ML070640062

LTR-CDME-07-22-NP, Revision 0, Responses to NRC Requests for Additional Information Re the Application of WCAP-16208-P, Revision 1, 'Nde Inspection Length for CE Steam Generator Tubesheet Region Explosive Expansions, 'To the Palisades Nucle

ML070640062
Person / Time
Site:	Palisades
Issue date:	02/28/2007
From:	Thomas Magee, Morgan E, Silva E Westinghouse
To:	Office of Nuclear Reactor Regulation
References
LTR-CDME-07-22-NP, Rev 0
Download: ML070640062 (21)

Text

NONPROPRIETARY ENCLOSURE 5 LICENSE AMENDMENT REQUEST REGARDING TUBESHEET INSPECTION DEPTH FOR STEAM GENERATOR TUBE INSPECTIONS AT PALISADES NUCLEAR PLANT LTR-CDME-07-22-NP, Revision 0, "Responses to NRC Requests for Additional Information Regarding the Application of WCAP-16208-P, Revision 1, 'NDE Inspection Length for CE Steam Generator Tubesheet Region Explosive Expansions,' to the Palisades Nuclear Power Plant." (Nonproprietary) 20 Pages Follow

WESTINGHOUSE NON-PROPRIETARY CLASS 3 I of'20 LTR-CDME-07-22-NP, Revision 0 Responses to NRC Requests for Additional Information Regarding the Application of WCAP-16208-P, Revision 1, "NDE Inspection Length for CE Steam Generator Tubesheet Region Explosive Expansions" to the Palisades Nuclear Power Plant February 2007 Prepared by: TPM (*)

Thomas P. Magee, Principal Engineer Chemistry, Diagnostics & Materials Engineering Reviewed by: EJS (*)

Edward J. Silva, Principal Engineer Chemistry, Diagnostics & Materials Engineering Approved by: EPM (*)

Earl P. Morgan, Manager Chemistry, Diagnostics & Materials Engineering

• ElectronicallyApproved Records,Are Authenticated in the ElectronicDocument Management System Westinghouse Electric Company LLC P.O. Box 355 Pittsburgh, PA 15230-0355

© 2007 Westinghouse Electric Company LLC All Rights Reserved

2 of 20 TABLE OF CONTENTS L ist o f T a ble s .................................................................................................................................. 3 L ist o f F igu re s ................................................................................................................................. 4 D e fi n ition s ....................................................................................................................................... 5 1.0 In tro d u c tio n ......................................................................................................................... 6 1.1 B a ck gro u n d .................................................................................................................... 6 1.2 Sum m ary ........................................................................................................................ 7 1.3 Quality Assurance ...................... ............................................................................... 7 2.0 Responses to Requests for Additional Information ........................................................ 8 2 .1 R A I # 5 ............................................................................................................................ 8 2.1.1 Response to RAI #5 ............................................................................................... 8 2 .2 R A I # 6 ............................................................................................................................ 9 2.2.1 Response to RA I #6 ............................................................................................... 9 2 .3 RA I # 8 .................................................. ....................................................................... 10 2.3.1 Response to RAI #8 ............................................................................................ 10 3.0 R e feren c es ......................................................................................................................... 17 Appendix A - Request for Additional Inform ation ................................................................... 18 Table of Contents February 2007 LTR-CDM E-07-22-N P Revision 0

3 of 20 LIST OF TABLES Table 1: Effect of Tubesheet Deflection for Palisades Steam Generators: Revised for Use of First Slip Loads and 583F Hot Leg, Using Revised Error Handling .............. 13 Table 2: Effect of Tubesheet Deflection for Palisades Steam Generators: Revised for Use of First Slip Loads and 583°F Hot Leg, Using Actual Temperature and Pressure Effects ................................................ 14 List ofFables February 2007 LTR-CDME-07-22-NP Revision 0

4 of 20 LIST OF FIGURES Figure 1: 95% Prediction Error Applied to Relationship between First Slip and Maximum Load for Rough Bore Samples ................................................................ 15 Figure 2: First Slip Pullout Force for 42 mail Wall Smooth Bore Tests (Data Includes 95% Prediction E rror) .............................................................................................. 16 List of Figures February 2007 LTR-CDME-07-22-NP Revision 0

5 of 20 DEFINITIONS BET - Bottom of the explansion transition.

