of PWSCC test result to primary water temperature of actual plants Using activation energy of PWSCC for Alloy 600 (130kJ/mol*1)

Parts Operating

temperature (˚C)

Testing time at 360 ˚C

(hr)

Extrapolated time

(year) VHN 321 110,925 80 BMI 289 95,965 310

152 SMAW 325

122,736 71

345 31

52 TIG 325

122,535 71

345 31 Mechanical

plug 325 8,958 5

*1 MRP-11, MRP-115


Conclusion

Constant load SCC tests for Alloy 690 TT in temperature accelerated PWR simulated water are have been conducting.

Alloy 690 TT CRDM Nozzle Material, Alloy 690 TT BMI Nozzle Material, Alloy 152/52 Weld joints show No PWSCC initiation for over 110,925 hr, 95,965 hr , 122,726 hr, respectively.

We also began PWSCC testing of Alloy 52/316 SS dissimilar joints, Alloy 690/52/152 with a cold-worked surface layer, and cold-worked Alloy 690 TT in order to evaluate the sensitivity of dissimilar joints’ penetration areas, surface layer treatment areas, and cold-worked machined areas to PWSCC.

These tests are ongoing. 21


Aknowledgement

This work has been performed as a joint research program supported by Japanese PWR utilities.

22

http://www.kepco.co.jp/english/index.html

http://www.japc.co.jp/english/index.html

http://www.kyuden.co.jp/en_index.html


Procedure at the time of stop and restart

24

σy

Nom

inal

Stre

ss

Nominal Strain

SART STOP

Temperature rising

Pressurization

Applying load

Cooling

Depressurization

Unloading


Current Data for Initiation Susceptibility

Result of constant load PWSCC tests Long-term PWSCC initiation life time has been verified However, recent data shows PWSCC crack growth rate of alloy 690 TT increased by cold work

S.Bruemmer: Alloy 690/52/152 PWSCC Collaboration Meeting (2011)

Such effect of cold work is not considered in the long

term constant load PWSCC test.

Degree of cold work of Alloy 690 TT components in PWR

plant was surveyed

25


Cold Worked Alloy 690 TT in PWR Plant

Unexpanded mechanical plug inserted into SG tube

Expanding by drawing the core Mechanical plug

Mechanical Plug Cylindrical device with tapered cavity, expanded inside a SG tube as leak resistant seal Expanding by drawing its core Material: Alloy 690 TT (except for the core)

Core

SG tube

Tube sheet

Plug (Alloy 690TT)

26


Cold Worked Alloy 690 TT in PWR Plant

Large plastic strain and residual stress

Mechanical Plug Large plastic strain and residual stress due to core displacement PWSCC failure experience:

•Alloy 600 mechanical plug PWSCC failure in North Anna 1(1989)

Approximate location of failure

Penetration of SG tube by ruptured plug shell

A failure example of North Anna 1

27

AN UPDATE ON ALLOYS 690/52/152 PWSCC INITIATION TESTING

Documents

Transcript of AN UPDATE ON ALLOYS 690/52/152 PWSCC INITIATION TESTING