ML20246M076

Summary of 890421 Meeting W/Util & Bechtel in Rockville,Md Re mid-cycle Steam Generator Tube Insp on 890421.List of Attendees & Viewgraphs Encl

ML20246M076
Person / Time
Site:	Millstone
Issue date:	05/10/1989
From:	Vissing G Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8905190031
Download: ML20246M076 (42)

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May 10, 1989 l Docket No. 50-336 LICENSEE: Northeast Utilities FACILITY: Millstone Unit No. 2

SUMMARY

OF MEETING L'ITH REPRESENTATIVES OF NORTHEAST UTILITIES CONCERNING A MID-CYCLE STEAM GENERATOR TUBE INSPECTION AT MILLSTONE 2 APRIL 21, 1989 INTRODUCTION On April 21, 1989 representatives of the NRC and Northeast' Utilities met at-the NRC of,fice in Rockville, Maryland to discuss the need for a mid-cycle steam generator tube inspection during Cycle 10 operation at Millstone, Unit No. 2. The attendar.ce list is provided in Enclosure 1. A copy of the slide presentation is provided in Enclosure 2.

DISCUSSION Since the staff has accepted the licensee's acticns regarding the repair of the steam generator tube plugs, this issue was not discussed. The licensee's.

actions regarding this issue are provided in Enclosure 2.

Jares Richardson, Assistant Director for Engineering, stated the staff's position regarding the application of the leak-before-break theory as it relates to steam generator tube failures. He indicated that the leak-before-break theory as it applies to steam generator tube failures is not a legitimate consideration. The NRC has not applied this theory to stearr generator tube failures and is not prepared to consider it for Millstone 2.

However,' the licensee indicated that the crack configurations in the tubes are such that make the. leak-before-break theory applicable. In addition, by July 1989, the licensee will have provided improved leak detection methods that would better detect leaks. The current leak limits are .1 gpm. They believe that Millstone 2 will have approximately 75 incipient tube failures for Cycle 10, leaks will be detected before the tubes would break and the unit would be shut down before a complete rupture of a tube. The licensee believes that it would be safe to operate during Cycle 10 without a mid-cycle steam generator tube inspection.

The licensee believes that of the 309 tubes, which indicated circumferential cracking in the recent inspection, 78% were present throughout Cycle 9 and would have been detected at the end of Cycle 8 if the same detection methods were used as were used during the recent inspection. Only 22% were prcpagated during Cycle 9 operation. This provides the licensee a basis to believe that any cracks which will propagate during Lycle 10 would survive the operating cycle without failure. They indicated that the nature of the cracks are such that there is enough metal ligaments remaining to prevent shearing of the tube.

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s The licensee believes that the causes of the cracks have been solved and that the crack propagation has been stopped. They also believe that their operators are well trained to handle steam generator tube failures. The staff, on the other hand, is concerned that, of the number of tubes involved, it would hard to believe that one could not completely fail.

The licensee indicated that a mid-cycle inspection would be a 100% inspection, would cost at least 130 man-rems, 36 days of shutdown, $36,000,00r in electricity costs and would come at an inopportune time when the need for power is critical.

CONCLUSIONS The staff indicated that consideration would be given to the licensee's position in determining whether a mid-cycle inspection would be ordered.

A~

Guy S. Vissing, Proj t Manager Project Directorate I-4 Division of Reactor Projects I/II

Enclosures:

As stated cc w/ enclosures:

See next page

4 4

• 4 The licensee believes that the causes of the cracks have been solved and that the crack propagation has been stopped. They also believe that their operators are well trained to handle steam generator tube failures. The staff, on the other hand, is concerned that, of the number of tubes involved, it would hard

- to believe that one could not completely fail.

- The licensee indicated that a mid-cycle inspection would be a 100% inspection, would cost at least 130 man-rems, 36 days of shutdown, $36,000,000 in electricity costs and would come at an inopportune time when the need for power is critical..

CONCLUSIONS The staff indicated that consideration would be given to the licensee's position in determining whether a mid-cycle inspection would be ordered.

