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St. Lucie, Units 1 and 2 - Participation in Additional Work Under the Support for Applicant Action Items 1, 2, and 7 from the Final Safety Evaluation on MRP-227, Revision 0 PA-MSC-0983 R2 Cafeteria Task 8 and Acceptance Criteria for Measure
	ML16063A007
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Site:	Saint Lucie
Issue date:	02/26/2016
From:	O'Brien P, Szweda K N; PWR Owners Group, Westinghouse
To:	; Office of Nuclear Reactor Regulation
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ML16063A004	List: L-2016-040, License Renewal Commitments, Reactor Vessel Internals Aging Management Plan, Response to Request for Additional Information; ML16063A007;
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	L-2016-040 PA-MSC-0983 Task 8, PWROG-16012-NP, Rev. 0
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Attachment 2 to Letter L-2016-040 PWROG Report No. PWROG-16012-NP, Rev. 0 I ZE D WATER REACTOR OWNERS GR!OU PPWROG PWROG-1 6012-NPPWROC Revision0 OWner$WESTINGHOUSE NON-PROPRIETARY CLASS 3St. Lucie Units 1 and 2 Participation inAdditional Work under the "Support forApplicant Action Items 1, 2, and 7 fromthe Final Safety Evaluation on MRP-227,Revision 0" PA-MSC-0983 R2 Cafeteria Task 8 and "Acceptance Criteria forMeasurement of CE Internals:

MRP-227SE Action Item 5" PA-MSC-0984:

Responding to Items I and 3Materials Committee PA-MSC-0983 Task 8February 2016'use WESTINGHOUSE NON-PROPRIETARY CLASS 3PWROG-1 6012-NPRevision 0St. Lucie Units 1 and 2 Participation inAdditional Work under the "Support forApplicant Action Items 1, 2, and 7 from theFinal Safety Evaluation on MRP-227,Revision 0" PA-MSC-0983 R2 Cafeteria Task8 and "Acceptance Criteria for Measurement of CE Internals:

MRP-227 SE Action Item 5"PA-MSC-0984:

Responding to Items 1 and 3PA-MSC-0983 Task 8Author: Karli N. Szweda for Cheryl L. Boggess*

Author: Paul O'Brien*Reactor Internals Aging Management Reactor Internals Design & Analysis IIResponse Report and Item 3 Response Attachment 1, Item 1 ResponseVerifier:

Micah C. Bowen* Verifier:

Bradford S. Grimmel*Reactor Internals Design & Analysis II Reactor Internals Design & Analysis IIResponse Report and Item 3 Response Attachment 1, Item 1 ResponseFebruary 2016Reviewer:

Karli N. Szweda*Reactor Internals Aging Management Approved:

Gerrie W. Delport for Eric A. Eggleston*,

ManagerReactor Internals Design & Analysis IIApproved:

Patricia C. Paesano*,

ManagerReactor Internals Aging Management Approved:

James P. Molkenthin*,

Program DirectorPWR Owners Group PMO*Electronically approved records are authenticated in the electronic document management system.Westinghouse Electric Company LLC1000 Westinghouse DriveCranberry

Township, PA 16066, USA© 2016 Westinghouse Electric Company LLCAll Rights Reserved WESTINGHOUSE NON-PROPRIETARY CLASS 3iLEGAL NOTICEThis report was prepared as an account of work performed by Westinghouse ElectricCompany LLC. Neither Westinghouse Electric Company LLC, nor any person acting on itsbehalf:1. Makes any warranty or representation, express or implied including the warranties offitness for a particular purpose or merchantability, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use ofany information, apparatus, method, or process disclosed in this report may not infringeprivately owned rights; or2. Assumes any liabilities with respect to the use of, or for damages resulting from the useof, any information, apparatus, method, or process disclosed in this report.COPYRIGHT NOTICEThis report has been prepared by Westinghouse Electric Company LLC and bears aWestinghouse Electric Company copyright notice. As a member of the PWR Owners Group, youare permitted to copy and redistribute all or portions of the report within your organization; however all copies made by you must include the copyright notice in all instances.

