Catawba Units 1 & 2, License Amendment Request ...C.7 The design coolant velocity at the fine inner screen should be approxinmately 2.0 ft/sec. The available surface area used in determining

r I , .

JAMES R. MORRISDukeg Vice President

kEnergy, Catawba Nuclear Station

4800 Concord Rd. / CNO1 VPYork, SC 29745-9635

803 831 4251

803 831 3223 fax

March 29, 2007

U.S. Nuclear Regulatory CommissionDocument Control DeskWashington, DC 20555-001

Subject: Duke Power Company LLC d.b.a. Duke Energy Carolinas,LLC

Catawba Nuclear Station, Units 1 and 2Docket Nos. 50-413 and 50-414

License Amendment Request Revising Catawba, Units 1and 2 Commitments to USNRC Regulatory Guide 1.82,Revision 0, "Sumps For Emergency Core Cooling andContainment Spray Systems" and Revising TechnicalSpecification Surveillance Requirement (SR) 3.5.2.8and Associated Bases.

In accordance with the provisions of Section 50.90 of Title 10of the Code of Federal Regulations (10CFR), Duke Power CompanyLLC d.b.a. Duke Energy Carolinas, LLC (Duke) proposes a licenseamendment request (LAR) for the Facility Operating Licenses(FOL), Updated Final Safety Analysis Reports (UFSAR) andTechnical Specifications for Catawba Nuclear Station, Units 1and 2. The proposed changes will ensure that as the modifiedsump strainer assemblies are installed for each unit, thecurrent licensing basis is accurate.

The purpose of this license amendment request is two fold:

(1) : Change the licensing bases for the Catawba NuclearStation (CNS) Units 1 and 2 containment sumps, asstated in the CNS UFSAR, by revising commitments toUSNRC Regulatory-Guide 1.82, Revision 0, "Sumps. forEmergency Core Cooling and Containment Spray Systems."The proposed changes are needed to:

w eoomwww. duke-energy. corn

March 29, 2007Nuclear Regulatory CommissionPage 2

a. delete the requirement or implication that twophysically separated containment sumps (one foreach train of RHR/CSS) must be maintained;

b. eliminate the requirement for trash racks;

c. clarify the wording to replace "trash racks andscreens" with the word "strainers"; and

d. describe the required ECCS Sump Strainer AssemblySurveillance.

(2): Revise Catawba Technical Specification SurveillanceRequirement (SR) 3.5.2.8: The use of the revisedgeneric terminology reflects the replacement sumpconfiguration, which does not include trash racks.

Attachment 1 provides the existing UFSAR page for Catawba Units1 and 2, marked-up to show the proposed changes.

Attachment 2 provides existing Technical Specifications andBases pages for Catawba Units 1 and 2, marked-up to show theproposed change.

Attachment 3 provides Duke' s evaluation of the LAR whichcontains a description of the proposed changes, the technicalanalysis, the determination that this LAR contains NoSignificant Hazards Considerations, the basis for thecategorical exclusion from performing an EnvironmentalAssessment/Impact Statement, and Precedents.

As communicated by our November 1, 2006 letter, Catawba Unit 2will install the sump strainer modification to supportresolution of GSI 191 during its fall 2007 refueling outage.Catawba Unit 1 will install the sump strainer modificationduring its spring 2008 refueling outage.

Based on the fall outage date for Unit 2, Duke is requestingreview and approval of this license amendment request by October1, 2007. Duke has determined that the NRC' s standard 30-daygrace period will be acceptable for the implementation ofrevised Technical Specification SR 3.5.2.8.

IL


The proposed licensing basis changes will become effective aseach of the Catawba Units enters Mode 4 operations subsequent tocQmpleting the sump modifications required by USNRC GenericLetter 2004-02, "Potential Impact of Debris Blockage onEmergency Recirculation During Design Basis Accidents atPressurized-Water Reactors." Until such time as thosemodifications are completed, each Catawba Unit will comply withthe current licensing basis commitments to Regulatory Guide1.82, Revision 0, "Sumps for Emergency Core Cooling'andContainment Spray Systems."

Reprinted Catawba Technical Specification and Bases pages willbe provided to the NRC upon issuance of the approved amendments.

Revisions to the Catawba UFSAR, necessary to reflect approval ofthis submittal, will be made in accordance with 10CFR50.71(e).

In accordance with Duke internal procedures and the QualityAssurance Topical Report, the proposed amendment has beenreviewed and approved by the Catawba Plant Operations ReviewCommittees and the Duke Corporate Nuclear Safety Review Board.

Pursuant to 10CFR50.91, a copy of this LAR has been forwarded tothe appropriate South Carolina state officials.

There are no regulatory commitments included in this document orits associated attachments.

Please direct any questions you may have in this matter to A. P.Jackson (803) 831-3742.

.0


xc w/ Attachments:

W. D. TraversAdministrator, Region IIU.S. Nuclear Regulatory CommissionAtlanta Federal Center61 Forsyth Street, Suite 23T85Atlanta, GA 30303

A. T. SabischNRC Senior Resident InspectorCatawba Nuclear Station

J. F. Stang, Jr. (addressee only)NRC Senior Project Manager (MNS and CNS)U.S. Nuclear Regulatory CommissionMail Stop 0-8 H4AWashington, DC 20555-0001

H. J. Porter, Assistant DirectorDivision of Radioactive Waste ManagementBureau of Land and Waste ManagementDepartment of Health and Environmental Control2600 Bull StreetColumbia, SC 29201


James R. Morris affirms that he is the person who subscribed hisname to the foregoing statement, and that all the matters andfacts set forth herein are true and correct to the best of hisknowledge.

James R.Worris, Vice President, Catawba Nuclear Station

Subscribed and sworn to me: -Date

_ _ _'__, Notary Public

My commission expires: _ _-_ _ -_ __ _ _

Date

,VA11 0/50,1

o0 eax 0L C r//na../1-1 isr m /Ok1 &;'/X':~5 i/ ~w~

f

ATTACHMENT 1

Marked-Up Catawba UFSAR

UFSAR Chapter I Catawba Nuclear Station

DiscussionThe Contaimnent Recirculation Sump at Catawba is designed to fully meet the regulatory positions of theregulatory guide with modifications to positions C.4, 6, and 7 as stated below.

C.4 The floor level in the vicinity of the coolant sump location should not slope down toward thesmnp.

C.6 An outer trash rack should be provided to prevent large debris from reaching the fine innerscreen. The strength of the trash rack should be considered in protecting the inner screenfrom missiles and large debris.

C.7 The design coolant velocity at the fine inner screen should be approxinmately 2.0 ft/sec. Theavailable surface area used in determining the design coolant. velocity should be based on

Insert I one-half of the free surface area of the fine inner screen to conservatively account for partialblockage- No horizontal screen should be considered in determining available surface area.

Reciulatorv Guide 1.83Inservice Inspection of Pressurized Water Reactor Steam Generator Tubes (Revision 1, 7/75).

DiscussionWestinghouse and BWI steam generators are designed to permit access to tubes for inspection andlorplugging. The inservice inspection program is discussed in the Technical Specifications.

The BWI steam generator design complies with the regulatory position with the following clarifications:

The Regulatory Guide addresses both new and in-service components. The RSGs are new componentsand as such comply with the appropriate sections oftthis regulatory guide. Specifically C.L .a, C. 1.b, C_2-C.3.a, and C.4.a. A 100 percent baseline inspection of the RtSG is performed prior to the unit being putinto service. BWVI acceptance criteria exceeds the NRC guidelines for wall thickness reductions in thatBMWI limits wall thickness reductions to no more than 15% versus 20% allowed in the NRC guidelines.

Regulatory Guide 1.84Code Case Acceptability - ASME Section I11 Design and Fabrication (Revision 16, 5/80).

