ML20204G578

Summary of 860627 Meeting W/Utils & Westinghouse in Bethesda,Md to Discuss P-star Analysis for Steam Generators at Facility.List of Attendees & Viewgraphs Encl

ML20204G578
Person / Time
Site:	Summer
Issue date:	07/31/1986
From:	Hopkins J Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8608070333
Download: ML20204G578 (17)

Text

1 July 31,1986 1

Docket No. 50-395 LICENSEE: South Carolina Electric & Gas Company FACILITY: V. C. Summer Nuclear Station

SUMMARY

OF MEETING WITH SOUTH CAROLINA ELECTRIC & GAS COMPANY GENERAL On June 27, 1986, the NRC staff met with the South Carolina Electric and Gas Company (SCEF.G) to discuss the P-Star analysis for steam generators at the V. C. Summer Nuclear Station. The meeting was held in Bethesda, Maryland.

A list of those persons who attended the meeting is included as Enclosure 1.

DISCUSSION Attached as Enclosure 2 is the meeting agenda and non-proprietary viewgraphs shown during the meeting. The main topic of discussion was the definition of an intact tube. The utility agreed to submitt infomation regarding inspection of repaired tubes and the NRC staff agreed to review in more depth the analysis regarding friction retaining a tube in the tubesheet.

S Jon B. Hopkins, Project Manager PWR Project Directorate #2 Division of PWR Licensing-A

Enclosures:

As stated cc w/ enclosures:

See next page DISTRIBUTION:

-Docket File OGC JHopkins EJordan NRC PDR BGrimes Local PDR ACRS (10)

PWRf2 Reading NRC Participants JPartlow LRubenstein AD#2 mPe,,a a P pkins LRuhe te,n 07Q86 'j 07 /86 07/31/86 8600070333 PDR 860731 ADOCK 05000395 PDR

ENCLOSURE 1 MEETING ATTENDEES June 27, 1986 NRC SCF8G ult 6pkins PTr67 DSellers Testes ESullivan DMalkmus CCheng APaglia JMuscara JRajan l

WESTINGHOUSE DUKE POWER COMPANY RKeating DMayes g

MProviano JDay CHirst GWhiteman JEsposito t

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s ENCLOSURE 2 NRC, MEETING TUBE REPAIR AND P-STAR CRITERIA BETHESDA. MARYLAND -

JUNE 27. 1986 3 PRESENTATION

1. INTRODUCTION SCE&G.

2. P* 8 ASIS REVIEW WESTINGHOUSE

3. INTACT TU8E SCE&G/ WESTINGHOUSE

a. Define Structural Limit -

b. Defects Below P*

c. Post Plugging Tube Degradation

d. Inspection Requirements

e. Definition

4. INSPECTION OF REPAIRED TUBES SCE&G

5. SU W RY Q SCE&G e

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2 e e RJBE PLUGGING CRITERION IN THE 1UBESHEET REGIm

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'IEONICAL SPECIFICATION PLUGGING LIMIT APPLIES 1HROUGH THE TUBE IMH ACCOUNT FOR TE CONSTRAINING EFFECT OF 'IHE 1UBESHEET DEFINE A REGIm WITHIN THE 1UBESHEET IN hMICH NO PLUGGING REQUIREMENTS hTED APPLY 9

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e e Tubesheet Plugging Criteria  :

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Indications need to be P. Plugged /Steeved a n '

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Indications need not l be Plugged / Sleeved l

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PULINT CRITERIN (P*) DEVELOPMENT BRIEF OEWIEK ASPECTS O WBE BURST h1LL NOT OCCUR h1 WIN WE 'IUBESHEET 0 WBE COL 1 APSE h'ILL NOT OCCUR k'IWIN WE WBESHEET O TECHNICAL SPECIFICATIm LEAKAGE LIMITS APPLY

-- CM SIDERATIE S 0 A FIXED OR CAP'IURED WBE END IS MAIhTAINED 0 PRIMARY 'IO-SECONDARY LEAKAGE IS LIMITED 0 *IUBE INTEGRITY IS MAIhTAINED UNDER LIMITING CmDITIES O WBE IhTEGRITY ABOVE P* IS DEKNSTRA'IED ( BY CSTIhUED ECT)

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ECT AXIAL UNCERTAlhTY

-- RESULTS O WBE PULINT IS PRECLUDED 0 'IUBES h*IW INDICATINS BELOK P* REMAIN IN SER\1CE O P* CRITERION DOES NUT APPLY TO PERIPHERAL WBES ANT)

SOE IhTERIOR WBES 1

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Potential Location of IDSCC L

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S/G Tube

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Tubesheet Eddy Current ,

Indication 4

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• I TRE ATMENT OF TUBESHEET TUBE INDICATIONS PREMISE 1

THE BASIC PREMISE TO BE APPLIED IS THAT IF A SEVERED TUBE END IS CONSTRAINED SUCH THAT IT CANNOT BECOME CLEAR OF THE TUBESHEET THE INTEGRITY OF THE BUNDLE IS CONSERVED, AND IF LEAKAGE IS LIMITED THE SAFETY CONSEQUENCES OF LEAKAGE HAVE BEEN APPROPRIATELY ADDRESSED.

