ML13074A794

Amendment I Operational Assessment for Songs Unit 2 Steam Generators for Tube-To-Tube Wear Degradation 100% Power Operation Case

ML13074A794
Person / Time
Site:	San Onofre
Issue date:	03/31/2013
From:	Intertek APTECH
To:	Office of Nuclear Reactor Regulation
References
TAC ME9727 1814-AG117-M0026, Rev 0, AES 13018304-2Q-1, Rev 0
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ENCLOSURE 1Amendment IOperational Assessment for SONGS Unit 2 SteamGenerators for Tube-to-Tube Wear Degradation100% Power Operation Case IntertekAES 13018304-2Q-1Controlled Document 1-8Revision 0March 2013Amendment IOPERATIONAL ASSESSMENT FOR SONGS UNIT 2 STEAM GENERATORSFOR TUBE-TO-TUBE WEAR DEGRADATION100% POWER OPERATION CASEPrepared ByIntertek APTECH601 West California AvenueSunnyvale, California 94086-4831Supplier Status StampVPL 1814-AG117-M0026 Rev 0 IQc: N/ANo: No:E-DESIGN DOCUMENT ORDER NO. 800918458_[,REFERENCE DOCUMENT-INFORMATION ONLY E-VIRP IOM MANUALMFG MAY PROCEED: OYES f"NO9 XNIASTATUS -A status is required for design documents and is optional for referencedocuments. Drawings are reviewed and approved for arrangements and conformance tospecification only. Approval does not relieve the submvter from the responsibilit,./ofadequacy and suitability of design. materials. and/or equipment represented.1. APPROVED2. APPROVED EXCEPT AS NOTED -Make changes and resubmiL.NOT APPROVED -Correct and resubmit for review. NOTi for field use.APPROVAL: (PRINT ISIGN B ATE)FLSthe 3113 1IOther.SCE DE(123) 5 REV. 3 07/11REFERENCE: SO 123-XXIV-37.8.26Intertek APTECHAES 13018304-2Q-1I-iSouthern California EdisonMarch 2013COLOR IS RELEVANT1814-AG117-M0026, REV. 0Page 1 of 41 This report was prepared by Intertek APTECH as an account of work sponsored by the organization named herein.Neither Intertek APTECH nor any person acting on behalf of Intertek APTECH: (a) makes any warranty, express orimplied, with respect to the use of any information, apparatus, method, or process disclosed in this report or that suchuse may not infringe privately owned rights; or (b) assumes any liabilities with respect to the use of, or for damagesresulting from the use of, any information, apparatus, method, or process disclosed in this report.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131814-AG117-M0026, REV. 0Page 2 of 41 APPROVAL RECORD SHEETReport No.: AES 13018304-2Q-1 Rev.: 0 Date: March 2013Report Title: "Amendment I -Operational Assessment for SONGS Unit 2 Steam Generatorsfor Tube-to-Tube Wear Degradation -100% Power Operation Case"Originated By:Reviewed By:Approved By:Verified By:QA Approved By:Project EngineerProject EngineerProject Manager'VerifierQA ManagerDateDatec3i / 2 /'2L.Date24 (3DateD teIntertek APTECHAES 13018304-20-1Southern California EdisonMarch 2013I-iii1814-AG117-M0026, REV. 0Page 3 of 41 TABLE OF CONTENTSSection PageExecutive Sum m ary ........................................................................................................ I-v1.1 Introduction ............................................................................................................... 1.1-11.2 Structural Requirem ents ................................................................................................. 1.2-11.2.1 Structural and Leakage Integrity ......................................................................... 1.2-11.2.2 Assessment Overview ........................................................................................ 1.2-21.2.3 Probabilistic Model ............................................................................................. 1.2-31.2.3 Tube Burst Model ................................................................................................ 1.2-41.2.4 Leak Rate Calculation ......................................................................................... 1.2-51.3 Assum ptions and Conditions ......................................................................................... 1.3-11.4 Analysis Input Param eters ............................................................................................. 1.4-11.4.1 Tubing Properties ................................................................................................ 1.4-11.4.2 Operating Parameters ......................................................................................... 1.4-11.4.3 Degradation Characterization .............................................................................. 1.4-21.4.4 State of Degradation -W ear Index ..................................................................... 1.4-31.4.5 Tube Support Distributions .................................................................................. 1.4-41.4.6 Probability of Detection ....................................................................................... 1.4-51.4.6.1 Inspected Population .................................................................................. 1.4-51.4.6.2 Undetected Population ............................................................................... 1.4-61.4.7 Tube-to-Tube W ear Initiation ............................................................................... 1.4-71.4.8 Degradation Growth Rates .................................................................................. 1.4-81.4.8.1 AVB and TSP Growth Models .................................................................... 1.4-81.4.8.2 TTW Growth Model .................................................................................... 1.4-94.9 Measurement Uncertainty ...................................................................................... 1.4-91.5 Operational Assessm ent ................................................................................................. 1.5-11.5.1 Analysis Cases .................................................................................................... 1.5-11.5.2 Structural Margin Evaluation ............................................................................... 1.5-11.5.3 Leakage Evaluation ............................................................................................. 1.5-21.6 Analysis Verification and Validation .............................................................................. 1.6-11.7 References ............................................................................................................... 1.7-11.8 Nom enclature ............................................................................................................... 