PNP 2012-021, Notification of Deviation from EPRI Steam Generator Management Program: PWR Steam Generator Examination Guidelines: Revision 7

Notification of Deviation from EPRI Steam Generator Management Program: PWR Steam Generator Examination Guidelines: Revision 7

ML121000292
Person / Time
Site:	Palisades
Issue date:	04/05/2012
From:	Gustafson O Entergy Nuclear Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PNP 2012-021
Download: ML121000292 (33)

Text

-===-Entergy PNP 2012-021 April 5, 2012 U. S. Nuclear Regulatory Commission A TIN: Document Control Desk Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel 269 764 2000 Otto W Gustafson Licensing Manager

SUBJECT:

Notification of Deviation from EPRI Steam Generator Management Program: PWR Steam Generator Examination Guidelines: Revision 7 Palisades Nuclear Plant Docket 50-255 License No. DPR-20

Dear Sir or Madam:

Entergy Nuclear Operations, Inc. (ENO) is providing notification of a deviation from the Electric Power Research Institute (EPRI) "Steam Generator Management Program:

Pressurized Water Reactor [PWR] Steam Generator Examination Guidelines:

Revision 7." The deviation is specifically from Appendix I of the examination guideline, "NDE System Measurement Uncertainties for Tube Integrity Assessments," for use in determination of non-destructive examination (NDE) system measurement uncertainties for tube integrity assessments, and is limited to axial outside diameter stress corrosion cracking (ODSCC) sizing.

The deviation will be in effect from the 2012 refueling outage steam generator inspection through the remaining life of the steam generators.

The deviation from the EPRI PWR steam generator examination guidelines has been reviewed and approved in accordance with ENO procedures and NEI 03-08, "Guideline for the Management of Materials Issues," guidance. This is a notification of a deviation only. No action is being requested from the NRC.

Details of the deviation are provided in Attachment 1.

Summary of Commitments This letter contains no new commitments and no revised commitments.

PNP 2012-021 Page 2 Sincerely, owg/jlk

Attachment:

1. Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators cc:

Administrator, Region III, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC

ATIACHMENT1 TECHNICAL JUSTIFICATION SUPPORTING DEVIATION FROM THE EPRI APPENDIX I ETSS FOR ODSCC SIZING FOR THE PALISADES STEAM GENERATORS 30 pages follow

ATTACHMENT 9.1 SHEET 1 Of2 ENGINEEAlNG REPORT COVER SHEET" INSTRUCnoNS Engineering R~

No.

PLP*RPT*12*

Rev 0

ENTERGY NUCLEAR Engineering Report Coyer Sheet Eagineeriag Report Tide:

00075 Page _,_ of 30 Technical JustWication Supporting Deviation from the EPRI Appendix I ETSS for OOSCC Sizing for the Palisades Steam Generators IPI 0 ANOI 0 EC No. 28627 New 181 IP2 0 AN02 0 EngineeriDI Report Type:

Revision 0 Cancelled 0

Superseded 0

Superseded by:

11>3 0 ECH 0 Applicable SUe(s)

JAF 0 GONS 0 PNPS 0 RBS 0 VY 0 WFJO Report Oripn:

181 Enletg)'

0 Vendor Quality-Related:

0 Yes

~ No WPO 0 PLP 1m Date:.l{ -'I -,:z..

Desisn Veriraed: __

~~NI.:;.:A~Des~il!l~V..=;en:..;;:

• fi~let~N~ot;..;:R,;:;eq~u::.:;it:.;;.ed~~ __

Design Verifier (if required) (Print NamelSign)

Dan Meatheanyl &"tl1l1lJttJ. N Date: ___

Reviewed by:

Date:

R.... _(PrintN.~

-0 Approved by: ___ "..-~~~G~eor~gee:..!Sc~h!gr~ad~e~~~~~V~_~~=_~,,",Date:

Supervisor I Manager (Print NameJSign) 4-5./'2..

