ML20217P144

Proposed Tech Specs 3.4.5 Re voltage-based Repair Criteria

ML20217P144
Person / Time
Site:	South Texas
Issue date:	04/02/1998
From:	HOUSTON LIGHTING & POWER CO.
To:
Shared Package
ML20217P123	List: ML20217P144 NOC-AE-000097, Application for Amends to Licenses NPF-76 & NPF-80, Incorporating Tech Specs 3.4.5 Re 1-volt voltage-based Repair Criteria for SG Tube Support plate-to-tube Intersections,Per GL 95-05
References
GL-95-05, GL-95-5, NUDOCS 9804090330
Download: ML20217P144 (46)

Text

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( r l REACTOR COOLANT SYSTEM l, STEAM GENERATORS SURVEILLANCE RE0VIREMENTS (Continued) l 3) A tube inspection (pursuant to Specification 4.4.5.4a.8) shall be performed on each selected tube. If any selected tube does s not permit the passage of the eddy current probe for a tube inspection, this shall be recorded and an adjacent tube shall be selected and. subjected to'a tube inspection. 4) Indications left in service as a result of application of the tube support plate voltage-based repair criteria shall be inspected by bobbin coil probe during all future refueling

outages, The tubes selected as the second and third samples (if required by c.

Table 4.4-2 or Table 4.4-3) during each inservice ir.spection may be subjected to a partial tube inspection provided: 1) The tubes selected for these samples include the tubes from those areas of the tube sheet array where tubes with imperfections were previously found, and 2' The inspections include those portions of the tubes where imperfections were previously found. d. For Unit 1, any tube allowed to remain in service per-Acceptance Criterion 11 (of Technical Specification' 4.4.5.4a) shall be l inspected via the rotating pancake coil (RPC) eddy current method over the F* distance. Such tubes are exempt from eddy current inspection over the portion of the tube below the F* distance which is not structurally relevant. 4 plate repair (( criteria requires a 100-percent bobbin coi f:r " i t L. mplementation of the. steam. generator tube / tube support e. for hot-leg and cold leg tube support plate intersections down to the lowest cold-leg tube support plate with known outside diameter i stress corrosion cracking ('dSCC) late intersections having ODSCC indications. The determination of the lowest cold-leg tube support p indications shall be based on the performance of at least a 20-percent random sampling of tubes inspected over their full length. The results of each sample inspection shall be classified into one of the following three categories. Cateoory Inspection Results C-1 Less than 5% of the total tubes inspected are degraded tubes and none of the inspected tubes are defective. 4 SOUTH TEXAS - UNITS 1 & 2 3/4 4-13 Unit 1 - Amendment No. 82 83,90 7 Unit 2 - Amendment No. 77

REACTOR COOLANT SYSTEM t STEAM GENERATORS SURVEILLANCE RE0VIREMENTS (Continued) { 4.4.5.4 Acceptance Criteria l ] a. As used in this specification: 1) Tubina or Tube means that portion of the tube or sleeve which forms the primary system to secondary system pressure boundary; 2) Imoerfection means an exception to the dimensions, finish, or I contour of a tube from that required by fabrication drawings or l s)ecifications. Eddy-current testing indications below 20% of tie nominal tube wall thickness, if detectable, may be considered as imperfections; j 3)

Dearadation means a' service ' induced cracking,

wastage, wear, or l general corrosion occurring on either inside or outside of.a tube; 4) Dearaded Tube means a tube containing imperfections greater l than or equal to 20% of the nominal wall thickness caused by degradation; ~ 5) % Dearadation means the percentage of the tube wall thickness l affected or removed by degradation; 6) Defect means an imperfection of such severity that it exceeds the plugging or repair limit. A tube containing a defect is defective; 7) Pluaaina Limit or Repair Limit means the imp'erfection depth at or beyond which the tube shall be removed from service by plugging or repaired by sleeving in the affected area because it may become unserviceable prior to the next inspection. The plugging or repair limit imperfection depths are specified in percentage of the nominal wall thickness as follows:

a. ' original tube wall 40%

b. Westinghouse laser welded sleeve wall 40% 5 '., % I is definition does not apply to tube support J plate intersections for which the voltage-based repair criteria are being applied. Refer to 4.4.5.4.a.12 for the repair limit applicable to these intersections. 8) Unservic.eJhlg describes the condition of a tube if it leaks or l contains a defect large enough to affect its structural integrity in the event of an Operating Basis Earthquake, a loss-of-coolant' accident, or a steam ~line or feedwater line break as specified in Specification 4.4.5.3c., above; j 9) TubeInspectionmeansaninspectionofthesteamgeneratortubel from the point of entry (hot leg side) completely around the' U-bend to the top support of the cold leg; and SOUTH TEXAS - UNITS 1 & 2 3/4 4-15 Unit 1 - Amendment No. 83,90 Unit 2 - Amendment No. 77 i 1

8 i REACTOR' COOLANT' SYSTEM' e '-STEAM GENERATORS S*JRVEILLANCE REOUIREMENTS 1 Continued) 10) Preservice Insnection means an inspection of the full length of l each tube in each steam generator performed by addy current techniques prior to service to establish a baseline condition of the tubing. This inspection shall be perfomed prior to initial POWER OPERATION using'the equipment and techniques expected to be used during subsequent. inservice inspections 11) F* criteria fFor Unit 1 onivl Tube degradationIbelow a l s >ecified distance from the hard roll contact point at or near 1 tie top-of-tubesheet (the F* distance) can be excluded from consideration to the acceptance criteria stated in this section (i.e.. plugging of such tubes is not required). The methodology for determination for the F* distance as well as the list-of tubes to which the F* criteria is not applicable is described in detail in Topical Report - BAW 10203P, Revision O. PMILL 4Wr4 Lr> 12) i L'c.M y Tube Nunoort Plate Pluaaina Limit is used for the [ disposition of at alloy 600 steam generator tube for continued service that is Txperiencing predominately axially oriented outside diameter stress corrosion cracking confined within the thickness' of the tube support plates. At tube support plate intersections, the plugging'(repair) limit is based on maintaining steam generator tube serviceability as described below: a) Steam generator tubes, whose degradation is attributed to outside diameter stress corrosion cracking within the bounds of the tube support plate with bobbin voltage less than or equal to the lower voltage repair limit (Note.1), 1 will be allowed to remain in service. b) Steam generator tubes, whose degradation is attributed to outside diameter stress corrosion cracking within the bounds of the tube support plate with'a bobbin voltage greater than the lower voltage repair limit (Note 1), will be repaired or plugged, except as noted in 4.4.5.4.a.12.c l

below, c)

Steam generator tubes,.with indications of potential ' degradation attributed to outside diameter stress corrosion cracking within the bounds of the tube support plate with a bobbin voltage greater than the lower voltage repair limit (Note 1) but less than or equal to the upper repair voltage limit (Note 2), may remain in service if a rotating pancake coil inspection does not detect degradation. Steam generator tubes, with indications of outside diameter stress corrosion cracking degradation with bobbin voltage greater than the upper voltage repair limit.(Note 2) will be plugged or repaired. SOUTH TEXAS --UNITS 1 & 2 3/4 4-16 Unit 1 - Amendment No. 876,90 Unit 2 - Amendment No. 7/

I i REACTOR COOLANT SYSTEM g.T STEAM GENERATORS SVRVEILLANCE RE0VIREMENTS (Co inued) d) Certain ntersections as identified in Framatome Technologies, Inc. Topical Report BAW-10204P, " South Texas Project Tube Repair Criteria for ODSCC At Tube Support Plates" will be excluded from application of the voltage-based repair criteria as it is determined that l these intersections may collapse or deform following a postulated LOCA + SSE event. e) If an unscheduled mid-cycle inspection is perfcrmed, the mid-cycle repair limits apply instead of the limits ~ identified in 4.4.5.4.a.12.a, 4.4.5.4.a.12.b, and 4.4 5.4.a.12.c. The mid-cycle repair limits will be I determined from the equations for mid-cycle repair limits f of NRC Generic Letter 95-05, Attachment 2, page 3 of 7. l Implementation of these mid-cycle repair limits should follow the same approach as-in TS 4.4.5.4.a.12.a. l 4.4.5.4.a.12.b, and 4.4.5.4.a.12.c. Note 1: The lower voltage repair limit is 1.0 volt for 3/4-inch diameter tubing.:r 2.0 =lt; f;r 7/9 ' =h S r t:r t d h;. Note 2: The upper voltage repair limit (V is calculated according to the methodology in Generic Letter 95 $)as supplemented. V may m differ at the TSPs and flow distribution baffle.