APPLICATION OF RG 1.121 IDENTIFICATION OF A DISTANCE, DESIGNATED P*, BELOW THE TOP OF THE TUBESHEET FOR WHICH TUBE DEGRADATION OF ANY. EXTENT WILL NOT RESULT IN A SEVERED TUBE END FROM BECOhDNG CLEAR OF THE TUBESHEET DURING NORMAL OR POSTULATED ACCIDENT CONDITIONS.

CONSIDERATIONS I. DEVELOPMENT OF THE ENGAGEMENT DISTANCE REQUIRED TO MAINTAIN A FIXED TUBE END CONDITION IN THE TUBESHEET WITH A POSTULATED CIRCUMFERENTIAL INDICATION.

2. LIMITATION OF PRIMARY-TO SECONDARY LEAKAGE CONSISTENT WITH i ACCIDENT ANALYSIS ASSUMPTIONS.

3. MAINTENANCE OF TUBE INTEGRITY UNDER POSTULATr.D '.IMITING CONDITIONS OF PRIMARY TO SECONDARY AND SECONDA 7 TO PRIMARY DIFFERENTIAL PRESSURE.

4

TUBESHEET EFFECTS RELATIVE TO THE PERFORMANCE OF DEGR ADED TUBES t

• BURST STRENGTH OF FULL DEPTH EXPANDED TUBES THE BURST STRENGTH OF THAT PORTION OF A TUBE LOCATED WITHIN THE TUBESHEET IS REINFORCED TO THE EXTENT THAT THE PRESENCE OF THE TUBE MATERIAL IS NOT NECESSARY,I.E., TUBE BURST IS OBVIATED BECAUSE DEFORMATION BEYOND THE EXPANDED OUTER DIAhETER IS ESSENTIALLY PRECLUDED.

• COLLAPSE STRENGTH OF FULL DEPTH EXPANDED TUBES THE COLLAPSE STRENGTH OF THAT PORTION OF THE TUBE LOCATED WITHIN THE TUBESHEET IS SIGNIFICANTLY INCREASED. COLLAPSE MODES WHICH ARE ACCOMPANIED BY LOCAL DEFORMATION BEYOND THE OUTER DIAMETER (GEOMETRICAL REACTION) ARE SIGNIFICANTLY

.RENGTHENED.

• LEAKAGE OF FULL DEPTH EXPANDED TUBES NO ACTUAL LEAKPATH IS EXPECTED DUE THE HARDROLLING OF THE TUBES INTO THE TUBESHEET. LEAK RATE EFFECTS HAVE BEEN ASSESSED BY ASSUMING A LEAK PATH TO EXI?T AND DETERMINING THE RELATIVE LEAKAGE WHICH WOULD OCCUR DURING POSTULATED ACCIDENT CONDITIONS.

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DEVELOPMENT OF THE P8 CRITERION

' DEVELOPMENT OF THE P* CRITERION IS BASED ON ASSUMING THAT A TUBE HAS BEEN DEGRADED TO THE POINT OF SEVERENCE WITHIN THE TUBESHEET. THE SEVERED TUBE IS POSTULATED TO MQVE UPWARD TO A POSITION WHERE THE EXTRADOS SURFACE OF THE U BEND APEX IS IN CONTACT WITH THE TUBE DIRECTLY ABOVE IT. UNDER OPERATING OR ACCIDENT CONDITIONS ADDITIONAL DISPLACEMENT MAY OCCUR.THE TOTAL AMOUNT OF UPWARD MOVEhENT HAS BEEN ADDRESSED BY THE FOLLOWING CONSIDERATIONS.

• MANUFACTURING CONSIDERATIONS ^

A STUDY OF THE FABRICATION AND ASSEMBLY PROCESS WAS CONDUCTED WHICH INCLUDED CONSIDERATION OF NOMINAL GAP DIMENSIONS AND MANUFACTURING STEPS WHICH COULD RESULT IN VARIATIONS TO THE NOMINAL DIMENSIONS. A MAXIMUM AS BUILT GAP VALUE WAS IDENTIFIED.

• THERMAL EXPANSION CONSIDERATIONS VERTICAL DISPLACEhENT OF A SEPARATED TUBE U-BEND WAS CONSIDERED TO BE THAT OF AN INTACT OUTBOARD NEIGHBOR TUBE -

U BEND.