DISTRIBUTION NOTICEThis report was prepared for the PWR Owners Group. This Distribution Notice is intended toestablish guidance for access to this information.

This report (including proprietary andnon-proprietary versions) is not to be provided to any individual or organization outside of thePWR Owners Group program participants without prior written approval of the PWR OwnersGroup Program Management Office. However, prior written approval is not required for programparticipants to provide copies of Class 3 Non-Proprietary reports to third parties that aresupporting implementation at their plant, and for submittals to the NRC.PWROG-.16012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3iiTable of Contents1 Purpose and Background..................................................

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1-12 Responses to Request for Additional Information.........,.................................

2-13 References................

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3-1Attachment 1Attachment 1: Non-Proprietary Summary Letter for Acceptance Criteria for Visual Examination of Gaps between Upper and Lower Core Shroud Subassemblies at St. Lucie Units 1 and 2 ................................................................................

Attachment 1-11 Background and Purpose.......................................................

Attachment 1-12 Methodology.....................................................................

Attachment 1-152.1 Methodology for SL1I.................................................

Attachment 1-152.2 Methodology for SL2..................................................

Attachment 1-173 Significant Assumptions.......................................................

Attachment 1-194 Acceptance Criteria.............................................................

Attachment 1-195 Summary of Results and Conclusions.......................................

Attachment 1-205.1 Summary of Results for SL2..........................................

Attachment 1-205.2 Summary of Results for SL1i.........................................

Attachment 1-216 References.....................

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Attachment 1-22PWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 31-11 PURPOSE AND BACKGROUND As requested by Florida Power & Light (FPL), St. Lucie Units I and 2, Westinghouse ElectricCompany LLC is providing this letter report under PA-MSC-0983, Revison 2, Task 8.FPL submitted a letter to respond to U.S. Nuclear Regulatory Commission (NRC) Request forAdditional Information (RAI) for the review of the St. Lucie Units 1 and 2 License RenewalApplication.

The NRC reviewed the information and identified areas where additional information is still needed.This report provides Westinghouse's responses, for Items I and 3 [1], as authorized by Mr.Scott Boggs, to support of FPL's request for service.PWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Atcmn -Attachment 1-1ATTACHMENT 1: NON-PROPRIETARY SUMMARY LETTER FORACCEPTANCE CRITERIA FOR VISUAL EXAMINATION OF GAPSBETWEEN UPPER AND LOWER CORE SHROUD SUBASSEMBLIES AT ST. LUCIE UNITS 1 AND 21 BACKGROUND AND PURPOSEThe core shroud (CS) assemblies at St. Lucie Unit 1 (SL1) and St. Lucie Unit 2 (SL2) are eachcomprised of an upper subassembly and a lower subassembly (refer to Figures 1-la and 1-2a).The bottom plate of the upper subassembly sits on the top plate of the lower subassembly.

Theelevation of this bottom plate/top plate interface is close to the axial center of the core;therefore, it is subjected to high levels of irradiation.

Figure 1-3 plots the irradiation distribution in these plates for a typical 2,800 MWt or 3,410 MWt Combustion Engineering (CE)-welded coreshroud. SL1 uses a typical 2,.800 MWt CS design. SL2 uses a shortened version of the 3,410MWt CS design. Therefore, the relative distribution of irradiation shown in Figure 1-3 can beconsidered representative of the CS designs for SL1 and SL2. The irradiation dose is highest atthe innermost corners of the interfacing plates, which are the eight re-entrant corner locations closest to the lateral center of the core (see Figures 1-lb and 1-2b). This irradiation producesboth gamma heating and void swelling in the interfacing plates. The gamma heating willproduce a temperature gradient between the center of the bottom plate/top plate combination (at the interfacing surfaces) and the outer surfaces of the bottom plate/top plate combination (see Figures 1-4a and 1-5a). This temperature

gradient, like the irradiation dose, will begreatest at the innermost corners of the interfacing plates (see Figures 1-4b and 1-5b). Thevoid swelling increases with temperature and irradiation dose; therefore, it will also be greatestat the innermost corners of the interfacing plates.These gamma heating and void swelling effects could result in a deflection of the upper CSsubassembly bottom plate relative to the lower CS subassembly top plate. The nature of thisrelative deflection is dependent on the manner in which the upper and lower CS subassemblies are attached.