BTA - Bore Trepanning Association process for machine boring. A process improvement employed for tubesheet drilling applicable to Plant CE2 (only one SG), CE3 and the Palisades replacement SGs.

Collar - Tubesheet mockups were fabricated from tubesheet bar stock material SA-508, Class 3. The machined bar stock in which a tube was explosively expanded was referred to in this project as a collar.

C* - The CE design explansion joint inspection distance.

EOC - End of Cycle.

Explansion - Explosive expansion of tubing into a Combustion Engineering steam generator tubesheet.

Joint - The tube and tubesheet contact surface area created by the explansion process.

Maximum load - The largest force encountered while pulling the tube out of the tubesheet.

NMC - Nuclear Management Company.

NODP - Normal operating differential pressure = RCS pressure minus SG pressure at normal fill power operating conditions.

] ICC RAI - Request for additional information.

Rough bore - The machined surface on the inside diameter of each laboratory specimen rough bore collar was drilled on a lathe to a surface roughness not greater than 250 micro-inches (AA) to mockup the gun-drilled tubesheet hole surface. Not applicable to Palisades.

SLB or MSLB - The design basis event known as main steam line break.

Smooth Bore - The machined surface on the inside diameter of each laboratory specimen smooth bore collar was drilled on a lathe to a surface roughness not greater than 250 micro-inches (AA) and then reamed to increase smoothness to mockup the BTA process tubesheet hole surface. Applicable to the Palisades steam generators.

TTS - Top of the tubesheet.

Definitions Febnmary 2007 LTR-CDME-07-22-NP Revision 0

6 of 20

1.1 BACKGROUND

The Westinghouse Owner's Group program to provide recommended tubesheet region inspection lengths, for plants with Combustion Engineering supplied steam generators with explosive expansions, was documented in report WCAP-l 6208-P and updated as Revision I (Reference 1). This inspection length is referred to as C* ("C-Star"). Reference 1 has been previously submitted to the NRC by other participants within the Westinghouse Owner's Group program.

Palisades intends to implement the C* alternate inspection and repair criterion, as described in Reference 1, with amendments that include the following:

Prior to implementing C*, the NRC requested that Palisades review RAI responses that had been submitted by other Westinghouse Owner's Group C* participants. This review was provided in LTR-CDME-06-40 (Reference 2), which was submitted to the NRC as "Palisades License Amendment Request Regarding Tubesheet Inspection Depth for Steam Generator Tube Inspections," dated May 30, 2006. Also, the NRC requested that Palisades address Palisades-specific issues related to the Palisades tube-tubesheet joint and hot leg temperature. These issues were addressed in LTR-CDME-06-80 (Reference 3). References 2 and 3 changed the C*

distance to 12.5 inches.

The NRC has recently issued eight requests for additional information (RAIs) regarding the Palisades submittal and the Westinghouse documents LTR-CDME-06-40 (Reference 2) and LTR-CDME-06-80 (Reference 3). These RAIs are provided in Appendix A. In the RAls, "Enclosure 4 to your May 30, 2006 letter" refers to Westinghouse document LTR-CDME-06-80 (Reference 3) and "Enclosure 6 of your May 30, 2006 letter" refers to Westinghouse document LTR-CDME-06-40 (Reference 2).

This document provides Westinghouse's response to RAIs 5, 6, and 8, as part of NMC contract 00013521 (Reference 4) (SAP ES-07-0596-RAI). The questions can be summarized as follows:

• NRC Question number 5 requests confirmation that if the force-per-unit-length for the most limiting specimen, based on load at "first move," were used to determine the required length of expanded tubes needed to resist pullout, this length would still be less than the proposed inspection distance. It also requests confirmation that in the evaluation of the 'no explansion residual contact pressure' case that tubesheet bow was accounted for.