13) Tube Repair refers to a process that reestablishes tube serviceability. Acceptable tube repair will be performed in l

accordance with the methods described in Westinghouse Reports l WCAP-13698, Revision 2, " Laser Welded Sleeves for 3/4 Inch Diameter Tube Feedring-Type and Westinghouse Preheater Steam Generators," April 1995 and WCAP-14653, " Specific Application of Laser Welded Sleaves for South Texas Project Power Plant Steam Generators," June 1996, including post-weld stress relief; Tube repair includes the removal of plugs that were previously installed as a corrective or preventive measure. A tube inspection per 4.4.5.4.a.9 is required prior to returning previously plugged tubes to service. l j b. The steam generator shall be determined OPERABLE after completing l the corresponding actions (plug or repair all tubes exceeding the plugging or repair limit and all tubes containing through-wall cracks) required by Table 4.4-2 and Table 4.4-3. 4.4.5.5 Reoorts a. Within 15 days following the completion of each inservice inspection ofsteamgeneratortubes,thenumberoftubespluggedorrepairedinl each steam generator shall be reported to the Commission in a Special Report pursuant to Specification 6.9.2; SOUTH TEXAS - UNITS 1 & 2 3/4 4-16a Unit 1 - Amendment No. 83,90 Unit 2 - Amendment No. 77 i { l

i REACTOR COOLANT SYSTEM STEAN GENERATORS SURVEILLANCE RE0UIREMENTS (Continued) b. The complete results of the steam enerator tube inservice inspection shall be= submitted to t e Commission in a Special Report pursuant to Specification 6.g.2 within 12 months following the completion of the inspection. This Special Report shall include: ) ) .1) ' Number and extent of tubes inspected, 2) Location and percent of wall-thickness penetration for each indication of an imperfection, and 3) Identification of tubes plugged or repaired. l Results of steam generator tube inspections which fall into Category - c. C-3 shall be reported in a Special Report to the Commission pursuant to Specification 6.9.2 within 30 days and prior to resumption of plant operation. This report shall provide a description of investigations conducted to determine cause of the tube degradation and corrective measures taken to prevent recurrence. d. For."..:. A implementation of the voltage-based repair criteria to tube support plate intersections, notify the Staff prior to returning the steam ~ generators to service should any of the following conditions arise: 1) If estimated leakage based on the projected end-of-cycle (or if l not practical, using the actual measured end-of-cycle) voltage distribution exceeds the leak limit (determined from the -licensing basis dose calculation for the postulated main steam; line break) for the next operating cycle. 2) If circumferential crack-like indications are detected at the l tube support plate intersections. 3) If indications are identified that extend beyond the confines l of the tube support plate. 4) If indications are identified at the tube support plate l elevations that are attributable to primary water stress corrosion cracking. 5) If the calculated conditional burst probability based on the l projected end-of-cycle (or if not practical, using the actgal measured end-of-cycle) voltage distribution exceeds 1 x 10', notify the NRC and provide an assessment of +,he safety significance of the occurrence. t I SOUTH TEXAS -_ UNITS 1 & 2 3/4 4-16b Unit 1 - Amendment No. 83,90 Unit 2 - Amendment No. 77

REACTOR COOLANT SYSTEM BASES l STEAM GENERATORSL(Continued), plants have demonstrated the capability to reliably detect degradation that has penetrated 20% of the original tube wall thickness. Repaired tubes are also included in the inservice tube inspection program. Exclusion of certain areas of Unit I tubes from consideration has been analyzed using an F* criteria. The criteria allows service induced degradation deep within the tubesheet to remain in service. The analysis methodology determines the length of sound fully rolled expanded tubing required in the uppermost area within the tubesheet to preserve r.eeded structural margins for all service conditions. -The remainder of the tube, below the F* distance, is considered not structurally relevant and is excluded from consideration to the customary plugging criteria of 40% throughwall. The amount of primary to secondary leakage from tubes left in service by application of the F* criterion has been determined by verification testing. This leakage has been considered in the calculation of postulated primary to secondary leakage under accident conditions. Primary to secondary leakage - during accident conditions is limited such that the associated radiological consequences as a result of this leakage is less than the 10 CFR 100 limits. ' " " ' The voltage-based repair limits of SR 4.4.5 implement the i guidance in GL 95-05 and are applicable only to Westinghouse-designed steam generator. JGs) with outside diameter stress corrosion cracking (ODSCC) located at the tybe-to-tube support plate intersections. The voltage-based repair limits are not applicable to other forms of SG tube degradation nor are they applicable to ODSCC that occurs at other locations within the SG. Additionally, the repair criteria apply only to indications where the . degradation mechanism is dominantly axial ODSCC with no significant cracks extending outside the thickness of the support plate. Refer to GL 95-05 for additional description of the degradation morphology. Implementation of SR 4.4.5 requires a derivation of the voltage structural limit from the burst versus voltage empirical correlation and then the subsequent derivation of the voltage repair limit from the structural limit (which is then implemented by this surveillance). The voltage structural limit is the voltage from the burst pressure / bobbin voltage correlation, at the 95-percent prediction interval curve reduced to account for the lower 95/95-percent tolerance bound for tubing material properties at 650'F (i.e., the 95-percent LTL curve). The voltage structural limit must be adjusted downward to account for potential flaw growth during an operating interval and to account for NDE uncertainty. -The upper voltage re air limit; V is determined from the structural voltage limit by app ying the fo1Nw,ing equation: Y ( _. _. _. K" V -Y -V st u NDE _. where V represent the allowance for flaw growth between inspections and V, represe$s the allowance for potential sources of error in the measurement E j the bobbin coil voltage. Further discussion of the assumptions necessary to j ' determine' the voltage repair limit are discussed in GL 95-05. SOUTH TEXAS - UNITS 1 & 2 B 3/4 4-3 Unit 1 - Amendment No. Bh83,90 Unit 2 - Amendment No. 77

. REACTOR COOLANT SYSTEM BASES ' OPERATIONAL LEAKAGE-(Continued) I T;,, U.,';. he ' leakage limits ' incorporated into -SR 4.4.6 L are more . restrictive than the standard operating leakage limits and are intended to provide'an additional margin to accommodate a crack which might grow at a greater than expected rate or unexpectedly extend outside the thickness of the tube' support plate. Hence, the reduced leakage Unit,' when combined with an effective leak rate monitoring program, providos moditional assurance that should a significant leak be experienced in service, it will be detected, and the plant shut down in.a timely manner. . Tr l':"; L ::dde steam generator tube leakage limit of 150 gpd for each steam generator not isolated from the RCS ensures that the dosage contribution from the tube leakage will be limited to a small fraction of 10 CFR Part 100 dose guideline valves in the event of either a steam generator ~ tube rupture or steam'line break. The 150 gpd limit per steam generator is conservative compared to.the assumptions used in the analysis of these accidents. The.150 gpd leakage limit per steam generator ensures that steam generator tube integrity is maintained in the event of a main steam line' rupture or under LOCA conditions. The 10 gpm IDF' ^FIED LEAKAGE limitation provides allowance for a limited amount of leakage a known sources whose presence will not interfere with the detection of UN wENTIFIED LEAKAGE by the Leakage Detection Systems. -The specified allowed leakage from any RCS pressure isolation valve is sufficiently low to ensure early detection of possible in-series check. valve failure. It is apparent that when pressure isolation is provh'ed by two in-series check valves and when failure of.one valve in the pair can go undetected for a substantial length'of' tim, verification of valve integrity is required.' Since these valves are impor; ant in preventing overpressurization and rupture of the ECCS low pressure piping which could result in a LOCA that bypasses containment, 'these valves should be' tested periodically to ensure low probability of gross failure. The Surveillance Requirements for RCS pressure isolation valves provide added' assurance of valve integrity thereby reducing the probability of gross valve failure and' consequent intersystem LOCA. Leakage from the RCS pressure isolation valve is IDENTIFIED LEAKAGE and will be considered as a portion of the allowed limit'. 3/4.4.7 CHEMISTRY The. limitations on Reactor Coolant System chemistry ensure that corrosion of the Reactor Coolant System is minimized and reduces the potential for Reactor Coolant System leakage or failure due to stress corrosion. Maintaining 1 SOUTH TEXAS -UNITS 1 & 2 8 3/4 4-4 Unit 1 - Amendment No. 83,90 j Unit 2 - Amendment No.77 ) i )

m l I l l l ATTACHMENT 5 l l PROPOSED CHANGES TO IMPROVED l TECHNICAL SPECIFICATIONS i l l l l l 1 i I i l E:\\WPNI.\\NRC-WK\\TSC48\\0097 DOC STI: 30547247

Programs and Manuals t 5.5 i 5.5 Programs and Manuals ) 5.5.9.2 steam Generator Tube Samnle selection and Insoection (continued) l 1. The tubes selected for these samples include the tubes I from those areas of the tube sheet array where tubes with imperfections were previously found W 2. The inspections include those portions of the tubes where imperfections were previously found. L For Unit 1. any tube allowed to remain in service oer accentance Criterion 11 (of Technical Snecification 5.5 9.4.a shal l be ins 3ected via the rotatina cancake coil (RPC) eddy current met 3od over the F* distance. Such tubes i are examnt from eddy current ins Section over the nortion of ~ 11ch is not structurally 1he tube below the F* distance w relevant. Tmolomantation of the steam cence-tor tube / tube L I runoort olatT reoair criteria reouires a 100-oercent bobbin I coil insoection for hot-leo and cold-leo tube suonort olate ~ intersections down to the lowest cold-leo tube su3nort olate ~ with known outside diameter stress corrosion cractina (ODSCC) indications. The determination of the lowest cold-l leo tube succort olate intersections havino ODSCC ~ indications shall' be based on the nerformance of at least a 20-oercent random samnlino of tubes insnected over their full lenath. 3 The results of each sample inspection shall be classified into one of the following three categories: l Cateaory Insoection Results C-1 Less than 5% of the total tubes inspected are degraded tubes and none of the inspected tubes are l defective. C-2 One or more tubes. but not more than 1% of the total tubes inspected are defective, or between 5% and 10% of the total tubes inspected are degraded tubes. C-3 More than 10% of ths total tubes inspected are degraded tubes or more than 1% of the inspected l tubes are defective. (continued) South Texas Units 1 & 2 5.0-15 Rev 0. 07/18/97

1 i Programs and Manuals 5.5 5.5 Programs and Manuals 5.5.9.4 Accentance Criteria (continued) i to the next insnection. The cluaaina or reoair limit imoerfection dent 1s are soecified in cercentaae of the j nomina) wall thictness as'follows-L, criainal tube wall M h,,, Westinahouse laser welded sleeve wall M snA 4e nm esi +n A M' n# + hn nam 4nsi + e nha o%11 + h 4 rte nne e. f5 E.dWs definition does not an31v to tube ~ supoort olate intersections for which t ie voltaae-based recair criteria are beina an311ed. Refer to S.6.9.4.a.12 ~ for the renair limit anolicalle to these intersections. 78 Unserviceable describes the condition of a tube if it leaks or contains a defect large enough to affect its structural integrity in the event of an Operating Basis Earthquake, a loss-of-coolant accident, or a steam line or feedwater line break as specified in Specification 5.5.9.3.c. above: l