At SL1, the upper and lower CS subassemblies are attached to one another andto the core support plate via eight tie rods. Tapered pins are inserted through the interfacing plates to provide lateral restraint and alignment between the two CS subassemblies.

Relativedeflection between these interfacing plates could produce gaps between the plates at the innerand outer peripheries of the interface (see Figure 1-6). Gamma heating and void swelling couldalso cause local increases in plate thickness.

Both of these effects would be greatest at theinnermost corners of the interfacing plates. The tie rods would continue to clamp the upper andlower CS subassemblies

together, and the tapered pins would continue to prevent lateraltranslation of one plate relative to the other. Therefore, plate-to-plate contact would bemaintained at the locations of maximum plate thickness

[i.e., at the circumferential locations ofinnermost

corners, between the inner and outer peripheries where the gaps occur (see Figure1-6)]. However, additional gaps could form between the two plates at circumferential locations away from the innermost

corners, where plate thicknesses are smaller, and these gaps couldextend through the bottom plate/top plate interface (see Figure 1-7). Accordingly, at SL1, therecould be two types of gaps between the interfacing plates of the upper and lower CSsubassemblies.

The gaps at the innermost corners would not extend through the bottomPWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-2plate/top plate interface; the gaps away from the innermost corners could extend through thisinterface.

At SL2, the bottom plate of the upper CS subassembly and the top plate of the lower CSsubassembly are attached to one another via a full penetration weld around the'outside circumference.

Relative deflection between these interfacing plates, due to gamma heating andvoid swelling, could produce gaps between the plates at the inner periphery of the interface (seeFigure 1-8). The largest gaps would occur at the innermost corners where the temperature gradients and void swelling are greatest.

The circumferential welded attachment between theupper and lower subassemblies would prevent the interfacing plates from separating at theirouter peripheries; therefore, the gaps between the interfacing plates would not extend throughthe interface, from inside to outside.At SLI and SL2, the gaps bdtween interfacing plates of the upper and lower CS subassemblies would have a thermal contribution and a void swelling contribution.

The thermal contribution would only be present during power operation.

The void swelling contribution would be presentunder all conditions, including plant shutdown, during which the physical examinations of the CSwill be performed.

Applicant/Licensee Action Item 5, as described in Sections 3.3.5 and 4.2.5 of [1], requires thatapplicants/licensees identify plant-specific acceptance criteria to be applied when performing the physical measurements required by the NRC-approved version of MRP-227 for distortion in -the gap between the top and bottom CS segments in CE units with CSs assembled in twovertical sections.

To comply with Applicant/Licensee Action Item 5, Westinghouse assumed the task of identifying and justifying an acceptable size for the gap between the interfacing plates of the upper andlower CS subassemblies for SL1 and SL2. The work associated with this task justified a gapsize that is measureable using the specified VT-I inspection resolution and that is acceptable interms of functionality.

A gap size was chosen and justified based on design and. as-builtconditions,

fluence, circumferential bounds of the gap (how far around the CS can the gapexist), stress, impact on adjacent reactor vessel internals components, impact on core andbypass flow rates, and potential effects on fuel management schemes.The products of this task are maximum allowable values for the gaps between the upper andlower subassemblies of the CSs at SL1 and SL2, as could be observed during plant shutdownwhen physical examinations would be performed.

These allowable gaps will be used asacceptance criteria during these physical examinations.

PWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Atcmn -Attachment 1-3IftI.I. ~ I -I Ill.L..1___

__I II I.1 I I__ __ll1L~~

__I I ILU{3.InII-oil-Jupper subassembly w.Q..P* " I I "MJII .I1-U ~ JJ _____ Z JL...r.I..l~....a'

.41r r -i f~1i II I II I I j~ ~' 2lower subassembly o__ I--Jna0br-* L aa~+/- , Lu ~ a .a.-.~ ... +/- L~ a~a = ________

_________

___Figure 1-1a: SL1 Core Shroud Assembly

-Elevation ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-4WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1-4Figure 1-1b: SL1 Core Shroud Assembly

-Plan ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-52P4~ PIc'NCr no-C ,~0-- Th.4- ;b 9~~' ;4mFiF~4no~welded attachment betweenupper and lower subassemblies 000~ FrYBfZ4IC5inFigure 1-2a: SL2 Core Shroud Assembly

-Elevation ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Atcmn -Attachment 1-6Ie©o(37.933DIMS. 6L50 APPLY 2"DFigure 1-2b: SL2 Core Shroud Assembly

-Plan ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-7WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1-7.... ... -Lower dpaWHigher dpaFigure 1-3: Irradiation Dose (dpa) Contour Plots in Central CS Horizontal Plates after 40 Fuel CyclesPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Atcmn -Attachment 1-8FEB 5 200918:56:38HotterColderFigure 1-4a: Temperature Gradients at Interface between Upper and Lower CS Subassemblies for SL1 -Elevation ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-9WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1-9FEB 5 2oo918:56:45PlOT NOJ. 6HotterColderFigure 1-4b: Temperature Gradients at Interface between Upper and Lower CS Subassemblies for SL1 -Plan ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atamnt11 Attachment 1-10FEB 24 200913 :10 :19HotterColderFigure 1-5a: Temperature Gradients at Interface between Upper and Lower CS Subassem blies for SL2 -Elevation ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-11WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1-11ANFEB 24 200913:08:50HotterColderFigure 1-5b: Temperature Gradients at Interface between Upper and Lower CS Subassemblies for SL2 -Elevation ViewPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-12WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1-12Smaximum strain at this surfacegap atinnermost cornersminimum strain at this surface~core shroud lower subassembly top plateminmu stana hi ufcSmaximum strain at this surfaceFigure 1-6: Gap between Upper and Lower CS Subassemblies at Innermost Corners for SLIPWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atchet11 Attachment 1-13innermost corner00, 900, 1800, or 2700 axisinnermost cornercontactcontactgap away frominnermost cornersFigure 1-7: Gap between Upper and Lower CS Subassemblies Away from Innermost Corners for SL1PWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-14WESTINGHOUSE NON-PROPRIETARY CLASS 3 Attachment 1-14maximumgapcore shroud lower subassembly botop plate..full-penetration weldFigure 1-8: Gap between Upper and Lower CS Subassemblies at Innermost Corners for SL2PWROG-1 6012-NPRevision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-152 METHODOLOGY As discussed in Section 1, the nature of the relative deflection between the interlacing plates ofthe upper and lower CS subassemblies, and the gaps resulting from these deflections, isdependent on the manner in which the upper and lower CS subassemblies are attached.

SL1uses a mechanical attachment (via tie rods); SL2 uses a welded attachment.

Therefore, twodifferent methodologies were employed to calculate these gaps. The first, described in Section2.1, was applied to SLI. The second, described in Section 2.2, was applied to SL2.2.1 METHODOLOGY FOR SL1Differential thermal expansion (due to gamma heating) and irradiation-induced void swellingcould cause local gaps to form between the interlacing plates of the upper and lower CSsubassemblies.

These gaps could occur both at, and away from, the innermost corners of theinterlacing plates (see Figures 1-6 and 1-7). Both types of gaps would have a thermalcontribution and a void swelling contribution.

The thermal contribution would only be presentduring power operation.

The void swelling contribution would be present under all conditions, including plant shutdown, during which physical examinations of the CS will be perlormed.

Maximum, bounding values for the thermal portions of these gaps were calculated usingconservative, simplifying methods:* The maximum and minimum temperatures in the CS assembly were obtained.

The maximum and minimum thermal strains were calculated.

The nominal thickness of a CS horizontal plate was obtained.

The maximum permissible as-fabricated local gap between CS plates was obtained.

