ML20205S426

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Forwards Proprietary & Nonproprietary Viewgraphs to Suppl Info Presented at 870305 Meeting Re Steam Generator Tube Integrity.Commitment Re Generator Leakage & Testing & Plugging Criteria Discussed.W/Application for Withholding
ML20205S426
Person / Time
Site: North Anna Dominion icon.png
Issue date: 04/01/1987
From: Stewart W
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19292H063 List:
References
86-689A, NUDOCS 8704070029
Download: ML20205S426 (61)
v • d • e


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VINGINIA ELECTRIC AND PowEn Coxl>Awy RIcitwoxn,VINGINIA 23261 W. L. Sn WART Vera Penniaant wrct... OPE RATION.

April 1, 1987 United States Nuclear Regulatory Commission Serial No.

86-689A Attention: Document Control Desk N0/RCB:jmj Washington, D.C.

20555 Docket Nos.

50-338 License Nos.

NPF-4 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNIT 1 STEAM GENERATOR TUBE INTEGRITY SUPPLEMENTAL REPORT On November 25, 1986, Virginia Electric and Power Company submitted a l

Westinghouse Electric Corporation report on North Anna Power Station Unit I steam generator tube integrity.

This report provided results of recent steam generator tube eddy current inspections, pulled tube examinations and tube integrity evaluations.

The report also discussed our plans for mitigating steam generator tube degradation. A meeting was held with the NRC staff on March 5, 1987 to discuss this report, the results of additional evaluations conducted by Westinghouse and plans for the upcoming Refueling Outage. The purpcse of this letter is to submit the supplemental information presented during the meeting, to revise our previous commitment regarding the limit on steam generator primary-to-secondary leakage and to address our steam generator inspection plans and plugging criteria for the upcoming outage.

Recent fractographic examination of a tube section removed from one of the North Anna generators during the 1985 Refueling Outage shows the presence of segmented cracking separated by ligaments.

In order to assure tube integrity under these conditions, an administrative primary-to-secondary leakage limit of 100 gallons per day per steam generator has been imposed.

Our current plans for the upcoming Refueling Outage are to perform eddy current testing on 100% of the steam generator tubes, to conduct profilometry to determine dent growth, to perform a stress relief demonstration at selected tube support plate intersections, and to stress relieve the Row 2 U-Bend areas.

As required by Technical Specifications, Virginia Power intends to plug tubes with clear through-wall eddy current indications of 2 40%.

In addition, we will plug those tubes which may become unserviceabic prior to the next inspection based on indication length, indication growth rate, and length measurement uncertainty.

0f oh338

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If, as a result of inspections conducted during the upcoming Refueling Outage, conditions are found which are significantly different from those we have described, we will notify you of those particulars.

J Copies of the March 5

presentation

slides, both proprietary and l

non-proprietary, are attached. Also attached is a Westinghouse authorization l

letter, CAW-87-018, Proprietary Information Notice, and accompanying Affidavit.

As one Attachment contains information proprietary to Westinghouse Electric Corporation, it is supported by an affidavit signed by Westinghouse, the owner I

of the information.

The affidavit sets forth the basis on which the information may be withheld from public disclosure by the Commission and addresses with specificity the considerations listed in paragraph (b)

(4) of i

j Section 2.790 of the Commission's regulations.

Accordingly, it is respectfully requested that the information which is proprietary to Westinghouse be withheld from public disclosure in accordance with 10CFR Section 2.790 of the Commission's regulations.

1 Correspondence with respect to the proprietary aspects of the Application for Withholding or the supporting Westinghouse Affidavit should reference CAW-87-018 and should be addressed to R. A. Wiesemann, Manager of Regulatory &

Legislative Affairs, Westinghouse Electric Corporation, P.O.

Box

353, Pittsburgh, Pennsylvania 15230-0355.

If you have any questions on this matter, please contact us.

Very truly yours,

\\Q1 W. L. Stewart Attachments 1.

Application for Withholding Proprietary l

Information l

l 2.

North Anna Unit 1 Tube Integrity Presentation (Proprietary) 3.