Discussion - WestinohouseI Westinghouse controls its suppliers to:

a- Limit the use of code cases to those listed in Regulatory Position C. 1 of the Regulatory Guide1.84 and 1.85 revision in effect at the time the equipment is ordered, except as allowed in item b.below.

b. Identif. and request permission for use of any code cases not listed in Regulatory Position C_ I ofthe Regulatory Guide 1.84 and 1.85 revision in effect at the time the equipment is ordered, whereuse of such code cases is needed by the supplier.

c. Permit continued use of a code case considered acceptable at the time of equipment order, wheresuch code case was subsequently annulled or amended.

1.7 -2,8 (24 APR 2006)

INSERT 1

Upon completion of the ECCS sump strainer assembly modificationsduring outage 2EOC15 for Unit 2 and lEOC17 for Unit 1, thefollowing Discussion section will apply:

Discussion

The Containment Recirculation Sump at Catawba is designed tofully meet the regulatory positions of the regulatory guide withmodifications to positions as shown below:

0.1 A configuration utilizing the containment sidestructure and floor as the intake structure boundaryis considered acceptable for those plants in whichthe post LOCA water level in the containment issufficiently high, thus making additional sumpdepressions in the floor non-productive. Redundanceshould be provided by two separate suction pipes.

0.2 The containment recirculation intake structure andsuction piping should be protected from high energypiping systems to the extent practical to precludedamage by whipping pipes or high-velocity jets ofwater or steam. ECCS redundancy begins at the sumpsuction pipes, and the need to provide ECCS/CSStrain separation within the common sump strainer isnot required in the absence of any credible loadswhich could fail the sump strainer.

C.3 The sumps should be located on the lowest floorelevation in the containment exclusive of thereactor vessel cavity. A substantial strainer isprovided to filter debris from recirculated coolant.The polar crane wall acts as a primary filter toprevent large debris from reaching the sump strainerassembly.

0.4 Exception is taken to this position.

C.6 The location of the sump strainer assembly shouldprovide protection from missiles and large debris.The polar crane wall can be credited as a primaryfilter to prevent large debris from reaching thesump strainer.

Revised Catawba UFSAR Page

C.7 A sump strainer design (i.e., size and shape) shouldbe chosen that is intended to preclude the loss ofNPSH to ECCS and CSS pumps from debris blockageduring the period that the ECCS is required tooperate and maintain long-term cooling.

C.8 Vortex suppression should be provided to precludeair entrainment in the recirculated coolant.

0.9 Sump strainers should be designed to withstand thevibratory motion of seismic events without loss ofstructural integrity.

C.10 The size of openings in the sump strainer should bebased on the minimum restrictions found in systemsserved by the sump. The minimum restriction shouldtake into account the overall operability of thesystem served.

C.12 Materials for the sump strainers should be selectedto avoid degradation during periods of inactivityand operation and should have a low sensitivity toadverse effects such as stress assisted corrosionthat may be induced by chemically reactive sprayduring LOCA conditions

C.13 The sump strainer should include access openings tofacilitate inspection.

0.14 Inservice inspection requirements for coolant sumpcomponents (the strainer assembly) should includethe following:

a. Coolant sump components should be inspectedduring every refueling period downtime, and

b. The inspection should be a visual examinationof the components for evidence of structuraldistress or corrosion.

ATTACHMENT 2Marked-Up Catawba

Technical Specifications and Bases

I

, 1

ECCS - Operating

SURVEILLANCE REQUIREMENTS (continued)

3.5.2

SURVEILLANCE- FREQUENCY

SR 3.5.2.6 Verify each ECCS pump starts automatically on an actual 18 monthsor simulated actuation signal.

SR 3.5.2.7 Verify, for each ECCS throttle valve listed below, each 18 monthsposition stop is in the correct position.

Centrifugal Charging Safety InjectionPump Injection Throttle Pump ThrottleValve Number Valve Number

N114 N1164N116 N1166N118 N1168N120 N1170

SR 3.5.2.8 Verify, by .. ,! inspection, v leach ECCS train containment 18 monthssUmp suction inlet is not restricted by debris and thesuction inlet trash racks and screens show no evidence

Of structural distress or abnormal corrosion.

Delete and Insert:Verify, by visual inspection, that the ECCS containment sump strainerassembly is not restricted by debris and shows no evidence of structuraldistress or abnormal corrosion.

Catawba Units 1 and 2 3.5.2-12 Amendment Nos. 173i!65

ECCS - OperatingB 3.5.2

BASES

SURVEILLANCE REQUIREMENTS (continued)

SR 3.5.2.5 and SR 3.5.2.6

These Surveillances demonstrate that each automatic ECCS valveactuates to the required position on an actual or simulated SI andContainment Sump Recirculation signal and that each ECCS pump startson receipt of an actual or simulated SI signal. This Surveillance is notrequired for valves that are locked, sealed, or otherwise secured in therequired position under administrative controls. The 18 month Frequencyis based on the need to perform these Surveillances under the conditionsthat apply during a plant outage and the potential for unplanned planttransients if the Surveillances were performed with the reactor at power.The 18 month Frequency is also acceptable based on consideration ofthe design reliability (and confirming operating experience) of theequipment. The actuation logic is tested as part of ESF Actuation Systemtesting, and equipment performance is monitored as part of the InserviceTesting Program.

SR 3.5.2.7

The position of throttle valves in the flow path on an SI signal isnecessary for proper ECCS performance. These valves have mechanicallocks to ensure proper positioning for restricted flow to a ruptured coldleg, ensuring that the other cold legs receive at least the requiredminimum flow. The 18 month Frequency is based on the same reasonsas those stated in SR 3.5.2.5 and SR 3.5.2.6.

SR 3.5.2.8

Periodic inspections of the containment sump suction inlet ensure that itis unrestricted and stays in proper operating condition. The 18 monthFrequency is based on the need to perform this Surveillance under theconditions that apply during a plant outage and on the need to haveaccess to the location. This Frequency has been found to be sufficient todetect abnormal degradation and is confirmed by operating experience.

Insert 1

INSERT 1

Upon completion of the ECCS sump strainer assemblymodifications during outage 2EOC15 for Unit 2 and lEOC17 forUnit 1, the following SR Bases will apply:

Periodic inspections of the ECCS containment sump strainerassembly (consisting of modular tophats, grating, plenums, andwaterboxes) ensure it is unrestricted and remains in properoperating condition. Inspections will consist of a visualexamination of the exterior surfaces of the strainer assemblyfor any evidence of debris, structural distress or abnormalcorrosion. The intent of this surveillance is to ensure theabsence of any condition which could adversely affect strainerfunctionality. Surveillance performance will not requireremoval of any tophat modules or grating, but the strainerexteriors shall be visually inspected. This surveillance is nota commitment to inspect 100 percent of the surface area of alltophats, but a sufficiently detailed inspection of exteriorstrainer surfaces is required to establish a high confidencethat no adverse conditions are present. The 18 month Frequencyis based on the need to perform this Surveillance under theconditions that apply during a plant outage and on the need tohave access to the location. This Frequency has been found tobe sufficient to detect abnormal degradation and is confirmedby operating experience.

