ML052350343

Southern Nuclear/Westinghouse Proposed Test Plan to Demonstrate Benefits of Zinc Additions to Mitigate PWSCC

ML052350343
Person / Time
Site:	Farley
Issue date:	08/25/2005
From:	Stinson M Southern Nuclear Operating Co
To:	Office of Nuclear Reactor Regulation
References
Download: ML052350343 (34)

Text

Southern Nuclear / Westinghouse Proposed Test Plan to Demonstrate the Benefit of Zinc Addition to Mitigate PWSCC Mike Stinson August 25, 2005 Aug 25, 2005 1

Purpose To determine if test data from the proposed program can be used to make informed decisions with respect to regulatory requirements.

Aug 25, 2005 2

Agenda

• Farley 2 background

• Overview of test plan

• Test design & expectations

• Benefits

• Feedback & discussion Aug 25, 2005 3

Description of Farley 2

• Three-loop, Westinghouse PWR 910 megawatts

• Initial Ops: 1981

• Renewal license expiration: 2041 Aug 25, 2005 4

Farley 2 Pilot Plant for Zinc Addition

• Laboratory and test reactor experiments indicated reduced general corrosion and PWSCC mitigation benefits of zinc addition

• EPRI sponsored demonstration plant

• Zinc injection began June 12, 1994

• RCS zinc concentration

• 30 ppb Cycles 10, 12 - 14

• 15 ppb Cycles 15 - 17 (post SG replacement)

Aug 25, 2005 5

Farley 2 Zinc Addition Experience

• Sig. Radiation benefit observed after S/G Replacement Plant EFPY Channel head dose rate (R/hr)

Farley 2 1.3 0.34 Watts Bar 1.15 2.3 Cook 2 1.11 3.0 Indian Point 3 1.07 3.1 No. Anna 1 1.36 5.0 Ringhals 2 1.34 4.0 Ref: EPRI TR-107566 Aug 25, 2005 6

Farley 2 Oxide Films

• Pulled SG tube film characterization Normalized Atomic Percent Normalized Atomic Percent 100%

Zn Fe Fe 80%

60%

Atom%

Zn Zn Cr Cr Fe Fe

% Cr 40% Cr Ni Ni

% 20% Ni Ni

% 0%

0 14 28 42 56 19 33 47 61 75 0 7 14 32 60 88 17 31 45 59 6 6 6 6 6 2 2 2 2 Depth (nm)

Depth (nm)

Cycle 9 Cycle 10 Ref: EPRI TR-106358-V1 Aug 25, 2005 7

Farley 2 Zinc Addition Experience

• Difficult to assess PWSCC benefit.

Alloy 600 / 82 / 182 Inspections 2002 2004 2005 2R15 2R16 2R17 CRDM Volumetric (UT) Volumetric (EC + UT) Replace (EA-03-009) + BMV + BMV RPV nozzles BMV (ISI Program)

RPV BMI BMV BMV (BL 2003-02)

PRZ nozzles Volumetric + surface BMV BMV (top)

(BL 2004-01) (1 nozzle) Volumetric + surface (2 nozzles)

Aug 25, 2005 8

Farley 2 CRDM Penetration Material

• B&W Tubular Products heat M3935

• Less than optimum annealing heat treat

• Heat M3935 used in penetrations of five RPV heads:

• Farley 2

• Davis-Besse

• Oconee 3

• Beaver Valley

• ANO 1 Aug 25, 2005 9

Heat M3935 Industry Experience Plant name # of  % # # required % of nozzles in industry inspected repair M3935 in heat heat no. by UT RV head no. M3935 with defect M3935 Oconee 3 68 49% 68 14 20%

Davis-Besse 5 4% 5 3 60%

ANO 1 1 <1% 1 1 100%

Beaver Valley 1 4 3% 4 4 100%

Farley 2 61 44% 61 0 0%

Total 139 139 22

% 100% 16%

Aug 25, 2005 10

Heat M3935 - Industry Locations that reqd repair 65 60 66 53 41 42 54 33 24 48 Orange 47 34 Oconee 3 (Spr 2001) 52 27 17 18 28 55 Orange striped 64 32 11 8 12 35 67 Oconee 3 (Fall 2001) 40 16 3 4 19 43 Red 59 23 7 1 9 25 61 Davis-Besse (Spr 2002) 39 15 2 5 20 44 Green 63 31 10 6 13 36 68 AN0 1 (Fall 2002) 51 26 14 21 29 56 Blue 46 30 22 37 49 Beaver Valley 1 (Spr 2003) 50 36 45 57 62 58 69 Aug 25, 2005 11

Heat M3935 Farley Unit 2 Locations 65 60 66 53 41 42 54 47 33 24 34 48 52 27 17 18 28 55

- M3935 64 32 11 8 12 35 67 locations 40 16 3 4 19 43 59 23 7 1 9 25 61

-Proposed 39 15 2 5 20 44 sample 63 31 10 6 13 36 68 locations 51 26 14 24 29 56 46 30 22 37 49 50 36 45 57 62 58 69 Aug 25, 2005 12

Whats different?

• Farley 2 is the only RPV head with heat M3935 that has not experienced cracking

• Farley 2 is the only plant that operated with heat M3935 and significant zinc chemistry

- Beaver Valley 1 started to add zinc in 2002 and noted SCC in M3935 in Spring 2003 (~20 ppb-mo.)

How can we determine what makes Farley 2 RPV head different?

Aug 25, 2005 13

Mock-up of Sample Removal Aug 25, 2005 14

Test Program Goal

• Demonstrate that zinc addition makes the surfaces of Alloy 600 more resistant to PWSCC.