89. Tube Insnection means an inspection of the steam i

generator tube from the mint of entry (hot leg side) completely around the U-:end to the top support of the cold leg: and 910. Preservice Insoection means an inspection of the full length of each tube in each steam generator performed by eddy current techniques prior to service to establish a baselineconditionofthetubingdEP.OoEPATLgectionshall This ins be performed prior to initial P. N Power Operation (Mode 1) using the equipment and techniques expected to be used during subsequent inservice inspections. IL, F* criteria FFor Unit 1 onivl Tube dearadation below a specified distance from the hard roll contact ooint at or near the too-of-tubesheet (the F* distance) can be l excluded from consideration to the accentance criteria stated in this section (i.e. oluaaina of such tubes is not reauired). The methodoloav for determination for the l F* distance as well as the list of tubes to which the F* criteria is not a3nlicable is described in detail in Tonical Reoort - MW 10203P. Revision 0. (continued) South Texas Units 1 & 2 5.0-21 Rev 0. 07/18/97 l

t Programs and Manuals 5.5 g -5.5 Programs and Manuals 5.5.9.4 Accantance criteria (continued)' 1 r-Tube Runnnrt " ate Pluaaina iimit is' used 4 for tie disnnsition of amra' lov 600 stamm oenerator tube - for continuad service that is exneriencina nrednminately axially orientad outside diameter stress corrosim ~ crackina confined within the thickness of the tuw sunnart olates. At tuhe suinart nlate intersections. the' oluaaina'fra3 air) ' imit in nsed en maiitaisina staam 'enerat6r tu ia servirpahi' ity as rescri 3ed Selow. a L. Steam oenerator tubes.' whose dearadation is l attributed t3 outside diameter stress corrosion crackina wit 111 the 30unds of the tuha sunnort l olate witi bnhiin voltaae less than or enisl to the i lower voltaae renair 'limit (Note 1). will be L allowed to remain in service I jL Staam aenerator tuhas. whose dearadation is attributed to outside diameter stress corrosion crackino wit 111n the bounds of the tube suniort olate with a hnhhin voltaan areater than tie ' nwar ~( vo' taae renair limit (Note 11. will be renaired or olucaed excent as noted in 5 5 9.4.a 12.c below. t Steam aenerator tubes. with indications of notential dearadation attributed to outside ) iiameter stress corrosion crackina within the 1

30unds of the tu3e suniort olate with a bnhhin voltaae areater than tie 'lower voltale renair limit l

(Note 1) but less than or enual to tie unner renair voltaae limit (Note 2) may remain in service if a l rotatina nancake coil insnection does not detect dearadation.- Steam oenerator tubes. with indications of outside diameter stress corrosion l-crackina dearadat'on with bnhh'n voltaae areater l L UNtT t1an the unner vo' taae renair limit (Note 2) will be niuaoed'or renaired. gL ' Certair1Dintersections as ' dentified in Framatnma Technoloaies Inc. Tonica' Renort BAW-10204P. " South Texas Proiect Tube Renair Cr teria for MSCC j At Tube Sunnart Plates" will'be exc"uded from (continued) South Texas Units 1 & 2 5.0-22 Rev 0. 07/18/97

Programs and Manuals 5.5 5.5 Programs and Manuals 5.5.9.4. Accentance Criteria (continued) ann'lication of the voltaae-based renair criteria as - it~ - s determined that these intersections may col' ante or deform followina a nostu' lated OCA + SSF event. ~ L If an unsche1uled mid-cvele insnection is nerformad tie liid-cycle renair limits anniv ~ L instead of the ' imits identified in 5.5 Q~.4.a 12 a. i 5.5.9.4 a 12.b. and 5.5.9.4.a.12.c. The mid-cvele renair limits will be determined from t1e enuations for mid-cyc' e renair of Nic Generic t etter 95-05. Attachmant 2. naae 3 of 7. unlarentation of these mid-cycle renair limits shou' c~ fo' low the same ant roach as in TS 5 5.9.4.a ML2 a. 5 5.9.4.a.12 b. anc 5 5.9.4.a.12 c. Note 1-The lower voltaae re3 air limit is '.0 volt for l 3/4-inch diamater tinina er 21 ;;' t: f:r '!E ' :h M t Note 2-The unner voltaae re3 air limit (V._iis calculated ggcordina to the mot iodoloov in Geheric t etter i 95-05 as sunn' amanted V._ may differ at the TSPs and flow distribution bafYle. IL Tube Renair refers to a 3rocess that reestablishes tube l-servicaahility. Accenta 31e tuba renair will be nerformed in acccrdance with t1e methods described" n Westinahouse Renorts WCAP-13698. Revision 2. "iaser We' ded S' eeves for L 3/4 Inch Diameter Tube Feedrina-Tme and Westin1 house l Preheater Steam Generators " Anri' ~1995 and WCA)-14653. 1 "Snecific Ano11 cation of l aser We' ded Sleeves for South l Texas Proiect Power P1 ant Steam Generators." < lune 1996 i i nc' udina nost weld stress relief. j 1 Tube renair includes the ramnval of niuas that were orevious' v installed as a coric-ctive or oreventive measure. A tube insnection ner 5.5 9.4.a.9 is reouired ~ orior to returnina nreviousiv niunaed tubes to service. b. The steam generator shall be determined OPERABLE after completing the corresponding actions (plug or renair all (continued) South Texas Units 1 & 2 5.0-23 Rev 0. 07/18/97 i-

Reporting Requirements 5.6 5.6 Reporting Requirements (continued) l-l l 5.6.98 Tendon Surveillance Reoort Any abnormal degradation of the containment structure detected during the tests required by the Pre-stressed Concrete Containment L Tendon Surve11hnce Program shall be reported to the NRC within 30 days. The report shall include a description of the tendon condition, the condition of the concrete (especially at tendon anchorages), the inspection procedures. the tolerances on cracking. and the corrective action taken. l 5.6.M2 Steam Generator Tube Insnection Reoort I The Steam Generator Tube Surveillance Program shall be documented in reports submitted to the NRC in accordance with the following: a. The number of tubes plugged or renaired in each steam generator shall be reported within 15 days following completion of the pregr-am insoection. b. Thecomp:leteresultsoftheSteamGeneratorTube-Serveil. ::: Pr~;r:: insoection shall be re months following completion of the pr~;r:= ported within 12 insnection and shall include: 1. Number and extent of tubes inspected. 2. Location and percent of wall thickness penetration for each indication of an imperfection, and 3. Identification of tubes plugged or renaired. c. The results of steam generator tube insstions which fall into Category C-3 shall be reported wit 11n 30 days ef-@e ~;10ticn of the pr^gr:= and prior to resumption of plant i operation. The report shall include a description of .j investigations conducted to determine the cause of the tube l degradation and corrective measures taken to prevent recurrence. L _. For M im31amantation of the voltaae-based renair criteria to tuw suonort olate intersections. notify the Staff orior to retu' nina the steam aenerators to service r ~ should any of the followina conditions arise-1. If estimated leakaae based on the croiected end-of-cycle (or if not oractical. usina the actual measured end-of-(continued) South Texas Units 1 & 2 5.0-38 Rev 0. 07/18/97 \\

l ATTACHMENT 6 i l i I l WESTINGHOUSE STEAM GENERATOR REPORT SG-98-01-004 r i i l i l l l-E:\\WPiNL\\NRC-WK\\TSC-98\\0097. DOC STI: 30547247

SG-98-01-004 SOUTH TEXAS PROJECT UNIT 2 Technical Bases Supporting Application For License Amendment: Voltage Based Repair Criteria per GL 95-05 1.0 Introduction The STP Unit 2 Technical Specifications currently assess steam generator tube operability based on an indicated 40% (by NDE) degradation depth. Accurate depth sizing of stress corrosion cracking in SG tubes is difficult, and SG tube burst and leakage integrity is ultimately dependent upon both flaw depth and length, the latter not incorporated into the current Unit 2 depth based Technical Specification tube repair criteria. Bobbin coil voltage analysis has been shown to provide a more accurate assessment of tube structuralintegrity than depth based phase analysis for tubes affected by outer diameter stress corrosion cracking (ODSCC). Therefore, the Voltage Based Repair Criteria for ODSCC at tube support plate (TSP) intersections, addressed by NRC Generic Letter 95-05, provides an alternative method for the assessment of SG tube repair requirements due to predominantly axially oriented ODSCC at TSP intersections. By directly relating bobbin voltage response to burst capnility, the voltage based repair criteria represents a more appropriate tube integrity assessment tool compared to depth sizing alone. The voltage based repair criteria has been implemented at 5 plants using Westinghouse steam generators with 7/8" OD mill annealed Alloy 600 tubing and 4 plants with Westinghouse steam generators using 3/4" OD mill annealed Alloy 600 tubing (the latter being Catawba 1, Byron 1, Braidwood I and South Texas Unit 1). The implementation of the criteria at these plants has justified continued operation for thousands of steam generator tubes with bobbin eddy current signals at TSP intersections which would have required repair using the current depth based criteria and industry plugging practices. STPNOC requests approval for use of the voltage based repair criteria per GL 95-05 for the upcoming 1998 Cycle 6 inspection (2RE06 outage) based on the detection of ODSCC at TSP intersections in 2RE05 and 2RE04. Therefore, the criteria will be implemented beginning with the Cycle 7 operating period. As the ODSCC mechanism at STP Unit 2 is in its early stages, application of the voltage based plugging criteria will prevent the unnecessary plugging of steam generator tubes at TSP intersections due to the uncertainty related to depth estimation of ODSCC at TSPs. The purpose of this attachment is to provide the technical basis supporting a license amendment request implementing the 1.0 volt repair criteria for steam generator tubes affected by ODSCC, according to the guidance of NRC Generic Letter 95-05 (Reference 1) at South Texas Unit 2. This attachment describes the STPNOC plan for implementation of the 1.0 volt repair limit and the requirements of GL 95-05. Sections 1 to 6 of Attachment 1 to GL 95-05 are addressed herein to summarize the STP Unit 2 plan, which meets the intent of GL 95-05, and is consistent with l 1 l