The maximum width of a CS horizontal plate from one of the eight innermost corners to theouter periphery was calculated (see Figure 1-1b).*This maximum plate width was applied to the two interlacing horizontal plates that form thebottom of the upper CS subassembly and the top of the lower CS subassembly.

Themaximum thermal strain was applied to the interlacing surlaces of these plates. Theminimum thermal strain was applied to the opposite surlaces of these plates (see Figure1-6).* For each plate, the differential thermal expansion was calculated between the interlacing surlace and the opposite surface.* Per Section 3, it is assumed that the plate is unrestrained and free to deflect as a circulararc in response to the imposed differential thermal expansion.

PWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atahet16 Attachment 1-16* The differential thermal expansion was applied as the difference between two circular arclengths, representing the deflected surfaces of the plate.* The vertical deflection at one end of the deflected plate was geometrically determined.

The maximum thermal gap between the innermost corners of the interfacing plates isdefined as twice the vertical deflection calculated for one plate.*The maximum thermal strain applies to the plate thickness at the innermost corners.

Theminimum thermal strain applies to the plate thickness away from the innermost corners.

Thedifferential plate thickness between the locations at and away from the innermost corners isdetermined using the difference between maximum and minimum thermal strain.* The maximum thermal gap between the interfacing plates away from the innermost cornersis defined as twice the differential thickness calculated for one plate.Maximum values for the void swelling portions of these gaps would be very difficult to predict,and were not explicitly calculated.

Instead, the following process was used to determine themaximum void swelling gaps:* A maximum void swelling gap was selected based on the ability to readily detect thepresence of gaps during the physical examinations of the CS assembly.

Relative magnitudes of void swelling gaps at different circumferential locations wereobtained.

The assumed maximum gap was used in conjunction with the relative gap data to determine the maximum void swelling gaps both at, and away from, the innermost corners of theinterfacing plates.* The maximum void swelling gaps were adjusted, as necessary, for the potential adversestructural and functional

effects, as identified below, to be acceptable.

The total gaps that could occur during power operation would include thermal swellingcontribution, void swelling contribution, and the permissible as-fabricated gaps. Maximum totalgaps were determined as follows:* The maximum total gap is equal to the sum of the thermal gap, the void swelling gap, andthe permissible as-fabricated gap.* The maximum total gaps were determined both at, and away from, the innermost corners ofthe interfacing plates.The potential adverse effects of these total gaps on the structural integrity of both the fuelassemblies and the reactor vessel internals, along with the potential system level effects, wereidentified and evaluated.

These potential adverse effects include:PWROG-16012-N P Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atahet-1 Attachment 1-171. structural effect on interfacing CS horizontal plates2. coolant flow jetting through the gap and impinging on the fuel assemblies

3. coolant flow jetting through the gap and impinging on the core support barrel (CSB)4. increased gamma heating of the CSB} directly adjacent to the gaps5. increased fluence applied to the CSB and the reactor vessel directly adjacent to the gaps6. turbulence in the main coolant flow adjacent to the gap7. effect on CS-to-CSB bypass coolant flow8. peripheral fuel assembly grid hanging up on the gap during insertion or withdrawal

9. inward deflection of interfacing CS horizontal plates encroaching on fuel space2.2 METHODOLOGY FOR SL2Differential thermal expansion (due to gamma heating) and irradiation-induced void swellingcould cause local gaps to form between the interfacing plates of the upper and lower CSsubassemblies.

The maximum gap would occur at the innermost corners of the interfacing plates (see Figure 1-8). This maximum gap would have a thermal contribution and a voidswelling contribution.

The thermal contribution would only be present during power operation.

The void swelling contribution would be present under all conditions, including plant shutdown, during which physical examinations of the CS will be performed.

Conservative, simplifying methods were employed to calculate a maximum, bounding value for the thermal portion of thismaximum gap.A maximum value for the void swelling portion of this maximum gap would be very difficult topredict, and is not explicitly calculated.

Instead, a maximum void swelling gap value wasselected based on the ability to readily detect the presence of gaps during the physicalexaminations of the CS.The maximum total gap that could occur during power operation would include the thermal andthe void swelling contributions, as well as the permissible as-fabricated gap. The following methodology was employed to determine this maximum total gap:* The maximum and minimum temperatures in the CS assembly were obtained.