1.8-1Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 2013I-iv1814-AG1 17-M0026, REV. 0 Page 4 of 41 EXECUTIVE SUMMARYThe San Onofre Unit 2 (Unit 2) plant has two new steam generators that replaced the originalCE-70 design. The replacement steam generators are MHI Model 116TT1 and began operationin Year 2010. The generators have completed one cycle of operation (Cycle 16) with durationof 1.718 years at power (20.6 months). In the first cycle of operation, the Unit 2 tubing hasexperienced wear degradation at points of contact with anti-vibration bar (AVB) U-bendsupports. There were 4348 indications detected at AVB contact points with a maximum Non-Destructive Examination (NDE) depth of 35%TW found during the end-of-cycle (EOC) 16 tubeexaminations. To a much lesser extent, wear at tube support plates (TSP) was also detected(364 indications) with a maximum NDE depth of 20%TW.While Unit 2 was in refueling, San Onofre Unit 3 (Unit 3) had a forced outage due to a leak inone of the steam generators after 338 days (0.926 years at power or 11.1 months). The leakwas due to tube-to-tube wear (TTW) at freespan locations within the U-bend region. Tube-to-tube wear in Unit 3 was caused by in-plane motion of tubes within a defined region of thebundle. The in-plane motion was due to conditions that created fluid-elastic instability (FEI) ofone or more tubes. Subsequent examination of Unit 2 steam generators specifically looking forTTW revealed two indications in steam generator (SG) 2E089. Because of the generic designsof both units, and the nature of the FEI, the possibility of having further initiation and progressionof TTW in Unit 2 is addressed.This report describes the Operational Assessment (OA) performed for the limiting steamgenerator (SG 2E-089) in Unit 2 for a simulated population of TTW degradation indicationsunder 100% power operation. The original Unit 2 OA was for reduced power operation at 70%.This report is Amendment I to the original OA. A full description of the 70% power OA is given inRef. 1.In Ref. 1, a probabilistic model representing the high-wear region of the tube bundle was usedto evaluate TTW for the next inspection interval. Calculated tube burst and leakage probabilitiesIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 2013I-v1814-AG117-M0026, REV. 0Page 5 of 41 were obtained by Monte Carlo simulation for initiation and growth of TTW. The results for burstand leakage were compared with the structural and leakage performance margin requirementsof Nuclear Energy Institute (NEI) 97-06. The performance standards for assessing tube integrityto the required margins are delineated in the Electric Power Research Institute (EPRI) IntegrityAssessment Guidelines (Ref. 2). This assessment established the probability of burst for theworst-case tube due to TTW predicted for the defined high-wear region.The Unit 3 wear behavior was used to establish the initiation and growth of TTW indications inUnit 2 steam generators. An empirical correlation based on a wear index parameter (measureof the state of wear degradation in each tube) provided the method for scaling the Unit 3 wearbehavior to Unit 2. Modifications were made to the original OA model to include a revised TTWgrowth rate distribution that incorporates the estimated initiation times associated with eachoccurrence of TTW in Unit 3 steam generators.Two OA analysis cases were evaluated based on the sizing techniques used to define the Unit3 TTW depths. Case 1 evaluated the situation where voltage based sizing for Eddy CurrentTesting Examination Sheet (ETSS) 27902.2 was used to establish the TTW depth distributionsand the correlated wear rate with wear index. The results for Case 1 indicate that the StructuralIntegrity Performance Criteria (SIPC) margin requirements are satisfied for an inspectioninterval length of 0.94 years at 100% power level. For Case 2, where the TTW depths wereresized by AREVA using a more realistic calibration standard, the SIPC margins will be met foran inspection interval length of 1.04 years at 100% power level. The plan for Unit 2 is tooperate for an inspection interval of 5 months at a 70% power to provide additional margin tothe industry requirements for tube integrity.Tube burst at 3xNOPD (Normal Operating Pressure Differential) is the limiting requirement forinspection interval length. Therefore, the accident-induced leakage requirements will besatisfied provided that burst margins at 3xNOPD are maintained during the inspection interval.Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 2013I-vi1814-AG117-M0026, REV. 0Page 6 of 41

1.1 INTRODUCTION

An Operational Assessment (OA) is a forward-looking evaluation of the steam generator (SG)tube conditions that is used to ensure that the structural integrity and accident leakageperformance will not be exceeded during the next inspection interval. The OA projects thecondition of SG tubes to the time of the next scheduled inspection outage and determines theiracceptability relative to the tube integrity performance criteria.San Onofre Unit 2 (Unit 2) OA for the next inspection interval is documented in the original OA(Ref. 1). The original OA was completed for 70% power level using operating parameters fortemperature, flow, and normal operating pressure differential (NOPD) for the tubes afterplugging (Ref. 1). The degradation mechanism evaluated is tube-to-tube wear (TTW). Tube-to-tube wear is caused by in-plane motion of tubes. The in-plane motion is due to conditions thatcreated fluid-elastic instability (FEI).San Onofre Unit 2 has two new steam generators that replaced the original CE-70 design. Thereplacement steam generators are MHI Model 116TT1 and began operation in 2010. Thegenerators have completed one cycle of operation (Cycle 16) with duration of 1.718 years atpower. In the first cycle of operation, the Unit 2 tubing has experienced wear degradation atanti-vibration bar (AVB) U-bend supports. Wear at tube support plates (TSP) was also detectedduring the end-of-cycle (EOC) 16 tube examinations. A schematic illustration of the tubesupports, AVBs labeled B01 through B12 and TSPs labeled 01C through 07C on the cold-legside and labeled 01H through 07H on the hot-leg side, is shown in Figure 1.1-1.This report serves as an amendment to the original OA. The analysis in this report performs anOA for 100% power. Similar to the original OA, probabilistic simulation methods were used.These methods establish the tubing structural and leakage margins following standard industryguidelines. These margins are compared with the structural integrity and leakage performancecriteria requirements of Nuclear Energy Institute (NEI) 97-06. The performance standards forassessing tube integrity to the required margins are provided in the Electric Power ResearchInstitute (EPRI) Integrity Assessment Guidelines (Ref. 2). This approach established theprobability of burst (POB) for the worst-case tube due to TTW.Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.1-11814-AG117-M0026, REV. 0Page 7 of 41 07H -7 ---43.66-06H0CI I43.G6'05H 05C -43.66"43.66102H 02C43.GG"01H -03CI *1l 4342A"TSH TS0CT HTEHS TEC ___Figure 1.1-1 SONGS Steam Generator Tube Support Structure Schematic (Ref. 1)Intertek APTECHAES 13018304-2Q-11814-AG117-M0026, REV. 0Southern California EdisonMarch 20131.1-2Page 8 of 41 1.2 STRUCTURAL REQUIREMENTSAn OA projects the condition of the steam generator tubes and establishes the allowableinspection interval over which tube integrity performance criteria will be satisfied. In this OA, theTTW degradation mechanism is evaluated for 100% power operation.1.2.1 Structural and Leakage IntegrityThe structural integrity performance criteria (SIPC) and accident-induced leakage performancecriteria (AILPC) applicable to any degradation mechanism including TTW are as follows (Ref. 2):Structural Integrity -"All in-service steam generator tubes shall retain structuralintegrity over the full range of normal operating conditions (including startup, operation inthe power range, hot standby, and cool down and all anticipated transients included inthe design specification) and design basis accidents. This includes retaining a safetyfactor of 3.0 against burst under normal steady state full power operation primary-to-secondary pressure differential and a safety factor of 1.4 against burst applied to thedesign basis accident primary-to-secondary pressure differentials. Apart from the aboverequirements, additional loading conditions associated with the design basis accidents,or combination of accidents in accordance with the design and licensing basis, shall alsobe evaluated to determine if the associated loads contribute significantly to burst orcollapse. In the assessment of tube integrity, those loads that do significantly affectburst or collapse shall be determined and assessed in combination with the loads due topressure with a safety factor of 1.2 on the combined primary loads and 1.0 on axialsecondary loads."Accident-Induced Leakage -"The primary to secondary accident leakage rate for thelimiting design basis accident shall not exceed the leakage rate assumed in the accidentanalysis in terms of total leakage rate for all steam generators and leakage rates for anindividual steam generator."Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.2-11814-AG117-M0026, REV. 0Page 9 of 41 For SONGS, the accident-induced leak rate is 0.5 gallons per minute (gpm) per generatorcumulative for all degradation mechanisms.The acceptance performance standard for structural integrity is (Ref. 2):The worst-case degraded tube shall meet the SIPC margin requirements with at least aprobability of 0.95 at 50% confidence.The worst-case degraded tube is established from the estimation of lower extreme values ofstructural performance parameters (e.g., burst pressure) representative of all degraded tubes inthe bundle for a specific degradation mechanism.The acceptance performance standard for accident leakage integrity is (Ref. 2):The probability for satisfying the limit requirements of the AILPC shall be at least 0.95at 50% confidence.The analysis technique for assessing the above conditions for TTW is a fully probabilisticassessment of the Unit 2 steam generators.1.2.2 Assessment OverviewA probabilistic OA involves the analytical evaluation of inspection data in conjunction with astructural (burst) model for comparing the likelihood of tube burst with the SIPC marginrequirements. Through-wall leakage probabilities must satisfy the accident-induced leak ratelimits. An allowable inspection interval is established by demonstrating the SIPC and AILPCstandards will be satisfied for the inspection interval.For the probabilistic OAs for TTW degradation, the probability of detection (POD), the wear rate,and initiation function for creating new wear indications are explicitly treated by statisticaldistributions for direct input to the structural model. In addition, distributions for tubing strengthand relational uncertainties on the tube burst model are addressed in accordance with industryguidelines.Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.2-21814-AG117-M0026, REV. 0Page 10 of 41 The OA for TTW is performed with a single-cycle model applied to a defined region where TTWis assumed active. The models for TTW initiation and the determination and assignment ofTTW growth rates are critical input variables to the OA.1.2.3 Probabilistic ModelA Monte Carlo simulation process was used to solve the probabilistic model for TTW. Thesimulation process is shown in Figure 1.2-1, which illustrates one Monte Carlo trial. Theprobabilistic model includes TTW initiation, growth, and structural integrity analysis for thedegraded tubes projected to the next inspection. Tubes that have been preventatively pluggedbased on wear patterns and other attributes have been removed from the population. Thisincludes Tubes R1 13 C81 and R1 11 C81 in SG-2E089 with detected TTW. The population oftubes at the start of the next inspection interval includes inservice tubes that have detected AVBand TSP wear and tubes with No Detectable Degradation (NDD) within the high wear region.Wear degradation of the steam generator tubing is simulated in the model for the population ofindications in the high wear region. The attributes assigned to each degraded tube are thedepth and length of the indications, material properties, and the degradation growth rate. Theseparameters are treated randomly and the calculation of burst pressure is made for eachindication in the population.The major steps in the process are:1) TTW initiations are predicted based on the wear degradation state. This isaccomplished with the total wear index parameter calculated from existing AVB and TSPwear. The initiation of TTW and initial depth is based on total wear index valuescalculated during operation as a result of further growth of AVB and TSP wear.2) Attributes are randomly defined for each degraded tube for a single trial representingone inspection interval. These include tube strength properties, the TTW degradedlength, and the TTW indication shape factor. The population of degraded tubes at thebeginning of the inspection interval contains the tubes with potential undetected TTW.3) Growth of the TTW degradation for