I g

Guy S. lissing, Project Manager Project Directorate I-4 Division of Reactor Projects I/II

Enclosures:

As stated cc w/ enclosures:

See next page

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. Mr. Edward J. Mroczka Millstone Nuclear Pcwer Station Northeast Nuclear Energy Company Unit No. 2 cc:

Gerald Garfield, Esquire R. M. Kacich, Manager Day, Berry and Howard Generation Facilities Licensing Ccunselors at Law Northeast Utilities Service Company City Place Post Office Box 270 Hartford, Connecticut 06103-34g9 Hartford, Connecticut 06141-0270 W. D. Romberg, Vice President D. O. Nordquist Nuclear Operations Manager of Ouality Assurance hortheast Utilities Service Company Northeast Nuclear Energy Company Post Office Box 270 Post Office Box 270 Hartford, Connecticut 06141-0270 Hartford, Connecticut 06141-0270 Kevin McCarthy, Director Regional Administrator Redistion Control Unit Region I Department of Environmental Protection U. S. Nuclear Regulatory Commission State Office Building 475 Allendale Road Hartford, Connecticut 06106 King of Prussia, Pennsylvania 19406 Bradford S. Chase, Under Secretary First Selectmen Energy Division Town of Waterford Office of Policy and Management Hall of Records 80 Washington Street 200 Boston Post Road Hartford, Connecticut 06106 Waterford, Connecticut 06385 S. E. Scace, Station Superintendent W. J. Raymond, Resident Inspector Millstone Nuclear Power Station Millstone Nuclear Power Station Northeast Nuclear Energy Company c/o U. S. Nuclear Regulatory Commission Post Office Box 128 Post Office Box 811 Waterford, Connecticut 06385 Niantic, Connecticut 06357 J. S. Keenan, Unit Superintendent Charles Brinkman, Manager Millstone Unit No. 2 Washington Nuclear Operations Northeast Nuclear Energy Company C-E Power Systems Post Office Box 128 Combustion Engineering, Inc.

Waterford. Connecticut 06385 12300 Twinbrook Pkwy Suite 330 Rockville, Maryland 20852

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,, DISTRIBUTION FOR MEETING

SUMMARY

DATED: May 10,1989 -

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B. Grimes (9A2)

NRC Participants- G. Vissing J. Stolz Keith R. Wichman H.F. Conrad Jim Richardson Angie Gilbert ,

ACRS (10)

B. Clayton (17D19)

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, ENCLOSURE 1 ATTENDANCE LIST FOR' MEETING WITH NORTHEAST UTILITIES CONCERNING STEAM GENERATOR TUBE ISSUES AT MILLSTONE 2 APRIL 21, 1989 NAME ORGANIZATION Guy Vissing, Project Manager ~NRR/DRP/PDI-4 C.Y. Cheng NRR/ DEST /EMTB Keith R. Wichman NRR/ DEST /EMTB H.F. Conrad NRR/ DEST /EMTB Fred Sears NUSCO Jack Keenan Millstone 2 SUPT Richard Kacich NU-Licensing Manager C.W. Hulman Bechtel-KWU Alliance J.F. Stolz NRR/DRP/PDI-4 Jim Richardson NRR/EAD -

- Fred Anderson NUSCO Fred Dacite Millstone 2 Engineering Supv.

Kamal Manoly NRR/ DEST Angie Gilbert NRR/00EA/DEAB J.F. Ely NU James M. Benson NUSCO Joe Fackelmann NUSCO William E. Hutchins NU-Lead MP2 Licensing Engineer i

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NORTHEAST NUCLEAR ENERGY COMPANY i MILLSTONE UNIT NO. 2 DOCKET N0. 50-336 APRIL 21, 1989 MEETING WITH NRC STAFF r

CYCLE 10 .

STEAM GENERATOR SAFETY ASSESSMENT I

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NORTHEAST UTILITIES ATTENDEES DR. C. F. SEARS VICE PRESIDENT NUCLEAR & ENVIRONMENTAL ENGINEERING J. S. KEENAN PLANT SUPERINTENDENT MILLSTONE UNIT NO. 2 l

F. R. DACIMO ENGINEERING SUPERVISOR

. MILLSTONE UNIT NO. 2 J. F. ELY SUPERVISOR GENERATION MECHANICAL ENGINEERING J. M. FACKELMAN PRINCIPAL ENGINEER NUCLEAR MATERIALS AND CHEMISTRY F. C. ANDERSON SENIOR ENGINEER NUCLEAR MATERIALS AND CHEMISTRY J. M. BENSON ENGINEER NUCLEAR MATERIALS AND CHEMISTRY R. M. KACICH MANAGER GENERATION FACILITIES LICENSING W. E. HUTCHINS ENGINEER GENERATION FACILITIES LICENSING i