1 SG-98-01-004 NRC approved updates to the originally issued GL 95-05 methods. Clarifications to the Section 3 " Inspection Criteria" articles are identified in the corresponding section of this attachment. These relste to implementation of the bobbin probe variability requirements (Section 3.c.2), the probe wear requirements (Section 3.c.3) and the use of alternate probes to the RPC probe. In addition, STPNOC is requesting the use of a voltage dependent probability of detection, the methodology of which was originally submitted to the NRC for review by NEI in December of 1996. i 1.1 South Texas Unit 2 Design Features t STP Unit 2 is a Westinghouse 4-loop pressurized water reactor plant which utilizes Model E2 steam generators (SG) with 3/4 inch diameter mill annealed Alloy 600 tubing and drilled hole stainless steel tube support plates (TSPs). A total of 15 tubes in SG D use thermally treated Alloy 600 tubing, and these tubes,' identified later, are excluded from application of the criteria since they are not constructed of Alloy 600 mill annealed tubing. While thermally treated Alloy 600 tube materialis less susceptible to stress corrosion cracking than mill annealed Alloy 600 tube material, should ODSCC develop in these tubes, the postulated corrosion morphology cannot be adequately determined without a tube pull. The benefit obtained by application of the criteria to these tubes is not perceived to be greater than the economic impact of a tube pull, should degradation occur in these tubes. The Model E2 SG incorporates a flow distribution baffle ~ (FDB) plate located approximately 8 inches above the top of the tubesheet, like the Unit 1 SGs, and similar to other SGs in which the voltage based plugging criteria are applied, such as the Model D4 steam generator. The tube holes located in the FDB design include an increased nominal tube to plate diametrical gap ranging from approximately 0.083" to 0.120", compared to a 0.017" to 0.021" nominal gap at the TSPs. Based on this increased tube to plate gap at the FDB, an upper voltage repairlimit based on providing tube structuralintegrity against a pressure equivalent of three times the normal primary to secondary tube differential pressure is provided. The design features of the South Texas Unit 2 steam generators are consistent with the scope of applicability of GL 95 05. While not specifically addressed by GL 05-05, the voltage. based repair criteria can be applied to the TSP intersections at STP Unit 2 without modification or exception due to the TSP material (405 SS). A large portion of the %" pulled tube data base is - taken from pulled tube data from the Doel-4 plant, which originally used Model El SGs with 405 SS TSPs, prior to SG replacement. Confirmatory eddy current testing was performed using both carbon steel and stainless steel TSP simulants to show that the primary mix channel bobbin coil voltage response is unaffected by the TSP material. The results of this testing is discussed in i greater detail in report section 3.0, "GL 95-05 Section 2." 2 j

1 I SG-98-01-004 1.2. Summary of the Voltage Based Repair Criteria The following items outline the specific requirements and actions assouated with the implementation of the voltage based repair criteria at STP Unit 2. -

• All tubes shall be inspected using the bobbin coil. The inspe.cion shall include all hot leg l

i TSP intersections and cold leg intersections down to the lowest TSP for which ODSCC has ~ been identified. Bobbin coil flaw indications greater than 1.0 volt shall be inspected by a rotating coil probe (or equivalent) to evaluate the presence of detectable ODSCC and to con 6rm that the dominant corrosion mechanism occurring is axially oriented ODSCC. Eddy current analysis guidelines shall be compatible with and satisfy GL 95-05 requirements. Technical Specification operationalleak rate limit (LCO 3.4.6.2) shall be reduced to 150 gpd \\ per steam generator. The STP Unit 2 normal operating condition leakage limit has been j previously reduced to the GL 95-05 value of 150 gpd. Axial ODSCC indications less than the lower voltage repair limit,1.0 volt, as measured by ' bobbin coil, may remain in service without further inspection or analysis. .{ ) Axial ODSCC bobbin coil indications greater than 1.0 volt and less than or equal to the upper voltage repair limit (Vuat) can remain in service if MRPC inspection indicates no detectable degradation. Axial ODSCC bobbin coilindications greater than 1.0 volt and less than or equal to the upper voltage repair limit (Vunt) must be repaired if MRPC inspection indicates detectable degradation.- 1 Axial ODSCC bobbin coil indications exceeding the upper voltage repair limit must be e repaired. Postulated Faulted condition primary to secondary leakage through indications to which the criteria is applied shall be calculated using accepted industry and NRC approved practices. Postulated leakage in the limiting steam generator shall be less than the bounding faulted condition leakage necessary to ensure that offsite doses remain within the 10 CFR 100 siting criteria and that control doses remain within GDC 19 limits. Projected tube burst probability at a pressure differential equal to the limiting faulted condition pressure differential shall be calculated using accepted industry and NRC approved practices and compared to the reporting value of 1.0 x 108 in the limiting steam generator. 1.8 Acknowledgment of GL 95-05 Performance Requirements Table 1 (provided on the following pages) presents an item by item identification of the . individual points of GL 95-05 which require utility action or present a specific analysis methodology. 3

j SG-98-01-004 Table 1 I Acknowledgment ofIndividual GL 95-05 Performance Criteria t GL 95 05 GL Methodology Comments Item Concurrence 1.b Followed The exclusion criteria listed will be followed. No intersections are excluded due to pernianent deformation potential from a combined LOCA + SSE event. Table 2 lists tubes excluded based on material properties. for FDB intersections is defined in Section 2. 2.a.1 Modified from The latest NRC approved database at the time of the inspection will be original version, utilized. Currently, the database defined in Reference 6, EPRI NP-7480-L, approved by NRC Addendum 1, is the latest NRC approved database for %" tubing. This database supersedes the database identified in GL 95-05. 2.a.2 Followed See response to section 2.a.1. 2.a.3 Followed See response to section 2.a.1. 2.b.1 Request for NRC Distribution of bobbin indications included in the SLB leakrate projection approval will be based on the voltage dependent probability of detection, or POPCD, as described in Reference 6. 2.b.4 Followed Consistent with the STP UFSAR, ICRP 2 dose conversion factors were used for calculation of maximum allowable SLB leak rates. These dose conversion factors are more conservative than the ICRP 30 data. 3.b Followed STPNOC will utilize the rotating pancake probe (RPC) or equivalent probe for confirmation of bobbin indications. 3.b.1 Followed RPC (or equivalent) will be used for inspection of bobbin voltages > 1.0 volt. 3.b.2 Followed RPC (or equivalent) will be used for inspection where copper could influence bobbin signal, possibly masking a 1.0 volt indication. 3.b.3 Followed RPC (or equivalent) will be used for inspection of all dents > 5 velts, possibly masking a 1.0 volt indication. 3.b.4 Followed RPC (or equivalent) will be used for inspection of large mixed residuals, possibly masking a 1.0 volt indication. 3.c2

Modified, The probe variability limits defined in the NRC letter dated March 18,1996 accepted by NRC will be implemented.

3.c.3

Modified, Limits on reinspection of tubes due to out of specification probe wear will be accepted by NRC followed according to the NRC letter daad February 9,1996.

3.c 4 Followed Data analysts will be trained and qualified in the use of the analysis guidelines and procedures specific for application of the criteria 4. Followed Tube removal r_ddance will be followed. 5.a Followed Operat'onalleakage (LCO 3.4. 6.2) has previously been reduced to 150 gpd / SG 5.b Followed STPNOC leakage monitoring techniques ace 5nsistent with Reference 7, and are adequate to meet GL 95-05 recommendations. 5.c Followed Known leaking tubes will be repaired. 6. Followed Reporting requirements will be followed. 4 I 1

SG-98-01-004 l 2.0 GL 95-05 Section 1: APPLICABILITY The repair criteria will be applied to axially oriented ODSCC indications at tube to TSP and FDB intersections (within the plate thickness) of the steam generator tube bundle. The relatively small bobbin voltages observed indicate that the degradation morphology is currently in its early stages of development. Of the 1056 observed bobbin indications at the TSPs,699 were removed from service due to the total plugging effort (including plugging for top of tubesheet, AVBs, etc). Of the 1050 total DSis,660 (62.5%) were confirmed by RPC as either multiple axial indications (MAI, 28 indications), single axial indications (SAI, 630 indications), or volumetric (2 indications). Consistent with Section 4.a of Attachment 1 to GL 95-05, a minimum of two tubes (and 4 intersections) will be removed from STP Unit 2 for destructive examination upon initialimplementation of the criteria. Tubes pulled from other plants using both 7/8" and 3/4" OD tubing for indications of ODSCC at TSPs have been shown to have crack morphology consistent with the EPRI database used for the supporting voltage correlations. It should be noted that the majority of the pulled tubes currently included in the %" tube pulled tube database have been removed from the Doel 4 plant, which also utilized Model E steam generators of a design similar to STP Unit 2, including the use of 405 SS drilled hole TSPs. Any other type of tube degradation or any other location in the tube bundle other than the TSPs shall continue to be evaluated in accordance with existing STP Unit 2 Technical Specifications. The observation of circumferential cracks, or primary water stress corrosion cracking associated with TSP indications, or ODSCC beyond the TSP thickness will be reported to the NRC prior to return to power. The voltage based repair criteria will not be applied at the following tube-to-TSP intersections of the steam generator tube bundle: 1. At locations where tubes with decradation could substantially deform or collaose durine nostulated LOCA + SSE loadine. Conservative analysis results summarized in Appendix A indicate that no intersections meet the criteria for exclusion based on permanent deformation exceeding 0.030" during the combined LOCA + SSE event. Appendix A provides a summary of the tube collapse determination methodology. Bounding LOCA rarefaction wave loadings for the surge line and accumulatorline breaks and STP Unit 2 seismic input data were used to perform the analyses outlined in Appendix A. The resulting loads on the TSPs are compared to data from a TSP crush test program to ultimately determine the susceptibility to tube deformation greater than the 0.030" limit and to define the list of excluded intersections. The NRC Staff has concluded that STP Unit 2 is in compliance with GDC 4, and that therefore, the probability of a rupture of the primary reactor coolant piping and surge line is extremely low. The dynamic effects of postulated pipe ruptures are therefore eliminated from the design basis. The technical support document for the Unit I voltage based plugging criteria application (approved by the NRC 5 i