ATTACHMENT 3Evaluation for License Amendment Request

1.0 GENERAL DESCRIPTION .............................................................................. 22 .0 BA CKGRO UN D ................................................................................................ 2

2.1 Current ECCS Sump Design ............................................................ 42.2 New ECCS Sump Strainer Assembly Design .............................. 5

3 .0 PRO PO SED CHANGES ...................................................................................... 63.1 Current Catawba Licensing Basis ............................................... 63.2 Proposed Technical Specification and Bases Changes ..... 73.3 Proposed Revisions to the Catawba UFSAR .......................... 9

4.0 TECHNICAL ANALYSIS and DISCUSSION ........................................... 204 .1 O v e rv i e w .................................................................................................... 204.2 Trash Racks Elimination and ECCS Sump StrainerAssembly Surveillance Discussion ..................................................... 21

4.3 Consideration of ECCS Strainer Single Failure ............. 235.0 REGULATORY SAFETY ANALYSIS ........................................................... 27

5.1 No Significant Hazards Consideration ................................ 275.2 Applicable Regulatory Requirements/Criteria: ................. 31

6.0 ENVIRONMENTAL CONSIDERATIONS ......................................................... 337 .0 PR E C E DEN T S ................................................................................................. 338 .0 REFERENCES ................................................................................................. 349.0 FIGURES

Figure 1: Current ECCS Sump Design DrawingFigure 2: Modified ECCS Sump Design Drawings and Photo

Page 1 of 34

1.0 GENERAL DESCRIPTION

Pursuant to 10CFR50.90, Duke Energy Carolinas, LLC (Duke)proposes a license amendment request (LAR) for the FacilityOperating License (FOL) and Updated Final. Safety AnalysisReport (UFSAR) for Catawba Nuclear Stations, Units 1 and 2.

The proposed license amendment seeks to revise existingcommitments to USNRC Regulatory Guide 1.82, Revision 0,"'Sumps for Emergency Core Cooling and Containment SpraySystems," as stated in the Catawba Nuclear Station (CNS)Unit 1 and Unit 2 UFSAR.

The proposed changes will ensure that as the modified sumpstrainer assemblies are installed at each of the twoCatawba Units, the current licensing basis is accurate. Thenew design consists of one strainer feeding two trains ofsuction piping.

Additionally, the License Amendment Request seeks to reviseCatawba Technical Specification Surveillance Requirement(SR) 3.5.2.8 by replacing the phrase "trash racks andscreens" with the term "strainers". The use of the revisedgeneric terminology reflects the replacement sumpconfiguration, which does not include trash racks, as wellas the existing unmodified design, thus negating the needfor the inclusion of a note to distinguish inspectionrequirements for each of the affected Units which wouldrequire an administrative change to remove at a later date.

Also, a revision of the surveillance process for the new*strainer assembly is included. This revision recognizesthat the new strainer assembly will present challenges to avisual inspection.

2.0 BACKGROUND

The Emergency Core Cooling System (ECCS) is designed tocool the reactor core and provide shutdown capabilityfollowing initiation of the following accident conditions:

1. Loss of Coolant Accident (LOCA) including a pipe breakor a spurious relief or safety valve opening in the

Page 2 of 34

RCS which would result in a discharge larger than thatwhich could be made up by the normal make-up system.

2. Rupture of a control rod drive mechanism causing a rodcluster control assembly ejection accident.

3. Steam or feedwater system break accident including apipe break or a spurious relief or safety valveopening in the secondary steam system which wouldresult in an uncontrolled steam release or a loss offeedwater.

4. A steam generator tube rupture.

The primary function of the ECCS is to remove the storedand fission product decay heat from the ;reactor core duringaccident conditions.

During Modes 1, 2, and 3, Tech Spec 3.5.2 requires anOPERABLE flow path capable of taking suction from theRefueling Water Storage Tank on a Safety Injection Signaland automatically transferring suction to the containmentsump during the recirculation phase of operation.

The flow path of containment sump water in recirculationthrough the Containment Spray and Emergency Core CoolingSystems is described in the following paragraphs.

Following a large break LOCA (LBLOCA), water exiting theContainment Spray System (CSS) spray nozzles cools theupper containment to reduce containment pressure andcollects in the refueling canal. Six (6) drains in thebottom of the canal allow the spray water to return tolower containment, inside the Crane Wall, where it re-joinsthe water in the recirculation sump and the ice meltexiting the Ice Condenser drains. Since the ContainmentSump Recirculation Screen Assembly is located in the"tunnel" area outside the Crane Wall, water must then passthrough numerous penetrations in the lower portion of theCrane Wall. Water entering the tunnel area must then passcircumferentially around the tunnel area until it reachesthe Sump Recirculation Screen.

In addition to CSS spray, water is injected directly intothe primary system via the ECCS to provide core cooling.For this injection flow path, water must pass through theResidual Heat Removal (RHR) pumps, RHR Heat Exchangers,

Page 3 of 34

Safety Injection Pumps, and Centrifugal Charging Pumpsbefore being injected to cool the fuel assemblies. Alongthe way it must pass through numerous gate, globe, check,and throttling valves. The water exits the primary systemat the break location (i.e., LBLOCA) and returns to lowercontainment, inside the crane wall, where it re-joins thewater in the recirculation sump.

For some small break LOCAs (SBLOCA), the CSS spray systemis not actuated; however, the ECCS actuates to inject waterdirectly into the primary system to provide core cooling.The water being injected is expected to fill thepressurizer and overflow to the pressurizer relief tank(PRT). If the event continues, the PRT rupture disc willrelieve and allow water to again return to lowercontainment, where it flows through the crane wall *to there-join the water in the recirculation sump.

2.1 Current ECCS Sump Design

The Catawba containment sumps provide a long termsource of cooling water to the Residual Heat Removaland the Containment Spray (CS) system. In general, thefloor grade of the Containment Building (552 footelevation at Catawba) is considered the containmentsump. The containment sump collects ice condensermelt, reactor coolant system spill [ includingEmergdncy Core Cooling System (ECCS)' injection water],and containment spray water and provides water for theECCS recirculation phase. Two suction lines (the ECCSrecirculation lines) are provided. Each ECCSrecirculation line supplies one train of ECCS and onecontainment spray pump. The ECCS recirculation linesare located on either side of the 1800 azimuth in theUnit 1 or 2 Reactor Buildings.

Each "sump" screen assembly consists of a horizontalsolid top and filtering screen panels which extendalmost to the floor. Above the ECCS intake pipe, thehorizontal solid top of the screen assembly is atapproximately 555' elevation. Beyond the ECCS intakepipe, the horizontal solid top extends slightly higherto approximately 558' elevation. The screen panelscontain an outer trash rack which prevents largedebris from reaching the inner fine screen. The finescreen prevents particles which are large enough to

Page 4 of 34

impair ECCS or containment spray performance frombeing drawn into these systems. The fine screen meshis sized to preclude any particle larger than 1/8" indiameter. This size is significantly smaller than thesize needed to prevent clogging of the NS spraynozzles. The top of the screen assembly containsholes which are 1/8" in diameter. This featureensures that the assemblies are self venting as thewater covers the top. Sump Recirculation Screenperformance, including the description of debristransport through the Containment, is discussed andevaluated in the Catawba UFSAR Section 6.2.2.2. Asummary drawing of this structure also appears in theUFSAR, Figure 6-111. Reference Figure 1.

2.2 New ECCS Sump Strainer Assembly Design

The Catawba modification removes the original ECCSSump structure described above and replaces it with a*structure consisting of tube modules (top-hats) madeof stainless steel, having two layers of perforatedplate for straining debris from the water. (ReferenceFigure 2.) The openings in the perforated plate do notexceed 3/32 inch diameter. The RHR/CSS recirculationlines are connected to the main plenum of the strainerassembly using 18 inch piping. Horizontal vortexsuppressors will be installed above the top-hatstrainer assemblies.

The Catawba strainer will be installed entirely insidethe pipechase outside the polar crane wall. There areno pipe whips .or water/steam jet loads projected tooccur within the Catawba pipechase.

These new sump structures are nuclear safety-related,QA Condition 1 assemblies designed to withstand safeshutdown earthquake loadings and protected fromtornado missiles by virtue of being located within theContainment Building which is, in turn, protected bythe seismically designed Reactor Building. Thesestructures are passive assemblies qualified for alldesign environmental conditions in the sump.