North Anna Unit 1 Tube Integrity Present 3 tion (Non-Proprietary)

p.

cc:

U. S. Nuclear Regulatory Comission 101 Marietta Street, N.W.

Suite 2900 Atlanta, GA 30323 Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station

h h' WESTINGHOUSE CLAZS 3

, to NS-NRC-87-3205 NORTH ANNA UNIT 1 STEAM GENERATOR TUBE INTEGRITY PRESENTATION WESTINGHOUSE ELECTRIC CORPORATION NUCLEAR ENERGY SYSTEMS P.

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ENERCY DISPERSIVE SPECTROSCOPY

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TSF # 1 Ni, Fe, Cr Ng, Cn Si, Za, S. Mn, C1

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WESTINGHOUSE PRESENTATION MATERIAL NORTH ANNA UNIT 1 I

MARCH 5,1987 I

1.

SG EDDY CURRENT INSPECTION ANALYSIS FOR AUGUST,1985 AND NOVEMBER,1985.

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RESULTS OF THE PULLED TUBES EXAMINATION.

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TUBE INTEGRITY EVALUATION.

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SIGNALS REPORTED AT NORTH ANA UNIT 1 NOVEMBER 1985 STEAM GENERATORS INSPECTION l

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PLUGGING STATUS, NORTH ANNA UNIT 1 STEAM GENERATORS Total Plugging Total As Percent l

Tubes Plugged Tubes Plugged Previous Plugging of Tubes Steam Generator Aunust 1985 November 1985 Plurring To Date Installed A

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SUMMARY

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JANUARY 1984 VERSUS NOVEMBER 1985 INSPECTIONS No. of Tubes No. of Indications Mean Indication Steam Generator Evaluated Evaluated Growth finches)

A Not inspected in 1/84)

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FOR LARGEST (STEAM GENERATOR C) GROWTH RATE CALCULATED FROM 1/84 TO 11/85 (14.7 EFPM) USING MEASURED LENGTHS FROM EACH INSPECTION Predicted Predicted Avg. Growth for Max. Calc. Indications Mean Growth 14 EFPM Length for 14 EFPM gg, finches) finches) finches)*

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EXAMINATION OF PULLED TUBES R3C41 AND R9C58 FROM SG C OF NORTH ANNA UNIT 1 (E

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MARCH 5,1987 WESTINGHCUSE ELECTRIC CORPORATION O

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1 SCOPE OF INVESTIGATION 1:

O NDE VISUAL EXAMINATION g

PHYSICAL MEASUREMENTS RADIOGRAPHY EDDY CURRENT ULTRASONIC EXAMINATION PROFILOMETRY O

DESTRUCTIVE EXAMINATION I

SECTIONING METALLOGRAPHY 23 METALLOGRAPHIC SAMPLES 45 CROSS SECTIONS EXAMINED HARDNESS PROFILES MICROSTRUCTURE O

CORROSION TESTING HUEY TEST REVERSE U-BEND TESTS AT 7500F IN STEAM OVALIZED SAMPLES

SCOPE OF INVESTIGATION (CONTINUED)

O CHEMICAL ANALYSIS ENERGY DISPERSIVE X-RAY SPECTROMETRY f-(EDS)

ELECTRON MICROBE ANALYSIS ESCA AND AUGER ANALYSIS LOCAL AREA pH SLUDGE ANALYSIS SUPPORT PLATE HOLE SCRAPING ANALYSIS

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O RECENT FRACTOGRAPHIC EXAMINATION O

CONCLUSIONS l

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A SINGLE CRACK MORPHOLOGY IS APPROACHED AS CRACK GROWTH CONTINUES BEYOND THE TUBE SUPPORT PLATE.

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O VERY SMALL SPORADICALLY OCCURRING LIGAMENTS ON ~

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THE LIGAMENTS SPACING BETWEEN MAJOR CRACK SEGMENTS IS IN THE RANGE OF 0.2 TO 0.4 INCHES.

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THE OD CRACK LENGTH IS APPROXIMATELY 0.12 INCHES LESS THAN THE ID CRACK LENGTH.

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COMPARIS0N OF EDDY CURRENT RESULT 5 A M METALL0 GRAPHY FOR TUBE R3C41HL I

Location Field E/C Laboratory E/C Metallography 1

1st 5.P.