L l-SG-98-01-004 staff) sites the use ofleak before break (LBB) application to exclude large break loaang.: The analysis performed by Westinghouse uses bounding LOCA inputs for the surge line and accumulator line breaks.' The LOCA loadings used conservatively bound all of the small break locations and sizes.' The tube exclusion analysis methodology employed by Westinghouse has been shown to be quite conservative. The NRC has permitted the use of small break combined event loadings for voltage based repair criteria evaluation for another plant with D4 steam generators (Reference 8) as well as for South Texas Unit 1. l 2. At tube-TSP intersections with dent airnala exceedina 5.0 Gobbin) volts. Any indications confirmed by RPC will be plugged or repaired (sleeved). 3. At tube TSP intersections where mixed residuala could mask a 1.0 volt bobbin volt ODSCC indication. Any indications confirmed by RPC will be plugged or repaired (sleeved). l. 4. At tube TSP intersections where concer denosits interfere with bobbin volt sienals. Any l-indications confirmed by RPC (or equivalent, i.e., + Point) will be plugged or repaired. No occurrence of copper deposits at a TSP intersection has been found for any Westinghouse SG for which the ARC has been applied. 5. At tube intersections in which the tube material is not consistent with the currently I accented database. A total of 15 tubes in SG D at STP Unit 2 use thermally treated Alloy L 600 tube material and these tube locations'are identified in Table 2. For NDE, structural l and leakage considerations, the responses of thermally treated and mill annealed tubing is expected to be similar. For conservatism, and since no corrosion degradation in thermally treated Alloy 600 tubing has been evidenced, or confirmed by tube pulls, the tubes listed in L Table 2 will be excluded from application of the criteria. The thermally treated tubes in Table 2 are expected to be less susceptible to stress corrosion cracking than mill annealed tubes. Table 2 ' South Texas Unit 2 SG D Tubes Excluded from Application of the Voltage Based Repair Criteria due to Use of Thermally Treated Alloy 600 Tube Material R13 C61 R14 C61 R15 C62 R16 C62 R13 C62 R14 C62 R15 C63 - R.16 C63 l R13 C63 R14 C63 R15 C64 L-R13 C64 R14 C64 R15 C65 R13 C65 6 l l

SG-98-01-004 8.0 GL 95-05 Section 2: TUBE INTEGRITY EVALUATION There are three principal engineering analyses that shall be performed during each 1.0 volt repair process at STP Unit 2: Prediction of SG bobbin voltage population distribution at end of ne.xt cycle. a. b. Calculation of SG tube leakage during a postulated steam line break (SLB). Calculation 'of SG tube burst probability during a postulated SLB. c. The latest approved EPRI database (3/4 inch diameter tubing) utilizing NRC approved data exclusion criteria will be applied in the voltage correlations (burst, probability ofleakage, SLB bk rate) used for the leak rate, burst probability and upper voltage repair limit calculations. The NRC approved industry protocol for updating the database will be followed by STPNOC. The methodchgy to be applied by STPMOC at STP Unit 2 for the performance of these analyses, including correlations which relate bobMn voltage amplitudes, free span burst pressure, probability ofleakage and associated leak rates is documented in Reference 2 and is consistent with the methodology of Attachment 1, Section 2 of GL 95-05. The NRC approved revisions to Reference 2 or equivalent methodology reports will be implemented. In addition, the upper voltage repair limit used to repair bobbin indications independent of RPC confirmation will be determined at each outage based on the guidance of Section 2.a.2 of GL 95-05. For example purposes, the EOC 5 bobbin signals are projected to EOC 6 (the current cycle) conditions using this methodology. At EOC 5,100% of the tubes in all four steam generators were inspected using the bobbin probe. As a less than 100% bobbin inspection was performed at EOC 4, growth values for DSIs inspected at EOC 3 but not EOC 4 were adjusted based on the estimated operating cycle lengths of Cycle 4 and Cycle 5 to develop Cycle 5 growths for these indications (see Figme 1). Using this growth projection, the limiting conditional tube burst probability at EOC 6, assuming the criteria were applied at EOC 5,' was found for SG A and determined to be 1.69 x 104, which is well below the GL 95-05 reporting limit of 1.0 x 104 The example case BOC 6 (assuming no tubes were plugged and assuming the criteria were applied at EOC 5) and EOC 6 bobbin voltage distributions for all 4 steam generators assuming a POD of . 0.6 are provided in Figures 2a thru 2d.. All tubes were assumed to have been left in service since the bobbin voltages were allless than the upper voltage repair limit. The low conditional burst probability calculated in the example using a POD of 0.6 should not be used to reduce the importance of the applicability of POPCD, it only shows that the occurrence of ODSCC at TSPs at STP Unit 2 is in its' early stages. 7 i

SG-98-01-004 SLB Tube Leak Rate - The calculated maximum allowable tube leak rate for STP Unit 2 during a postulated main steam line break (SLB) event shall not exceed 5.0 gpm in the faulted loop (calculated at room ' temperature conditions). This value was established for the STP Unit i voltage based repair criteria implementation and applies to both Units. The 5.0 gpm leak rate value in the faulted loop (with leakage in the intact loops equal to the Technical Specification normal operation leakage limit of 150 gpd) will not result in either control room dose exceeding the GDC 19 limit . or the off. site dose exceeding 10% of the 10 CFR 100 guidelines for accident initiated iodine spiking or off site dose exceeding the 10 CFR 100 guidelines for preaccident iodine spiking, and therefore is consistent with the STP Unit 2 licensing basis. Ifit is determined during the operating ' cycle that this leakage limit might be exceeded, the reporting requirements of Section - 6.'a.1 will be followed. The calculated leakrate limit and maximum allowable leakrate values for STP Unit 2 are speci5ed as room temperature values, therefore, these values are compared using a consistent set of reference conditions.- ' Consistent with the guidance of Section 2.c, the STP Unit 2 SLB leak rate analysis performed . prior to returning the SGs to service may be performed based on the projected next EOC voltage distribution or the actual measured distribution at a given outage. The method selected at a given outage will be based on outage schedule constraints, particularly the ability to complete the growth rate analysis prior to reetart. Leak rate analysis for STP Unit ' 7ill be performed for a limiting primary to secondary pressure differential of 2407 psig, which represents the - pressurizer PORV setpoint of 2335 psig plus 3% accumulation effects. The NRC staff has concluded that the STP Unit 2 pressurizer PORVs and associated block valves will be available during postulated accident or transient event recovery, and therefore can be relied upon to control RCS pressure during accident or transient recovery. Using the EOC 5 voltage distributions for the STP Unit 2 SGs, projected EOC 6 SLB leak rates. were simulated assuming no tubes were plugged at EOC 5 since all of the bobbin voltages were . less than~the upper voltage repair limit. Using a POD of 0.6,' the limiting leak rate is found to be

0.0139 gpm in SG A (room temperature conditions). The simulated leak rates, burst probabilities and largest simulated indication voltages 'are provided in Table 3. These simulations are exceptionally conservative since 699 of the 1056 total TSP indications were

- plugged at EOC 5, and the simulation of SLB leakage was done at a pressure differential of 560 2 psig, whereas availability of pressurizer PORVs and block valves will permit the RCS to be controlled to a maximum of 2335 psig (plus 3% accumulation) during recovery from a postulated . SLB event. ' Also contained in Table 3 are the simulation results for SG A (largest growth) and SG B (largest number BOC 6 indications) using actual BOC 6 voltage distributions, which include the plugging effects. 8 s A

SG-98-01-004 Table 3 STP Unit 2 EOC 6 Leak Rate and Burst Probability Simulation Results Assuming No Tubes Plugged at EOC 5 SG Leak Rate (gpm) Burst Probability Largest Simulated Ind. Voltage A 0.0139 1.69 x 10 4 2.50 B 0.005!i 8.98 x 104 2.50 0 0.0042 6.05 x 10 4 1.90 D. 0.0013 2.37 x 10 4 1.80-STP Unit 2 EOC 6 Leak Rate and Burst Probability Simulation Results Using Actual 300 6 Voltage Distribution A 0.0062 4.9 x 10 4 2.30 h B 0.0027 2.6 x 10 4 2.30 Note: Leak Rate and burst probability based on SLB AP of 2560 psig. Conservative for STP Unit 2 due to PORV availability during SLB recovery limits AP to.2335 psig + 3% accumulation. The offsite dose calculations have been performed consistent with GL 95-05 recommendations and other analyses previously approved by the NRC related to the GL 95-05 plugging criteria. The SLB leak rate limit for Unit 2 is consistent with the Unit I limit. The analysis of SLB effects upon the reactor core, fuel, and DNBR potential described in the South Texas UFSAR indicates no DNB occurs for any rupture assuming the most reactive assembly is stuck in the fully withdrawn position for the SLB event. ~ Pressurizer PORV Availability 1 Per Section %.4.4 of the South Texas Units 1 and 2 Tech Spees, LCO 3.4.4 requires that both pressurizer PORVs and their associated block valves shall be OPERABLE during Modes 1, 2, and 3. Action statements are included in the Technical Specifications which limit PORV inoperability to a maximum of I hour. Unlike most other PWRs, the South Texas 1 and 2 PORVs and block valves can be relied upon to function during transient or accident recovery conditions. The South Texas PORVs and block valves are safety class 1 valves and within the scope of a quality assurance program in compliance with 10 CFR 50, Appendix B. The South Texas 1 and 2 PORVs are solenoid - operated, Class 1E powered, and are seismically and environmentally qualifi d. The pilot valve e which causes activation of the PORV is operated by a 125 VDC solenoid powered by battery backed vital switchgear EIA11. The AC supply for the switchgear is ESF diesel backed. The l South Texas 1 and 2 solenoid operated PORVs and block valves are included in the ISI program covered by Subsection IWV of Section XI of the ASME Code. The PORV block valves are included in the South Texas expanded MOV test program. By design, the operability of the 9