The objective of the new strainer design is to provideacceptable flow with minimal head loss at thespecified debris loads and to ensure adequate NPSH to

Page 5 of 34

the RHR/CSS Pumps during the post-LOCA RecirculationPhase. The new strainer offers approximately 2000square feet of surface area versus the original 135square feet total for the original sump screens. Whencompleted, the installation of the revised sump designis intended to resolve concerns associated with GSI-191. The changes made enhance the existing design byproviding a larger surface area for the filtration ofdebris.

3.0 PROPOSED CHANGES

3.1 Current Catawba Licensing Basis

NUREG-0954, "Safety Evaluation Report by the Office ofNuclear Reactor Regulation US Nuclear RegulatoryCommission in the Matter of Duke Power Company CatawbaNuclear Station Units 1 and 2," Supplement 2, Section6.3.4.1 "Preoperational testing", contains thefollowing statement: "In a letter dated January 14,1983, the applicant provided a detailed comparisonbetween the configurations of the McGuire and Catawbasumps." "... Confirmatory Issue 23 is resolved."Confirmatory Issue 23 required a detailed comparisonof McGuire versus Catawba ECCS sump and screenparameters to demonstrate that McGuire scale modeltesting applied to Catawba.

Catawba UFSAR Chapter 1.7, "Regulatory Guides," statesthat the Containment Recirculation Sump at Catawba isdesigned to fully meet the regulatory positions ofRegulatory Guide 1.82, Rev 0, with modifications topositions C.4, 6, and 7 as stated below:

C.4 - The floor level in the vicinity of thecoolant sump location should not slope toward thesump.

C. 6- The outer trash rack should be provided toprevent large debris from reaching the fine innerscreen. The strength of the trash rack should beconsidered in protecting the inner screen frommissiles and large debris.

Page 6 of 34

C.7 - The design coolant velocity at the fineinner screen should be approximately 2.0 ft/sec.The available surface area used in determiningthe design coolant velocity should be based onone-half of the free surface area of the fineinner screen to conservatively account forpartial blockage. No horizontal screen should beconsidered in determining available surface area.

Chapter 6 of the UFSAR states:

The two screen assemblies and the vortexsuppressor are located between the polar cranewall and the containment vessel. Piping subjectto breaks that result in the need forrecirculation capabilities are located inside thecrane wall and are thus isolated from therecirculation sump screen assemblies.

3.2 Proposed Technical Specification and BasesChanges

The proposed license amendment seeks to revise CatawbaTechnical Specification Surveillance Requirement (SR)3.5.2.8 to reflect the ECCS Sump modification. Thismodification encloses the ECCS Containment Sumpsuction pipe inlets, thus making them an integral partof the strainer assembly.

Catawba Technical Specification SR 3.5.2.8 currentlystates:

Verify, by visual inspection, each ECCS traincontainment sump suction inlet is not restrictedby debris and the suction inlet trash racks andscreens show no evidence of structural distressor abnormal corrosion.

It is proposed that Catawba Technical Specification SR3.5.2.8 be revised to state:

Verify, by visual inspection, that the ECCScontainment sump strainer assembly is notrestricted by debris and shows no evidence ofstructural distress or abnormal corrosion.

Page 7 of 34

The Bases document for Catawba Technical SpecificationSR 3.5.2.8 currently states:

Periodic inspections of the containment sumpsuction inlet ensure that it is unrestricted andstays in proper operating condition. The 18 monthFrequency is based on the need to perform thisSurveillance under the conditions that applyduring a plant outage and on the need to haveaccess to the location. This Frequency has beenfound to be sufficient to detect abnormaldegradation and is confirmed by operatingexperience

It is proposed that the Catawba TechnicalSpecification Bases document for SR 3.5.2.8 be revisedto add:

Upon completion of the ECCS sump strainerassembly modifications during outage .2EOC15 forUnit 2 and lEOC17 for Unit 1, the following SRBases will apply:

Periodic inspections of the ECCS containment sumpstrainer assembly (consisting of modular tophats,grating, plenums, and waterboxes) ensure it isunrestricted and remains in proper operatingcondition. Inspections will consist of a visualexamination of the exterior surfaces of thestrainer assembly for any evidence of debris,structural distress or abnormal corrosion. Theintent of this surveillance is to ensure theabsence of any condition which could adverselyaffect strainer functionality. Surveillanceperformance will not require removal of anytophat modules or grating, but the strainerexteriors shall be visually inspected. Thissurveillance is not a commitment to inspect 100percent of the surface area of all tophats, but asufficiently detailed inspection of exteriorstrainer surfaces is required to establish a highconfidence that no adverse conditions arepresent. The 18 month Frequency is based on theneed to perform this Surveillance under theconditions that apply during a plant outage and

Page 8 of 34

on the need to have access to the location. ThisFrequency has been found to be sufficient todetect abnormal degradation and is confirmed byoperating experience.

These changes are required to reflect constraints inthe new strainer assembly design. A detailedjustification of this change is included in theTechnical Analysis and Discussion portion of thisdocument under the header: "Trash Racks Eliminationand ECCS Sump Strainer Assembly SurveillanceDiscussion."

3.3 Proposed Revisions to the Catawba UFSAR

Revisions to the Catawba UFSAR related to the strainermodification will be made through the normal UFSARupdate process as the modifications are installed.However, it is proposed to revise Section 1.7 of theUFSAR due to the upcoming ECCS sump strainer assemblymodification to reflect a change in the site'scommitments to Regulatory Guide 1.82, "Sumps forEmergency Core Cooling and Containment SpraySystems",Rev.0. The attached Table 1, is included atthe end of this section to provide a vehicle for easycomparison of the regulatory guide criterion, currentexceptions, and the proposed revision.

Page 9 of 34

Table 1Comparing Current and Future State Regulatory Guide 1.82, Rev.0 Criterion

Reg. Guide 1.82, Rev 0 Current Criteria Proposed Criteria Justification for theRegulatory Position Revision

C.l: A minimum of two The current A configuration The current exception tosumps should be commitment conforms utilizing the Regulatory Position C.l isprovided, each with to the Regulatory containment side revised to reflect the newsufficient capacity to Position. structure and floor as ECCS containment sumpserve one of the the intake structure strainer design. Redundancyredundant halves of boundary is considered of passive strainerthe ECCS and CSS acceptable for those components located insystems plants in which the shielded areas (i.e., not

post LOCA water leve subject to failure), is notin the containment is required to meet the GDCsufficiently high, criterion of sustained corethus making additional cooling capability. Theresump depressions in are no credible passivethe floor non- failures.productive. Redundanceshould be provided bytwo separate suctionpipes.

Page 10 of 34

Table 1Comparing Current and Future State Regulatory Guide 1.82, Rev.0 Criteria I


C.2: Redundant sumps The current The containment The current exception toshould be physically .commitment conforms recirculation intake Regulatory Position C.2 isseparated from each to the Regulatory structure and suction revised to clearly stateother and from high- Position. piping should be Duke's position fhat ECCSenergy piping systems protected from high redundancy begins at the sumpby structural barriers energy piping systems suction pipes, and the needto the extent to the extent to provide ECCS/CSS trainpractical, to preclude practical to preclude separation within the commondamage to the sump damage by whipping sump strainer is not requiredintake filters by pipes or high-velocity due to the absence of anywhipping pipes or jets of water or credible loads which couldhigh-velocity jets of steam. ECCS redundancy fail the ECCS containmentwater or steam begins at the sump sump strainer.

suction pipes, and theneed to provide Reference the "ConsiderationECOS/OSS train of ECCS Strainer Singleseparation within thecommon sump strainer

is not required in theabsence of anycredible loads whichcould fail the sumpstrainer.