• NRC Question number 6 requests an analysis of the effect of applying the 95-percent prediction interval to the projection of the first-slip load values for the Ringhals data.

" NRC Question number 8 requests a discussion of rounding-up the inspection length to 12.6 inches rather than rounding-off to 12.5 inches.

Introduction February 2007 LTR-CDME-07-22-NP Revision 0

7 of 20 1.2

SUMMARY

RAls applicable to Palisades were addressed. The required C* inspection distance has been investigated to include the NRC requested effects. The C* distance remains at 12.5 inches below the bottom of the tube to tubesheet expansion transition, as noted in References 2 and 3. This value applies to each tube inspected at the hot leg tubesheet region using the Plus PointTM coil for the Palisades steam generator tube inspection.

1.3 QUALITY ASSURANCE The work that is presented in this document was completed and reviewed under the requirements of the Westinghouse Quality Assurance Program (Reference 5).

Introduction February 2007 LTR-CDME-07-22-NP Revision 0

8 of 20 2.0 RESPONSES TO REQUESTS FOR ADDITIONAL INFORMATION 2.1 RAI #5 The calculation of the inspection distancefor the hot-leg tubesheet region used the lower 95-percent prediction houndJbr the measuredand projectedsmooth-bore, 'first-slip"pullout values plotted in Figure 3 of Enclosure 4 to your May 30, 2006 letter (Reference 3). As discussed in the RAI responses to previous C* reviews (i.e., Section 2.1.4 in Enclosure 6 ofyour May 30, 2006 letter {Reference 2}), use of the load at 'first slip" assumes that the "first move" results from gripper slippage or other movement besides movement of the tube within the tubesheet.

Since this assumption about the 'first move" was not verified, andgiven that all tubes should resist pulloutfrom the tubesheet, confirm that if the force-per-unit-lengthforthe most limiting specimen, based on load at 'first move," were used to determine the requiredlength of expanded tubes needed to resistpullout, this length would still be less than the proposed inspection distance (12.5 inches).

The staff notes that in Section 2.4.3 of Enclosure 6 (Reference 2) (which addresses the first-slip criteriafor smooth-bore samples), the final two paragraphsexplain that even if there were no explansion residual contact pressure between a tube and tubesheet in the Palisadessteam generators,a length of 6. 75 inches is enough to resist the three-times normal operating differentialpressure. The discussion identifies differential thermal expansion and expansion from the tube internalpressure as the sources of the resistance to tube pullout. Although this was referred to as the "most extreme case, " it is not clear if the eJfect of tubesheet bow was included Please discuss whether your evaluation consideredthe effect of tubesheet bow.

2.1.1 Response to RAI #5 In responding to RAt #5, the second paragraph is addressed first.

Tubesheet bow was indeed included in the evaluation of the case where there is no as-installed explansion residual contact pressure.

This is a condition which does not exist in the Palisades steam generators. In this hypothetical case, the only contact pressure between the tube and the tubesheet would be a result of differential thermal expansion and the transmittance of internal pressure through the tube wall.

This case was provided as a bounding case. Other definitions for pullout, where there is some degree of residual contact pressure from the explosive expansion process, also include contact pressure from differential thermal expansion and the transmittance of internal pressure, and thus have higher contact pressures than this hypothetical case.

The calculation that includes tubesheet bow is shown in Table 8 of Enclosure 6 (Reference 2).

Table 8 of Enclosure 6 (Reference 2) consists of ten columns. The last group of three columns and the group of columns 5-7 provide the calculation results for the "No Residual Load" and "First Slip Limiting Sample" cases, respectively. The first four columns are common to both Responses to Requests for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

9 of 20 groups. Reference I provides a full description of the derivation of similar tables, such as Table 6-5 of Reference 1.