L SG-98-01-004 PORVs is not based on the automatic control function. Inoperabidty of the PORVs automatic function during manual operation does not result in inoperability of the PORVs manual operation. The South Texas 1 and 2 Technical Specifications incorporate the recommendations . provided in Enclosure A and Enclosure B of GL 90-06, thereby resolving Generic Issues 70 and 94. The NRC Staff has concluded in SER Amendment No. 55 to NPF-76 (Unit 1) and SER TAmendment No. 44 to NPF 80 (Unit 2), that the PORVs and their associated block valves satisfy Generic Issues 70 and 94. . As the South Texas pressurizer PORVs and block valves can be relied upon during transient and accident recovery conditions, operator action will result in RCS pressure being maintained well below the PORV setpoint. The maximum SLB pressure differential for burst and leakage . analyses is then 2407 psig based on the pressurizer PORV setpoint of 2335 psig plug 3% measurement uncertainty allowance. Voltage Dependent Probability of Prior Cycle Detection (POPCD) Section 2.b.1 of GL 95 05 includes a bobbin coil probability of detection (POD) of 0.6. This POD 'value is considered exceptionally conservative, especially for larger voltage indications. GL 95- - 05 states that an alternative POD function can be used, if one becomes available, and is subsequently approved by the NRC. NRC approvalis requested to apply the EPRI voltage dependent POD described in Reference 6. With a constant POD, as recommended by GL 95-05, an additional percentage of an indication is included in the RPC distribution for leak and burst analyses for each detected indication. Large voltage, POD-driven indications are included in the BOC distributions even if repaired and these indications contribute significantly to the projected leak rates and tube burst probabilities. . Since the ARC experience data indicate that POD approaches unity above about 2.5 to 3.5 volts, the larger voltage POD-driven indications are unsubstantiated in the analysis above a few volts. and represent a large portion of the projected SLB leak z ate and conditional burst probability. For ARC applications,~ the important indications are those that could significantly contribute to EOC leak or burst probability. These significant indications can be expected to be detected by ' bobbin and confirmed by RPC. Thus, the population ofinterest for APC POD assessments is the - -1 L EOC. RPC confirmed indications that were detected or not detected at the EOC.: inspection. EOC. is the end of the just completed operating cycle and EOC..: is the end of the previous operating cycle. This POD definition accounts for undetected indications, indications below the ' detection threshold and new indications. Consequently, there is no need to modify the 4 - associated POD va!ues or otherwise account for new indications. Using the information provided 10 J

SG-98-01-004 in Reference 6, it is concluded that a large (15 inspections of 8 plants) ARC field experience database is available and has been applied to develop a voltage dependent POD. The recommended POD, based on the lower 95% confidence limit of the data, is lower than the NRC recommended POD value of 0.6 below about 0.5 volts, increases to 0.9 at 1.2 volts, and approaches unity at 2.5 to 3.5 volts. Flaw population growth increases the need to apply a voltage dependent POD to reduce the number of high voltage " phantom" indications included in the leak and burst analysis as a result of applying a constant POD of 0.6. Application of Unconfirmed Indications in 300 Distribution GL 95-05, Section 2.b.1 provides an option for applying a fraction of unconfirmed (RPC NDD) indications in the BOC voltage distribution. NRC approval for applying a fractional representation of the RPC NDDs in the SLB leak rate projection has been approved at Beaver Valley Unit 1. Currently, a sufficient database for RPC NDDs does not exist for South Texas 2. A subsequent update submittal may be presented by STPNOC once sufficient data has been collected to include a fractional representation of the RPC NDDs into the SLB leak rate projection. This data will compare the RPC NDDs left in service at EOCoa and EOCo. Inspection data from other plants indicates that typically about 50% of the RPC NDDs progress to detectable RPC indications from one cycle to the next, compared to the GL 95-05 guidance which includes all RPC NDDs in the SLB leak rate projection. Voltage Growth Due to Defect Progression The more conservative growth rate of the previous two cycles shall be used for the projection of bobbin voltage distribution during the next operating cycle, consistent with Section 2.b.2(2) of GL 95-05 and existing practice (Reference 2). Both BOC and corresponding EOC bobbin indications at a tube TSP intersection are necessary to specify a growth data point. Growth data from both cycles may be combined if necessary to obtain at least 200 data points in the distribution, otherwise industry data will be used. If > 200 indications are available on a per SG basis, the more limiting of SG specific or all SG combined growth will be used. Negative growth rates shall not be used in growth rate distributions used to make voltage projections although they shall be used in establishing average growth for determining the upper voltage repair limit of 2.a.2 and 2.a.3. Using the 1997 (EOC 5) inspection data and conservatively allotting 65% of the total growth to Cycle 5 for indications not inspected at EOC 4, the 95% cumulative probability growth rate at EOC 5 is 0.243 volts. This adjustment is conservative compared to the ratio of the estimated Cycle 4 and Cycle 5 lengths used for this example,475 EFPD and 450 EFPD, respectively. The actual EFPDs for Cycle 4 and 5 may vary by a few days from these example values. The average absolute growth (for the entire cycle) for this distribution is 0.136 volts. A histogram plot of the 11

SG-98-01-004 EOC 5 bobbin voltage growth rates is provided in Figure 1. This figure is a representation of the growth trends at South Texas Unit 2. On an EFPY basis, the 95% and average growths are 0.197 and 0.110 volts, respectively. If the two-cycle growths for indications not inspected at EOC 4 are adjusted based on the ratio of Cycle 5 length divided by the combined Cycle 4 + Cycle 5 ' length, the 95% and average absolute growths are 0.222 volts, and 0.120 volts, respectively. On an EFPY basis, the 95% and average growths (adjusted by cycle length) are 0.190 volts and 0.10 volts, respectively. Comparison of Bobbin Voltages for 405 SS and Carbon Steel TSP Material GL 95-05 defines applicability of the voltage based repair limits to drilled hole carbon - steel TSPs. South Texas Unit-2 has drilled hole 405 SS TSPs. This section addresses the influence of the TSP on the voltage response of flaws to demonstrate applicability of ~ the voltage based repair limits to 405 SS TSPs. The EPRI database approved by the NRC for application to the voltage based repair limits include data from Plant E-4 (Doel 4) which is a Model E steam generator, nearly identical to STP Unit 2, with dnlled hole 405 SS TSPs. There are 21 Plant E-4 data points fairly uniformly distributed from 0.2 to 15.7 volts in the burst correlation and 11 data points from 6.02 to 16.2 volts in the leak rate correlation. These data points are compared with data from other EPRI database domestic pulled tubes and model boiler specimens with carbon steel TSPs in Figures 3 and 4. The Plant E-4 data span the regression fit to the data and demonstrate consistency with the other data from SGs with carbon steel TSPs. Therefore, the Plant E-4 data support application of the voltage b'ased repair criteria to STP Unit 2 with stainless steel TSPs. An assessment of the influence of the TSP material on voltage measurements can also be obtained by comparing voltages for machined flaws such as the ASME holes and axial EDM slots. Bobbin voltages were normalized to 2.75 volts for the 550/130kHz mix on the 20% ASME holes with no TSP, which is the GL 95-05 voltage normalization. Separate voltage normalizations were made after mixing on a carbon steel TSP and on a 405 stainless steel TSP. The carbon steel mix was '.Mn used to measnre voltages for the ASME holes and axial slots with a carbon steel TSP over the flaws. The same { measurements were made using the stainless steel mix and a stainless steel TSP. A comparison of the voltage measurements for the machined flaws is given in Table 4. The agreement for the two TSP materials is good for the axial slots with the only significant difference in that the stainless steel TSP voltage for the 60% slot is about 10% lower 12

SG-98-01-004 than the carbon steel TSP while the 40%,80% and 100% slot voltages agree within about 1%. For the ASME holes, the stainless steel TSP voltages are about 510% higher for the 20% and 60% holes while agreement is within 1% for the 100% hole. The reasonable agreement for the ASME holes and axial slots between carbon steel and stainless steel

TSPs supports the good agreement found for the EPRI database shown in Figures 3 and

4. The data base used in Figures 3 and 4 includes pulled tube data from Byron 1 and Braidwood 1 which has not yet been officially recognized in the ARC data base by the NRC. Use of this data base results in a structurallimit voltage of 4.79 volts for a AP of 3657 psi as opposed to a structural limit voltage of 4.70 volts for a AP of 3657 psi using

' the currently approved data base. Overall, it is concluded that the voltage based repair limits can be applied to SGs with drilled hole stainless steel TSPs as well as the more common drilled hole carbon steel TSPs. The major contribution of the Plant E-4 data to the EPRI database for burst and leakage support the application to both stainless and carbon steel TSPs. Table 4. Comparison of Voltage Responses for Carbon and Stainless Steel TSPsm Carbon Steel TSP and Stainless Steel TSP and Carbon Steel Sttpport Stainless Steel Support Mix Mir Flaw Volts Flaw Volts ASME Drilled Hole Flaws 20% 2.24 2.46 60% 4.05 4.24 100% 5.03 5.01 Axial Slots 40% 0.45 0.45 00% 1.45 1.28 30% 3.38 3.40 100 % 44.18 44.57 Notes:

1. Bobbin voltages normalized to 2.75 volts on the 20% ASME holes with no TSP for the 550/130 kHz mix with separate normalizations for the carbon steel and stainless steel mixes.