Page 11 of 34

Table IComparing Current and Future State Regulatory Guide 1.82, Rev.0 Criteria

Reg. Guide 1.82, Rev 0Regulatory Position

Current Criteria Proposed Criteria Justification for theRevision

C.3: The sumps shouldbe located on thelowest floor elevationin the containmentexclusive of thereactor vessel cavity.At a minimum, the sumpintake should beprotected by twoscreens (1) an outertrash rack and (2) afine inner screen. Thesump screens shouldnot be depressed belowthe floor elevation

The currentcommitment conformsto the RegulatoryPosition.

The sumps should belocated on the lowestfloor elevation in thecontainment exclusiveof the reactor vesselcavity. A substantialstrainer is providedto filter debris fromrecirculated coolant.The polar crane wallacts as a primaryfilter to preventlarge debris fromreaching the sumpstrainer assembly.

A new exception to RegulatoryPosition C.3 is requested inorder to reflect the new sumpstrainer design. Theintended functions of thetrash rack are provided byalternate means. Referencethe "Trash Racks Eliminationand ECCS Sump StrainerAssembly" discussion.

The complex geometry of the

C.4: The floor level The floor level in Exception is taken to new strainer design

in the vicinity of the the vicinity of the this position. accommodates settling debris

coolant sump location coolant sump location without affecting the

should slope gradually should not slope performance adversely.

down away from the toward the sumpsump

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Table 1Comparing Current and Future State Regulatory Guide 1.82, Rev.0 Criteria

Reg. Guide 1.82, Rev 0 -Current Criteria Proposed Criteria Justification for theRegulatory Position Revision

C.5: All drains from The current No Changes are Not Required.the upper regions of commitment conforms required.the reactor building to the Regulatoryshould terminate in Position.such a manner thatdirect streams ofwater, which maycontain entraineddebris, will notimpinge on the filterassemblies

C.6: A vertically The outer trash rack The location of the A new exception to Regulatorymounted outer trash should be provided to sump strainer assembly Position C.6 is requested torack should be prevent large debris should provide reflect the new ECCSprovided to prevent from reaching the protection from containment sump strainerlarge debris from fine inner screen. missiles and large design. The intendedreaching the fine The strength of the debris. The polar functions of the trash rackinner screen. The trash rack should be crane wall can be are provided by alternatestrength of the trash considered in credited as a primary means. Reference the "Trashrack should be protecting the inner filter to prevent Racks Elimination and ECCSconsidered in screen from missiles large debris from Sump Strainer Assembly"protecting the inner and large debris reaching the sump discussion.screen from missiles strainer.and large debris

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Table 1Comparing Current and Future State Regulatory Guide 1.82, Rev.0 Criteria K.

Reg. Guide 1.82, Rev 0 Current Criteria I Proposed Criteria Justification for the

Regulatory Position Revision

C.7: A verticallymounted fine innerscreen should beprovided. The designcoolant velocity atthe inner screenshould beapproximately 6 cm/sec(0.2ft/sec). Theavailable surface areaused in determiningdesign coolantvelocity should bebased on 1/2 of thefree surface area ofthe fine inner screento conservativelyaccount for partialblockage. Only thevertical screensshould be consideredin determiningavailable surface area

The design coolantvelocity at the fineinner screen shouldbe approximately 2.0ft/sec. The available*surface area used indetermining thedesign coolantvelocity should bebased on one-half ofthe free surface areaof the fine innerscreen toconservativelyaccount for partialblockage. Nohorizontal screenshould be consideredin determiningavailable surfacearea

A sump strainer design(i.e., size and shape)should be chosen thatis intended topreclude the loss ofNPSH to ECCS and CSSpumps from debrisblockage during theperiod that the ECCSis required to operateand maintain long-termcooling.

The current exception to RegulatoryPosition C.7 is revised to reflectthe new ECCS containment sumpstrainer design and eliminate non-conservatisms. The main thrust ofGSI-191 and Generic Letter 2004-02is the recognition that theimplicit assumption contained inthe guidance (directing anevaluation of strainer surface areathat incorporates 50% blockage) isnon-conservative. Rather thanusing a pre-set blockage 'rule ofthumb,' licensees are expected toassess strainer performance usingevaluations that take plant-specific factors such as debrissources, flow rates and NPSHmargins into account. The modifiedECCS containment sump assembly wasdesigned using the methodologycontained in NEI 04-07,"Pressurized Water Reactor SumpPerformance EvaluationMethodology," Rev 0, and theassociated NRC Safety EvaluationReport. The completion of chemicaleffects studies and otherevaluations is required to confirmthat Catawba's ECCS recirculationfunctions under debris loadingconditions will be in fullcompliance with the ApplicableRegulatory Requirements section ofNRC Generic Letter 2004-02.

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C.8: A solid top deck The current Vortex suppression A new exception tois preferable, and the commitment conforms should be provided to Regulatory Guide 1.82, Rev.top deck should be to the Regulatory preclude air 0, Regulatory Position C.8designed to be fully Position. entrainment in the is proposed so as to reflectsubmerged after a LOCA recirculated coolant. the new sump strainerand completion of the design. Vortex suppressionsafety injection and the elimination of air

entrainment will be providedby gratings. The efficacy ofthe horizontal gratingserving as a vortexsuppressor was demonstratedthrough qualificationtesting.

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Reg. Guide 1.82, Rev 0 Current Criteria Proposed Criteria Justification for the

Regulatory Position Revision

C.9: The trash rack The current Sump strainers should A new exception to Regulatory

and screens should be commitment conforms be designed to Position C.9 is requested to

designed to withstand to the Regulatory withstand the reflect the new ECCS

the vibratory motion Position. vibratory motion of containment sump strainer

of seismic events seismic events without design. The intended

without loss of loss of structural functions of the trash rack

structural integrity. integrity are provided by alternatemeans. Reference the "Trash

Racks Elimination and ECCSSump Strainer Assembly"discussion.

C.10: The size of The current The size of openings A new exception to Regulatory

openings in the fine commitment conforms in the sump strainer Position C.10 is requested to

screen should be based to the Regulatory should be based on the reflect the new ECCSon the minimum Position. minimum restrictions containment sump strainer

restrictions found in found in systems design. The new strainer

systems served by the served by the sump. design does not rely on fine

sump. The minimum The minimum screens. Thus, the reference

restriction should restriction should to a "fine screen" is

take into account the take into account the replaced by a reference to a

overall operability of overall operability of "sump strainer."the system served the system served.

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C.11: Pump intake The current No change to the The strainer assembly islocations in the sump commitment conforms criteria is requested. designed to meet thisshould be carefully to the Regulatory criterion.considered to prevent Position.degrading effects suchas vortexing on thepump performance

C.12: Materials for The current Materials for the sump A new exception to Regulatorytrash racks and commitment conforms strainers should be Position C.12 is requested toscreens should be to the Regulatory selected to avoid reflect the new ECCSselected to avoid Position. degradation during containment sump strainerdegradation during periods of inactivity design. The intendedperiods of inactivity and operation and functions of the trash rackand operation and should have a low are provided by alternateshould have low sensitivity to adverse means. Reference the "Trashsensitivity to adverse effects such as stress Racks Elimination and ECCSeffects such as assisted corrosion Sump Strainer Assembly"stress-assisted that may be induced by discussion.corrosion that may be chemically reactiveinduced by the spray during LOCAchemical reactive conditions.spray during LOCAconditions

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Table IComparing Current and Future State Regulatory Guide 1.82, Rev.0 Criteria


C.13: The trash rack The current The sump strainer A new exception to Regulatoryand screen structure commitment conforms should include access Position C.13 is requested toshould include access to the Regulatory openings to facilitate reflect the new ECCSopenings to facilitate Position. inspection, containment sump strainerinspection of the design. The intendedstructure and pump functions of the trash racksuction intake are provided by alternate

means. The suction intakesare internal to the strainerassembly with the new design.Reference the "Trash RacksElimination and ECCS SumpStrainer Assembly"discussion.