Distorted Dent Axial Indications CD and ID Aktal Attack

'j Within TS Pl., CD Contained Within 9/16" Long, Intersection.

40-1005 Deep.

Max. Depth & Length:

00: 255 0.1" ID: 505 0.2" 2nd 5.P.

94% Clear 5 Axial Indications Two Axial Crack Systems i

Indication at 3 Orientations ID Initiated, Intem.

(All10. Max 901)

Cracks 0.8 in.

Above to 0.2 in.

Below 5.P. Max.

Penetration-100%

155 00 SCC at Several Locations Within SP elevation 3rd 5.P.

Distorted Dent Single Axial Not Examined to Date Indication at Edge of SP ID-Nax>90%

i Top of NI MI No Attack Tubesheet Tubesheet NI NI No Attack Crevice NI = No Indication.

  • This classification was not generally applied in the field to characterize dent Lissajous ffgures. The field data for ttis tube wem categorized to facilitate distinctions among the intersections examined.

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COMPARIS0N OF ED0Y CURRENT RESULTS AND prTALLOGRAPHY FOR TU8E R9C58HL Location Field E/C Laboratory E/C Metallography 1

Ist S.P.

Distorted Axial Indication CD and 10 ' Attack

(

Indication Within and Up to Within Intersection Plus Dent 0.15" above TSP and Up to 0.3" Above 00, 40% Deep at Top of S.P.

Top Edge, 80%

[-

Deep Within Max. Depth and Length:

Intersection 00: 40%

0.2"

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ID: 85%

0.6"*

Top of NI NI No Attack Tubesheet Tubesheet NI MI Very Minor OD Attack Crevice NI = No Indication

  • = Estimated C

4" f

SUMMARY

DE TUBE EXAMINATION RESULTS

-(

O STRESS.C.ORROSION CRACKING (SCC) FROM THE OD AND THE ID IN THE DENTED TUBE SUPPORT PLATE REGION

(-

WAS OBSERVED.

NO SIGNIFICANT SCC WAS FOUND ON THE TUBING IN

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O THE VICINITY OF THE TUBESHEET.

O NO SPECIFIC CAUSATIVE CHEMICAL AGENT WAS IDENTIFIED.

O THE HARDNESS, GRAIN SIZE AND GENERAL MICROSTRUCTURE OF THE TUBING WERE TYPICAL FOR THE MANUFACTURING PROCESS AT THE TIME THE TUBING WAS FABRICATED.

O ACCELERATED TESTING OF HIGHLY STRESSED SPECIMENS SHOWED THAT THE TUBING IS SUSCEPTIBLE -

TO PRIMARY WATER SCC.

O THE ID INITIATED STRESS CORROSION CRACKING OF THE TUBING IS ATTRIBUTED TO DEFORMATION RESULTING FROM THE DENTING PROCESS.

O O

ID CRACK LOCATION CORRELATED WITH THE OVALITY OF THE TUBE.

O FRACTOGRAPHIC EVALUATION OF SPECIMENS SHOWS THE PRESENCE OF LIGAMENTS.

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TUBE INTEGRITY

l EVALUATION j

l e APPLICABLN LIMITING CRITERIA OF REG. GUIDE 1.121 i

e CHARACTERIZATION OF THE TUBE DEGRADATION e APPLICABLE BURST DATA AND EVALUATION TECHNIQUES

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i o APPLICABLE LEAK DATA AND EVALUATION TECHNIQUES o RESULTS OF THE EVALUATION l

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4, APPLICABLE REGULATORY I.121 GUIDE CRITERIA PARAGRAPH CJ.d 3

THE MAXIMUM PERMISSIBLE LENGTH OF THE LARGEST SINGLE CRACK SHOULD BE SUCH THAT THE INTERNAL PRESSURE TO CAUSE CRACK

~

PROPAGATION AND TUBE RUPTURE IS 3 TIMES GREATER THAN THE NORMAL OPERATING PRESSURE DIFFERENTIAL ADEQUATE MARGIN SHOULD BE PROVIDED FOR POSTULATED ACCIDENT CONDITION LOADINGS TO PRECLUDE THE PROPAGATION OF THE LARGEST PERMISSIBLE LONGITUDINAL CRACK RESULTING IN TUBE RUPTURE PRIMARY-TO. SECONDARY LEAKAGE RATE LIMITS FROM THE LARGEST PERMISSIBLE LONGITUDINAL CRACK UNDER NORMAL OPERATING CONDITIONS WILL ENSURE ORDERLY PLANT SHUTDOWN AND ALLOW TIME FOR REMEDIAL ACTION IF THE CRACK SIZE INCREASES BEYOND THE PERMISSIBLE LIMITS DURING SERVICE

