ML052350343

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Southern Nuclear/Westinghouse Proposed Test Plan to Demonstrate Benefits of Zinc Additions to Mitigate PWSCC
ML052350343
Person / Time
Site: Farley  Southern Nuclear icon.png
Issue date: 08/25/2005
From: Stinson M
Southern Nuclear Operating Co
To:
Office of Nuclear Reactor Regulation
References
Download: ML052350343 (34)
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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

  • 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 Aug 25, 2005 6

Ref: EPRI TR-107566

Farley 2 Oxide Films

  • Pulled SG tube film characterization Normalized Atomic Percent Ni Cr Fe 0%

20%

40%

60%

80%

100%

0 14 28 42 56 196 336 476 616 756 Depth (nm)

Atom %

Zn Fe Cr Ni Normalized Atomic Percent Ni Cr Fe Zn 0%

20%

40%

60%

80%

100%

0 7

14 32 60 88 172 312 452 592 Depth (nm)

Atom%

Zn Fe Cr Ni Cycle 9 Cycle 10 Aug 25, 2005 7

Ref: EPRI TR-106358-V1

Farley 2 Zinc Addition Experience Difficult to assess PWSCC benefit.

Alloy 600 / 82 / 182 Inspections 2002 2R15 2004 2R16 2005 2R17 CRDM (EA-03-009)

Volumetric (UT)

+ BMV Volumetric (EC + UT)

+ BMV Replace RPV nozzles (ISI Program)

BMV RPV BMI (BL 2003-02)

BMV BMV PRZ nozzles (BL 2004-01)

Volumetric + surface (1 nozzle)

BMV BMV (top)

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

Farley 2 Davis-Besse Oconee 3 Beaver Valley ANO 1 Aug 25, 2005 9

Heat M3935 Industry Experience Plant name

  1. of nozzles heat no.

M3935 in industry heat no.

M3935 inspected by UT

  1. required repair 68 14 3

1 4

0 22 16%

5 1

4 61 139 100%

% of M3935 in RV head with defect Oconee 3 68 49%

20%

Davis-Besse 5

4%

60%

ANO 1 1

<1%

100%

Beaver Valley 1 4

3%

100%

Farley 2 61 44%

0%

Total 139 Aug 25, 2005 10

Heat M3935 - Industry Locations that reqd repair 1

9 25 61 59 23 8

24 6

22 58 60 5

13 29 49 69 62 66 36 45 57 46 30 37 26 14 56 63 31 10 36 68 67 64 39 15 20 44 40 16 4

19 43 32 11 12 35 52 27 17 28 55 53 48 54 33 41 42 7

34 18 47 65 21 51 3

2 50 Orange Oconee 3 (Spr 2001)

Orange striped Oconee 3 (Fall 2001)

Red Davis-Besse (Spr 2002)

Green AN0 1 (Fall 2002)

Blue Beaver Valley 1 (Spr 2003)

Aug 25, 2005 11

Heat M3935 Farley Unit 2 Locations Aug 25, 2005 12 1

9 25 61 59 7

23 8

24 6

22 58 60 5

13 29 49 69 62 65 66 36 45 57 50 46 30 37 51 26 14 24 56 63 31 10 36 68 67 64 2

39 15 20 44 40 16 3

4 19 43 32 11 12 35 52 27 17 18 28 55 47 53 48 54 34 33 41 42

- M3935 locations

-Proposed sample locations

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

  • M3935 base material

~2.8

~4.3 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 ID specimen OD specimen Aug 25, 2005 22 Strips would be removed from the ID and OD surface of the Farley 2 material

- Assume red surfaces have zinc removed

- Assume green surfaces tested with zinc

Basic Approach to machine specimens Without Zinc With Zinc Aug 25, 2005 23

  • Carefully handle
  • Preserve zinc in films
  • Cold work (increase stress)
  • Continue to test with typical concentrations of zinc in the water
  • Carefully handle
  • Remove zinc using a process w/o affecting oxide film (e.g. LOMI)
  • Cold work (increase stress)
  • Continue to test without zinc in the simulated primary water

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.

Estimate specimens from Farley 2 would be ~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 Material that can be practically extracted from head penetrations is limited -

requires subsized specimens The material surfaces will have significant radioactivity, >3R/hr (cannot be decontaminated)

Testing is costly and time consuming Risks Special subsized specimens and test fixtures need to be designed and demonstrated Subsized specimens may be difficult to handle May be difficult to compare subsized sample data with large sample data Aug 25, 2005 27

Heat M3935 Service Experience Farley 2 started to add zinc at

~9.6 EDY 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

1.0 10.0 100.0 EDY at 600 deg F Median Rank Estimated Time to 10% Initiation Log. (Estimated Time to 10% Initiation)

Aug 25, 2005 28

Projected Performance at Elevated Temperature High test temperatures will accelerate cracking Need to accelerate cracking to demonstrate zinc effectiveness 600F 680F 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

0.1 1.0 10.0 100.0 Effective Years Median Rank Estimated Time at 600F to 50% Initiation Estimated Time at 653F to 50% Initiation Estimated Time at 662F to 50% Initiation Estimated Time at 680F to 50% Initiation Log. (Estimated Time at 600F to 50%

Initiation)

Aug 25, 2005 29

Anticipated Performance at Elevated Temp & Stress Crack Initiation Tests (no Zinc) in 680F lab primary water 80%

90%

100%

110%

120%

130%

140%

0.1 1.0 10.0 Time at Temperature (years)

% Service Stress 100% service stress 110% service stress 120% service stress 140% service stress estimate with Zn surface Assumed 1st failure of Farley specimen with zinc surface Zinc improvement factor Aug 25, 2005 30

Proposed Program -

Tasks & Schedule 24 27 30 mo.

12 15 18 21 0

3 6

9 Test Specimen Development &

Experimental Facility Relocation Comparison of Data Analysis of Effect Initiate Baseline Specimen Testing Initiate Farley 2 Specimen Testing Receive and characterize Farley material Project Timeline - Crack Initiation Complete Baseline Specimen Testing Complete Farley 2 Specimen Testing 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 nozzlesBulletin 2004-01 MRP Inspection Guidelines (e.g., MRP-139)

Aug 25, 2005 33

Feedback Aug 25, 2005 34

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