13 1

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( SG-98-01-004 I Clarifications to GL 95-05 Section 2, Tube Integrity Evaluation Calculation of conditional burst probability and SLB leak rate will be performed using a voltage dependent probability of detection, referred to as probability of prior cycle detection, or POPCD, as opposed to a constant probability of detection of 0.6. The POPCD reference curve will be that defined in Addendum 1 to EPRI NP 7480-L, or later updates that reflect the latest combined j industry response for both 7/8" OD and 3/4" OD SG tubing. The use of POPCD in SLB leakrate { and conditional burst probability assessments represents a reasonable and logical approach to realistic EOC population projections. Establishment of Upper Voltage Repair Lirnits (V.ri) for TSP and FDB Intersections l The soltage structurallimit is the voltage from the burst pressure bobbin voltage correlation, at the 95% prediction interval curve reduced to account for lower tolerence limit material l l properties at 650 degrees F. The voltage structurallimit must be adjusted for flaw growth ( during an operating interval and to account for NDE uncertainty. The upper voltage repair I limit, Vuri, is determined from the following equation: Vori = V.i - Vgr - Vw. where Ver represents the growth allowance and Vw. represents the allowance for potential sources of error, including analyst variability. The structurallimit voltage is taken from the latest NRC approved database (currently contained in Reference 6). For TSP intersections, the structural limit voltage is generally established based on a pressure loading of 1.43 times the bounding SLB pressure differential of 2560 psi, or 3601 psi, since the proximity of the TSP prevents burst during normal operating' conditions. Specifically for STP Unit 2, pressurizer PORVs and block valves will be available and can be relied upon to operate during accident recovery conditions, and the applicable faulted condition AP becomes 1.43 times 2407 paid (where the value 2407 psid represents PORV actuation setpoint of 2335 psig in the faulted loop plus 3% uncertainty due to accumulation), or 3442 psid. The term paid represents a differential pressure from atmospheric, and is therefore consistent with the gauge pressure. Based on the operational characteristics of the STP Unit 2 PORVs, a 3% uncertainty allowance is considered conservative. The increased tube to FDB gap does not provide sufficient constraint such that burst will not occur within the FDB. Therefore, the FDB voltage structural limit is established using a pressure loading of 3 times the normal operating pressure differential across the SG tubes. The current maximum SG tube AP for STP Unit 2 is approximately 1210 psid, and the limiting 3AP value is therefore 3630 psi. For analysis purposes and to take into account future tube plugging effects upon steam pressure output, a 3AP value of 3675 psi will be used. For a limiting faulted conditions AP of value of 3442 psid the value of V.i for the TSP is defined to be 16

SG-98-01-004 5.45 volts and for the limiting 3AP value of 3675 psid, V.i for the FDB is defined to be 4.47 volts. i The calculation of the structurallimit voltages was performed using regression coefficients corresponding to the latest NRC approved data base for %" tubing, which includes the original GL 95-05 data base updated using South Texas 1 pulled tube data points. Using the above equation, with values for Va. of 20% of Vori and Ver of 60% of Vori, Vori for the TSP and FDB are established to be 3.03 volts and 2.48 volts, respectively. As the criteria will be implemented at the bginning of Cycle 7, the growth allowance applied must be representative of the projected Cycle 7 operating length, or approximately 329 days. Therefore, the growth allowance applied j for Cycle 7 to establish Vuriis determined to be the limiting Cycle 5 growth of 60% times the ratio of Cycle 7 to Cycle 5 lengths (329 days /439 days), or 45%. Using this growth allowance and Va. allowance of 20%, Vori for the TSP and FDB are ultimately established to be 3.30 volta and 2.71 volts, respectively. Bobbin voltage growth analyses were performed for the EOC 5 indications which met the criteria for growth analysis. From Tables 5 and 6 it is seen that the BOC voltages are quite low, and therefore small growths represent large percentage voltage growths, and may be a cause of the apparent large percentage voltage growth rates seen in Steam Generators A and C. Of the total 703 growth indications,694 had BOC 5 bobbin voltages less than 0.75 volts. BOC 5 voltages for indications not inspected at EOC 4 were developed by adjusting the EOC 3 to EOC 5 growth based on the Cycle 4 and Cycle 5 EFPD values. The growth for Cycle 5 for these indications was I adjusted by the ratio of the approximated Cycle 5 EFPD to the combined Cycle 4 plus Cycle 5 EFPD value, or 450 EFPD / 925 EFPD = 0.4865. The BOC 5 voltage was then determined by subtracting this adjusted growth value from the EOC 5 bobbin voltage. Of the 703 total growth indications,442 had to be adjusted by this methodology. If the growth indication population is segregated at 0.5 volts as opposed to 0.75 volts, it is seen in Table 6 that 624 of the 703 total growth indications had a BOC 5 bobbin voltage less than 0.5 volts. 17

SG-98-01-004 Table 5 South Texas Unit 2 Average Voltage Growth During Cycle 5: < 0.75, > 0.75 Volts BOC Voltage Range Number of Avg. Voltage Avg. Voltage Growth Percent Growth Indications BOC5 Cycle 5 - EFPY Cycle 5 EFPY Composite of AllSteam Generators Entire Voltage - 703 0.31 0.12 - 0.10

39%

32% -Range Vboc < 0.75 volts 694 0.31 0.12 0.10 39% 32% Vboc 2 0.75 volts 9 0.90 0.23 0.19 26% 21% Steam Generator A ' Entire Voltage - 144 0.35 0.21 0.17 60 % 49% Range Vboc < 0.75 volta 141 0.34 0.20 0.16 59% 47% Yboc 2 0.75 volts 3 0.80 0.41 0.33 51 % 41% Steam Generator B Entire Voltage 195 0.33 0.07 0.06 21% 18% Range Vboc < 0.75 volta 192 0.32 0.07 0.06 22 % 19% Vboc 2 0.75 volts 3 0.96 0.34 0.28 35 % 29% Steam Generator C . Entire Voltage 189 0.30 0.14 0.12 47% 40% Range Vboc < 0.75 volta 187 0.29 0.14 0.12 48% 41% Vboc 2 0.75 volts 2 0.82 0.05 0.04 6% 5% Steam Generator D Entire Voltage 175 0.29 0.07 0.06 24%. 21% Range Vboc < 0.75 volts 174 0.28 0.07 0.06 25% 21% - Vboc 2 0.75 volts 1 1.01 0.11 -0.09 11 % -9% l 18

/

SG-98-01-004 Table 6 South Texas Unit 2 Average Voltage Growth During Cycle 5: < 0.5, > 0.5 Volts BOC Voltage Range Number of Avg. Voltage Avg. Voltage Growth Percent Growth Indications BOC5 Cycle 5 EFPY Cycle 5 EFPY Composite of All Steam Generators. Entire Voltage 703 0.31 0.12. 0.10 39% 32% Range Vboc < 0.5 volta 624 0.28 0.11 0.09 39% 32% Yboc 2 0.5 volts 79 0.60 0.18 0.14 30% 23% Steam Generator A Entire Voltage 144 0.35 0.21 0.17 60% 49% Range Vboe < 0.5 volts - 120 0.30 0.18 0.15 60% 50 % Yboc2 0.5 volta 24 0.61 0.32 0.26' 52% 43% Steam Generator B Entire Voltage 195 0.33 0.07 0.06 21% 18 % Range Vboc < 0.5 volts 171 0.29 0.07 0.06 24% 21 % Vboc 2 0.5 volts 24 0.59 0.10 0.08 17% 14 % Steam Generator C Entire Voltage 189 0.30 0.14 0.12 47% 40% Range Vboc < 0.5 volts 168 0.26 0.14 0.12 54 % 46% Vboc 2 0.5 volts 21 0.60 0.15 0.12 2S% 20% Steam Generator D Entire Voltage - 175 0.29 0.07. 0.06 24 % 21% Range Vboc < 0.5 volta 165 0.27 0.07 0.06 26% 22%- Vboc 2 0.5 volts 10 0.60 0.09 0.07 15% 12% l I. j 19 )

SG-98-01-004 l 4.0 GL 95-05 Section 3: INSPECTION CRITERIA i All SG tubes will be insy;.ed with the bobbin coil during each normally scheduled refueling i outage at STP Unit 2. The inspection willinclude all hot leg tube to TSP intersections and 'all I . cold-leg tube to TSP intersections down to the lowest cold leg TSP with identified ODSCC. Data l acquisition and analysis will be performed to provide consistent methodology as that described l l GL 95-05, as updated by the clarifications listed below, which include use of the updated probe i I' wear guidelines 'and new probe acceptability guidelines. The supplementary guidance of Section 3 of GL 95-05 will be applied with the clarifications noted below. Any indication with bobbin voltage exceeding 1.0 volta shall be inspected with a rotating pancake coil (RPC) or equivalent, and shall be repaired if the bobbin indication is confirmed as a flaw by RPC. Any indication will oe plugged or repaired regardless of any RPC inspection results, if the bobbin voltage exceeds - l1 the upper voltage repair limit as obtained per Section 2.a.2 of GL 95 05. For STP Unit 2, specific L upper voltage repair limits are separately developed for both TSP and FDB intersections. L Clarifications to Section 3, Inspection Criteria l~ 1. In a letter dated January 23,1996, the Nuclear Energy Institute provided a methodology for meeting the new probe variability criteria in GL 95-05 Section 3.c.2. The NRC requested i additionalinformation in a letter dated February 9,1996 from Brain Sheron to Alex Marion of NEI.' Initial NRC concurrence of this methodology was provided in a letter from Mr. Brian Sheron to Alex Marion of NEI, dated March 18,1996. Additionalindustry information was provided in a NEI letter dated October 10,1996, which dealt with test data I for probes manufactured by Westinghouse and Zetec. Briefly summarized, this methodology requires, in part, that the primary frequency and mix frequency voltage response cf a new probe be compared to the nominal response determined by the vendor to ensure that the new probe is within 10% of the nominal response for both the primary and mix channels. I, In a letter from Brian Sheron to Dave Modeen of NEI, the NRC determined that NEI has . provided sufScient information in response to the NRC staff request in the February 9,1996 letter. STPNOC will follow the guidance provided in the NRC letter dated March 18,1996 as supplemented by the test data contained in the NEIletter dated October 10,1996. 2. In a letter dated January 23,1996, the Nuclear Energy Institute provided an alternative to the probe wear criteria in GL 95-05. NRC concurrence of this methodology was provided in a letter from Mr. Brain Sheron to Mr. Alex Marion of NEI, dated February 9,1996. Briefly summarized, this alternative to the GL 95-05 probe wear criteria requires that when a probe does not pass the probe wear check (15%), all tube locations inspected with the worn probe having detected indications with amplitudes greater than or erm

• 75% of the 4

repair voltage limit (i.e.,1.0 volt for 3/4" OD tubes) will be reinspect J with a new 20 )

SG-98-01-004 acceptable probe. STPNOC will follow the guidance provided in the NRC letter dated February 9,'1996.