• Quantify the improvement in life provided by zinc additions.

Aug 25, 2005 15

What is significant about the Farley 2 Alloy 600?

• Exposed to zinc in the primary coolant since 1994

- Integrated zinc exposure 1600 ppb-months at last inspection

- Integrated zinc exposure 1900 ppb-months at RV head replacement

- High susceptibility heat allows comparison testing to show the beneficial effects of zinc Aug 25, 2005 16

Farley U2R17 RV Head Replacement

• Plan to collect two penetration samples

• penetrations # 14 and # 16

• M3935 base material

~4.3

~2.8 Aug 25, 2005 17

Proposed Program Objectives

• Harvest Alloy 600 Heat M3935 material from the Farley 2 reactor vessel head.

• Characterize surface chemistry

• Assess crack initiation by performing lab tests of segments containing the Zn conditioned material

• Compare samples with and without zinc in film

• Demonstrate benefits of Zn additions Aug 25, 2005 18

Characterize the incorporation of -zinc

• Can compare depth of zinc infiltration in films

• With Cycle 9 exam (pre-zinc)

• With Cycle 10 exam, (310 ppb-months exposure)

• Key questions

• What is the current surface zinc concentration

• How deep has the zinc diffused into the oxide film

• What are the film characteristics

• Can provide limited material to other organizations Aug 25, 2005 19

Prove benefit regarding crack initiation Basic idea

• Fabricate test specimens keeping as-is surface films intact

• Divide specimens into two groups

• Carefully remove zinc from the surface films of one group

• Perform comparison testing Aug 25, 2005 20

Harvest two Heat M3935 penetrations Aug 25, 2005 21

Anticipated Geometry OD specimen ID specimen Strips would be removed from the ID and OD surface of the Farley 2 material

- Assume red surfaces have zinc removed Aug 25, 2005 - Assume green surfaces tested with zinc 22

Basic Approach o machine specimens With Zinc Without Zinc

• Carefully handle

• Carefully handle

• Preserve zinc in films

• Remove zinc using a

• Cold work (increase process w/o affecting stress) oxide film (e.g. LOMI)

• Continue to test with

• Cold work (increase typical concentrations stress) of zinc in the water

• Continue to test without zinc in the simulated primary Aug 25, 2005 water 23

Typical method for testing crack initiation behavior

• Westinghouse has used this configuration to test service & lab Alloy 600/182 Aug 25, 2005 24

Sample size comparison Size (L=3.7) of Bent beam previously used.

stimate specimens om Farley 2 would e ~1.5 long.

Aug 25, 2005 25

Anticipated specimen configuration Subsized specimen Westinghouse will shrink the test fixtures to test subsized specimens.

Aug 25, 2005 26

Key Challenges Constraints Risks

• Material that can be practically

• Special subsized specimens extracted from head penetrations is limited - and test fixtures need to be requires subsized specimens designed and demonstrated

• The material surfaces will have

• Subsized specimens may be significant radioactivity, >3R/hr difficult to handle (cannot be decontaminated)

• May be difficult to compare

• Testing is costly and time subsized sample data with consuming large sample data Aug 25, 2005 27

Heat M3935 Service Experience 90%

80%

70%

60%

50%

Estimated Time to 10% Initiation Log. (Estimated Time to 10% Initiation) 40%

30%

20%

Farley 2 started to add zinc at 10% ~9.6 EDY 0%

1.0 10.0 100.0 EDY at 600 deg F Aug 25, 2005 28

rojected Performance at levated Temperature 0%

680F 600F Need to accelerate cracking to demonstrate 0%

zinc effectiveness 0%

0%

Estimated Time at 600F to 50% Initiation Estimated Time at 653F to 50% Initiation 0%

Estimated Time at 662F to 50% Initiation 0% Estimated Time at 680F to 50% Initiation Log. (Estimated Time at 600F to 50%

Initiation) 0%

0%

0%

0%

0.1 1.0 10.0 100.0 High test temperatures Effective Years will accelerate cracking Aug 25, 2005 29

Anticipated Performance at Elevated Temp & Stress Crack Initiation Tests (no Zinc) in 680F lab primary water Assumed 1st failure of 140% Farley specimen with zinc surface Zinc improvement factor 130%

120%

% Service Stress 110%

100%

90%

80%

0.1 1.0 10.0 Time at Temperature (years) 100% service stress 110% service stress 120% service stress 140% service stress estimate with Zn surface Aug 25, 2005 30

Proposed Program -

Tasks & Schedule Project Timeline - Crack Initiation Receive and characterize Farley material Complete Farley 2 Initiate Farley 2 Specimen Testing Specimen Testing 0 3 6 9 12 15 18 21 24 27 30 mo.

Initiate Baseline Complete Specimen Testing Baseline Specimen Comparison Test Specimen Development & Testing of Data Experimental Facility Analysis of Relocation Effect Aug 25, 2005 31

Expected Results &

Implications

• Zinc exposed surfaces of Heat M3935 will show reduced crack initiation compared to similar surfaces with the zinc removed

• Extended crack initiation duration relaxes the need for frequent inspections Aug 25, 2005 32

Benefits

• Inspection Requirements

- CRDM Order EA-03-009

• Replacement RV heads Alloy 690

- RPV nozzles ASME XI - ISI Program

- RPV BMI Bulletin 2003-02

- PRZ nozzles Bulletin 2004-01

- MRP Inspection Guidelines (e.g., MRP-139)

Aug 25, 2005 33

Feedback Aug 25, 2005 34