• PRESSURE ELONGATION CONSIDERATIONS AXIAL ELONGATION OF AN INTACT OUTBOARD NEIGHBOR TUBE U BEND WAS CONSIDERED TO PERMIT ADDITIONAL UPWARD M6VEMENT OF A SEVERED TUBE U-BEND.

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. 1. " OUTBOARD NEIGHBOR" STRUCTURAL LIMIT -

Minimum allowable wall to resist failure due loading of a postulated separated P* tube during a postulated SLB.

AXIALLY ORIENTED INDICATIONS -

Expected case if degradation occurs in the VC Summer steam generators.

Through-wall indications could exist and still' resist failure.

CIRCUHFERENTIALLY ORIENTED INDICATIONS -

Case 1 - Outboard Neighbor Plugged -

Minimum Wall thickness Normal 0.0036 inch. 8.4 %

Upset 0.0045 inch, 10.1 %

Faulted 0.0035 inch, 8.1 %

C Evenly thinned 360 degrees around circumference.

,Envelopes cracklike degradation .

Case 2 - Outboard Neighbor Active -

Minimum Will Thickness Normal 0.007 inch, 16.8 %

Upset 0.009 inch, 20.1 %

Faulted 0.007 inch, 16.3 %

Evenly thinned 360 degrees around circumference.

Includes SLB pressure differential loading.

Leak-Before-Break expected apply.

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4. ' INTACT" NEIGHBOR DEFINITION -

Indications Above3P* - Plant Technical Specification.

Currently Plugged - Considered as Intact.

Greater than 92 % for 360 Degrees - NOT Considered Intact.

Post Inspection Tube Remaining in Service - Considered Intact.

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PLUGGED TUBE CORROSION CONSIDERATIONS O PRIMARY SIDE

- TEMPERATURE STRESS

- HYDROGEN PARTIAL PRESSURE O SECONDARY SIDE

- CONTAMINANT CONCENTRATION

- TEMPERATURE

- STRESS ~ ,

- CONTAMINANT REMOVAL O FI LD EXPERIENCE j - O DETECTION -

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SUMMARY

O PRIMARY SIDE CORROSION RATES ARE EXPECTED TO BE MINIMAL AFTER TUBE PLUGGING

- DRY ENVIRONMENT IS LIKELY  ;

- TEMPERATURES ARE LOWER IN INACTIVE TUBE

- LACK OF HYDROGEN, IF TUBE IS WET, WILL RESULT IN VERY LOW CORROSION RATE.

O SECONDARY SIDE CORROSION MAY CONTINUE AFTER TUBE PLUGGING IN SOME CASES BUT THE CORROSION RATE WILL BE SIGNIFICANTLY REDUCED.

LOWER TEMPER TURE OF PLUGGED TUBE LACK OF HEAT FLUX WILL PRECLUDE FURTHER CONCENTRATION OF CONTAMINANTS REMOVAL OF RESIDUAL CONTAMINANTS TO THE BULK ENVIRONMENT WILL OCCUR AT A RATE DEPENDENT UPON LOCAL GEOMETRY AND HYDRAULIC CONDITIONS.

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SUMMARY

(cont) i . .

O CONTAMINANT REMOVAL AND CORROSION INHIBITION ACTIONS MAY RESULT IN CESSATION OF CORROSION.

. OPTIONS:

~ SLUDGE LANCING CREVICE FLUSHING / BUNDLE FLUSH CHEMICAL CLEANING

- BORIC ACID APPLICATION

- ELIMINATION OF CONTAMINANT INGRESS O OPERATIONALLY INDUCED STRESSES ARE SIGNIFICANTLY LOWER IN A PLUGGED VERSUS AN ACTIVE TUBE. HOOP STRESS IS REDUCED TO A GRESTER EXTENT THAN AXIAL STRESSES.

1 O SEPARATION OF INCONEL 600 TUBING IS NOT KNOWN TO OCCUR IN PLUGGED TUBES BASED ON FIELD AND LABORATORY KNOWLEDGE.

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" INTACT TUBE i

AN INTACT TUBE IS ANY TUBE THAT DOES NOT CONTAIN DEFECTS WHICH WOULD RESULT IN ITS INABILITY TO RESIST THE LOAD IMPOSED BY A SEPARATED TUBE. THE STRUCTURAL LIMIT IS MET BY ANY TUBE WITH A 3600 CIRCUMFERENTI AL INDICATION WITH LESS THAN 92 F'ERCENT WALL PE OF OR BY AN AREA OF WALL REMAINING EQUAL TO OR GREATER THAN 135

. NOMINAL WALL THICKNESS (WHICH CORRESPONDS TO A REMAIAING CROSSECTIONAL AREA OF O.034 IN 2 ),

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