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r TUBE DEGRADATION CHARACTERIZATION L*

FIELD EDDY CURRENT INSPECTION RESULTS REVEALED BOTH CLEAR AND DISTORTED INDICATIONS AT AND EXTENDING BEYOND THE TUBE SUPPORT PLATE ELEVATIONS. THE EDDY CURRENT SIGNAL DISTORTION IS ATTRIBUTED TO TUBE DENTING LABORATORY EDDY CURRENT OF TWO PULLED TUBES SHOWED ID INITIATED CRACK LIKE INDICATIONS ON THE TUBING NEAR THE EDGES OF THE SUPPORT PLATE EXTENSIVE PROFILOMETRY ON THE PULLED TUBES MEASURED UP TO 8 PERCENT TUBE OVALITY ATTRIBUTED TO TUBE DENTING. THESE

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SAME RESULTS INDICATED ONLY A SMALL AMOUNT OF PERMANENT 1

DEFORMATION METALLOGRAPHY OF THREE SUPPORT PLATE AREAS HAS REVEALED THE PRESENCE OF BOTH OD AND ID INITIATED ATTACK:

o ID INITIATED SCC IS MORE SEVERE THAN THE OD INITIATED SCC l

e THE SCC INVOLVED TWO PARALLEL COLINEAR AXIAL PATTERNS i

OF CRACKS (AVERAGE LENGTH OF AN INDIVIDUAL CRACK IS 0.1 INCH) EXTENDING FROM 0.8 INCH ABOYE THE TSP TO 0.2 INCH BELOW THE TSP.

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SATISFYING THE REG. GUIDE I.121 CRITERIA FOR SINGLE CRACKS WHEN DEGRADATION DEPTH IS PREDICTABLE 1

e FACTOR OF SAFETY OF 3.0 IS ASSURED BY MEETING THE MINIMUM ACCEPTABLE WALL THICKNESS REQUIREMENTS.

THE MINIMUM ACCEPTABLE WALL THICKNESS IS 8.019 INCH.

e THE LARGEST PERMISSIBLE SING 1.E CRACK SIZE IS DETERMINED THAT WILL NOT RESULT IN TUBE hUPTURE UNDER POSTULATED l

ACCIDENT PRESSURE LOADINGS (2650 PSI). THE CRACK j

SIZE IS{

]deC*

r 1

i e IT IS VERIFIED THAT THE LEAKAGE LIMIT WILL ALLOW AN 4

ORDERLY SHUTDOWN WITH ADEQUATE SAFETY MARGIN.

THE STANDARD TECHNICAL SPECIFICATION LEAKAGE RATE LIMIT OF $00 GFD CORRESPONDS TO A SINGLE CRACK LENGTH OF[

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i SATISFYING THE REG. GUIDE I.121 CRITERIA FOR SINGLE CRACKS i

WHEN DEPTH IS NOT PREDICTABLE i

A -(-

e WITH DEPTH UNPREDICTABLE,IT IS ASSUMED THAT SOME CRACKS MAY SOON PENETRATE THROUGH-WALL. THUS, A FACTOR OF SAFETY OF THREE OF BURST CAPABILITY OVER NORMAL OPERATION PRESSURE (3 X 1400 EQUALS 4200 PSI)

MUST BE PROVIDED ASSUMING A THROUGH-WALL CRACK.

THE SINGLE CRACK LENGTH THAT PROVIDES A BURST

]d 4C CAPABILITY OF 4200 PSI IS[

i e IN ORDER TO PROVIDE FOR AN ORDERLY SHUTDOWN PROVIDING ADEQUATE BURST CAPABILITY OVER TF2 POSTULATED ACCIDENT PRESSURE OF 2650 PSI, A.