the inspection interval is established by samplingfrom the Unit 3 wear rate distribution dependent on the total wear index at the time ofinitiation. The TTW growth model differs from the version used in the original OA (asIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.2-31814-AG117-M0026, REV. 0Page 11 of 41 discussed in section 1.4.8). The size distribution of the TTW degradation is defined inthis step.4) The population of TTW indications is evaluated for burst pressure and leakage at theend of the inspection interval. The degraded tube with the lowest burst pressure isrecorded for each trial to establish the distribution of worst case values for comparingwith the SIPC margin requirements and acceptance standards. Likewise, the leakageprobabilities for each trial are recorded to determine the 95% probability with 50%confidence (95-50) leak rate for comparison with AILPC.The simulation process generates a record of the results of all trials performed from whichoverall burst and leakage probabilities are calculated and appropriate distributional informationobtained.The OA methodology is discussed in Sections 3 and 5 of the original OA. The same fullyprobabilistic modeling approach and numerical algorithm was followed for computing tube burstprobabilities for TTW degradation.1.2.4 Tube Burst ModelTTW indications are characterized by axial volumetric degradation with limited circumferentialextent. The burst pressure for TTW is computed from the burst relationship for length and depthdimensions of axial wear given in Ref. 3:Pb = 0.58(Sy +Su)(t/Ri)1 +L(d/t)+ 291 Psi+ZOB (1.2-1)SL+2t _where:Pb is the estimated burst pressureSY is the yield strengthSu is the ultimate tensile strengtht is the wall thicknessR, is the tube inner radiusIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.2-41814-AG117-M0026, REV. 0Page 12 of 41 L is the characteristic degradation lengthd is the characteristic wear depthd/t is the fractional normalized depthRelational uncertainty in Eq. 1.2-1 is represented by the standard normal deviate, Z, (-oo < Z <oo),and GB, the standard error of regression (GB = 282 psi). The burst equation, when used with thestructural significant dimensions (LST and dsT), produces consistently conservative burstpressure estimates compared with tube burst data (Ref 3).1.2.5 Leak Rate CalculationLeakage predictions for wear-related degradation are subject to large uncertainties. Wearprofiles at incipient leakage can vary significantly from simple slits to large holes caused by theblowout of thin membranes. For these situations, absolute leakage rates are not generallycomputed. Rather, the probability of through-wall penetration is established from projectedmaximum depths and ligament rupture calculations. A ligament rupture is where the indicationpops through the remaining wall without causing tube burst. For TTW, leakage at limitingaccident conditions (i.e., main steam line break) will not be controlling on inspection intervallength. The depths required for burst at SIPC are much smaller (bounding) than the depthsnecessary to produce ligament rupture (pop-through) events under accident pressures. SIPC istherefore the controlling criteria.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.2-51814-AG117-M0026, REV. 0Page 13 of 41 F-K"Figure 1.2-1 -Operational Assessment Logic Flowchart (One Monte Carlo TrialIllustrated)Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.2-61814-AG117-M0026, REV. 0Page 14 of 41 1.3 ASSUMPTIONS AND CONDITIONSThe following are the major assumptions and analysis conditions used in this and the originalOA model for TTW and input parameters:1) TTW is analyzed as a stochastic process of independent events based on the state oftube support wear degradation of each individual tube in the high wear region at anypoint in time during the inspection interval.2) The critical region for evaluation is assumed as a box area defined by Rows 70 to 140and Columns 60 to 120. This region bounds the high-wear region in the U-bends.3) The state of wear degradation at tube supports for a given tube is assumed to becharacterized by the summation of NDE depths at AVBs and TSPs wear locations. Thisis defined as the "wear index" for a degraded tube. This is the same index definition asused in the original OA as described in Ref. 1.4) The Unit 3 data for TTW is used to define the likelihood of initiating TTW and what willbe the TTW growth rate. These data are used to establish the probability of initiationand growth of TTW in Unit 2 through the wear index parameter.5) The wear rate is based on constant growth on depth rather than constant wear volumebasis. This assumption is conservative since wear generally evolves on a constantvolume rate basis where the rate of change in depth will decrease as wear progresses.6) It is assumed at the start of Cycle 17, that any tube within the high wear region caninitiate TTW including tubes with no detected support wear at the beginning of the cycle.This is a conservative assumption.A key analysis condition in the probabilistic model is a measurable amount of AVB and TSPwear precedes tube instability and subsequent tube-to-tube contact.The assumptions and conditions below are used only in this OA:1) A variable non-zero initiation-time analysis is used to establish TTW growth rates.2) The NOPD for Cycle 17 is based on TCOLD restoration implementation with 3% plugging.Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.3-11814-AG117-M0026, REV. 0Page 15 of 41 1.4 ANALYSIS INPUT PARAMETERSThe input parameters for the OA for TTW by fully probabilistic methods are discussed in thissection. Much of this information is given in the original OA but is summarized below forcompleteness.1.4.1 Tubing PropertiesEach Unit 2 steam generator has 9727 tubes. The steam generator tubing has an outsidediameter of 0.75 inch and a nominal wall thickness of 0.043 inch. The tube material is Alloy 690thermally treated (A690 TT). The mechanical properties corrected to a temperature of 650°Fwere provided by AREVA with the following parameters for Sy + Su:Tubing Yield plus Ultimate Strength Values (psi)Parameter S/G 88 S/G 89SY + Su (mean) 115,361 116,633SY + Su (St. Dev) 2,023 2,504Sy+ Su (min) 108,700 109,900Sy+ Su (max) 121,600 123,900These values were obtained from the certified material test report (CMTR) data sheets for thesupplied tubing. A plot of the distribution is shown in Figure 1.4-1.1.4.2 Operating ParametersTube pressure differential under normal operating conditions during Cycle 16 was 1430 psi(Ref. 4). The operating conditions assumed for the next cycle of operation for 100% powerconditions after plugging are listed below (Ref. 5).Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-11814-AG117-M0026, REV. 0Page 16 of 41 Cycle 17 Operating ParametersParameter 100% PowerThermal power (MWt)/SG 1729Tcold, (F) 550RCS pressure, (psia) 2250Steam pressure, (psia) 926NOPD, (psi) 1324Note: NOPD with TCOLD restoration implemented at 100% w/3% pluggingThree times normal operating pressure (3xNOPD) for the inspection interval is 3972 psi. Foraccident conditions, maximum steam line break pressure is assumed at 2560 psi (Ref. 1). Thelimiting SIPC requirement is 3xNOPD.1.4.3 Degradation CharacterizationTubes assumed to be susceptible to TTW are located in the high wear region. Wear patternsfor AVB and TSP wear were within a region of tubes defined by rows 70 to 140, and columns 60to 120. The table below shows the nature of degradation within the defined high-wear region.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-21814-AG117-M0026, REV. 0Page 17 of 41 Summary of Degraded Tubes in the SG 2E-089 Steam Generator High Wear Region atBOC 17 (Ref. 1)Description (High Wear Region) SG 2E-089Total Number of Tubes 2121Tubes Plugged* 211*Number of TTW Indications 2Number of AVB Indications 2537Number of TSP Indications 90TSP Indications with No AVB wear 11BOC Tubes with Wear Degradation 560BOC NDD Tubes 1350*Note: Three additional tubes were preventatively plugged after the original OA.They were conservatively treated as in-service tubes in this analysis forconsistency with the original OA.Previously undetected wear indications at AVB and TSP supports are randomly assigned to theNDD tubes using the cumulative distributions developed from past observed active wear for SG2E-089 as shown in Figure 1.4-2. Depths for these wear indications are defined by the PODperformance for the bobbin probe (see Section 1.4.6).The shapes of the TTW indications were determined by line-by-line +PointTM sizing for Unit 3tubes. The shape factor parameter (F) is defined as the ratio of maximum depth of theindication to the structural average depth of the indication, dMAx/dsT. The shapes were relativelyflat (F=1.0) with long structural lengths. The structural lengths (LsT) as determined by thestructural-minimum method using the profile data from Unit 3 is shown in Figure 1.4-3 (Ref. 1).The cumulative distribution function (CDF) of these data is fitted to a log-normal model.1.4.4 State Of Degradation -Wear IndexTTW is assumed to initiate when the tube becomes unstable in the in-plane direction under localfluid-elastic conditions. TTW is analyzed as a random process of independent events based onthe state of degradation of each individual tube in the high wear region during the inspectioninterval. This OA uses wear degradation at tube supports (AVBs and TSPs) as a directindicator of both the likelihood of occurrence and severity of TTW during the inspection interval.Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-31814-AG117-M0026, REV. 0Page 18 of 41 A key assumption in the probabilistic model is that a measurable amount of AVB and TSP wearprecedes tube instability and subsequent tube-to-tube contact.The total wear index is used to define the state of degradation of individual tubes. The totalwear index parameter relates the observed AVB and TSP wear states of each tube in the high-wear region to both TTW initiation and growth rate. The same total wear index model used inthe original OA is used in this analysis. The total wear index model is based on the summationof AVB and TSP wear depths in a given tube.Total Wear Index = AVB Wear + TSP WearWI [AVB depth]i + I" [TSP depth], (1.4-1)where the total wear index is defined in %TW.This measure was chosen to capture both the total amount of wear as well as the loss ofeffective support, both of which are assumed to be precursors to in-plane tube instability and theinitiation of TTW for a given tube. The total wear index measures the loss of wall thickness dueto the vibratory activity of the tube. This loss of wall thickness can adversely affect supporteffectiveness from changes in tube to support gaps.1.4.5 Tube Support DistributionsThe model considers two cases which assume additional support wear in tubes located in thehigh wear region:1) Tubes with no detected wear that may have low level of wear at tube supports2) Tubes that have detected support wear but may develop additional wear at tubesupports during the next inspection intervalThe number of affected supports is reflected in the wear index on a tube-by-tube basis. Thenumber of affected tube supports used in this analysis for Unit 2 is shown in Figure 1.4-2.The Unit 2 data shown in Figure 1.4-2 for the number of affected wear locations was used toassign wear at support locations in those tubes with no detected wear in the most recentIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-41814-AG117-M0026, REV. 0Page 19 of 41 inspection. All tubes with no detected wear within the high wear region are conservativelyassumed to have wear at an assigned number of AVB and TSP locations at the start of the nextinspection interval. The number of tube support locations assigned with AVB and TSP wear isdetermined by sampling from the cumulative distributions derived from Figure 1.4-2. Onaverage, each tube with no detected wear is assigned five tube support locations with wear.Wear depths are assigned at these wear locations based on the POD for the bobbin probe asdiscussed in Section 1.4.6.For tubes in the high wear region with detected support wear, additional support wear locationswere assigned. Operating experience (OE) for a similar replacement steam generator providesdata on the evolution of tube support wear after two cycles of operation. The number ofadditional AVB supports that developed wear in the second cycle of operation depends on thenumber of first cycle detected AVB wear locations in each tube. The OE data were used in theOA to add AVB wear locations at the start of the Cycle 17 inspection interval using a statisticalrepresentation. Since the number of TSP wear locations in the OE data did not increase, onlythe increase AVB wear locations was modeled in the OA. When new AVB wear locations areadded to a given tube, wear is assumed to start at the beginning of the inspection interval froman initial zero depth.Wear from all AVB and TSP supports (including the newly added AVB support locations) areused in the total wear index for the tube.1.4.6 Probability of Detection1.4.6.1 Inspected PopulationThe probability of detection performance of the bobbin probe demonstrates it is capable