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Reg. Guide 1.82, Rev 0 Current Criteria Proposed Criteria j Justification for the

Regulatory Position_ Revision

C.14: Inservice The current Inservice inspection A new exception to Regulatory

inspection commitment conforms requirements for Position C.14 is requested to

requirements for to the Regulatory coolant sump reflect the new ECCS

coolant sump Position. components (the containment sump strainer

components (trash strainer assembly) design. The intended

racks, screens, and should include the designs the tendedfunctions of the trash rack

pump suction inlets) following: are provided by alternateshould include the means. Reference the "Trashfollowing: a. Coolant sump Racks Elimination and ECCS

components should Sump Strainer Assembly"

a. Coolant sump be inspected during discussion.components should every refuelingbe inspected period downtime,during every andrefueling perioddowntime, and b. The inspection

should be a visualb. The inspection examination of the

should be a visual components forexamination of the evidence ofcomponents for structural distressevidence of or corrosion.structuraldistress orcorrosion.

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I I

4.0 TECHNICAL ANALYSIS and DISCUSSION

4.1 Overview

Generic Letter 2004-02, "Potential Impact of DebrisBlockage on Emergency Recirculation During DesignBasis Accidents at Pressurized-Water Reactors," statesthat the current 50% screen blockage assumptionidentified in Regulatory Guide (RG) 1.82, Revision 0,"Sumps for Emergency Core Cooling and ContainmentSpray Systems," should be replaced with a morecomprehensive means of assessing debris effects on aplant-specific basis. The 50% screen blockageassumption did not require a plant-specific evaluationof the debris-blockage potential and may result in anon-conservative analysis for screen blockage effects.

As stated in Duke's letters of March land September1, 2005, Catawba confirmed the Emergency Core CoolingSystem (ECCS) and Containment Spray System (CSS)recirculation functions under debris loadingconditions would be in compliance with the regulatorypositions listed in the Regulatory RequirementsSection of Generic Letter 2004-02 by December 31,2007. The design of the modified containment sumpstructure will accommodate the effects of debrisloading as determined by baseline and refinedevaluations specific to Catawba. These evaluationsuse the guidance of NEI 04-07, "Pressurized WaterReactor Sump Performance Evaluation Methodology,"Revision 0, dated December 2004, as amended by theNRC' s Safety Evaluation Report.

As communicated in the November 1, 2006 letter,Catawba Unit 2 will install the sump strainermodification to support the resolution of GSI 191during its fall 2007 refueling outage. As discussed inthe same letter, Catawba Unit 1 will install the sumpstrainer modification prior to entry into Mode 4operations after May 19, 2008.

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4.2 Trash Racks Elimination and ECCS Sump StrainerAssembly Surveillance Discussion

Generically, as discussed in Regulatory Guide 1.82,Rev. 0, the design functions of trash racks are toprotect the fine inner screens structurally and toprevent large debris from reaching the fine innerscreens.

Duke has determined trash racks tobe unnecessarybased on the following considerations,:

1. Regulatory Guide 1.82 position regarding trashracks is predicated on the broad range ofpossible sump locations for various PWRcontainment designs.

2. Catawba' s sump strainer is located entirelywithin the pipechase area. As a result, it willnot be subjected to missile loads, jetimpingement, or pipe whip. It is thereforeconcluded that structural protection offered bytrash racks is not a design function required forthe replacement strainer design. Thus, preventinglarge debris from reaching the fine innerscreen/strainer elements is the only potentialfunction that would be served by trash racks.

3. All debris-laden flow to the strainer is firstfiltered by passage through crane wallpenetrations.

4. Most of the debris that might transport throughthe crane wall and most of the large debrisgenerated in the pipechase must traverse atorturous flow path before nearing the modifiedsump strainer due to the large number ofstructures and interferences that would providecapture of large debris.

These containment building and modified sump strainerfeatures effectively provide the design function oftrash racks (mitigating debris transport to the ECCSSump Strainer) and negate the need for trash racks atthe sump intake.

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The proposed license amendment seeks to revise CatawbaTechnical Specification Surveillance Requirement (SR)3.5.2.8 to reflect the ECCS containment sumpmodification. This modification encloses thecontainment sump suction inlet, thus making it anintegral part of the strainer assembly. The use ofthe term "strainers" reflects the replacement sumpconfiguration, which does not include trash racks.The use of the term "ECCS containment sump strainerassembly" allows the surveillance to apply to theexisting unmodified ECCS containment sump screen aswell as the new modified sump strainer.

The proposed changes modify the requirements of SR3.5.2.8 by removal of the word "train". The word"train" is no longer required since the new design hasone large strainer assembly feeding two trains ofsuction piping.

The terminology change from "trash racks and screens"to "strainers" provides a more appropriate,, andgeneric description of the new configuration thatstrains through perforated stainless steel plates.The modification, which adds the new strainer assemblyto each unit, is being designed based on inputs fromevaluations completed or to be done in response toGeneric Letter 2004-02. The new strainers arefunctionally equivalent to trash racks and screens formeeting the requirements of 10CRF50.46(b) (5) for longterm cooling. The use of the word "ECCS containmentsump strainer assembly" will not affect theimplementation of SR 3.5.2.8 for the unmodified unit.

The statement: "This surveillance is not a commitmentto inspect 100 percent of perforated plate area" isdue to the size, complexity, and location of the newstrainer assembly. Normal inspection areas will bedefined as those regions of the strainer assembly thatcan be accessed by an inspector for a normal visualinspection without disassembling the strainer assemblyor the protective grating located above the strainers.The intent of this surveillance is to ensure theabsence of any condition which could adversely affectstrainer functionality. Gratings located above thestrainers will be installed per criterion C.8 of

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Regulatory Guide 1.82, "Sumps for Emergency CoreCooling and Containment Spray Systems",Rev.0. Due tothe larger strainer assembly sizei some of the gratingand portions of the strainers will be against theouter wall of the pipechase. Thus, some of the tophat assemblies, portions of top hat assemblies, andportions of the plenums will be inaccessible withoutdisassembling the structure.

The gratings for vortex suppression, while presentinga challenge to the inspection, also serve to keepforeign material from reaching the strainers duringnormal operation and during outages. The strainerassembly will be carefully installed with cleanlinesschecks throughout the process. Once the entirestrainer assembly is installed with vortex suppressiongrating in place there will be no mechanism duringnormal operation to foul the strainers with debris.Inspecting the. entire surface area of the strainerassembly during each outage would put the strainers atrisk of damage when the protective grating over thestrainers was disassembled out of the way to allowinspection of the covered area. Limiting the visualinspection to regions that do not require disassemblywill also help minimize the dose to individualsperforming the inspection. Since the strainers areconstructed of stainless steel it is very unlikelythat they would corrode during normal operation. Asufficiently detailed inspection of the exteriorstrainer surfaces to establish a high confidence thatno adverse conditions are present using normal visualinspection techniques, as described above, will meetthe goal of assuring that the strainer units remainclean and have no structural distress or abnormalcorrosion.

4.3 Consideration of ECCS Strainer Single Failure

Regulatory Guide 1.82, Rev. 0, includes criteria forthe physical separation of containment sumps assumingthe potential for damage exists due to structuralinteraction (missiles, pipe whip) or otherconsequences (jet impingement) following an initiatingevent requiring subsequent use of the sump. RegulatoryGuide 1.82, Revision 3, contains the following

Paqe 23 of 34

statement on page 1.82-6: "Consistent with the plantlicensing basis single-failure criterion, redundantECC Sumps and sump outlets should be separated to theextent practical to reduce the possibility that asingle event could render both sumps inoperable.