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NRC MEETING AGENDA -

MILLSTONE UNIT NO. 2 STEAM GENERATOR ASSESSMENT 1989 REFUELING OUTAGE INTRODUCTION / VICE PRESIDENT OVERVIEW NUCLEAR & ENVIRONMENTAL ENGINEERING DR. C. F. SEARS TUBE PLUG REPAIR PIPING SYSTEM ENGINEERING PROGRAM JAY ELY OVERALL CRACK NUCLEAR MATERIALS & CHEMISTRY ASSESSMENT J0E FACKELMAN STRUCTURAL PIPING SYSTEMS ENGINEERING CONSIDERATIONS JAY ELY OPERATING SAFETY PLANT SUPERINTENDENT PERSPECTIVE JACK KEENAN

SUMMARY

& VICE PRESIDENT CONCLUSIONS NUCLEAR & ENVIRONMENTAL ENGINEERING DR. C. F. SEARS l

l

PljRPOSE OF MEETING 0 TO BRIEF THE NRC 0F ACTIONS TAKEN TO REPAIR SUSPECT TUBE PLUGS DURING THE 1989 REFUELING OUTAGE.

O TO SUMMARIZE THE RESULTS OF EDDY CURRENT TESTING CONDUCTED DURING THE 1989 REFUELING OUTAGE TESTING TECHNIQUES /RESULTS PLUGGING AND STAKING PROGRAMS 0 TO DEMONSTRATE THE NNECO CONCLUSION THAT MILLSTONE UNIT NO. 2 TUBE INTEGRITY IS ASSURED FOR OPERATION THROUGH CYCLE 10.

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1 INTRODUCTION

INTRODUCTION MILLSTONE UNIT NO. 2 STEAM GENERATOR STATUS 0 AGGRESSIVE PURSUIT OF STEAM GENERATOR CHEMISTRY 0 SECONDARY SIDE STRESS CORROSION CRACKING 0 ENHANCED STATE OF ART INSPECTIONS AND EVALUATION 0 TUBE PLUG DEGRADATION  !

0 ONG0ING SAFETY AND OPERABILITY EVALUATIONS I

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0 WELL-DEFINED LEAK DETECTION AND OPERATOR RESPONSE O CYCLE 10 OPERATION IS SAFE 1

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STEAM GENERATOR TUBE PLUG REPAIR PROGRAM

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, MILLSTONE UNIT NO. 2 STEAM GENERATOR TUBE PLUG REPAIR SCOPE O TWO HEATS (NX 3962 AND NX 3513) 0F PLUG MATERIAL WERE FOUND TO BE SUSCEPTIBLE TO PRIMARY WATER STRESS CORROSION CRACKING.

0 302 PLUGS FROM HEAT NX3513 WERE INSTALLED BETWEEN 12/86 AND 2/88. NO PLUGS FROM HEAT NX3962 WERE INSTALLED.

0 THE 30P. SUSCEPTIBLE PLUGS ARE MIXED WITH LESS SUSCEPTIBLE PLUGS IN 779 LOCATIONS - 446 HOT LEG AND 333 COLD LEG.

O INDUSTRY EXPERIENCE WAS COMBINED WITH LABORATORY TEST DATA TO DEFINE TIME TO CRACKING AS A FUNCTION OF TEMPERATURE. ON THIS BASIS, ALL P0TENTIALLY SUSCEPTIBLE HOT LEG TUBE PLUGS WERE REPAIRED. COLD LEG TUBE PLUGS WILL NOT CRACK OVER THE NEXT FUEL CYCLE, AND S0 THEY WERE f!0T REPAIRED.

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MILLSTONE UNIT NO. 2 STEAM GENERATOR TUBE PLUG REPAIR ,

CRITERIA 0 REPAIR SHOULD PRECLUDE PARTIAL TUBE RUPTURE i RESULTING FROM PLUG FAILURE.