(AGE LIMIT CORRESPONDING

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TO{

} OR y

ULD BE NEEDED.

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EFFECT OF LIGAMENTS ON THE LEAKAGE RATE AND BURST CAPABILITY OF CRACKED TUBING 4r C C 1

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SATISFYING THE REG. GUIDE 1.121 CRITERIA FOR AGGREGATE CRACKS WHEN DEPTH IS NOT PREDICTABLE l

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APPRQXIMATE LIGAMENT EFFECT ON CRACKED TURE STRENGTH 3

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CRACK LENGTH.

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RESULTS OF THE EVALUATION l

3 o THE CRITERIA OF REG. GUIDE I.12I ARE SATISFIED

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FOR SINGLE CRACKS WITH UNPREDICTABLE DEPTH WHEN THROUGH-WALL CRACE LEjGTHS MITED T0'0.40 INCH] #'

A LEAKAGE RATE LIMIT OF LD ASSUR1E THAT SINGLE CRACES WOULD NOY EXCE D THIS LENGTH AND THAT A BURST CAPABILITY OF 4200 PSI IS PROVIDED.

1 THE LARGEST PERMISSIBLE SINGLE CRACE SIZE IS 0.67 INCH FOR POSTULATED ACCIDENT LOADINGS.

o A MORE LIMITING LEAKAGE RATE LIMIT OF

)#

WOULD PROVIDE SUFFICIENT ASSURANCE OP TUBE INTEGRITY 1

FOR POSSIBLE SEGMENTED CRACE CONDITIONS.

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NORTH ANNA #1 CYCLE VI - Vil REFUELING OUTAGE

(

STEAM GENERATOR INSPECTION PROGRAM ko EDDY CURRENT INSPECTION o

INSPECT ALL TUBES IN-SERVICE FULL LENGTH USING f_.

CONVENTIONAL BOBBIN COIL (MAG. BIAS) PROBES FOR

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GENERAL REG. GUIDE 1.83 PURPOSES o

CLASSIFY RESULTS FOR TSP SIGNALS DENT - DISTORTED DENT - DISTORTED INDICATION - CLEAR INDICATION

] c pATION LENGTH [

MEASURE ly#dR COMPARISON TO 11/85 FOR ALL Di o

CLEAR AND DISTORTED INDICATIONS TO DETERMINE CRACK PROPAGATION RATE o

ROTATING PANCAKE COIL (RPC) TESTING o

PERFORMED ON THERMAL STRESS RELIEF SAMPLE POPULATION: 50/100 INTERSECTIONS: ALL BEFORE,50 AFTER o

TUBES TO BE PULLED FOR METALLOGRAPHY AND/OR BURST TESTING o

PROFILOMETRY o TEST WITH B&W PROFIL 360 SYSTEM TUBES EXAMINED WITH SAME METHOD IN 1984 (~125 PER SG)

I COMPARISON DATA WILL HELP ASSESS THE RATE OF o

DENTING PROGRESSION IF ANY i

i

' NORTH ANNA #1 TUBE PLUGGING CRITERION 4

APRIL,1987 IN ACCORDANCE WITH EXISTING PRACTICE, THOSE CLEAR

{.'_ INDICATIONS ASSESSED ;t.40% THROUGH-WALL WILL BE

. PLUGGED.

PROGRESSION RATE - CRACK EXTENSION RATE - WILL BE DERIVED FROM COMPARISON OF NEW CLEAR INDICATIONS WITH THEIR 11/85 LENGTHS.

(

DISTORTED INDICATIONS WILL BE ANALYZED TO DETERMINE THE APPARENT CRACKED TUBE LENGTH IN LIEU OF THE UNAVAILABLE DEPTH OF PENETRATION.

THE ARITHMETIC SUM OF CRACKED TUBE LENGTH, CRACK EXTENSION RATE, AND LENGTH MEASUREMENT UNCERTAINTY MUST PROVIDE COMFORTABLE MARGIN RELATIVE TO THE CRITICAL CRACK LENGTH -

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~ * *

.

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