ofreliably detecting AVB wear, TSP wear, and TTW indications in the U-bend region. Theprobability of detection for eddy current test techniques has been established from industry dataand made available through published Examination Technique Specification Sheet s (ETSS).For ETSS 96004.1, Rev. 13, the POD function is shown as a log-logistic function in Figure 1.4-4.For comparison, the POD function for +PointTM inspection (ETSS 27902.2) is also plotted in thisfigure. The log-logistic model for POD and the parameters for the examination techniques usedfor support and TTW, are given below:Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-51814-AG117-M0026, REV. 0Page 20 of 41 POD(h) 1 + exp[A + B Log(h)]j (1.4-2)Probe ETSS Intercept (A) Slope (B)Bobbin 96004.1 10.61 -11.20+PointTM 27902.2 14.24 -17.22where h = d/t and is the degradation depth in % TW. The parameters for ETSS 96004.1 werederived from hit-miss ECT data used to establish the ETSS data statistics.Tubes within the high-wear region that had significant AVB and TSP wear in Unit 2 had receivedbobbin probe examination. Subsequent to the Unit 3 inspection findings, supplemental +PointTMinspections were performed in Unit 2 to look for TTW with an improved POD. Two TTWindications were found in SG 2E-089 and no indications were detected in SG 2E-088. The mostsusceptible group of tubes within the high-wear region has been examined with a more sensitiveinspection with an improved POD.1.4.6.2 Undetected PopulationThe POD function is used to define the population and depth of the undetected AVB, TSP, andTTW indications at the start of the inspection interval.For the tubes with no detected wear within the high-wear region, wear sites are assigned atAVB and TSP locations that are assumed to develop wear during the inspection interval(discussed in section 1.4.5). The wear depths are defined by the bobbin probe PODperformance for an assumed threshold level (POD < 0.05).I' 1 1Ln[ (POD) -Logl0(h)= RN (OD) (1.4-3)where:Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-61814-AG117-M0026, REV. 0Page 21 of 41 h is the wear depth equal to (d/t), expressed as % TWPOD is the assumed threshold level for NDD (POD < 0.05)RN is a randomly selected number between 0 and 1A and B are constants (intercept and slope) in the log-logistic function for the bobbinprobe PODThe wear depths are determined by a random process with equation 1.4-3 used for eachassigned support wear location in the 1350 tubes without detected wear. The bobbin probePOD is used in this process.1.4.7 Tube-To-Tube Wear InitiationThe initiation of TTW was established through an empirical model relating the probability ofinitiation (POI) for TTW to the total wear index parameter. The same POI model developed forthe original Unit 2 OA (Ref. 1) is used in this OA (see Figure 1.4-5). This model is based on thetotal wear index value for each tube within the high-wear region. The total wear indexparameter relates the observed AVB and TSP wear states of each tube in the high-wear regionto the POI function. Further details on the benchmarking process to obtain the POI modelparameters for Unit 2 are discussed in Ref. 1.The Unit 2 initiation model is implemented such that both the POI and the time when initiationoccurs can be established. It is possible undetected TTW may exist in some tubes at the startof the inspection interval or may initiate during the inspection interval. The initiation modelincludes these possibilities, which are illustrated in Figure 1.4-6. In the figure, the total wearindex for an example tube at BOC and EOC for the Cycle 17 inspection interval is shown. Theinitiation of TTW is evaluated using a random process. TTW does not initiate when thecombination of the EOC total wear index and the random sample produces a value greater thanPOI curve.For cases where initiations are predicted to occur during the inspection interval, the point ofinitiation is determined by the intersection of the random sample with the POI value for themodel function as shown by the "X" on the middle dashed line. In this case, initiation iscalculated to occur at a wear index between the inspection interval BOC and EOC values. Theinitiation time is determined by linear interpolation of the total wear index over time. The TTWIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-71814-AG117-M0026, REV. 0Page 22 of 41 indication is assumed to start growing at the time of initiation with an initial depth of zero and ata wear rate determined from the total wear index value at the time of initiation.The bottom horizontal dashed line in Figure 1.4-6 shows the case when initiation was calculatedto occur during the prior inspection interval (Cycle 16). In this case, TTW initiation is determinedto have occurred during Cycle 16. Because the tube had no detected TTW at EOC 16, the TTWindication is assumed to continue to grow from the beginning of the Cycle 17 inspection interval.The starting depth is determined by a random selection process from the lower 5% detectionlevel of the +PointTM POD curve, with a wear rate determined from the Cycle 17 BOC total wearindex value. The time of growth is the inspection interval length.1.4.8 Degradation Growth RatesWear rates for three mechanisms are required for the OA of TTW. The required wear ratedistributions are for AVB wear, TSP wear, and TTW. All wear rates are conservatively based ona constant growth in depth.1.4.8.1 AVB and TSP Growth ModelsThe AVB and TSP wear rates are used to evaluate the increase in total wear index for eachtube during the inspection interval. The increase in total wear index is due to the individualgrowth in AVB and TSP wear depths. The wear rates for AVB degradation were developedfrom Unit 2 EOC 16 NDE data (Ref. 1). The distribution of wear depths at each of the 12 AVBand 14 TSP tube intersections for Unit 2 is shown in Figure 4-8 of the original OA (Ref. 1). AVBand TSP wear rates used in this OA are the same as those used in the original OA.The wear rate distributions for AVB and TSP wear are shown in Figure 1.4-7. The AVB wearrate distribution was developed using conservative wear data (AVBs 4 to 9 as discussed in Ref.1 for Group 3) from both steam generators. The TSP wear rate distribution uses all the datafrom both steam generators. The two functions are based on a lognormal statistical model forsampling in the simulation.Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-81814-AG117-M0026, REV. 0Page 23 of 41 1.4.8.2 TTW Growth ModelThe TTW growth rates for Unit 2 were developed from the TTW wear depth data observed inUnit 3. To establish TTW growth rates for 100% power operation for Unit 2, a variable initiation-time model was used to estimate the time at which TTW began in each affected tube in Unit 3.This approach differs from that used in the original OA (Ref 1) for 70% power where TTWinitiation was assumed to occur at beginning of Cycle 16 for Unit 3 (i.e., zero initiation time).The development of the variable initiation-time model is discussed in Ref. 6.The results of the variable initiation-time model on TTW growth rate is shown in Figure 1.4-8.The two OA cases for ETSS 27902.2 sizing and AREVA resizing model of the TTW depths arediscussed in the original OA (Ref 1). The TTW growth rates were calculated and the regressionlines shown in Figure 1.4-8 for the two sizing cases yields the following parameters for 100%power:Case Intercept Slope Error(%TW) Slope (%TW)ETSS Sized 30.565 0.0594 13.93AREVA Resized 23.072 0.06416 14.16The residuals from the regression analysis are well modeled by a normal distribution over therange of interest for wear index. The relational error for both regression models is normallydistributed with a mean of zero and a standard deviation as given in the above table.1.4.9 Measurement UncertaintyMeasurement uncertainty for sizing of indications is defined in the ETSS for estimating actual(true) structural parameters (depth and length) from NDE wear size data. The 70% and 100%power OA total wear index was based on NDE measured data for both the correlation andpredictive models so that adjusting for measurement error was not required.The need for including measurement uncertainty was assessed for assigning TTW wear depthand growth rates. Initial TTW depths were assigned at beginning of the interval based onIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.4-91814-AG117-M0026, REV. 0Page 24 of 41

+PointTM POD which has negligible measurement error. Growth applied during the inspectioninterval was derived from Unit 3 +PointTM depth sizing (ETSS 27902.2) where the systematicerror from linear regression is very small. Therefore, sizing uncertainty is not significant forestimating TTW growth rates.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-101814-AG117-M0026, REV. 0Page 25 of 41 U-.-001.00.90.80.70.60.50.40.30.20.10.01SONGS-2 Tubing Strength at 650°F....... .. ... ..-.-2SG882--- 2SG89U.. _ _ _106108110112114 116 118Sy + SU, (ksi)120 122124 126 128Figure 1.4-1 -Distribution of Tubing Strength Properties at 650°FIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-11Page 26 of 411814-AG117-M0026, REV. 0 SONGS-2 Distribution of Wear at AVB Supports280U12SG8802SG89Ez240220200180-160-140-120-100-80-60-40-20-0-U]0[!nR I1 2 3 4 5 6 7 8Number of Affected Supports9 10 11 12SONGS-2 Distribution of Wear at TSP Supports0Ez0 1 2 3 4 5 6 7 8 9 10 11 12 13 14Number of Affected SupportsFigure 1.4-2 -Support Locations per Tube Exhibiting AVB and TSP Wear in Unit 2Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-121814-AG117-M0026, REV. 0Page 27 of 41 TTW Structural Length Distribution1.00.90.80.7.2 O.60 0.50 0.40.30.20.10.00 1 2 3 4 5 6 7 8 9 10Structural Length,LST (inches)Figure 1.4-3 -Structural Length Distribution for TTW in Unit 3Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-13Page 28 of 411814-AG117-M0026, REV. 0 SONGS ECT Techniques1.00.90.80.70ILC.2 0.6i 0.5-0.4.00 0.3a.0.20.10.0-Bobbin Probe (ETSS 96004.1)-+Point (ETSS 27902.2)0 2 4 6 8 1012 14 16 1Depth, dlt (%TW)8 20 22 24 262830Figure 1.4-4- Probability of Detection for Tube WearIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-141814-AG117-M0026, REV. 0Page 29 of 41 TTW Initiation ModelC0.21.00.90.80.70.60.50.40.30.20.10.0* SONGS-3 Data_ --Beta Distribution Fit-B-Adjusted Distribution for SONGS-2+- I in I I-0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300Total Wear Index, WI (%TW)Figure 1.4-5- Tube-to-Tube Wear Initiation Model Based on Total Wear IndexIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-15Page 30 of 411814-AG117-M0026, REV. 0 SONGS-2 Tube-to-Tube Wear Initiation Model1.00.9-0.8-0.7BOCNon InitiationRegionEO(tNolnitiation00C.0.6-0.50.4-0.3-Initiation During I ICyl 6adNDD atI',/EOC 16Initiation Region0.200.1AIn-SONGS-2 POI Model (100% Power)w Wear Index at BOC and EOCK TTW Initiation00V0 20 40 60 80 100 120 140 160 180 200 220Total Tube Wear Index, WI (% TW)240 260 280 300Figure 1.4-6 -Illustration of TTW Initiation Model EstimationIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-161814-AG117-M0026, REV. 0Page 31 of 41 AVB Wear Rate -Group 3 (Both SGs)Li-.2E0 2 4 6 8 10 12 14 16 18 20 22 24Wear Rate, WR (%TW per Years at Power)TSP Wear Rate (Both SGs)ag00NSU1.00.90.80.70.60.50.40.30.20.10.00 2 4 6 8 10 12 14 16 18 20Wear Rate, WR (%TW per Years at Power)Figure 1.4-7 -Wear Rate Distributions for AVB and TSP Wear MechanismsIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-171814-AG117-M0026, REV. 0Page 32 of 41 ETSS 27902.2 Sizing110100900.-80' 702L 60e 504030201000 50 100 150 200 250 300 350 400 450 500 550 600 650Total Wear Index, WI (%TW)AREVA Resized1101009080m 701L60e 50.40.6 30201000 50 100 150 200 250 300 350 400 450 500 550 600 650Total Wear Index, WI (%TW)Figure 1.4-8 -Tube-to-Tube Wear Rate as a Function of Wear IndexIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.4-181814-AG117-M0026, REV. 0Page 33 of 41 1.5 OPERATIONAL ASSESSMENT1.5.1 Analysis CasesThe OA for TTW degradation was performed by Monte Carlo simulation with 10,000 trialsapplied to produce the minimum burst pressure and maximum depth distributions at thecompletion of the inspection interval. Two cases were evaluated that look at the effect of TTWrate models as described below:Case 1 -Tube-to-tube wear rate based on the Unit 3 wear depths sized with ETSS 27902.2(Ref. 1)Case 2 -Tube-to-tube wear rate based on the Unit 3 wear depths sized with AREVA hybridvoltage model (Ref. 1)Each case was evaluated for 100% power operation. The planned inspection interval is 5months.The NOPD value is 1324 psi and includes 3% plugging and TcoLo restoration.1.5.2 Structural Margin EvaluationThe structural analysis to establish the margins to tube burst was performed for the two analysiscases. The parameters for the input distributions are given in Table 1.5-1.The structural analysis for tube burst was completed for a range of inspection intervals. ThePOB was determined from the distribution of worst case burst pressures which is compared tothe SIPC margin of 3xNOPD. The POB was determined as a function of inspection interval asshown in Figure 1.5-1. The performance standard for SIPC margin for the POB for the TTWmechanism is 5%.The following allowable inspection interval lengths have been computed:Intertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.5-11814-AG117-M0026, REV. 0Page 34 of 41 Inspection Interval Lengths at POB = 5%1 Years atAnalysis Case Y 1 P100% PowerCase 1 -ETSS 27902.2 Sizing 0.94Case 2 -AREVA Resized 1.04The allowable inspection interval at 100% power is 11 months based on Case 1.1.5.3 Leakage EvaluationDue to the long and flat nature of TTW degradation, the tube burst at 3xNOPD is more limitingthan the accident-induced leakage criteria. The limiting condition for the inspection interval isbased on the SIPC.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.5-21814-AG117-M0026, REV. 0Page 35 of 41 Table 1.5-1OPERATIONAL ASSESSMENT INPUT PARAMETERSTTW FOR Unit 2Distribution Type Parameters S/G 89 (1) Basis (2)Log- Intercept, A 10.61 ETSS 96004.1Probability of Detection Logistic Slope, B -11.20 (Ref. 12)Log- Intercept, A 14.24 ETSS 27902.2Probability of Detection Logistic Slope, B -17.22 (Ref. 13)Mean Ln(WR) 1.68 Unit 2AVB Wear Rate (% TW per Years at Power) Log Normal Std Dev Ln(WR) 0.45 (Ref. 6b)Max Rate 20Mean Ln(WR) 1.71TSP Wear Rate (% TW per Years at Power) Log Normal Std Dev Ln(WR) 0.26 Unit 2Max Rate 20 (Ref. 6b)Intercept 30.565 Unit 3TTW Rate (% TW) (3) ETSS 27902.2 Normal Slope 0.0594 (Ref. 13)Std Dev 13.93(3 Intercept 23.072 Unit 3TTW Rate (% TW) AREVA Resized Normal Slope 0.06416 (Ref. 14)Std Dev 14.16TTW Initiation Model Beta Shape 1 9.839 Unit 3Shape 2 39.138 (Ref.1Oa & 16))Structural Length LST, (in.) Log Normal Mean Ln (LST) 1.28 Unit 3Std Dev Ln (LsT) 0.26 (Ref. 11)Shape Factor, F = dMAx/dsT Normal Mean (F) 1.00 Unit 3Std Dev (F) 0.0 UiMean (Sy + Su) 116,633 Unit 2Strength, Sy, + S, (psi) Normal Std Dev (Sy + Su) 2,504 CMTR DataMin (Sy + Su) 109,900 SG 2E-089Max (Sy + Su) 123,900 (Ref. 1Ob)1325 Unit 2Normal Operating Pressure Differential, (psi) Constant NOPD at 100% 1305 (Ref 71305 (Ref. 7 & 9)Unit 2Limiting Accident Pressure Differential, (psi) Constant LAPD 2560 (Ref 3(Ref. 3)SCE RTSInspection Interval Length (Years at Power) Constant 0.42 Report(4)Notes(1) Wear in SG 2E-089 is limiting(2) Databases for Unit 2 and Unit 3 data and other listed references are from cited references in original OA (Ref. 1)(3) TTW rates are shown in Figure 1.4-8(4) Return to Service Report (Ref. 8)Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.5-31814-AG117-M0026, REV. 0Page 36 of 41 Operational Assessment for TTW for Cycle 17 at 100% Power0.160.140.12o. 0.1*~0.08j0.0600.040.02070% Power, Original OA, ETSS Sizing70% Power, Original OA, AREVA Resizing IE3 100% Power, NOPD=1 324 psi, ETSS Sizing-100% Power, NOPD=1324 psi, AREVA Resizing---Mid-Cycle 17 (5 Months at Power) I-Cycle 17 (1.578 Years at Power)-SIPC Margin, POB < 0.05 -1l' I* I' I0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6Inspection Interval, (Years at Power)Figure 1.5-1 -Probability of Burst at 70% and 100% Power Levels for TTW Growth RateModels Based on Case I -ETSS 27902.2 Sizing and Case 2 -AREVA Resizing ModelsIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.5-41814-AG117-M0026, REV. 0Page 37 of 41 1.6 ANALYSIS VERIFICATION AND VALIDATIONA special-purpose computer program called TTWEARU2 Revision 1 (R1) was developed toperform the Monte Carlo simulation and required calculations as shown in Figure 1.2-1. Thisprogram is a revised version of the original program used for the 70% power OA. Verificationand validation of TTWEARU2 Rev. 1 followed Intertek APTECH Quality Assurance Proceduresfor computer software and hardware systems as described in Section 3.5 of the original OAreport (Ref. 1). The documentation of the verification and validation of TTWEARU2 R1 isgiven in Ref. 7.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.6-11814-AG117-M0026, REV. 0Page 38 of 41 1.7 REFERENCES1. "Operational Assessment for SONGS Unit 2 Steam Generators for Upper Bundle Tube-to-Tube Wear Degradation at End of Cycle 16," Intertek APTECH Report NumberAES 12068150-2Q-1, (September 2012).2. "Steam Generator Integrity Assessment Guidelines, Revision 3," Electric PowerResearch Institute, Steam Generator Management Program, EPRI Report 1019038,(November 2009)3. "Steam Generator Degradation Specific Management Flaw Handbook, Revision 1,"1019037, Electric Power Research Institute, Steam Generator Management Program(December 2009)4. Letter from A. Matheny (SCE) to A. Brown (AREVA), "Numerical Values for the SteamGenerator Operational Assessment San Onofre Nuclear Generating Station, Units 2 and3," (February 8, 2012)5. "Operating Parameters of Unit-2 RSGs for Various Power Levels after Plugging," MHIL5-04GA602, (January 23, 2013)6. Calculation-C-8304-3, "initiation Time Model to Determine Tube-to-Tube Wear Rates forUnit 3 -RAI #2," Rev. 2, Intertek Project AES 13018304-2Q, (February 22, 2013)7. "Verification of Program TTWEAR_U2 R1 for the Operational Assessment for SONGSUnit 2," Calculation No, AES-C-8304-5, Intertek APTECH, (March 2013)8. Letter from Peter T. Dietrich (SCE) to Elmo E. Collins (NRC), Confirmatory Action Letter-Actions to Address Steam Generator Tube Degradation, San Onofre Nuclear GeneratingStation, Unit 2, October 3, 2012.Intertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.7-11814-AG117-M0026, REV. 0Page 39 of 41 1.8 NOMENCLATUREAcronym DescriptionSG 2E-088 Unit 2 Steam Generator 88SG 2E-089 Unit 2 Steam Generator 89SG 3E-088 Unit 3 Steam Generator 88SG 3E-089 Unit 3 Steam Generator 893xNOPD Three times normal operating pressure differential95-50 95% probability at 50% confidenceAILPC Accident Induced Leakage performance CriteriaAVB Anti-vibration barBOC Beginning of operating cycleCM Condition monitoringCYC Length of cycleEOC End of operating cycleEPRI Electric Power Research InstituteETSS Examination Technique Specification SheetsGPM Gallons per minuteNDD No degradation detectedNDE Non destructive examinationNEI Nuclear Energy InstituteOA Operational assessmentPOB Probability of burstPOD Probability of detectionPOI Probability of initiationQA Quality assuranceRAI Request for additional informationRN Random numberSG Steam generatorIntertek APTECH Southern California EdisonAES 13018304-2Q-1 March 20131.8-11814-AG117-M0026, REV. 0Page 40 of 41 REPORT ACRONYMS (Cont'd)AcronymDescriptionSIPCSRTSPTTWTWUnit 2Unit 3WIWRStructural Integrity Performance CriteriaStability ratioTube support plateTube-to-tube wearThrough wallSan Onofre Unit 2 (also SONGS-2)San Onofre Unit 3 (also SONGS-3)Total wear indexWear rateIntertek APTECHAES 13018304-2Q-1Southern California EdisonMarch 20131.8-21814-AG117-M0026, REV. 0Page 41 of 41