O REPAIR SHOULD HAVE STRUCTURAL MARGINS WHICH MEET ORIGINAL REQUIREMENTS (COMPONENT SPECIFICATION),

GENERAL REPAIR REQUIREMENTS (ASME XI), AND LICENSE. ,

REQUIREMENTS (R.G.1.121) .

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0 REPAIR SHOULD HAVE A SERVICE LIFE IN EXCESS OF THE -

COMPONENT.

O REPAIR SHOULD CAPTURE P0TENTIAL LOOSE PARTS (INCLUDING ITSELF). 1 0 REPAIR SHOULD LIMIT LEAKAGE IN ACCORDANCE WITH LICENSED ALLOWABLES.

1

. MILLSTONE UNIT NO. 2 {

STEAM GENERATOR TUBE PLUG REPAIR

]

RESULIS 0 THE SELECTED REPAIR IS A LEAK LIMITING CAPSCREW WHICH THREADS INTO THE PLUG EXPANDER, IS I PRELOADED; AND IS TACK WELDED TO THE PLUG SKIRT. l 0 FINITE DIFFERENCE DYNAMIC ANALYSIS SHOWED THAT THE CAPSCREW PREVENTS PLUG TOP IMPACT BY DISPLACING I

PRIMARY COOLANT AND LIMITING ADDED COOLANT DURING THE EVENT.

O TESTING AND ANALYSIS DEMONSTRATED COMPLIANCE k".!H l ORIGINAL SPECIFICATION, ASME, AND R.G. 1.121 REQUIREMENTS.

O THE I600 CAPSCREW IS THERMALLY TREATED AFTER ALL COLD WORK. PRELOAD STRESSES ARE BELOW YIELD.

THUS, IT WILL NOT CRACK BEFORE THE TUBING WHICH HAS 14 '1ARS OF SERVICE WITHOUT OBSERVED PWSCC.

O THE DESIGN, PRELOAD, AND HIGH PENETRATION TACK ,

WELD ASSURE THAT NO LOOSE PARTS WILL BE CREATED.

0 THE CAPSCREWS LIMIT LEAKAGE TO AN AVERAGE OF 0.003 GPM AND A MAXIMUM 0F 0.01 GPM EVEN IF ALL 302 l LEAK. l l

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OVERALL CRACK ASSESSMENT 1

STEAM GENERATOR EXAMINATION SCOPE TEST DESCRIPTION # OF TESTS  % OF POPULATION l B0BBIN TO FIRST 24,593 TUBE ENDS 100%

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l BOBBIN FULL LENGTH 4,237 TUBES 29% i SEGMENTED B0BBIN APPROX. 1,000 TUBES 20%

'R0TATING PANCAKE 12,556 TUBE ENDS 100% WITHIN {

COIL CRACK B0UNDARY j ULTRASONIC TEST 10 TUBE ENDS I

CRACK NDE FINDINGS 0 309 TUBE END CRACKS IDENTIFIED 1989 (CYCLE 9),

27 TUBE END CRACKS IDENTIFIED CYCLE 8.

O CRACKS CIRCUHFERENTIALLY ORIENTED AND LOCATED AT THE TOP 0F THE TUBESHEET.

0 EACH " CRACK" IS MADE UP OF SEVERAL MICR0 CRACKS, '

WITH THE OVERALL CRACK EXTENT RANGING FROM 140 To 3290 BY ROTATING EDDY CURRENT PROBE.

O CRACK LENGTHS LIMITED i

CRACK INITIATION ESTIMATES-ROTATING PROBE DATA i

42, 1989 CRACKS STUDIED (SG1, HL) 1 90% PRESENT EOC 8 (1988) 10% "NEW" EOC 9 (1989)

B0BBIN PROBE DATA 309, 1989 CRACKS STUDIED 78% PRESENT (1988) 22% "NEW" (1989) se

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NDE SUWiARY 0 T!iOROUGH INSPECTION OF ALL REGIONS OF THE STEAM GENERATORS PERFORMED, USING STATE-0F-THE-ART NDE j

TECHNIQUES BEYOND THOSE REQUIRED BY TECH. SPECS. 4 0 ESSENTIALLY ALL TUBE FLAWS (PITS AND CRACKS) WERE LOCATED ABOVE THE TUBESHEET WITHIN THE HIGHER SLUDGE REGION.