The maximum and minimum thermal strains were calculated.

The nominal thickness of a CS horizontal plate was obtained.

PWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atahet-1 Attachment 1-18* The maximum permissible as-fabricated local gap between CS plates was obtained.

The maximum width of a CS horizontal plate from one of the eight innermost corners to theouter periphery was calculated (see Figure 1-2b).*This maximum plate width was applied to the two interfacing horizontal plates that form thebottom of the upper CS subassembly and the top of the lower CS subassembly.

Themaximum thermal strain was applied to the interfacing surfaces of these plates. Theminimum thermal strain was applied to the opposite surfaces of these plates (see Figure 1-8).* For each plate, the differential thermal expansion was calculated between the interfacing surface and the opposite surface.* Per Section 3, it is assumed that the plate is unrestrained and free to deflect as a circulararc in response to the imposed differential thermal expansion.

The differential thermal expansion was applied as the difference between two circular arclengths, representing the deflected surfaces of the plate.* The vertical deflection at one end of the deflected plate was geometrically determined.

The maximum thermal gap is defined as twice the vertical deflection calculated for oneplate.* A maximum void swelling gap was selected based on the ability to readily detect thepresence of gaps during the physical examinations of the CS.* The maximum total gap is equal to the sum of the thermal gap, the void swelling gap, andthe permissible as-fabricated gap.The potential adverse effects of this maximum total gap on the structural integrity of both thefuel assemblies and the reactor vessel internals, along with the potential system level effects,were identified and evaluated.

These potential adverse effects include:1. structural effect on interfacing CS horizontal plates (including attachment weld)2. turbulence in the main coolant flow adjacent to the gap3. peripheral fuel assembly grid hanging up on the gap during insertion or withdrawal

4. inward deflection of interfacing CS horizontal plates encroaching on fuel spaceAs discussed in Section 1, the circumferential welded attachment between the upper and lowerCS subassemblies would prevent the interfacing horizontal plates from separating at their outerperipheries.

Therefore, any gaps between the interfacing plates would not extend through thePWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atahet-1 Attachment 1-19interface, from inside to outside, and would not accommodate coolant flow jetting or neutronstreaming.

Accordingly, the following potential adverse effects were eliminated fromconsideration:

1. no coolant flow jetting through the gap and impinging on the fuel assemblies

2. no coolant flow jetting through the gap and impinging on the CSB3. no increased gamma heating of the CSB directly adjacent to the gaps4. no increased fluence applied to the CSB and the reactor vessel directly adjacent to the gaps5. no effect on CS-to-CSB bypass coolant flow3 SIGNIFICANT ASSUMPTIONS As a conservative, simplifying

measure, adopted to provide a bounding value for the gapbetween the interfacing horizontal plates of the CS upper and lower subassemblies, it isassumed that deflection of the plates is unrestrained, and that each plate is free to deflect as acircular arc in response to imposed differential thermal expansion.

4 ACCEPTANCE CRITERIA1. The maximum total gaps between the interfacing horizontal plates of the upper and lowerCS subassemblies, which occur during plant operation, must be acceptable from bothstructural and functional standpoints.

2. The maximum gap during plant shutdown, constituting the acceptance criterion for physicalexamination of gaps in the CS, must be within the range that can be detected by VT-i visualexamination.

Per [2, paragraph 2.3.6.3b.1

.]: "Remote EVT-1 or VT-I examination processes shall be demonstrated as capable of resolving lowercase characters...

withcharacter heights no greater than 0.044 in. (1.1 mm) at the maximum examination distance."

To distinguish between different characters of 0.044-inch height, it is reasonable to concludethat features of one-half that size (i.e., 0.022 inches or greater) can be resolved by VT-ivisual examination.

Therefore, the acceptance criterion for physical examination of gaps inthe CS must be -> 0.022 inches.PWROG-1 6012-NP Revision 0PWROG-16012-NP February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-20S SUMMARY OF RESULTS AND CONCLUSIONS Differential thermal expansion (due to gamma heating) and irradiation-induced void swellingcould cause local gaps to form between the interfacing plates of the upper and lower CSsubassemblies.