Catawba' s licensing bases for single failures, asreflected in Chapters 3.0 and 6.0 Catawba UFSAR,assumes that during the short-term period (i.e.,within the first 24 hours following the initiatingincident), the single failure is limited to thefailure of an active component to complete itsfunction as required. Should a single failure occurduring the long-term period rather than the short-term, the engineered safety features are designed totolerate an active failure or a passive failurewithout loss of its protective function.

SECY-77-439, "Single Failure Criterion," states thefollowing:

However, in applying the Criterion, it is not assumedthat any conceivable failure could occur. For example,reactor vessels or certain types of structuralelements within systems, when combined with otherunlikely events, are not assumed to fail because theprobabilities of the resulting scenarios of events aredeemed to be sufficiently small that they need not beconsidered. In general only those components which arejudged to have a credible chance of failure areassumed to fail when the Single Failure Criterion isapplied.

SECY-77-439, Section 3.B states the following:

During the long-term ECCS recirculation coolingmode, the most limiting active failure, or singlepassive failure equal to the leakage that would*occur from a valve or pump seal failure, isassumed. The basis for not including otherpassive failures during the long term is based onengineering judgment that such failures (pipe orvalve, breaks) have an acceptably low likelihoodof occurrence during the long-term phase of aloss-of-coolant accident. Analysis of ECCSperformance in WASH-1400 indicate that passivefailures of valves and piping are relatively

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small contributors to the ECCS unavailabilityduring both injection and recirculation modes ofoperation.

Due to the fact that no modifications or changes aremade to any ECCS control or protection system, valveoperators, pumps, or instrumentation (e.g.,level/pressure switches), it is reasonable to concludeactive failure response is unaffected by the proposedchanges. The actuation and alignment of the ECCS inresponse to a LOCA are unaffected. Swapover to sumprecirculation, including any required manual operatoractions, will take place as before the modification.

The consideration of passive failures is more relevantsince the new strainer is a passive device. Passivefailures are usually limited to piping systems, pumpseals, flanges, gaskets and similar components.Structural failures are typically not imposed on QACondition 1 safety-related structures, systems orcomponents (SSCs) not subjected to loads outside oftheir design bases.

Regulatory Guide 1.82, Rev. 0 establishes a positionthat redundant ECC Sumps should be provided. Theinferred intent of this position is to reduce thepossibility that a single event could render both ECCSumps inoperable. A single, shared (non-redundant)strainer meets the intent of this requirement if itcan be shown that it is not susceptible to failure ina manner which would result in the loss of both trainsof RHR/CSS. Active components whose credible failurescould render the ECCS inoperable have redundance builtinto their design. Passive components, on the otherhand, do not require such redundance because they aredesigned such that neither a consequential failure norsingle passive failure is credible, and if so, theintent of Regulatory Guide 1.82 and Generic Letter2004-02 is met.

Catawba stuctural analyses conclude that there are nohigh energy line break loads, jet impingement loads ormissile loads applicable to the containment sumpstrainer assemblies located in the pipechase. Section6.2.2.2 of the Catawba UFSAR states:

Page 25 of 34

Piping subject to breaks that result in need forrecirculation capabilities are located inside thecrane wall and are thus isolated from therecirculation sump screen assemblies. Thisphysical isolation protects the screen assembliesfrom pipe whip and jet impingement, and alsoeliminates air entrainment in the recirculatingfluid caused by jet effects on the liquid surface.In addition the crane wall keeps insulation andother debris directly generated by the break fromgetting into the annular region where the sump islocated.

In summary, given that the strainers are seismicallyqualified, fully passive components, there are nocredible failures which could adversely affect thesump strainer structures at Catawba. The presumptionthat a single passive structural failure would allowunfiltered water to be introduced into an RHR or CSSPump is not warranted. Therefore, the need tomaintain two physically separated containment sumps orECCS/CSS train separation within the same sump isunnecessary due to the absence of any reasonableassumptions that would require that level ofredundancy and protection. Such redundancy does notresult in any increase in safety.

An ECCS system design with multiple means of accessinginventory for recirculation clearly is in the interestof greater safety. Redundancy of trains andduplication of active components such as ECCS Sumpisolation valves provide greater assurance andreliability that the safety function of continuing toprovide coolant flow to the core will be met.

There are two considerations which preclude theability to provide each train of ECCS with its owndedicated strainer having sufficient surface area toresolve Generic Safety Issue (GSI) 191:

a. Fibrous Debris Challenge

At Catawba, the primary large break LOCAdebris reaching the strainers is projectedto be fibrous insulation. The projectedmaximum volume is in the range of several

Page 26 of 34

V

hundred cubic feet. With this largevolumetric challenge, a compact, surface-intensive strainer design is not suited tothe goal of minimizing head loss. Instead, aless compact design that optimizes bothsurface area and interstitial volume (i.e.,one that allows space to accommodate theanticipated debris load) is required.

b. Available Space

There are two primary restrictions on availablespace. First, because Catawba is an icecondenser plant with small containmentbuildings, space is limited. Second, Duke choseto resolve GSI-191 concerns with a design thatensures full submergence of the strainer duringall postulated scenarios. The limitingsubmergence case for ECCS containment sumpoperation at Catawba is a small break LOCAwhich limits the maximum height of the strainerassembly.

The objective of the new strainer design is to provideacceptable flow with minimum head loss at the specifieddebris loads and ensure adequate NPSH to the ECCS/CSS Pumpsduring the post-LOCA Recirculation Phase. Wheninstallation is completed, the new sump strainer design isintended to resolve concerns associated with GSI-191. Thechanges made enhance the existing design by providing alarger sump strainer surface area.. The completion ofchemical effects studies and other evaluations is requiredto confirm that Catawba' s ECCS recirculation functionsunder debris loading conditions will be in full compliancewith the Applicable Regulatory Requirements section of NRCGeneric Letter 2004-02.

5.0 REGULATORY SAFETY ANALYSIS

5.1 No Significant Hazards Consideration

Duke Energy Carolinas, LLC (Duke) has concluded thatoperation of Catawba Nuclear Station Units 1 & 2, inaccordance with the proposed changes to the UFSAR andlicensing basis does not involve a significant hazards

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consideration. Duke's conclusion is based on itsevaluation, in accordance with 10CFR50.91(a) (1), ofthe three standards set forth in 10CFR50.59(c) asdiscussed below:

A. Does the proposed amendment involve asignificant increase in the probability orconsequences of an accident previouslyevaluated?

Response: No.

Implementation of the proposed amendmentdoes not significantly increase theprobability or the consequences of anaccident previously evaluated. Thecontainment sump strainer structuresfunction to mitigate the consequences of anaccident. As stated in Generic Letter 2004-02, "Potential Impact of Debris Blockage onEmergency Recirculation During Design BasisAccidents at Pressurized-Water Reactors,"the current 50% screen blockage assumptionidentified in Regulatory Guide (RG) 1.82,Rev. 0, "Sumps for Emergency Core Coolingand Containment Spray Systems," should bereplaced with a more comprehensive means ofassessing debris effects on a plant-specificbasis. The 50% screen blockage assumptiondid not require a plant-specific evaluationof the debris-blockage potential and usuallyresults in a non-conservative analysis forscreen blockage effects.

As stated in Duke' s letters of March 1 andSeptember 1, 2005, Catawba confirmed theEmergency Core Cooling System (ECCS) andContainment Spray System (CSS) recirculationfunctions under debris loading conditionswould be in compliance with the regulatorypositions listed in the RegulatoryRequirements Section of Generic Letter 2004-02. The design of the modified containmentsump structure will accommodate the effectsof debris loading as determined by abaseline and refined evaluations specific toCatawba. These evaluations use the guidance

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of NEI 04-07, "Pressurized Water ReactorSump Performance Evaluation Methodology,Revision 0," dated December 2004, as amendedby the NRC' s Safety Evaluation Report.