O PITTING NONACTIVE, EXCEPT IN A DISCRETE REGION

-(l" TO 3" ATS); ONLY ON A SMALL NUMBER OF TUBES.

O A DECREASE IN THE RATE OF CRACKING WAS OBSERVED FROM CYCLE 8 TO CYCLE 9 (78% OF THE END OF CYCLE 9 CRACKS INITIATED PRIOR TO EOC 8).

0 ULTRASONIC TESTING CONFIRMED PULLED TUBE FINDING 0F METAL LIGAMENT /MICR0 CRACK SEGMENT MORPHOLOGY.

O TOTAL OF 433 TUBES REQUIRED REPAIR.

304* FOR CRACKS i 129 FOR OTHER REASONS

• 5 TUBES CRACKED ON BOTH ENDS l

.- .j SECONDARY CHEMISTRY 1

0 OUTSTANDING BE_K CHEMISTRY PERFORMANCE LAST 2 CYCLES (8 & 9). l 0 LOCAL CONCENTRATING PROCESS ASSOCIATED WITH TUBESHEET SLUDGE.

O CHEMISTRY IMPROVEMENTS ASSOCIATED WITH ANION / CATION IMBALANCE.

O LOCAL CAUSTIC CHEMISTRY CYCLE 8 DUE TO ION IMBALANCE.

0 LOCAL CAUSTIC ESSENTIALLY ELIMINATED LAST CYCLE, BORIC ACID.

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~, CRACK MECHANISM / MORPHOLOGY REVIEW OF AVAILABLE DATA 0 EXAMINATION OF LEAKING TUBE SG 1 L25/R19 REMOVED E0C 8.

O PLANT OPERATING EXPERIENCE ECT INSPECTIONS LEAK MONITORING CHEMISTRY 0 TUBE STRESS ANALYSIS FOR MP2 SG'S O FIBER OPTIC EXAMINATION E0C 9 0 LABORATORY TEST DATA DEGRADED EGGCRATE PROGRAM BORIC ACID TREATMENT QUALIFICATION INCONEL 600 SCC DATA BASE O OPERATING EXPERIENCE AT OTHER PLANTS REMOVED TUBE EXAMINATIONS BORIC ACID TREATMENT EXPERIENCE BURST TESTS OF REMOVED TUBES 4

FACTORS WHICH CONTRIBUTE TO STRESS CORROSION CRACKING 0F THE MILLSTONE UNIT N0. 2 STEAM GENERATOR TUBES 0 BULK WATER IMPURITIES FROM CYCLE 7 THROUGH BEGINNING OF CYCLE 9, ALTHOUGH VERY LOW IN LEVEL,

' PRODUCED CAUSTIC CONDITIONS WHEN CONCENTRATED.

(THIS CONDITION CORRECTED EARLY IN CYCLE 9).

O REMAINING SLUDGE PROVIDES STEAM BLANKETED REGION AT TOP 0F TUBESHEET AND ALLOWS IMPURITIES TO CONCENTRATE. SLUDGE ALSO CONTAINS COPPER AND OTHER ELEMENTS WHICH MAY ACCELERATE THE CORROSION PROCESS.

O REGIONS OF HIGHER STRESSES IDENTIFIED IN TUBE BUNDLE. CRACKS OCCURRED IN THE HIGHER STRESS REGIONS. (DENTING ARRESTED).

CORROSION M@EL 0 STRESS CORROSION DETERMINED TO BE THE CAUSE OF THE CRACKING WITH CAUSTIC CONSIDERED THE MOST LIKELY CORROSIVE SPECIES.

0 NUMBER OF CRACKS DETECTED CONSISTENT WITH CAUSTIC ENVIRONMENT FOR APPR0XIMATELY 2 CYCLE, FOLLOWED BY IMPLEMENTATION OF BORIC ACID TREATHENT.

O TIME REQUIRED TO INITIATE AND PROPAGATE A CRACK IS LONGER FOR COLD LEG THAN HOT LEG.

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0 CRACKING INITIATED AS SEPARATE "MICR0" CRACKS 1 (WHICH EVENTUALLY LINKED-UP TO FORM THE OBSERVED ) l

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0 MACR 0 CRACKS IDENTIFIED BY ROTATING PROBE EDDY CURRENT 0 MICR0 CRACKS INITIATE AND GROW.

O LIGAMENTS BETWEEN CRACKS PROVIDE STRUCTURAL STRENGTH.

O MICR0 CRACK LINKUP ASSOCIATED WITH LEAKAGE.

0 LEAK BEFORE BREAK BEHAVIOR DEMONSTRATED BY TUBE SG 1 L25/R19.

0 EXISTENCE OF LIGAMENTS BETWEEN CRACKS CONFIRMED IN ULTRASONIC TESTING.

O LEAK BEFORE BREAK BEHAVIOR CONFIRMED BY BURST TESTS OF TUBES CONTAINING CIRCUMFERENTIAL STRESS CORROSION CRACKS REMOVED FROM NORTH ANNA.

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PROJECTIONS OF FUTURE CRACKING 0 THE FORMATION OF NEW INCIPIENT CRACKS APPEARS TO HAVE STOPPED OR GREATLY SLOWED DURING CYCLE 9.

0 EXTRAPOLATION OF CRACKING TREND OBSERVED IN CYCLE 9 INDICATES THE POSSIBILITY OF ABOUT 75 ADDITIONAL CRACKS DEVELOPING TO A DETECTABLE STAGE BY END OF CYCLE 10. THIS ASSUMES AN ADEQUATE POPUMTION OF INCIPIENT CRACKS. .

O THE MAJORITY OF THESE CRACKS ARE EXPECTED TO BE LOCATED ON THE COLD LEG RATHER THAN THE HOT LEG DUE TO THE GREATER TIME BETWEEN THE FORMATION OF INCIPIENT CRACKS AND PROPAGATION OF THOSE CRACKS'.

O THE REDUCED NUMBER OF NEW CRACKS DECREASES THE PROBABILITY OF A SIGNIFICANT TUBE LEAK BY A FACTOR OF AT LEAST 4 COMPARED WITH THE PREVIOUS CYCLE.

THE PROBABILITY OF A SIGNIFICANT TUBE LEAK IS CONSIDERED EXTF.EMELY SMALL DUE TO THE ESTABLISHED

" LEAK BEFORE BREAK" MORPHOLOGY, LACK OF SIGNIFICANT LEAKAGE WITH OBSERVED CRACKS, AND PAST SUCCESSFUL OPERATING EXPERIENCE.

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SUMMARY

/ CONCLUSIONS 0 ALL SIGNIFICANT CRACKS IDENTIFIED AND PLUGGED DURING THE PRESENT E0C 9 INSPECT 0IN.

O ABOUT 80 PERCENT OF THE CRACKS HAD ACTUALLY FORMED i DURING CYCLE 8, BUT WERE IDENTIFIED IN PRESENT OUTAGE (E0C 9) AS A RESULT OF AN IMPROVED NDE PROGRAM.

O CRACK PATTERN IN THE 309 TUBE ENDS BOUNDED BY PREVIOUS STRUCTURAL EVALUATION OF PULLED TUBE (L25R19), PROVIDING " LEAK BEFORE BREAK" ASSURANCE IN COMBINATION WITH 0.1 GPM LEAK LIMIT.

O CRACK INITIATION MINIMIZED OR ELIMINATED BY CHEMISTRY IMPROVEMENTS / BORIC ACID TREATMENT.

0 THE 309 CRACKS DID NOT CREATE A SAFETY PROBLEM EVEN THOUGH MOST CRACKS WERE PRESENT FOR AT LEAST ONE CYCLE.

0 ANY REMAINING INCIPIENT CRACKS (FORMED PRIOR TO B0RIC ACID TREATMENT) EXPECTED TO PROPAGATE TO l

DETECTABLE STAGE DURING CYCLE 10. ABOUT 75 CRACKS EXPECTED. CRACK MORPHOLOGY SIMILAR TO THAT IN PREVIOUSLY IDENTIFIED CRACKS EXPECTED. '

0 THE GREAT MAJORITY OF THE INCIPIENT CRACKS EXPECTED TO BE LOCATED ON COLD LEG DUE TO SLOWER KIHETICS, O POSTULATED CIRCUMFERENTIAL CRACKS NOT A SIGNIFICANT SAFETY PROBLEM SINCE POSTULATED CRACK BEHAVIOR MEETS " LEAK BEFORE BREAK" CRITERIA.

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STRUCTURAL INTEGRITY INPUT 0 TECHNICAL SPECIFICATION FOR LEAKAGE j i

0.1 GPM PRIMARY-TO-SECONDARY LEAKAGE LIMIT 0 BASES CIRCUMFERENTIAL FLAWS STRUCTURAL MARGIN TO R.G. 1.121 LEAK BEFORE BREAK BEHAVIOR EXPECTED 0 STRUCTURAL INTEGRITY

IATERIALS ENVIRONMENTAL  :

STRESSES CYCLE LENGTH 0 CRACK MORPHOLOGY ROTATING PANCAKE COIL (RPC) SIMILAR TO L25R19 UT CHARACTERIZATION 1

STRUCTURAL INTEGRITY ANALYSIS OF TUBE L25R19 0 CALCULATE CROSS-SECTION GEOMETRY FROM A MONTAGE OF i PHOT 0MICR0 GRAPHS O EVALUATE POST-PLUGGING CRACK GROWTH 0 COMPUTE SAFETY MARGINS OF PREPLUGGING CRACK SIZE -

. ESTIMATE SIZE AT INITIAL LEAKAGE AND CORRESPONDING SAFETY MARGINS 0 SENSITIVITY ANALYSIS FOR LEAKAGE MEASUREMENT ERROR AND ACCIDENT CONDITION LEAKAGE 0 E'7ABLISH R.G. 1.121 ALLOWABLE UNIFORM CIRCUMFERENTIAL CRACK SIZES - 79% THROUGHWALL 0 MAXIMUM THROUGHWALL CIRCUMFERENTIAL EXTENT AT R.G. 1.121 LIMIT IS 1300 ARC.

l 0 COMBINED PART AND THROUGHWALL DEFECT 2540 i

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LEAKAGE ALLOWABLES 0 TEST DATA ON PULLED TUBES AND LABORATORY DEFECTED TUBES CORRELATES LEAKAGE TO ARC LENGTH OPENING (0.1 GPM APPR0X. 400 0F ARC) ,

0 TRENDED LEAK RATE DATA ON L25R19 CORRELATES WITH TEST DATA (35 0 => 65 ) 0AND MORPHOLOGY 0 BURST TESTS ON DEGRADED TUBES ESTABLISHES LOAD CARRYING CAPABILITY OF LIGAMENTS 0 ACCIDENT CONDITION LEAKAGE-DESIGNED TO LIMIT OFFSITE DOSE DURING POSTULATED ACCIDENTS 0 CHANGE IN LEAKAGE RATE DUE TO ACCIDENT CONDITION BASED ON ANALYSIS'AND CONFIRMED BY TEST DATA

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LEAK RATE MONITORING 0 TECHNICAL SPECIFICATIONS LEAK RATE LIMIT 0.1 GPM (144 GPD) 0 LEAK DETECTION 0 STEAM JET AIR EJECTOR GASEOUS RADIATION ,

MONITOR 0 S/G BLOWDOWN TANK EFFLUENT RADIATION MONITOR 0 PERIODIC " GRAB" SAMPLES 0 N-16 SYSTEM (7/15/89) 0 RADIATION MONITOR SETPOINTS ADJUSTED TO PROVIDE

" ALERT" ON INCREASING LEVELS -

0 CHEMISTRY PERSONNEL ON-SHIFT 0 ALL LEAK RATE DATA PLOTTED 0 REVIEWED DAILY BY STATION MANAGEMENT 0 "0N-CALL" SR0 ENGINEERS PROVIDE ASSISTANCE TO THE OPERATING SHIFT 0 UNIT HISTORY 0 OPERATOR TRAINING FOR STEAM GENERATOR TUBE LEAKAGE

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SUW4ARY MILLSTONE UNIT NO. 2 STEAM GENERATOR OPERABILITY 0 TUBE PLUG PROBLEMS ADDRESSED .

O SYSTEM CHEMISTRY ACIDIC 0 DETECTABLE CRACKS - PLUGGED AND STABILIZED 0 DEGRADATION ESSENTIALLY STOPPED 0 OPERATIONAL MONITORING I

0 REASONABLE ASSURANCE NO DECREASE IN SAFETY 0 CONTINUING TO STUDY AND EVALUATE 0 DO NOT FEEL MIDCYCLE INSPECTION IS NEEDED l

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