Accordingly, the total gap at any location would include a thermal contribution and a void swelling contribution.

The thermal contribution would only be present during poweroperation.

The void swelling contribution would be present under all conditions, including plantshutdown, during which physical examinations of the CS will be performed.

Per Sections 2.1 and 2.2, the maximum thermal gaps were explicitly calculated, and themaximum void swelling gap was selected based on the ability to readily detect the presence ofgaps during physical examinations of the CS. Initially, a maximum void swelling gap of 0.125inches was assumed to satisfy this subjective requirement.

For SL2, this maximum void swelling gap was combined with the maximum thermal gap and thepermissible as-fabricated gap to obtain a maximum total gap. This maximum total gap occurs atthe innermost corners of the interfacing plates, and there are no through-gaps because theinterfacing plates are welded together at their buter peripheries.

The potential adverse effectsof this maximum total gap, identified in Section 2.2, were evaluated and determined to beacceptable with one qualification.

These results are summarized, and the qualification isdescribed, in Section 5.1.However, for SL1, the interfacing plates are not welded together.

As discussed in Section 1, themaximum gaps (at the innermost corners) do not extend through the interface, but it is possiblethat smaller through-gaps could form at locations away from the innermost corners.

Additional adverse effects associated with these through-gaps are identified in Section 2.1. It was notpossible to demonstrate that all of these additional adverse effects are acceptable with amaximum void swelling gap of 0.125 inches. Specifically referring to adverse effect number 7,the additional bypass flow through these through-gaps caused the total bypass flow to exceedthe allowable percentages of 4.2% defined in [3, Table 15.2.11-1].

This bypass flow analysisassumed that these through-gaps extended around the entire circumference of the interfacing plates. This assumption is conservative;

however, because the locations of maximum voidswelling (defining the points of plate-to-plate contact) are circumferentially localized, thethrough-gaps could certainly extend around most of the circumference.

Accordingly, it wasnecessary to reduce the magnitude of the assumed maximum void swelling gaps so that thebypass flow criteria could be satisfied.

Results of this process are summarized in Section 5.2.5.1 Summary of.Results for SL2The maximum acceptable value for the gap between the interfacing plates of the CS upper andlower subassemblies during normal operation is 0.453 inches. This maximum gap, whichoccurs at the innermost corners of these interfacing plates, reflects both differential thermalexpansion (from gamma heating) and irradiation-induced void swelling, and also includes thepermissible as-fabricated gap. The structural and functional effects associated with thePWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Atahet12 Attachment 1-21presence of this gap, identified in Section 2.2, have been evaluated and are acceptable.

However, the acceptability of one of these effects (i.e., inward deflection of interfacing CShorizontal plates encroaching on fuel space) was confirmed using Westinghouse fuel assemblyparameters.

This effect will also be acceptable with other fuel assemblies, provided that thoseother fuel assemblies satisfy the following criteria:

1. The axial locations of the spacer grids on the other fuel assemblies must be compatible withthose on the Westinghouse fuel assemblies, as would be required with a mixed core of bothfuel assembly types.2. The amount by which the spacer grids overhang the fuel rods on the other fuel assemblies must be greater than the maximum inward deflection of the interfacing CS horizontal plates,which is 0.042 inches. A minimum spacer grid/fuel rod overhang of 0.050 inches willprovide acceptable margin.That portion of the total gap due to differential thermal expansion (0.313 inches) would only bepresent during power operation.

That portion of the total gap due to irradiation-induced voidswelling would be present under all conditions, including plant shutdown, during which physicalexaminations of the CS will be performed.

During plant shutdown, the maximum value for the gap between the interfacing plates of theupper and lower CS subassemblies, reflecting irradiation-induced void swelling and accounting for the permissible fabrication gap, is 0.125 inches. The maximum gap would occur at theinnermost corners.Based on these results, a maximum, bounding gap between the interfacing plates of the upperand lower CS subassemblies, as could be present during plant shutdown, is set at 0.125 inchesat the eight innermost corners.