Removal of the implied licensing basisrequirement to physically separate thecontainment sump into two halves or provideECCS train separation within the samecontainment sump will not impact theassumptions made in Chapter 15 of theCatawba UFSAR. There are no changes in anyfailure mode or effects analysis associatedwith this change. Since there are nocredible failures which could result in theintroduction of unfiltered debris within thestrainer assembly beyond the design limits,the need to maintain this physicalseparation is not warranted.

Although the configurations of the existingcontainment sump trash racks and screen andthe replacement sump strainer assemblies aredifferent, they serve the same fundamentalpurpose of passively removing debris fromthe sump's suction supply of the supportedsystem pumps. Removal of trash racks doesnot impact the adequacy of the pump NPSHassumed in the safety analysis. Likewise,the change does not reduce the reliabilityof any supported systems or introduce anynew system interactions. The greatlyincreased surface area of the new straineris designed to reduce head loss and reducethe approach velocity at the strainer facesignificantly, decreasing the risk of impactfrom large debris entrained in the sump flowstream.

Thus, based on the above, the proposedchange does not involve a significantincrease in the probability or consequencesof an accident previously evaluated.

B. Does the proposed amendment create thepossibility of a new or different kind of

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accident from any accident previouslyevaluated?

Response: No.

The proposed licensing basis changes willnot create the possibility of a new ordifferent kind of accident. The ECCScontainment sump serves as a portion of theECCS accident mitigation system. It is,therefore, not an accident initiator.Duke's evaluation concludes that there areno credible failures which could result inthe introduction of debris within thestrainer assembly and clog downstreamcomponents. Accordingly, there is no changein the consequences of an accidentpreviously evaluated in the UFSARs.

Catawba is replacing the ECCS Sump trashracks and screens with strainer assembliesin support of the response to Generic Letter2004-02. These strainer assemblies arepassive components in standby safety systemsused for accident mitigation. As such, theycannot be accident initiators.

A change to Catawba Technical SpecificationSurveillance Requirement 3.5.2.8 does notalter the nature of events postulated in theSafety Analysis Report nor do they introduceany unique precursor mechanisms.

Therefore, the proposed changes will notcreate the possibility of a new or differentkind of accident from any accidentpreviously evaluated.

C. Does the proposed amendment involve asignificant reduction in the margin ofsafety?

Response: No.

Margin of safety is related to theconfidence in the ability of the fissionproduct barriers to perform their design

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functions during and following an accidentsituation. These barriers include the fuelcladding, the reactor coolaRt system, andthe containment system. The performance ofthe fuel cladding, the reactor coolantsystem, and the containment system will notbe impacted by the proposed change.

Nuclear safety is greatly enhanced by theproposed licensing basis changes by ensuringconsistent interpretation and implementationof their requirements.

As previously stated, Duke's evaluationconcludes that there are no credible failuremechanisms which could result in theintroduction of debris above design limitswithin the strainer assembly and clogdownstream components. The partitioning ofthe containment sump into two halves istherefore unnecessary and does not result inany increase in safety or protection.

The proposed change to TechnicalSpecification SR 3.5.2.8 will have no effecton the manner in which safety limits,limiting safety system settings, or limitingconditions for operation are determined norwill there be any effect on those plantsystems necessary to assure theaccomplishment of protective functions. Theproposed change does not adversely affectthe fuel, fuel cladding, Reactor CoolantSystem, or containment integrity.

Thus, it is concluded that the proposedchanges do not involve a significantreduction in the margin of safety.

5.2 Applicable Regulatory Requirements/Criteria:

Catawba' s position with respect to Regulatory Guide1.82, Revision 0, as currently described in theirUFSARs, has been revised to:(1) delete the requirementor implication that two physically separatedcontainment sumps (one for each train of RHR/CSS) mustbe maintained; (2) Eliminate the requirement for trash

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racks; (3) Clarify the wording to replace "trash racksand screens" with the word "strainers"; and (4)Describe the required ECCS Sump Strainer AssemblySurveillance.

Adherence to the criteria of 10CFR50, Appendix A,General Design Criteria (GDC) 34, 35, 38, and 41 areenhanced through the adoption of the proposedlicensing basis changes.

Although the configurations of the existing sumpscreen and the replacement strainer assemblies aredifferent, they serve the same fundamental purpose ofpassively removing debris from the sump's suctionsupply of the supported system pumps. Removal oftrash racks does not impact the adequacy of the pumpNPSH assumed in the safety analyses.

This LAR is being submitted in accordance with 10 CFR50.90.

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6.0 ENVIRONMENTAL CONSIDERATIONS

The proposed change does not involve a significant hazardsconsideration, a significant change in the types of orsignificant increase in the amounts of any effluents thatmay be released offsite, or a significant increase inindividual or cumulative occupational radiation exposure.Therefore, the proposed change meets the eligibilitycriteria for categorical exclusion set forth in 10 CFR51.22(c) (9).

Pursuant to 10 CFR 51.22(b), an environmental assessment ofthe proposed change is not required.

7.0 PRECEDENTS

The stations listed below are currently using or plan touse a single, shared strainer design. None of thefacilities listed below are committed to Regulatory Guide1.82, Revision 0. The listing is not intended to be allinclusive but is provided to confirm that a single sharedstrainer concept will not be unique to Catawba:

Oconee Nuclear Station, Units 1, 2, and 3: Asreflected in their UFSAR, each of the Oconee Units hasa common undivided containment sump.

H. B. Robinson 2: As reflected in their UFSAR,Robinson has a common containment sump.

Turkey Point: Turkey Point Units 3 and 4 utilize asingle set of strainer modules.

Similar changes have been approved for:

Oconee Nuclear Station, Units 1 and 2, by NRC SafetyEvaluation Report (SER) dated Nov 1, 2005,

Wolf Creek by NRC SER dated Oct 5, 2006, and

Comanche Units 1 and 2 by NRC SER dated Oct 5, 2006.

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8.0 REFERENCES

Catawba Nuclear Station (CNS) electronic UFSAR, effectivedate October 24, 2006, Revision 12 including TrackingTool.

CNS Technical Specifications through amendments 234/230.

NRC Bulletin 2003-0.1, Potential Impact of Debris Blockageon Emergency Sump Recirculation at PWRs.

Generic Letter 2004-02, Potential Impact of DebrisBlockage on Emergency Recirculation During Design BasisAccidents at PWRs

Drawing CN-1080-54 revision 16, Recirculation Sump ScreenAssembly.

Calculation CNC-1223.12-00-0056, Containment RecirculationSump Documentation of Information Related to Design ofStructures and Comparison to Design at McGuire NuclearStation.

Response to Generic Letter 2004-02, dated 9-1-2005.

Responses to NRC Bulletin 2003-01, dated 8-7-2003 and 5-27-2004.

NEI 04-07, "Pressurized Water Reactor Sump PerformanceEvaluation Methodology," Rev. 0, December 2004, Vol. 1 andVol. 2 - "Safety Evaluation by the Office of NuclearReactor Regulation Related to NRC Generic Letter 2004-02,"Revision 0, December 6, 2004.

Regulatory Guide 1.82, Revision 0.

CD-100493, Unit 1 Scope Description- ECCS Sump Strainer(Document No. CNC-1223.12-00-0056, Rev.2)

Catawba Nuclear Station SER (2/22/1983), section 6.2.2,Containment Heat Removal System

January 14, 1983 -Response to the' NRC Comparing McGuireand Catawba sump tests (Response to Q 440-113); Pages 440-127, 440-128.

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1 p

9.0 FIGURES

Figure 1: Current ECCS Sump Design DrawingFigure 2: Modified ECCS Sump Design Drawings and Photo

Figure 1: Current ECCS Sumnp Design Drawing

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Documents

Catawba Units 1 & 2, License Amendment Request ...C.7 The design coolant velocity at the fine inner screen should be approxinmately 2.0 ft/sec. The available surface area used in determining