3. - GL 95-05 (Background, Page 3 of 7) permits use of alternates to the rotating pancake coil for RPC inspections. Currently, the + Point probo is considered by the industry as an acceptable alternative to R20. STPNOC will utilize the + Point probe for TSP indication confirmation at EOC 6 and + Point or equivalent probe at later inspections.

Section 4: TUBE dEMOVAL AND EXAMINATIONffESTING. The STP Unit 2 program for tube removal and examination will comply with the guidance of ' - Section 4 of GL 95-05. Currently, no tubes have been removed from STP Unit 2. Consistent. with the Section 4 recommendations of GL 95-05, upon the initialimplementation of voltage based repair criteria, a minimum of four hot-leg TSP intersections will be removed from STP Unit 2. Section 5: LEAKAGE' The Technical Specification operational leakage limit, LCO 3.4.6.2.c, addressing steam generator . tube leakage, has been changed to 150 gpd in any SG. This Tech Spec change was initiated for' ~ Unit 2 when the laser welded sleeving process was licensed. SG tubes with known leaks will be repaired prior to returning the SGs to service, consistent with GL 95 05. ' Section 6:. REPORTING REQUIREMENTS STPNOC will comply with the reporting requirements of Section'6 of GL 95-05. 21

i SG-98-01-004 REFERENCES 1. L NRC Generic Letter 95-05: " Voltage-Based Criteria for Westinghouse Steam Generator Tubes Affected by Outside Diameter Stress Corrosion Cracking," August 3,1995 j c i l 2. Westinghouse WCAP-14277, Revision 1, "SLB Leak Rate and Tube Burst Probability- . Analysis Methods for ODSCC at TSP Intersections," December 1996 - 3} ' NRC letter from Brian Sheron (NRR) to Alex Marion of NEI dated February 9,1996 i < 4. NEI letter from' Alex Marion to Brian Sheron of NRC (NRR) dated January 23,1996 - 5. NEI letter from Alex Marion to Brian Sheron of NRC (NRR) dated October 10,1996 ' 6. EPRI Report NP 7480-L Addendum 1, " Steam Generator Tubing Outside Diameter Stress Corrosion Cracking at Tube Support Plates Database for Alternate Repair Limits,1996 Database Update", November 1996 7. EPRI TR 104788 R, "PWR Primary to-Secondary Leak Guidelines," November 1997 8.- NRC Letter from Ramin R. Assa, Project Manager, NRR, to Commonwealth Edison Co., " Safety Evaluation Regarding Leak Before-Break Analysis - Byron Station, Units 1 and 2-, and Braidwood Station,~ Units 1 and 2", dated October 25,1996 9. .NRC Letter from Brain Sheron to David Modeen of NEI, dated July 29,1997

10. NSD E-SGDA-98 0014, " Identification ofInput Information Used for Development of SG 01-004", 1/20/98 *

11. HL&P Letter ST-HL-AE-3659, " Response to Generic Letter 90-06," 12/21/90

12. HL&P Letter St-HL-AE-3642, ' Proposed Amendment to the Unit 1 and Unit 2 Technical Specifications M.4.4 and %.4.9.3," 12/21/90

.13. South Texas Project Updated Final Safety Analysis Report ' Internal Westinghouse Reference used for preparation of this evaluation, not to be s -submitted to NRC. I l t-L f 22 'I

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i SG-98-01-004 Appendix A Analysis Methodology Used for Performance of Tube Exclusion . Analysis for Application of Voltage Based Repair Criteria: South Texas Unit 2 28

t i SG-98-01-004 Appendix A Analysis Methodology Used for Performance of Tube Exclusion l Analysis for Application of Voltage Based Repair Criteria: Discussion of Analysis Relative to application of the voltage based plugging criteria and integration with other plant conditions, the most limiting accident condition is a combined seismic safe L shutdown earthquake (SSE) plus loss of coolant accident (LOCA). For the combined LOCA + SSE event, the potential exists for yielding of the tube support plate in the f vicinity of the wedge groups, accompanied by deformation of the tubes and subsequent l-loss of flow area and possible in-leakage due to opening of axial cracks. The wedges are as their name implies, wedge shaped steel components which are used to provide radial contact between the TSP and wrapper at multiple locations around the periphery of the TSP. l Combined Plate Loads. l t l Seismic loads result from motion of the ground during an earthquake. The SSE excitation of the steam generator is defined in the form of acceleration response spectra at the steam generator supports. To perform the analysis, the response spectra are l converted into acceleration time history input. Acceleration time histories for the L nonlinear analysis are synthesized from El Centro Earthquake motions, using a frequency suppression / raising technique, such that the resulting spectrum in each of the l axes closely envelopes the original specified spectrum. The resulting F ^ histories are then simultaneously applied at each steam generator support. For ts Sah Texas 2

tube exclusion analysis, results of a response spectra seismic analysis for South Texas L

taken from Westinghouse Report WNET-150, "Model E2 Stress Report Plant SpeciSc Seismic Analysis South Texas Nuclear Power Plant Units 1 and 2" were used to develop non linear plate loads. A factor of 3 was applied to the response spectra values to establish the non-linear plate loads. The bounding plate load was applied to all plates. H Leak before break of the primary loop piping has been approved by the NRC for South Texas 2. In Reference 8, the NRC indicates the acceptability of the use of small break loadings for such analyses when LBB has been approved. The LOCA hydraulic forcing functions used for the South Texas 2 analysis are taken from a thermal / hydraulic 29

l SG 98-01-004 analysis of a Model D5 steam generator, and are considered conservative for the South Texas 2 SGs. To validate the use of the D5 LOCA rarefaction loads for South Texas 2, the hot to-cold leg pressure drops across the U bends were compared for the D5 and E steam generators for a large break, surge line break, and accumulator line break. This ) comparison indicates that the large break AP for the Model E SG was approximately 1% { greater than the D5 AP, while the D5 APs for the surge line and accumulator line breaks were greater than the Model E APs. Although larger in shell diameter than a D5 SG, the tube bundle geometries between the D5 and E SGs are considered very similar and the D5 results can therefore be applied to the South Texas 2 Model E SGs. A comparison of the time history characteristics for the surge line and accumulator line breaks was performed for the D5 and E SGs, indicating good agreement between the two, further substantiating the use of the D5 results. For South Texas 2, the surge line and accumulator line break inputs for the D5 SG were used and are considered bounding i since the surge and accumulator line breaks represent a limiting transient for the RHR line break. Therefore, the LOCA input forcing functions used for South Texas 2 are conservative based on the acceptance of the LBB methodology at South Texas and use of the larger surge and accumulator line break inputs. LOCA loads are developed as a result of transient flow, and temperature and pressure fluctuations following a postulated pipe break. As a result of a LOCA event, the steam generator tubing is subjected to primary fluid rarefaction wave loadings and steam generator shaking loads due to the coolant loop motion. LOCA shaking loads are considered insignificant for the bounding LOCA loads used, therefore, the rarefaction wave loading provides the only significant contributing loadings with respect to tube deformation. The LOCA and SSE load are combined using a square root of the sum of the squares technique. In reacting the load among the various wedge groups, a cosine distribution is assumed among the wedges that are loaded. Typically, only half of the wedge groups are loaded at any given time. In determining the load distribution for seismic and LOCA loads, the directionality of the load is considered. LOCA loads are uni-directional, in that they only act in the plane of the U bend. Seismic loads on the other hand are random, and can act in any direction. Calculations are performed to determine load factors for the various plates, grouping the TSP by commonality of their wedge group locations. The . load factors are not a function of th9 wedge group size, only oflocation. Applying these load factors, overall TSP load for each of the wedge groups are determined. 30

a SG-98-01-004 LTube Deformation 1 4 In estimating the number of deformed tubes, the results of TSP crush tests for Model D steam generators are used. The applicability of using the Model D tests is based on a comparieon of Model D and Model E plate geometries, summarized in Table A-1. Based on the comparison of these geometric parameters, the Model D test piece is judged applicable to the Model E plate. The deformation criteria for establishing a tube as being susceptible to in-leakage has been previously established for similar analyses to be 0.030" diametrical. It has been previously judged that deformation of this level will not result in significant in leakage. Using the crush test data, a correlation is developed between - elastic plate load and the number of tubes that would have a deformation of 0.030" or greater. This correlation is used to approximate the number of affected tubes. For the South Texas 2 analysis, TSP material certifications were available which showed the actual TSP material property values were greater than the ASME Code minimum values. These actual material property values were used in the analysis. In order to account for the thicker Model E top plate, top plate loads were scaled downward by the ratio of the - top plate thickness to the actual test plate thickness. To account for the higher yield strength of the South Texas 2 plates, the yield point of the plates is scaled upwards. Once yielding begins, the plates were assumed to follow the same inelastic slope as the test plates. The applied combined loadings were then compared to the expected load to cause permanent deformation of the South Texas 2 TSPs and from this comparison, it was determined that the South Texas 2 TSPs will not experience deformation such that the tubes in the wedge regions will experience a diameter deformation of greater than 0.030". Therefore, no tubes are tc be excluded from application of the criteria due to a collapse potential. Comparison of Tube Support Plate Hole Patterns Model D vs. Model E - ~ Parameter Test Plate (Model D) Model E ~ Tube llole Diameter 0.7735" 0.776" Flow Hole Diameter 0.5075" 0.5075" Tube Pitch 1.0625" 1.08" Plate Rim Thickness 0.432" 1.26" - Plate Yield Strength 35.7 Ksi 54.9 Ksi l [ c 31 .}}