In Table 8 of Enclosure 6, the term "Fz Contact Load" is the residual contact pressure. This value has been set to zero for all elevations within the tubesheet for the "No Residual Load" case. In contrast, this value is [ ]a,.,, for all elevations in the tubesheet for the "First Slip Limiting Sample" case. The "Fz net" columns are simply the sum of columns three, four, and the applicable value for "Fz Contact Load." Column three, "Fz Dilation Load" is simply column two, "Fx Dilation Load" multiplied by an assumed friction factor of [ ]",c'e "Fx Dilation Load" is the tubesheet hole dilation load in the direction perpendicular to the tube axis that results from tubesheet bow under accident conditions (the negative value indicates a reduction in load).

Thus tubesheet bow was included in the "No Residual Load" case.

Regarding the question posed in the first paragraph, any of the specimens, including the most limiting specimen, that might be evaluated under a "first move" criteria will have a residual load of zero or greater. Thus the "No Residual Load" case described above bounds any "first move" case. As the bold lettering in Table 8 of Enclosure 6 (Reference 2) shows, an engagement length of [ ]icx is sufficient to resist pullout. After adding NDE positional error to this value, I ]a~Ce (Reference 1), it is still well below the 12.5 inspection length. If the "No Residual Load" case is below the inspection length, then so would a "First Move Limiting Specimen" be well below the inspection length.

2.2 RAI #6 For the Ringhals test data, the first-slip pullout values plotted in Figure 3 ofEnclosure 4 (Reference 3) were projectedfrom the measured,inaximumn-load values. Please discuss the effect on Figure 3 and your leakage analyses if a conservative bound (i.e., 95-percentprediction interval) were used to project thefirst-slip load values for the Ringhals data.

2.2.1 Response to RAI #6 In Enclosure 4 (Reference 3), Figure 1 demonstrates that there is a strong relationship between maximum load and first slip. Figure 2 provides a projection of the first slip data from the smooth bore maximum load data. Figure 3 of Enclosure 4 (Reference 3) provides laboratory data and projected data to develop a pullout load vs. joint length relationship.

Westinghouse applied an accounting for all errors by using a 95% prediction bound.

Westinghouse maintains that this accounting for errors was applied correctly.

In a November 28, 2006 teleconference with the NRC staff, it was clarified that the staff was not expecting an additionalerror adjustment, rather that the error adjustment be applied to the prediction methodology.

Information Additiona! Information for Additional Febniary 2007 Responses to Requests for to Requests February 2007 I rR-CDME.-07-22-NP Revi-ion 0

10 of 20 The application of a 95% prediction interval to the data shown in Figure 1 of Enclosure 4 (Reference 3) shows that there is as much as a [ ]ac~e error in the projection methodology (see Figure 1 of this document).

Subtracting [ ]*,c" from the projected values that were shown in Table 1 of Enclosure 4 (Reference 3), yields the plot of first slip pullout force as a function of joint length shown in Figure 2 of this document. The linear regression of the data shown in Figure 2 of this document already contains the 95% lower prediction bound correction, thus the regression line itself is used in the calculation of inspection distance.

The curve from Figure 2 of this document is applied to the "Axial Force" column in Table 1 of this document. The table also includes the "RCS Pressure and Diff. Thermal Axial Force" change noted in the response to RAI #8 [

]a"cc Interpolating from 'Uncorrected Joint Length that Meets Leakage Criteria' lengths of[ ]a[ (Section 2.3.1 of Reference 3) yields 'Corrected Joint fc Leakage Criteria' lengths of [ ]a,cc Length that Meets Correcting for NDE positional error, ]",C a, (Reference 1), yields an inspection distance of 12.5 inches.

2.3 RAI #8 According to Section 2.5 of Enclosure 4 (Reference 3), the proposed inspection distance of 12.5 inches is based on adding the [ ]a`c,e non-destructive examination axial-position uncertainty to the values of "JointLength that Meets Leakage Criteria," [

]ace = 12.53, it would be conservative to use a value of 12.6 inches rather than 12.5 inches. Please discuss your plans to modify your proposal to use 12.6 inches as the proposed distancefor the alternate repaircriteria(and inspection) in the hot-leg region of the tubesheet.

2.3.1 Response to RAI #8 It is Westinghouse's position that rounding-up, rather than rounding-off, is unwarranted, thus the value should remain as 12.5 inches.

The evaluation used to determine the inspection length includes many conservatisms. Some of these conservatisms are not easily quantified but are nevertheless quite significant, such as the assumption the ALL of the tubes in the steam generator are COMPLETELY SEVERED below the inspection length. However, some of the conservatisms in the evaluation can be quantified.

There are many conservatisms employed in the calculation of the inspection distance. Some of these calculations already employ rounding of values in the conservative direction. Conservative rounding on top of conservative rounding, which is on top of the use of a 95% prediction interval, presents an unrealistic set of constraints.

The following is an example of the conservative rounding that was used in the determination. It shows that the 12.5 inch inspection distance is warranted.

Responses to Requests for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

II of 20 Table 3 of Enclosure 4 (Reference 3) is used to calculate the inspection length, before NDE positional error is included. The value of [ ]",c,e shown for "RCS Pressure and Diff.

Thermal Axial Force" is a value based on a value used in the CEOG Task 1154 work (Reference 6). The value of [ ]iL,.e at Palisades. Qualitatively, the thicker wall means that less of the internal pressure is transmitted though the tube wall, thus the contact pressure is lower. The [ ],CC value also employs conservative rounding.

The value for "RCS Pressure and Diff. Thermal Axial Force" is Ia,ce The equations for calculating the transmittance factor were provided in Section 2.1.2 of Reference 2.

The contact force due to differential thermal expansion is

]a,c,e Responses to Requests for Additional Infonnation February 2007 LTR-CDME-07-22-NP Revision 0

12 of 20 However, the value used in the CEOG Task 1154 report was [

]a~c~e If this value is then rounded-up, the inspection length becomes 12.5 inches. Thus the present inspection length of 12.5 inches remains valid and should not be changed.

Responses to Requests for Additional Infomration February 2007 LTR-CDME-07-22-NP Revision 0

13 of 20 Table I: Effect of Tubesheet Deflection for Palisades Steam Generators: Revised for Use of First Slip Loads and 583°F Hot Leg, Using Revised Error Handling RCS Pressure and Diff.

Thermal Initial Dilation Net Equiv. Curn.

Axial Axial Axial Axial Axial No-Dilate No-Dilate Depth in Force Force Force Force Force Net / Initial Length Lenggth ab~c Tubeshect (in) (Ib) (lbt) (lbO (Ibf) (lbf) Ratio (itn) (in)

Responses to Requests for Additional Inforeation February 2007 LTR-CDME-07-22-NP Revision 0

14 of 20 Table 2: Effect of Tubesheet Deflection for Palisades Steam Generators: Revised for Use of First Slip Loads and 583°F Hot Leg, Using Actual Temperature and Pressure Effects RCS Pressure Initial Dilation Net Equiv. Cum.

Axial and Diff. Thermal Axial Axial Axial No-Dilate No-Dilate Depth in Force Axial Force Force Force Force Length Length a.b,c Tubesheet (in) (IbO (Ibf) (Ibf) (Ibf) (Ibf) Net / Initial Ratio (in) (in)

F F + +/- 5 1 4- 5 F F 4 4- 4 + + +

F ~ + + 4 + + +

F + + + + + + +

F + + + 4 + +/- 4 F F + 4- 4 -F S F t. 4 -F I + + +

F 4 4 + 4 + + +

F 4 4 -F I -F 4- 5 F 4 4 + 4 + + I F 4 4 + I +/- 4 F 4 4 -F 1 -F -F S 4 4 4 -F I 4- + +

F 4 4 + I 4- + 4 4 4 4 -F 1 4- 5

+ + 4 F I 4- + +

+ + 4 F I + 4 4 + 4 F 4 -F +

4 4 4 F I -F S Responses to Requests for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

15 of 20 a,b,c Figure 1: 95% Prediction Error Applied to Relationship between First Slip and Maximum Load for Rough Bore Samples Responses to Requests for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

16 of 20 a.b*c Figure 2: First Slip Pullout Force for 42 mil Wall Smooth Bore Tests (Data Includes 95% Prediction Error)

Responses to Requests for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

17 of 20

3.0 REFERENCES

I. Westinghouse Report, WCAP- I6208-P, Revision 1, "NDE Inspection Length for CE Steam Generator Tubesheet Region Explosive Expansions," May 2005.

2. Westinghouse Document, LTR-CDME-06-40-P, Revision 1, "Comments on the Application of WCAP- I 6208-P, Revision 1, 'NDE Inspection Length for CE Steam Generator Tubesheet Region Explosive Expansions' to the Palisades Nuclear Power Plant," May 2006. Referred to as "Enclosure 6" in the NRC RAIs of Appendix A.

3. Westinghouse Document, LTR-CDME-06-80-P, Revision 1, "Palisades Tubesheet Inspection Depth," May 2006. Referred to as "Enclosure 4" in the NRC RAIs of Appendix A.

4. NMC Contract 00013521, "C STAR NRC SUBMITTAL NRC RAI RESPONSES,"

January 1I, 2007.

5. "Nuclear Services Policies & Procedures," Westinghouse Quality Management System -

Level 2 Policies and Procedures, Effective 6/30/06.

6. Westinghouse Report WCAP-15720, Revision 0, "NDE Inspection Strategy for Tubesheet Regions in CE Designed Units," CEOG Task 1154, July 2001.

References February 2007 I.TR-CDME-07-22-N P Revision 0

18 of 20 APPENDIX A - REQUEST FOR ADDITIONAL INFORMATION In the following set of RAls, "Enclosure 4 to your May 30, 2006 letter" refers to Westinghouse document LTR-CDME-06-80 (Reference 3).

"Enclosure 6 of your May 30, 2006 letter" refers to Westinghouse document LTR-CDME-06-40 (Reference 2).

REQUEST FOR ADDITIONAL INFORMATION (RAI)

LICENSE AMENDMENT REQUEST FOR REVISED STEAM GENERATOR REPAIR CRITERIA (C* CRITERIA)

PALISADES NUCLEAR PLANT NUCLEAR MANAGEMENT COMPANY. LLC DOCKET NUMBER 50-255 1 The proposed amendment is intended to allow tubes with flaws to remain in service if the flaws are located below a certain depth in the hot-leg region of the tubesheet. This will require proposing an alternative to the 40-percent, through-wall depth criteria in the Palisades' Technical Specifications (TSs). Please discuss your plans to revise TS 5.5.8.c as follows:

A. Indicate there is an alternative to the 40-percent repair criteria.

B. Define the repair criteria in the hot-leg tubesheet region (i.e., depth below which flaws may remain in service, and the starting point for the depth measurement).

C. Define the repair criteria for the region of the hot-leg tubesheet in which neither the alternate repair criteria nor the 40-percent through-wall criteria apply (i.e.,

tubes with flaws within the C* distance will be plugged on detection).

D. State that all flaws located below this depth may remain in service, regardless of size.

2. Proposed TS 5.5.8.d defines the portion of tube that must be inspected, "from 12.5 inches below the tube-to-tubesheet expansion transition inlet to the tube-to-tubesheet weld at the tube outlet ... " Since the C* criteria is an alternate repair criteria rather than an inspection criteria, it does not change the objective in the current TS 5.5.8.d to detect flaws from the inlet tube-to-tubesheet weld to the outlet tube-to-tubesheet weld. If the C*

Appendix A - Request for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

19 of 20 criteria is properly defined as an alternate repair criteria (as discussed in #1 above), then inspection below the C* distance in the hot-leg region would no longer be required because of the phrase, "... and that may satisfy the applicable tube repair criteria" in TS 5.5.8.d. Please discuss your plans to modify proposed TS 5.5.8.d to remove the reference to the C* distance and restore the wording approved in the Technical Specifications Task Force 449 amendment (i.e., ". . . from the tube-to-tubesheet weld at the tube inlet to the tube-to-tubeshect weld at the tube outlet, and that may satisfy ... "). In addition, the staff notes that the 12.5-inch C* distance is measured from the top of the tubesheet or the bottom of the expansion transition, whichever is lower.

3. The basic premise of the C* amendment is that there is a 12.5-inch, non-flawed portion of the tube fully expanded into the tubesheet. To ensure the region remains free of flaws, an inspection of 100 percent of the inservice tubes in the tipper region of the tubesheet will need to be performed every 24 effective full-power months, or one refueling outage interval, whichever is less. As a result, please discuss your plans to revise your proposed TS 5.5.8.d to add this inspection requirement (e.g., by adding a paragraph 5.5.8.d.4). The staff notes that if an additional paragraph 5.5.8.d.4 is added, it will need to be referenced in 5.5.8.d (i.e., "In addition to meeting the requirements ofd. d, d.2, d.3, and d.4 below..

. ."1).

4. Please confirm that structural and leakage integrity will be assessed if significant indications are found within the inspected region of the tubesheet. The staff recognizes that the current approach of plugging flaws on detection within the C* distance should provide a high level of confidence that no potential leaking or structurally significant flaws are identified in this region. However, such an approach can not ensure it with certainty.

5. The calculation of the inspection distance for the hot-leg tubesheet region used the lower 95-percent prediction bound for the measured and projected smooth-bore, "first-slip" pullout values plotted in Figure 3 of Enclosure 4 to your May 30, 2006 letter. As discussed in the RAI responses to previous C* reviews (i.e., Section 2.1.4 in Enclosure 6 of your May 30, 2006 letter), use of the load at "first slip" assumes that the "first move" results from gripper slippage or other movement besides movement of the tube within the tubesheet. Since this assumption about the "first move" was not verified, and given that all tubes should resist pullout from the tubesheet, confirm that if the force-per-unit-length for the most limiting specimen, based on load at "first move," were used to determine the required length of expanded tubes needed to resist pullout, this length would still be less than the proposed inspection distance (12.5 inches).

The staff notes that in Section 2.4.3 of Enclosure 6 (which addresses the first-slip criteria for smooth-bore samples), the final two paragraphs explain that even if there were no explansion residual contact pressure between a tube and tubesheet in the Palisades steam generators, a length of 6.75 inches is enough to resist the three-times normal operating differential pressure. The discussion identifies differential thermal expansion and expansion from the tube internal pressure as the sources of the resistance to tube pullout.

Although this was referred to as the "most extreme case," it is not clear if the effect of Appendix A - Request for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0

20 of 20 tubesheet bow was included. Please discuss whether your evaluation considered the effect of tubesheet bow.

6. For the Ringhals test data, the first-slip pullout values plotted in Figure 3 of Enclosure 4 were projected from the measured, maximum-load values. Please discuss the effect on Figure 3 and your leakage analyses if a conservative bound (i.e., 95-percent prediction interval) were used to project the first-slip load values for the Ringhals data.

7. The staff notes that the page numbers listed on the cover sheets of Enclosures 2 and 3 (pages 5.5.8-11 and 5.5.8-12) do not match the page numbers on the bottom of the enclosed TS pages (pages 5.0-11 and 5.0-12). Please clarify which are the correct page numbers for these TS pages. In addition, the staff notes that proposed TS page 5.0-12 should identify the "Provisions for SG tube inspections. (continued)" as item "d" rather than item "e."

8. According to Section 2.5 of Enclosure 4, the proposed inspection distance of 12.5 inches is based on adding the [ ]`,ce non-destructive examination axial-position uncertainty to the values of "Joint Length that Meets Leakage Criteria," [

]," = 12.53, it would be conservative to use a value of 12.6 inches rather than 12.5 inches. Please discuss your plans to modify your proposal to use 12.6 inches as the proposed distance for the alternate repair criteria (and inspection) in the hot-leg region of the tubeshect.

Appendix A - Request for Additional Information February 2007 LTR-CDME-07-22-NP Revision 0