EN*OC-147 REV 5

Res MDMP Deviation Form Utility: Entergy Applicable Site(s) and Unit No.: Palisades Utility Contact(s): Sieve Brown Steam Generator Program Fleet Lead John Hager Steam Generator Program Owner Palisades Issue Program (IP) activity or document: SGMP - EPR1 Steam Generator Examination Guidelines Revision 7 Scope / Description of Deviation: The ETSS approved In "EPRI PWR Steam Generator Examination Guidelines - Revision 7, Appendix ID will not be used. An attemative ETSS will use the Combustion Engineering (eE) sub-set of the approved tube sizing data but be otherwise identical to the Appendix I approved ETSS. This deviation will impact OOSCC sizing only.

Reason for Deviation: Overly Conservative Sizing for Combustion Engineering Tubing Technical Justification for Deviation: Attached Time Frame the Deviatlon will be in Effect: 2012 (1 A22) refueling outage steam generator inspection until steam generator is retired or replaced.

Deviation to this IP requirement is classified as NEEDED.

Prepared By: John Hager Palisades SG Program Owner per PCRS action CR-PlP-2011-Q§396 CA-O?

Date: January 6. 2012 Approved/Concurrence By: Pan Meatheany ANO SG Program Owner per peRS action CR*PlP-2011-06396 CA"()3 Approved/Concurrence By: Robert Q'Quinn WF3 SG Program Owner per PCBS action CR-PLP*2011-06396 CA-04 Supervisor: George Schrader per PeAS action CR*pLP-2011-QQ6396 CA-02 Date:

January 6. 2012 Date: ?/z Z/Z()/ L Date: 3-Zl.-I\\..

Date:

20f30

Res MDMP Deviation Form Entered into CA Process as a Site CR by:

=..:Jo~h~n:....:.H..:.::a:::lgL:=.e!....r _--==D:.!:::a~te::.:..:...:.N~o~v~em=be~r-=2=2.1...:' 2=::0::..,:1..,:.1 CR Number: CR-PLP-2011-06396 IP Notification Date: PCRS action CR-PLP-2011-06396 CA-05 NRC Notification Date: PC AS action CR-PLP-2011-06396 CA-06 30f30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators

1.

Proposed Deviation Palisades will deviate from the Ineeded" requirement contained in the "EPRI PWR Steam Generator Examination Guidelines - Revision 7", section 6.2 to use an approved Examination Technique Specification Sheet (ETSS) for OOSCC sizing. Palisades will instead use a modified ETSS for OOSCC. The modified ETSS will be identical to the ETSS approved per Appendix I of the examination guidelines with the exception that only the sub-set of data from CE plants will be used instead of the combined fleet data set used in the approved ETSS.

The deviation will be in effect starting in the 2012 (1 R22) refueling outage steam generator inspection for the remaining life of the existing Palisade steam generators.

The "EPAI PWR Steam Generator Examination Guidelines - Revision 7",

Appendix I provides guidance for determining NDE system measurement uncertainties for tube integrity assessments. Two NOE system performance measures are needed;

1) Probability of detection (POD) and

2) Sizing accuracy.

This deviation addresses sizing accuracy only.

Both performance measures are quantified using functional measures over the expected range of the structural variable. NOE technique qualification and documentation, including both destructive and NDE. shall be performed under 10CFR50 Appendix B Quality Assurance Program.

The condition relative to steam generator examination control parameters that the proposed deviation addresses:

EPRI PWR Steam Generator Examination Guidelines requirement (Section 6.2): Inspection of SG tubes shall be conducted using qualified techniques capable of detecting and characterizing the degradation mechanisms identified in the degradation assessment. The qualification of NDE techniques shall comply with the requirements specified in Appendix H or Appendix I. It is recommended that the degradation assessment consider Examination Technique Specification Sheet (ETSS) in effect six months prior to the examination.

Appendix I has verified data sets. This deviation uses a Combustion Engineering (CE) subset of the well vetted data of Appendix 128432. There is a reasonable basis to submit a deviation request for maximum depth sizing of axial ODSCC indications at Palisades. The regression slope and standard error of regression for the full Appendix 128432 data set are retained. however the intercept 4 of 30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators parameter is changed to that indicated by the CE data set. This provides an across the board reduction of NDE maximum depth sizing of 11.23 % TW.

3.

Background

The Steam Generator Degradation Assessment and Repair Criteria for 1 R21 (2010 refueling outage) were documented in EC-24725 [Reference 2]. The technique sheets (ETSS) used during this outage were documented in EC*25517 "Acquisition Technique Sheets (ACTS) and Analysis Technique Sheets (ANTS)"

[Reference 3]. The equivalencies based on the EPRI Appendix H II approved methods are documented in the site equivalency report. This site equivalency ensures that a qualified or equivalent technique and probability of detection will be utilized to identify the flaws.

Site validation of all techniques used in 1 R21 (2010 refueling outage) was performed and documented in the site equivalency report.

EC-25627 documents the Technical Deviation for Steam Generator Eddy Current Testing using EPRI Appendix I for ODSCC Sizing [Reference 7] to be used starting with the 1R22 (2012 refueling outage).

4.

Technical Justification Introduction A comprehensive review of axial OOSCC in Palisades steam generators shows that Appendix 128432 over sizes maximum depth values for axial ODSCC at Palisades. There is a reasonable basis to submit a deviation request for maximum depth sizing of axial ODSCC indications at Palisades. The request is relatively modest since it uses the Combustion Engineering (CE) subset of the well vetted data of Appendix 128432. The regression slope and standard error of regression are retained. Only the intercept parameter is changed. This provides an across the board reduction of NDE maximum depth sizing of 11.23 %TW.

This will lead to about a 1000 psi increase in calculated condition monitoring burst pressures and much better matching of projected and measured NDE maximum depths.

Results of a comprehensive review of axial OOSCC in Palisades steam generators are presented in the following sections. Past inspection and in situ testing results were examined. Tube integrity projections for future operating cycles were developed using a multi-cycle, fully probabilistic Monte Carlo program. This program provides quantitative descriptions of both past and projected future degradation states. The program tracks both detected and undetected degradation sites over multiple cycle of operation. Both actual and NDE measured degradation severity is included. Confidence in the accuracy of tube integrity projections is provided by matching of past inspection results with 50f30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for OOSCC Sizing for the Palisades Steam Generators computer calculations. There are three key elements in the comparison of calculated and observed degradation states in past inspections. These are:

Numbers of observed degradation sites Distributions of observed maximum crack depths Distributions of observed axial crack lengths The following sections describe the present state of axial ODSeC degradation in Palisades steam generators. calculations of past and projected future degradation states. evaluations of detection and NDE sizing issues relative to use of EPRI Appendix I ETSS documents and an evaluation of both the need for a deviation from Appendix I and the adequacy of the technical grounds for a deviation.

Axial OOSCC Degradation in Palisades Steam Generators Axial OOSCC has been observed primarily at eggcrate intersections and near the top of the tubesheet in the sludge pile region. A small number of freespan and vertical support indications have also been observed. Figure 1 shows a plot of cumulative number of eggcrate intersection axial OOSCC indications versus operating time in EFPY. Figure 2 shows a plot of cumulative number of axial OOSCC indications near the top of the tubesheet, TIS, versus operating time.

Currently there are about twice as many cumulative eggcrate intersection indications as there are indications near the top of the tubesheet. The progression rate of degradation is often treated with Weibull statistics. The Weibull slope reflects the rate of progression and the Weibull scale parameter reflects the time at which significant degradation will be observed. The Weibull slope for both eggcrate and TIS axial OOSCC is about 5.3. Typical values for ODSCC or pwsce degradation range from about 2 to 6. Thus the progression rate for OOSCC at Palisades is near the high end of past observations for mill annealed Alloy 600 tubing. The onset of discovery of axial ODSeC at about 9 EFPY falls in a typical range for CE steam generators with mill annealed Alloy 600 tubing. The current extent of axial OOSCC degradation at both eggcrate and TIS locations makes long term projections somewhat inaccurate. Inspection results from the next two refueling outages should allow reasonable long term projections.

60f30

Te.chnical Justification Supporting Deviation from the EPRI Appendix I ETSS for OOSCC Sizing for the Palisades Steam Generators The number of degradation sites is only one aspect of degradation severity.

Distributions of maximum crack depth and axial crack length are needed to complete the analysis. Figure 3 plots the cumulative distributions of NOE total crack lengths for both eggcrate intersections and TIS locations at 1 R21 (2010 refueling outage). Results from both steam generators are combined. Crack lengths at eggcrate intersections are Significantly longer than those observed near the top of the tubesheet. However, the NOE total crack length is an overestimate of the structural effective crack length on which burst pressure calculations are based. On average, the structural effective crack length is about 0.66 times the total crack length. Figure 4 compares the total crack length distribution for Palisades' eggcrate locations versus an estimated structural length distribution from a plant with a similar total crack length distribution for axial OOSCC. This difference makes a substantial impact on observed and projected tube integrity. Axial crack profiling provides the structural effective crack length. Once determined for about 30 cracks the end of cycle distribution of structural effective lengths remains relatively stable from one inspection to the next. The crack length distributions for axial OOSCC at Palisades are unexceptional.

Figure 5 shows the cumulative distribution of NOE measured maximum crack depths at eggcrate locations at 1 R21 (2010 refueling outage). Again results are combined for both steam generators. Maximum depths using the Appendix I 28432 methodology are deeper than the previous regression method. The proposed deviation request sizing results lie between the two plots. Maximum depths using the Figure 6 shows the cumulative distribution of NOE measured maximum crack depths at TIS locations at 1R 21 (2010 refueling outage). There is a about a 7% TW difference at smaller depth between the amplitude sizing results for EPRI Appendix 128432 and Appendix 128431. EPRI Appendix 128431 applies to the sludge pile region. Since the average +Pt probe voltage of TIS indications is greater than eggcrate indications any amplitude based depth sizing method will show somewhat larger depths for TIS cracks compared to cracks at eggcrate intersections.

At 1 R21 (2010 refueling outage) in situ pressure testing was perfonned on three axial OOSCC indications, SG A R4 C59 at 01H, SG A R9 C150 at 02H and SG B R75 C96 at TSH. Crack profiling together with evaluation of structural effective depths and structural effective lengths per ETSS Appendix 128432 showed that in situ testing was required. The applicable temperature compensated 3~P is 4510 psi. In an attempt to demonstrate that the depth sizing was overly conservative in situ testing was conducted at elevated pressures of 5700,5900 and 5700 psi respectively. Structural and leakage integrity was demonstrated at these pressures. All 3 indications passed in situ testing at these elevated pressures.

Using structural effective depths and lengths per Appendix 128432 along with the associated sizing uncertainties the probability of each indication surviving the given in situ test pressures can be calculated. These probabilities are 0.68, 0.65 and 0.75 respectively. The product of these three values is the probability that aI/

70f30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for oosec Sizing for the Palisades Steam Generators three indications will pass testing at the elevated test pressures. This probability is 0.33. Therefore the fact that all three indications passed in situ testing offers no strong evidence that sizing per Appendix 128432 for axial OOSCC indications is overly conservative. Similarly the lack of any significant change in the post in situ +Pt probe voltage compared to pre test values is not particularly informative.

The 0.5 probability of burst for indication R9 C150 in a room temperature in situ test is 6500 psi. This is 800 psi higher than the actual test pressure. Plastic blunting of cracks at high loads will increase the crack widths which can substantially increase the +Pt probe voltage response. However, the degree of plastic blunting is highly non linear with test pressure. A test to 88% of the expected burst pressure did not significantly change the +Pt voltage response.

Additionally ligament strengthening between crack segments in the total macro-crack occurs in 95% of all SCC cracks for both OOSCC and PWSCC. These ligaments bridge the macro-crack faces providing current paths which reduce the

+Pt voltage response. This adds to the nonlinearity of the voltage response with pressure and renders comparisons with EOM slots highly problematic.

In situ test results at elevated pressures and pre and post test +Pt voltage measurements do not offer strong evidence that EPRI Appendix 128432 sizing of Palisades' axial OOSCC indications is overly conservative. These results do re-enforce the application of the method of condition monitoring by sizing and analysis that does not require axial crack profiling that is presented in the EPRI Steam Generator Tube Integrity Assessment Guideline [Reference 7]. The structural effective depth can be estimated as the maximum depth divided by a factor of 1.25. The structural effective axial length is considered to be bounded by the +Pt probe NDE total length. In Figures 7 and 8 this approach is followed to compute the CM limit curve for a 3~P of 4100 in terms of maximum NDE depth and +Pt NDE total crack length for eggcrate and TIS axial oosec indications at 1 R21 (2010 refueling outage). Maximum depth sizing per Appendix 128432 is applied along with the associated uncertainty. Results are also shown for EPRI Appendix 128431 sizing for TIS indications. With this approach condition monitOring structural integrity is shown to be met via NOE sizing and analysis without employing axial crack profiling.

Axial ODSCC Multi-Cycle Fully Probabilistic Analysis Results A multi-cycle fully probabilistic Monte Carlo analysiS was performed for axial OOSCC at eggcrate intersections for Palisades Steam Generator A which is the limiting steam generator for this degradation mechanism. Calculations extended from 1 R16 (2003 refueling outage) to 1 A23 (2013 refueling outage). Calculated inspection results are benchmarked with the latest inspection observations at 1R21 (2010 refueling outage).

The key inputs to the Monte Carlo program are:

Weibull statistics for crack initiation POD curve parameters NOE Sizing parameters 80f30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators Maximum depth crack growth rate distribution Crack length distribution Material strength distribution The program outputs both the calculated actual as well as NOE measured degradation state for each simulated inspection. Burst pressures and leak rates are evaluated for all degradation sites. The key structural and leakage integrity figures of merit are the projected worst case burst pressures at 0.95 probability and the projected SLB accident leak rate at 0.95 probability. Operational assessment structural integrity is demonstrated if the worst case burst pressure is greater than the 3L\\P pressure of 4100 psi. Leakage integrity is demonstrated if the projected SLB leak rate is less than the accident induced leakage performance criteria, AILPC.

As noted earlier, confidence in the accuracy of tube integrity projections is provided by matching of past inspection results with computer calculations with the three key elements in the comparison being:

Numbers of observed degradation sites Distributions of observed maximum crack depths Distributions of observed axial crack lengths Since the input Weibull crack initiation statistics are adjusted to match past observations the success of this comparison is a given. The same is true for crack length distributions. A crack length growth rate allowance can be included but after multiple cycles with a plug on detection repair scenario the EOC crack distribution becomes essentially stable. Comparison of observed and calculated NDE maximum depth distributions is thus the key assurance that operational assessment projections are accurate. This comparison is dominated by the POD curve and NDE sizing parameters.

Figure 9 shows a plot of number of eggcrate axial OOSCC indications in SG A versus operating time. The best estimate Weibull projection is included as well as the calculated results. The calculated results are intentionally conservative and matched to the last inspection result to assure a conservative tube integrity projection for the next operating cycle. The calculated EOC structural length distribution matches the input structural length distribution in Figure 4.

Figure 10 plots candidate input POD curves. The bobbin POD curve per EPRI Appendix 128413 is shown along with a POD curve obtained by only using pulled tube data from CE steam generators in 128413. These curves are very similar.

Two additional curves are included. One was obtained from a pulled tube POD program for SONGS Unit 2 conducted in the late 1990's. The other most limiting POD curve is from a recent extensive program to improve the POD for freespan axial ODSCC in Once through Steam Generators (OTSG's).

Computer projected and observed NDE maximum crack depth distributions for 1 R21 (2010 refueling outage) are plotted in Figure 11. Inspection data is 90f30

Technical Justification Supporting Deviation from the EPR. Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators presented using the EPRI Appendix 128432 sizing method, the previous regression method and the deviation request method. The EPRI Appendix 128413 POD curve over estimates the ability to detect smaller crack depths.

Projections using the SONGS 2 POD curve match the previous regression method results at the median level. The projected range of inspection results is wider than the observed range of results indicating that the standard deviation of the sizing uncertainty is less the expected value of about 12 % TW. PrOjected NDE crack sizes from the most pessimistic POD curve, OTSG freespan axial ODSCC, match well with the deviation request method The use of a POD curve equal to or better than that of EPAI Appendix 128413 is does not match the inspection data. Both the SONGS 2 POD curve and the OTSG POD curve appear to be more realistic and argue that maximum depth sizing per the deviation request method is much more realistic than the EPRI Appendix 128432 method. The next section provides a cogent argument to use only data for CE plants from EPRI Appendix 128432 to develop the NOE regression parameters for sizing of axial ODSCC at Palisades that is termed the deviation request method It should be noted that an argument that the POD value at larger depths must be very close to 1 since no very large depths were observed at 1 R21 (2010 refueling outage) is unpersuasive. Multi-cycle fully probabilistic projections show that multiple applications of even a relative poor POD curve, such as the OTSG curve, over several inspections will make an observation of a very large crack depth a very low probability event.

The prOjected worse case burst pressures at 0.95 probability are plotted in Figure 12 versus operating time. 1R21 (2010 refueling outage) is at 15.5 EFPY.

Structural integrity is projected over the next two cycles and beyond. These prOjections are based on a conservative number of projected indications and, more importantly, the worst case OTSG POD curve. No leakage is projected at SLB accident conditions. There is no issue with structural or leakage integrity over the next several cycles.

Axial OOSCC Sizing Issue at Palisades The previous section demonstrated that any proposed use of a POD curve equal to or better than that of Appendix 128413 for detection of eggcrate axial OOSCC at Palisades is unrealistically optimistic. Rather a more adverse POD curve must be used in operational assessments to successfully predict degradation severity.

The remaining issue is NDE sizing of axial oosec at Palisades. Figure 13 plots actual maximum crack depth versus +Pt probe peak to peak voltage at 300 kHz from EPRI Appendix I 28432. There are four sets of data, pulled tubes from CE plants at low maximum depths, pulled tubes from OTSG's at intermediate depths, pulled tubes from Westinghouse plants covering a broader range of depths and laboratory specimens at large depths. These selected sets of data form a reasonable consistent set of NDE sizing data for development of regression 10 of 30

Technical Justification Supporting Deviation from the EPR. Appendix. ETSS for OOSCC Sizing for the Palisades Steam Generators sizing parameters. However, when more data from CE plants, as tabulated in the EPRI 1014983 Steam Generator In-Situ Pressure Test Guidelines, is plotted it is easily seen than most data from CE plants falls substantially below the EPRI Appendix 128432 regression line. This is illustrated in Figure 14.

The question at hand is whether axial oosec indications of Palisades are well represented by the total data set in EPRf Appendix 128432 or rather by some subset of this data. Tubing dimensions are not an issue. Figure 15, from Rev. 3 of the EPR' Steam Generator In Situ Pressure Test Guidelines shows that a plot of % TW depth versus +Pt probe voltage is essentially unaffected by standard tubing dimensions. The other factors affecting the +Pt probe voltage are conducting paths across the crack faces provided by ligaments in crack networks and corrosion products. Crack morphology and corrosion products vary between steam generators. For example freespan axial oosec in OTSG's often exhibits a significant component of IGA leading to the eariy term of "Groove IGA".

Figure 14 shows that the +Pt probe voltage response of axial oosec in some CE plants differs from the total data set of Appendix 128432.

Inspection results at Palisades and multi-cycle Monte Cario prOjections of degradation severity show that this behavior is also characteristic of Palisades.

This may be a result of the manufacturing differences between CE and Westinghouse steam generators. The C-E bending process uses a rotating wheel die to control bend radius. The tube is clamped to the wheel die. As the wheel die is rotated, the tube is pulled along the wheel die. A movable pressure forming die located on the extrados of the tube controls ovality. The pressure die is translated with the tube and is in contact with the wheel die during the bending process. This process is expected to result in a condition where increaSing bend radius is associated with decreasing longitudinal strain. The bending process also eliminates the potential for shear strain at the U-bend flanks. In the Westinghouse process a stationary bend die is used with a movable pressure forming die located at the tube extrados. The movable pressure forming die is rotated, pulling the tube with it. In this case, it can be postulated that a shear strain could be introduced at the flanks if an off nominal tube geometry is encountered (Reference 10).

A regreSSion fit using CE plant data from EPRI Appendix 128432 provides essentially the same slope as the total data set. The intercept parameter changes from 78.98 %TW to 67.75 %TW. The regression fit just shifts to the regression line to the right by 11.23 % TW as shown in Figure 16. A substantially larger shift is obtained if other data from CE plants is included. Use of only CE plant from data EPRI Appendix 128432 preserves the highly structured procedures of EPRI Appendix I 28432. The fact that the standard error of regression fit of only CE plant data is smaller that of the total dataset of EPRI Appendix I 28432 argues that the standard error of regression for maximum depth per EPRI Appendix I 28432 should be retained.

11 of 30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators There is a reasonable basis to submit a deviation request for maximum depth sizing of axial oosec indications at Palisades. The request is relatively modest since it uses the CE subset of the well vetted data of Appendix 128432. The regression slope and standard error of regression is retained. Only the intercept parameter is changed. This provides an across the board reduction of NOE maximum depth sizing of 11.23 % TW. This will lead to about a 1000 psi increase in calculated condition monitoring burst pressures and much better matching of projected and measured NOE maximum depths.

12 of 30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSeC Sizing for the Palisades Steam Generators 1~~--------------------------------------------------------~

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2.2 2.4 2.6 NOE Total Crack Length Figure 8 Condition Monitoring Structural Integrity Plot, ITS Axial OOSCC 1 R21 (2010 refueling outage) 20 of 30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for OOSCC Sizing for the Palisades Steam Generators 180 i 160 u

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18 20 Figure 9 Cumulative Number of Eggcrate Axial oosec Indications versus Operating Time. Best Estimate and Structural Integrity Projections 21 of 30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for oosee Sizing for the Palisades Steam Generators 0.95 0.9 0.85 0.8 0.75 0.7 S 0.65 I 0.6

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o 10 20 30 40 50 60 70 80 90 100 Maximum Depth, %TW Figure 10 Candidate Bobbin POD CUives for Detection of Eggcrate Axial OOSCC 22of30

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- - - - Projections using Appendix 128413:

I POD I*...... Projections using SONGS 2 POD 11 Oe\\4atlon Request Method 60 70 80 90 NDE Maximum Depth Figure 11 Comparison of Projected and Actual NDE Maximum Depth Distributions for 1 R21 (2010 refueling outage) 23 of 30 100

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSee Sizing for the Palisades Steam Generators 8000

~ 7000 1i Sl e 6000 Q.

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I Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators 100 I 90 80 70 60 I

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+Pt Probe 300 kHz Voltage, volts, pp Figure 14 Maximum Depth versus +Pt Probe Voltage, Appendix 128432 and EPRI 1014983 Data for CE Plants 26 of 30 10

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators 00 Axial and Circumferential EOM Slots An Tubing Sizes 3.---------------------------------------------------------~

~

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• Circumferential. 0.875 dia., 0.050 wall

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10 20 30 40 50 Depth, % TW

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X 80 90 100 Figure 15 +Pt Probe Voltage versus % TW for OD EDM Notch Eddy Current Standards, All Tubing Sizes, Axial and Circumferential Notches 270f30

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+Pt Probe 300 kHz Voltage, volts, pp 10 Figure 16 Maximum Depth versus +Pt Probe Voltage per Appendix I 28432 Plus Curve Fit Using Only CE Plant Data per Appendix I 28432 28 of 30

Technical Justification Supporting Deviation from the EPRI Appendix I ETSS for ODSCC Sizing for the Palisades Steam Generators 5.0 Condition Monitoring The as-found conditions were performed using both the Appendix I and the previous technique. Based on the sizing of the flaws found in 1 R21 (2010 refueling outage), a fully probabilistic analysis was required. This analysis predicted a probability of - 4% of burst, up from the previous outage value of -

1.5%. As the generators age, it is predicted that the unit will become runtime limited due to the over sizing.

6.0 Summary A comprehensive review of axial outside diameter stress corrosion cracking (OOSCC) in Palisades steam generators was performed. Tube integrity projections for future operating cycles were developed using a multi-cycle, fully probabilistic Monte Carlo program. This provided a means to examine the impact and accuracy of detection and non-destructive testing (NDE) maximum depth sizing capabilities. The technical deviation makes the argument that any proposed use of a probability of detection (POO) curve equal to or better than that of EPRI Appendix 128413 is inadequate in matching inspection data for axial OOSCC at eggcrate intersections. Using this same technical deviation EPRI Appendix 128432 over sizes maximum depth values for axial oosec at Palisades. There is a reasonable basis to submit a deviation request for maximum depth sizing of axial ODSeC indications at Palisades. The request is relatively modest since it uses the Combustion Engineering (eE) subset of the well vetted data of EPRI Appendix 128432. The regression slope and standard error of regression are retained. Only the intercept parameter is changed. This provides an across the board reduction of NDE maximum depth sizing of 11.23 % TW. This will lead to about a 1000 psi increase in calculated condition monitoring burst pressures and much better matching of projected and measured NDE maximum depths.

Based on the statistical analysis addressed in this report and the positive results coming from the Palisades inspection 1 R21 (2010 refueling outage), use of the Regression analysis is considered appropriate and meets the intent and requirements of the EPRI guidelines. Therefore, it is acceptable to use the regression analysis from this point forward for axial ODSCC.

7.0

References:

1. EPRI PWR Steam Generator Examination Guidelines, Revision 7

2. EC-24725 - (SG-SGMP-10-22) "Steam Generator Degradation Assessment and Repair Criteria for RF21"

3. EC-25517 - "Acquisition Technique Sheets (ACTS) and Analysis Technique Sheets (ANTS)"

4. EPRI ETSS 128432

5. CEOG Task No. 1151, "+Pt Coil Sizing Study for Axial Crack Profiling" 29 of 30

Technical Justification Supporting Deviation from the EPR. Appendix I ETSS for ODSeC Sizing for the Palisades Steam Generators

6. EC-25627 - Technical Deviation for Steam Generator Eddy Current Testing using EPRI Appendix I for ODSCC Sizing

7. EPRI Steam Generator Tube Integrity Assessment Guideline, Revision 3

8. EPRI In-Situ Pressure Testing Guidelines, Revision 3

9. Entergy procedure EN-DC-202, "NEI 03-08 Materials Initiative" 10.EC24725 1R21 (2010) Steam Generator Degradation Assessment 300f30