These innermost corners correspond to the re-entrant cornersidentified for coverage via enhanced visual examination (EVT-1) in [4, Table 4-2]. This gap maybe used as an acceptance criterion for these examinations of the SL2 CS. This acceptance criterion is greater than the minimum value of 0.022 inches defined in Section 4.5.2 Summary of Results for SL1The maximum acceptable value for the gap between the interfacing plates of the CS upper andlower subassemblies during normal operation is 0.128 inches. This maximum gap, whichoccurs at the innermost corners of these interfacing plates, reflects both differential thermalexpansion (from gamma heating) and irradiation-induced void swelling.

This maximum gapincludes the permissible as-fabricated gap. The maximum gap away from the innermost corners is 0.053 inches. The structural and functional effects associated with the presence ofthese gaps, identified in Section 2.1, have been evaluated and are acceptable.

Those portions of these total gaps due to differential thermal expansion (0.058 inches at theinnermost corners and 0.010 inches away from the innermost corners) would only be presentPWROG-1 6012-NP Revision 0February 2016 WESTINGHOUSE NON-PROPRIETARY CLASS 3Attachment 1-22during power operation.

Those portions of the total gaps due to irradiation-induced voidswelling would be present under all conditions, including plant shutdown, during which physicalexaminations of the CS will be performed.

During plant shutdown, the maximum gap due to void swelling, which occurs at the innermost

corners, is 0.055 inches. The maximum void-swelling gap away from the innermost corners,which is derived from the corner gap using relative void swelling gap distributions, is 0.028inches. The total gaps during plant shutdown, which include the permissible fabrication gap, are0.070 inches at the innermost corners and 0.043 inches away from the innermost corners.Based on these results, a maximum, bounding gap between the interfacing plates of the CSupper and lower subassemblies, as could be present during plant shutdown, is set at 0.070inches at the eight innermost corners.

These innermost corners correspond to the re-entrant corners identified for coverage via enhanced visual examination (EVT-1) in [4, Table 4-2]. Thisgap may be used as an acceptance criterion for these examinations of the SLI CS. Thisacceptance criterion is smaller than the initially-assumed value of 0.125-inch (see Section 5),but is still greater than the minimum value of 0.022 inches defined in Section 4. The gaps awayfrom the innermost

corners, which are derived from the corner gaps, as discussed above, neednot be examined.

6 REFERENCES

1. Letter from the U.S. NRC to Neil Wilmshurst of EPRI, "Revision 1 to the Final SafetyEvaluation of Electric Power Research Institute (EPRI) Report, Materials Reliability Program(MRP) Report 1016596 (MRP-227),

Revision 0, 'Pressurized Water Reactor (PWR) Internals Inspection and Evaluation Guidelines' (TAO No. ME0680),"

December 16, 2011. (ADAMSAccession Number ML1 1308A770)

2. Materials Reliability Program:

Inspection Standard for PWR Internals

-2012 Update (MRP-228, Rev 1). EPRI, Palo Alto, CA: 2012. 1025147.3. St. Lucie Nuclear Power Plant Unit 1 Final Safety Analysis Report, Amendment No. 25.4. Materials Reliability Program:

Pressurized Water Reactor Internals Inspection andEvaluation Guidelines (MRP-227-A).

EPRI, Palo Alto, CA: 2011. 1022863.PWROG-1 6012-NP Revision 0February 2016 Attachment 2 to Letter L-2016-040 PWROG Report No. PWROG-16012-NP, Rev. 0 I ZE D WATER REACTOR OWNERS GR!OU PPWROG PWROG-1 6012-NPPWROC Revision0 OWner$WESTINGHOUSE NON-PROPRIETARY CLASS 3St. Lucie Units 1 and 2 Participation inAdditional Work under the "Support forApplicant Action Items 1, 2, and 7 fromthe Final Safety Evaluation on MRP-227,Revision 0" PA-MSC-0983 R2 Cafeteria Task 8 and "Acceptance Criteria forMeasurement of CE Internals: