DCL-04-070, Response to NRC Request for Additional Information Regarding License Amendment Request 03-15, Steam Generator Tube Repair Using Leak Limiting Alloy 800 Sleeves and Revision to Technical Specification Table 5.5.9-2, 'Steam

Response to NRC Request for Additional Information Regarding License Amendment Request 03-15, Steam Generator Tube Repair Using Leak Limiting Alloy 800 Sleeves and Revision to Technical Specification Table 5.5.9-2, 'Steam

ML041610228
Person / Time
Site:	Diablo Canyon
Issue date:	06/04/2004
From:	Oatley D Pacific Gas & Electric Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
DCL-04-070
Download: ML041610228 (21)

Text

Pacific Gasand Electfc Company David H.Oatley Diablo Canyon Power Plant Vice President and PO. Box 56 General Manager Avila Beach, CA 93424 June 4, 2004 Fax:805.545.4234 PG&E Letter DCL-04-070 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 Response to NRC Request for Additional Information Regarding License Amendment Request 03-15, "Steam Generator Tube Repair Using Leak Limiting Alloy 800 Sleeves and Revision to Technical Specification Table 5.5.9-2, 'Steam Generator (SG) Tube Inspection"'

Dear Commissioners and Staff:

PG&E Letter DCL-03-132, dated October 22, 2003, submitted License Amendment Request (LAR) 03-15, "Steam Generator Tube Repair Using Leak Limiting Alloy 800 Sleeves and Revision to Technical Specification Table 5.5.9-2, 'Steam Generator (SG) Tube Inspection."' LAR 03-15 proposes to change Technical Specification (TS) Section 5.5.9, "Steam Generator (SG) Tube Surveillance Program," and TS Section 5.6.10, uSteam Generator (SG) Inspection Report," to allow use of leak limiting Alloy 800 sleeves to repair degraded SG tubes as an alternative to plugging the SG tubes. The LAR also proposes to remove an unnecessary reporting requirement contained in TS Table 5.5.9-2, "Steam Generator (SG) Tube Inspection."

On March 8 and May 14, 2004, the NRC staff requested additional information required to complete the review of LAR 03-15. PG&E's responses to the staff's questions are provided in Enclosure 1. Enclosure 2 provides the revised marked-up TS page 5.0-16 and Enclosure 3 provides the retyped TS page 5.0-16. The revised TS page 5.0-16 contained in Enclosures 2 and 3 supersedes the TS page 5.0-16 contained in Enclosures 2 and 3 of PG&E Letter DCL-03-132.

TS page 5.0-16 has been revised in order to reflect the revision of Westinghouse Electric LLC Report WCAP-15919-P, "Steam Generator Tube Repair for Westinghouse Designed Plants with 7/8-inch Inconel 600 Tubes Using Leak Limiting Alloy 800 Sleeves," dated August 2003, from Revision 00 to Revision 01. The revision of WCAP-1 5919-P from Revision 00 to Revision 01 is currently in progress.

PG&E will submit WCAP-15919-P, Revision 01, to the NRC when the revision is complete.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• South Texas Project

• Wolf Creek

Document Control Desk PG&E Letter DCL-04-070 Fl" June 4, 2004 Page 2 The responses provided in this submittal do not affect the results of the technical evaluation or the no significant hazards consideration determination previously transmitted in PG&E Letter DCL-03-132.

If you have any questions, or require additional information, please contact Stan Ketelsen at (805) 545-4720.

Sincerely, David H. Oatley Vice President and General Manager - Diablo Canyon kjse/4328 Enclosures cc: Edgar Bailey, DHS Bruce S. Mallett David L. Proulx Diablo Distribution cc/enc: Girija S. Shukla A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

• Comanche Peak

• Diablo Canyon

• Palo Verde

• South Texas Project

• Wolf Creek

PG&E Letter DCL-04-070 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION Docket No. 50-275 Inthe Matter of ) Facility Operating License PACIFIC GAS AND ELECTRIC COMPANY) No. DPR-80 Diablo Canyon Power Plant ) Docket No. 50-323 Units 1 and2 ) Facility Operating License No. DPR-82 AFFIDAVIT David H. Oatley, of lawful age, first being duly sworn upon oath says that he is Vice President and General Manager- Diablo Canyon of Pacific Gas and Electric Company; that he has executed this response to the NRC request for additional information on License Amendment Request 03-15 on behalf of said company with full power and authority to do so; that he is familiar with the content thereof; and that the facts stated therein are true and correct to the best of his knowledge, information, and belief.

David H. Oatley Vice President and General Manager - Diablo Canyon Subscribed and sworn to before me this 4th day of June 2004.

SANDR EATHERL.

Notary"Public Publc (1-§ 1cormbsslon NokuyPWu #- Cautfmia 14265 County of San Luis Obispo SCLUObbpo t State of California  ;= 2 7

Enclosure 1 PG&E Letter DCL-04-070 PG&E Response to NRC Request for Additional Information Regarding License Amendment Request 03-15, "Steam Generator Tube Repair Using Leak Limiting Alloy 800 Sleeves and Revision to Technical Specification Table 5.5.9-2, 'Steam Generator (SG) Tube Inspection."'

Questions Received on March 8 and May 14, 2004 NRC Question 1:

On page 8 of the License Amendment Request, the operational experience of Alloy 800 is discussed. It is stated that, "... a significant number of sleeves have been in operation for a number of years with no degradation or significant leakage."

Describe what is meant by "significant leakage." In terms of the leakage that has occurred, describe and detail the causes of leakage, describe the conditions under which leakage was observed, and compare the magnitude of the observed leakage to the leakage values provided in WCAP-15919-P, Revision 0.

PG&E Resnonse:

Westinghouse is not aware of any reported leakage in operational steam generator (SG) tubes in which leak limiting Alloy 800 sleeves have been installed. The use of the term "significant leakage" was used to describe that no leakage could be identified with a sleeved tube even though the sleeve is leak limiting.

NRC Question 2:

Please discuss your plans for including references to your responses to the request for additional information (RAI) in the parts of the Technical Specification where you reference WCAP-15919-P, Revision 0, since both the Westinghouse Electric LLC WCAP report and the RAI reflect the technical basis for this License Amendment Request.

PG&E Response:

As a result of the NRC RAI, Westinghouse Electric LLC Report WCAP-15919-P, "Steam Generator Tube Repair for Westinghouse Designed Plants with 7/8-inch Inconel 600 Tubes Using Leak Limiting Alloy 800 Sleeves (proprietary),"

Revision 00, dated August 2003, and WCAP-1 5919-NP, "Steam Generator Tube Repair for Westinghouse Designed Plants with 7/8-inch Inconel 600 Tubes Using Leak Limiting Alloy 800 Sleeves (non-proprietary)," Revision 00, dated August 2003, will be updated to incorporate the response to the RAI where appropriate. The responses to RAI questions 1, 3, 4, 5, 6, 7, and 9 will be incorporated in revised WCAP-1 5919-P and revised WCAP-15919-NP. The response to question 8 is already contained in the WCAP on page 8-3 and therefore no change is required to the WCAP for the response to this question. The response to questions 10 and 11 1

Enclosure I PG&E Letter DCL-04-070 address the reason for the difference in stress and fatigue analysis results for the sleeve designs for 7/8-inch and 3/4-inch SG tubes. This information is not appropriate to be contained in the WCAP for each particular sleeve design and therefore no change is required to the WCAP for the response to questions 10 and 11.

The revision of WCAP-1 5919-P from Revision 00 to Revision 01 is currently in progress. PG&E will submit WCAP-1 5919-P, Revision 01, to the NRC when the revision is complete. Technical Specification (TS) page 5.0-16 contained in PG&E Letter DCL-03-132, "License Amendment Request (LAR) 03-15, Steam Generator Tube Repair Using Leak Limiting Alloy 800 Sleeves and Revision to Technical Specification Table 5.5.9-2, 'Steam Generator (SG) Tube Inspection,"' dated October 22, 2003, referenced WCAP-1 5919-P, Revision 00, dated August 2003.

TS page 5.0-16 has been revised in order to reflect the current revision of WCAP-15919-P to Revision 01. Enclosure 2 provides the revised marked-up TS page 5.0-16 and Enclosure 3 provides the retyped TS page 5.0-16. The revised TS page 5.0-16 contained in Enclosures 2 and 3 supersedes the TS page 5.0-16 contained in Enclosures 2 and 3 of PG&E Letter DCL-03-132.

NRC Question 3:

On page 13 of the License Amendment Request, you indicatedthat the WCAP-15919-P, Revision 0 structuralanalysis assumed 10 inadvertent spray cycles while the Diablo Canyon Power Plant (DCPP) FinalSafety Analysis Report (FSAR)

Table specifies 12 inadvertentspray cycles. Given that you are assuming 10 spray cycles ratherthan the 12 spray cycles analyzed in your FSAR, your operating experience to-date (in terms of number of spray cycles), and the limited time these sleeves will be in service, discuss what controls will be in place to ensure that 10 spray cycles will not be exceeded. In addition, discuss whether a license condition is warranted.

PG&E Response:

During an internal review of WCAP-1 5919-P for applicability to another plant, Westinghouse recognized that the design transients (and associated transient cycles) analyzed in WCAP-1 5919-P did not necessarily bound each of the Model 51 SGs. As a result, Westinghouse reviewed the equipment specifications for several Model 51 SGs (including DCPP) to determine a bounding set of design transients. The new set of design transients included 60 inadvertent spray cycles.

New axial loads were calculated for this bounding set of design transients with the same methodology as WCAP-1 5919-P except the temperature distribution in the sleeve-tube assembly was calculated using a one-dimensional, steady-state heat balance. Using a more realistic temperature distribution resulted in lower axial loads and a lower overall fatigue usage factor than what is presented in WCAP-1 5919-P.

Thus, DCPP can withstand up to 60 inadvertent spray cycles and still be bounded 2

Enclosure 1 PG&E Letter DCL-04-070 by the existing licensing report. WCAP-1 591 9-P will be updated to reflect the revised calculation for the new set of design transients and to document that 60 inadvertent spray cycles was assumed. The use of 60 inadvertent spray cycles will bound the 12 inadvertent spray cycles specified in the DCPP FSAR Table.

Questions on Westinghouse Report WCAP-1 5919-P, Revision 0. August 2003 (for 7/8-inch sleeves)

NRC Question 4:

On page 4-3, Section 4.3 (Sleeve-Tube Assembly), it is stated that an installed Westinghouse Alloy 800 Leak Limiting sleeve may be re-rolled (for a rolledjoint) or re-expanded (for a hydraulicallyexpandedjoint), if the sleeve does not meet the minimum requirements.

A. Discuss in detail the sleeve installation steps necessary to minimize the need to perform re-rolls or re-expansions.

B. On page 1-1, Section 1.1 (Purpose), it is stated that tube plugs will be installedif a sleeve installation is unsuccessful orif there is degradationin the pressure boundary section of the sleeve or sleeved tube. List and discuss the installation conditions that would lead to a conclusion that the installation was unsuccessful.

C. Discuss the limits on the number of re-rolls and re-expansions that can be appliedto a sleeve. Discuss whether the cold work loads generated by the re-rollor re-expansion affect the structuralintegrity of the sleeve/tube assembly.

PG&E Response:

Question 4A The sleeve expansion process is controlled by repair software loaded on a workstation. After the sleeve is positioned at the proper location, the expansion process is activated. This program will determine when the sleeve contacts the tube and when tube yield begins. This value (in pounds per square inch) is then utilized to determine the amount of piston stroke required to properly expand the tube. The piston stroke is measured by a linear voltage displacement transducer mounted in the expansion cabinet. There is no operator control of this process, other than to terminate it. If a bladder or fitting fails during the expansion process, then the expansion is unacceptable. If this expansion is the first set of three, then the tool may be lowered and another set of expansions performed in the same tube. Should this set of expansions be properly performed, the tool can be repositioned at the unacceptable expansions and re-expanded using pressure control. The pressure is determined from the successful set of expansions and must be performed in the 3

Enclosure 1 PG&E Letter DCL-04-070 same tube. The same concept applies if the lower set of expansions is unacceptable. The pressure reading from the upper set of expansions may be used to re-expand the lower set. In both cases, an acceptable set of expansions must be made in a sleeved tube using software control in order for a re-expansion to be performed.

The total number of rolling operations that can be performed on a sleeve to tube joint is six, two of which must meet the torque value requirements. This number was based on testing performed on plug rolled joints and sleeve rolled joints. The reason for performing a re-roll is that the minimum torque value was not reached, and the proper wall thinning was not established. The re-roll operation is intended to increase the wall thinning value by increasing the torque applied. There is a necessary increase in cold working due to this operation, but no more than had the proper torque value (and wall thinning) been reached on the initial rolling operation.

Based upon testing, the sleeve/tube pullout loads and leak rate characteristics of the joint are not affected by the re-roll operation.

In the case of the expansion joint, the same logic applies, except that a pressure value must be reached instead of a torque value. A total of six expansions may be attempted in order to reach the proper pressure value, and subsequent expansion size. Based upon testing, the sleeve/tube pullout loads and leak rate characteristics of the joint are not affected by the re-expansion operation.

The details provided in this response, regarding minimizing the number of re-rolls and criteria for plugging, will be included in the vendor's sleeving installation process procedures.

Question 4B The following sleeve installation conditions would be cause to take a sleeved tube out of service by plugging:

1. As discussed in the previous paragraphs, an unacceptable set of expansions would be a cause to plug a sleeved tube. This condition would occur if an acceptable set of expansions, with software control, could not be performed.

2. If the torque value for the rolled joint did not fall within the proper torque range, a sleeved tube would be plugged.

3. If the two sets of expanded joints were not positioned at the proper elevation, then the sleeved tube would be plugged. This could occur due to operator error in positioning the sleeve and performing the first set of expansions with the tool in the lower position, resulting in a sleeve positioned in the tube lower than required. Additionally, there is a requirement that the lowest of the upper expansions be separated from the highest of the lower expansions by a minimum of 0.4 inch. This condition would result from the operator 4

Enclosure 1 PG&E Letter DCL-04-070 positioning the tool incorrectly during sleeve installation and would be identified during the baseline eddy current test (ECT) program.

4. If the baseline ECT program identifies any type of unacceptable indication in the pressure boundary of the tube/sleeve assembly, then the tube would be plugged.

The details provided in this response, regarding minimizing the number of re-rolls and criteria for plugging, will be included in the vendor's sleeving installation process procedures.

Question 4C The total number of rolling operations that can be performed on a sleeve to tube joint is six, two of which must meet the torque value requirements. This number was based on testing performed on plug rolled joints and sleeve roll joints. The reason for performing a re-roll in a SG is that the minimum torque value was not reached, and the proper wall thinning was not established. The re-roll operation is intended to increase the wall thinning value by increasing the torque applied. There is a necessary increase in cold working due to this operation, but no more than had the proper torque value (and wall thinning) been reached on the initial rolling operation.

Based upon testing, the sleeve/tube pullout loads and leak rate characteristics of the joint are not affected by the re-roll operation.

In the case of the expansion joint, the same logic applies, except that a pressure value must be reached instead of a torque value. A total of six expansions may be attempted in order to reach the proper pressure value, and subsequent expansion size. Based upon testing, the sleeve/tube pullout loads and leak rate characteristics of the joint are not affected by the re-expansion operation.

The details provided in this response, regarding minimizing the number of re-rolls and criteria for plugging, will be included in the vendor's sleeving installation process procedures. It should be noted that during a recent leak limiting Alloy 800 sleeve installation campaign at another plant, over 500 sleeves were installed with only 2 requiring re-roll after the initial roll application.

NRC Question 5:

On pages 4-6 to 4-7, Section 4.5.6 (Nondestructive Examination), the WCAP-15919-P, Revision 0 (Aug. 2003) report deleted any reference to visual examination of the tube inside diameter(ID)after installation of the sleeve. In the WCAP-15918-P, Revision 0 (Nov. 2002) report, this visual examination was said to verify that the conditioning process had been completed. No explanation regarding the omission was given in the August 2003 WCAP report.

5

Enclosure 1 PG&E Letter DCL-04-070 Discuss how the completion of the conditioning process will be verified without visual examination of the tube ID afterinstallation of the sleeve.

PG&E Response:

An evaluation of the field experience with tube conditioning performed by Westinghouse subsequent to publication of WCAP-15918-P, Revision 0, indicates that sufficient controls exist to ensure adequate conditioning of the tube surface without visual inspection. A 100 percent tube conditioning visual inspection has been performed in 600 tubes that were to be sleeved in four power plants.

Additionally, another 15 were inspected as part of a 10 percent random inspection at another plant. No axial scratches or loose particles were identified in this inspection.

Based upon this information, Westinghouse is confident that process control is sufficient for the conditioning process. Verification will be performed by the use of the normal in-process instructions and quality assurance surveillance.

NRC Question 6:

On pages 5-2, Section 5.1 (Background),the inspection detection capability for the sleeve and tube was discussed.

A. Clarify whether the eddy current techniques intended for inspection of the sleeve/tube assembly are qualified to detect cracks that may by present, given the sleeve/tube configuration. Discuss the basis which shows that flaws can be reliably detected, given the sleeve/tube configuration. Discuss the number of sleeve/tube samples having stress corrosion cracking flaws and the inspection results for these samples. Discuss the number of flaws simulated in the nickel band of the sleeves. In addition, discuss the effectiveness of eddy current inspections of the parent tube immediately behind the sleeve's nickel band (i.e., when the lower part of the 72 sleeve is situated inside the tubesheet).

B. In your Technical Specifications,'ou indicate that each leak-limiting sleeve will be inspected using a +Point coil or equivalent qualified technique during the post-installation examination and for all future refueling outages.

Historically, the NRC staff has not specified an exact technique for performing steam generator tube inspections, since the staffs interpretation of the steam generator tube inspection requirements in the Technical Specifications in conjunction with Appendix B is that the inspections are to be performed with techniques capable of detecting all flaw types which may potentially be present at the locations that require inspection. The staff acknowledges there are some exceptions, particularly when the technique is important in assessing the severity of the degradation (e.g., the bobbin coil inspections required for implementation of the voltage-based repair criteria). Given that you have specifically referenced the +Pointm coil for performing the sleeve inspections, discuss the extent to which the +PointTM coil will be able to 6

Enclosure 1 PG&E Letter DCL-04-070 detect all forms of potential degradation in the tube-sleeve assembly. For example, discuss the effectiveness of the +PointTM coil in detecting 45-degree cracks, etc.

PG&E Response:

Question 6A As stated in Section 5.1 the ECT technique was qualified in accordance with Appendix H of the EPRI PWR Steam Generator Examination Guidelines, Revision 5, dated September 1997. As stated in Section 5.2, the qualification program was performed on actual sleeve/tube assemblies that included electric discharge machined (EDM) notches in both components at each of the transitions and expansion zones (i.e., joints), to the depths described. The program included sixteen sleeve/tube assemblies containing laboratory grown stress corrosion cracks in the parent tube behind the sleeve. Because of the Appendix H requirements, these flaws could not be used in the qualification data set; however, this data is useful for reviewing real flaws and supplementing the EDM data set. Inasmuch as it is not considered to be part of the pressure boundary, none of the flaws were located behind the nickel band.

The eddy current technique was qualified for the following flaw types and locations:

1. Primary water stress corrosion cracking (PWSCC) in the upper hydraulic expansion region and transitions, freespan, and in the lower roll expansion in the sleeve inside diameter (ID).

2. Intergranular attack/stress corrosion cracking (IGA/SCC) in the upper hydraulic expansion region and transitions, freespan, and in the lower roll expansion transition in the sleeve outside diameter (OD).

3. PWSCC in the parent tube ID behind the sleeve starting at the lowest hydraulic expansion in the top set of expansions up to the top of the sleeve.

4. IGA/SCC in the parent tube OD behind the sleeve starting at the lowest hydraulic expansion up to the top of the sleeve.

The +Pointfm coil qualification for the leak limiting Alloy 800 sleeve did not include flaws behind the nickel band. However, calibration standards fabricated for the inspection of the tungsten inert gas (TIG) welded sleeve included axial EDM notches in the parent tube at the location of the nickel band as well as the microlok band immediately above. The lower roll joint in the TIG sleeve is identical to that of the leak limiting Alloy 800 sleeve. The notches are all nominally 0.375 inches in length and are 100 percent, 70 percent, and 50 percent deep. The notches are separated by approximately 120 degrees. Inthe lower band (nickel) only the 100 percent notch is clearly detectable. In the upper band (microlok) all three notches are clearly 7

Enclosure I PG&E Letter DCL-04-070 detectable. As the parent tube will be inspected in the hardroll joint region prior to sleeve installation, and no parent tubes with detectable degradation in this area will be sleeved, detection capabilities involving the nickel band are not applicable.

Subsequent inspection after operation, if required, will identify partial through-wall degradation of the parent tube above and below the nickel band. Furthermore, it should be noted that axial degradation of the parent tube in the hardroll region coincident with the nickel band would not prevent the sleeve from performing its intended design function. The compressive nature of residual stresses below the expansion transition, coupled with the thermal expansion characteristics of the tubesheet, tube, and sleeve, and inherent residual preload associated with mechanical roll expansion are expected to result in a condition where the design function of the sleeve is not compromised for postulated axial degradation within the nickel band region.

Note: The sleeve/tube pressure boundary described on page 5-3 and in Figure 5-1 is incorrect. As is the case for the same joint on the TIG welded leak tight sleeve, the pressure boundary transitions from the sleeve to the tube below, not within, the rolled joint as shown in the following revised Figure 5-1.

8

Enclosure 1 PG&E Letter DCL-04-070 Sleeve Tube Denotes pressure boundary I

FIGURE 5-1 TZ STLEVE PRESSURE BOUNDARY DESCRIPTION 9

Enclosure 1 PG&E Letter DCL-04-070 Question 6B The eddy current technique qualifications were performed on the probable flaw orientation as required by Appendix H. These include circumferential and axial cracks as well as volumetric indications. Corrosion testing of sleeve/tube samples indicated that in the event cracking did occur it would be oriented in these directions.

In all cases, the technique was able to detect sufficiently small flaws to ensure the structural integrity of the sleeve/tube assembly.

The response to Question 6A lists the forms and locations of potential degradation for which the +PointTM coil is qualified according to Appendix H standards. Industry experience regarding PWSCC below the expansion transition indicates that the observed flaws are predominantly either axially or circumferentially oriented, with little oblique characteristics. Those with oblique characteristics have not approached a 45-degree angle. Therefore, 45-degree angle indications are not included in the Appendix H qualification.

Furthermore, previous evaluation of residual stresses in explosive and hydraulically expanded tubesheet joints suggests that the residual stresses are likely compressive below the expansion transition. Thus, an external stress riser must be present to initiate a flaw. This stress riser is believed to be an artifact of tubesheet hole drilling, and as such would not be expected to be oriented at 45 degrees. All observed indications to date existing below the expansion transition have been either axially or circumferentially oriented.

Nevertheless, should a flaw with a 45-degree angle be present, the design of the

+Pointm coil is such that a perfect 45-degree flaw should produce no signal when the coil is static and centered over the flaw. However, when the coil is rotating in a helical scan and approaches the flaw, the circumferentially sensitive coil leg senses the flaw before the axially sensitive coil reaches the flaw resulting in detection.

+Pointm testing of an OD EDM notch in a lab sample clearly demonstrates detection of a 45-degree flaw. The probe manufacturer was also consulted on this issue. Their effort indicates the same result.

NRC Question 7:

On page 6-2, Section 6.2.1 (PrimarySide Performance), it is stated that, "Some oxygen will initially be present within the sleeve/tube crevice, however any tendency to trap oxygen will be reduced with this design because of joint leakage at lower temperatures. Based on this, oxygen-rich crevice conditions are not considered to last long enough after startup to be of concern. " This statement implies that there could be a path for oxygen or corrosive impurities to enter and exit the crevice/annulus between the sleeve and tube joint during heat-up and cooldown of the plant. Oxygen may not be trapped, but the impurities may be trapped in the annulus.

10

Enclosure 1 PG&E Letter DCL-04-070 Discuss whether there is a potential corrosion problem as a result of trapping corrosive materials in the crevice. Discuss whether these deposits could degrade the performance of the sleeve/tube assembly.

PG&E Response:

Experience with leak limiting Alloy 800 tubes in European SGs, as well as testing in fault secondary environments referenced in Section 6, indicates Alloy 800 exhibits excellent corrosion resistance under both primary and secondary nominal and fault environments. Further, examination of in-service sleeved tubes with similar crevices, although of the welded Alloy 690 design, have not shown any corrosion attack associated with crevice deposits.

NRC Question 8:

On pages 8-15 to 8-17 (Tables 8-2A to 8-2C), it is shown that the sleeve and tube regions have three different temperatures. In the footnote for each table, the primary temperature (sleeve inside diameter) and secondarytemperature (tube outside diameter) were used to calculate the temperature for the tubes undernormal operation.

A. Discuss whether the temperatureassigned to the sleeve, uppertube, and lower tube would result in a conservative temperaturegradient within the sleeve/tube assembly wall. Discuss the implications of using the calculated temperature gradientin terms of meeting the American Society of Mechanical Engineers (ASME) Code allowable stress.

B. The temperaturesassigned and calculated in Tables 8-2A to 8-2C are apparentlybased on the temperatureprofiles in the hot leg side of the tube bundle. Discuss whether the thermal stresses calculatedaccording to the ASME Code bound the thermal stresses for the tubes in the cold leg side of the tube bundle.

PG&E Response:

Question 8A The calculation of axial loads in the subject report does not take credit for a temperature gradient in the sleeve-tube assembly. It is conservatively assumed that the lower tube is at the secondary temperature and the sleeve remains at the primary temperature. Hence, axial loads are based on the difference in bulk fluid temperature. More recent calculations have been performed (using one-dimensional heat transfer models) that credit the temperature gradient in the sleeve-tube assembly and show significantly lower axial loads. Thus, the assumptions in the licensing report for tube and sleeve temperatures are considered conservative.

11

Enclosure 1 PG&E Letter DCL-04-070 Question 8B The axial loading in the tube-sleeve assembly is directly related to the temperature difference between the sleeve and the tube. Since the primary (sleeve) temperature on the cold leg side will always be lower than the primary temperature on the hot leg side, the existing calculation is bounding for all locations in the tube bundle.

NRC Question 9:

On page 8-19, Section 8.3.3 (Effect of Tube Prestress Prior to Sleeving), the impact of the prestressed state of a locked-in tube to be sleeved on the sleeve installation process is discussed Clarify whether sleeve installation would add additional residualstresses to a locked-in tube, causing the tube to exceed the allowable stresses in the ASME Code.

PG&E Response:

Installing a sleeve will provide additional support to an existing tube. In general, tubes that become locked into a tube support do so during normal operation (e.g., from tube denting). Thus, during normal operation the tube will be in a zero-stress condition. As the tube cools a small tensile stress could develop in the tube between the attachment points in the tubesheet and the lock-in point at the first tube support. It is then assumed that a sleeve is installed while the tube is in a tensile stress condition. As the tube-sleeve assembly is heated during plant startup both components will expand and the preload on the tube will decrease. Since the leak limiting Alloy 800 sleeve will want to expand more than the tube, the tube will expand back to the zero-stress condition at normal operation and the sleeve will be in compression.

During a transient the sleeve will restrain the tube from contracting as much as it would if it were unsleeved, thereby limiting the amount of tensile stress on the tube.

Thus, the amount of stress on a sleeved tube will be less than an unsleeved tube that is locked in the first tube support. A more detailed discussion of installation stresses is contained in Section 7.4 of the report.

NRC Question 10:

On pages 8-27 to 8-32, Section 8.51 (Analysis of Sleeve Material), higher thermal stresses were calculatedfor various transientconditions for the 7/8-inch tube-sleeve assembly than for the 3/4-inch tube sleeve assembly. Forexample, aftera postulatedreactortrip, the calculated value for skin thermal stresses was higher for the 7/8-inch tube-sleeve than for the 3/4-in tube-sleeve (see pages 8-38 and 8-39 of WCAP-15918-P, Revision 0 (Nov. 2002)). From this data, the calculatedmaximum 12

Enclosure 1 PG&E Letter DCL-04-070 stress intensity ranges (Sxr) were calculated to be higher for the 7/8-inch tube-sleeve than for the 3/4-inch tube-sleeve (Westinghouse plants).

Noting that the staff recognizes that Sxr for both the 7/8-inch and 3/4-inch tube-sleeve configurations is within the ASME allowable, discuss the reason and significance of the higher value for Sxr for the 7/8-inch tube-sleeves.

PG&E Response:

There are two reasons why the 7/8-inch tube sleeve assembly has higher thermal stresses than the 3/4-inch tube sleeve assembly. First, the sleeve used in 7/8-inch SG tubes is 48 mils thick while the sleeve used in 3/4-inch SG tubes is 40 mils thick.

For a given temperature difference, there is a higher AT (and therefore a higher thermal stress) across the thicker sleeve. The second reason the 7/8-inch sleeve-tube assembly has higher thermal stresses is the primary and secondary temperatures assumed in the analysis. The analysis of the 7/8-inch tube-sleeve assembly assumes a AT of 127 degrees F. The analysis of the 3/4-inch tube-sleeve assembly assumes a AT of 93.5 degrees F. The higher AT for the 7/8-inch tube-sleeve assembly results in significantly higher thermal stresses.

It should be noted that the thermal stress calculations presented in WCAP-1 5918-P and WCAP-1 5919-P assume a linear temperature gradient across the sleeve and tube that is equal to the AT between the sleeve ID and the tube OD. This assumption is conservative because it ignores any nonlinearity of the thermal gradient. As noted in the response to Question 3, Westinghouse has recalculated the thermal gradients based on a one-dimensional steady-state heat balance. This evaluation documented a reduction in the thermal stress for both the 7/8- and 3/4-inch tube sleeve assemblies. However, no changes were made to the associated reports since they represent conservative, yet still acceptable, thermal stress values.

NRC Question 11:

On page 8-36, Section 6.0 (Fatigue Evaluation), the accumulated fatigue in the sleeve material for Spxr peak stress range (Westinghouse Model 51 steam generators) for 7/8-inch sleeves was many times higher than that for 3/4-inch sleeves (see pages 8-50 and 8-51 of WCAP-15918-P, Revision 0 (Nov. 2002)).

Noting that the staff recognizes that the accumulated fatigue value for both 7/8-inch and 3/4-inch sleeves in Westinghouse steam generators is within the ASME allowable, discuss the reason and significance of the higher value for accumulated fatigue for the 7/8-inch sleeves.

13

Enclosure 1 PG&E Letter DCL-04-070 PG&E Response:

The largest contribution to accumulated fatigue for the Westinghouse Model 51 SGs (Table 8-8C in WCAP 15919-P) is from the alternating stress (Sa) that results from the difference between zero percent power steady-state conditions and 100 percent power steady-state conditions. The corrected Sa for this condition is 34.0 kips per square inch (ksi). The largest contribution to accumulated fatigue for the Westinghouse Model D4 SGs (Table 8-8D in WCAP 15918-P) is from the Sa that results from the difference between feedwater cycling and 100 percent power steady-state conditions. The corrected Sa for this condition is 30.6 ksi. Although these values are within approximately 10 percent of each other, small differences in stress conditions can make relatively large differences in accumulated fatigue since the fatigue curves are not linear. Westinghouse does not consider the difference in fatigue usage factor between the 3/4-inch and 7/8-inch tube sleeves to be significant.

As described in the response to Question 3, Westinghouse has recalculated fatigue of the leak limiting Alloy 800 sleeve for a revised set of design transients that includes transients not previously addressed in WCAP-15919-P. The results of this calculation confirm that the methodology used in WCAP-1 5919-P to calculate accumulated fatigue of the 7/8-inch sleeve is bounding for DCPP.

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Enclosure 2 PG&E Letter DCL-04-070 MARKED-UP TECHNICAL SPECIFICATION PAGE 5.0-16

Programs and Manuals 5.5 5.5 Programs and Manuals 5.5.9 Steam Generator (SG) Tube Surveillance Program (continued)

2) Axial cracks in tubes returned to service using W* shall have the upper crack tip below the BWT by at least the NDE measurement uncertainty, and below the top of tube sheet (TTS) by at least the NDE measurement uncertainty and crack growth allowance, such that at the end of the subsequent operating cycle the entire crack remains below the tubesheet secondary face.

3) Resolvable, single axial indications (multiple indications must return to the null point between individual cracks) within the flexible W* length can be left in service. Alternate RPC coils or an ultrasonic test (UT) inspection can be used to demonstrate return to null point between multiple axial indications or the absence of circumferential involvement between axial indications.

4) Tubes with inclined axial indications less than 2.0 inches long (including the crack growth allowance) having inclination angles relative to the tube axis of < 45 degrees minus the NDE uncertainty, ANDECA, on the measurement of the crack angle can be left in service. Tubes with two or more parallel (overlapping elevation), inclined axial cracks shall be plugged or repaired. For application of the 2.0-inch limit, an inclined indication is an axial crack that is visually inclined on the RCP C-scan, such that an angular measurement is required, and the measured angle exceeds the measurement uncertainty of ANDECA.

5) Circumferential, volumetric, and axial indications with inclination angles greater than (45 degrees - ANDECA) within the flexible W*

length shall be plugged or repaired.

6) Any type of combination of the tube degradation below the W*

length is acceptable.

{I) Tube Repair refers to a process that establishes tube 9 ~serviceability.' Tube repair of defective tubes will be perfrmed by installation of the leak-limiting sleeve as described in

> WetingouseRepot WCP-1519-P Reision 01.

2. The SG tube integrity shall be determined after completing the corresponding actions (plu or repai all tubes exceeding the plugging,~j eir mit) required by Table 5. -2.

e. Reports The contents and frequency of reports concerning the SG tube surveillance program shall be in accordance with Specification 5.6.10.

DIABLO CANYON - UNITS 1 & 2 5.0-16 Unit 1- Amendment No. 4 442, o5 Unit 2 - Amendment No. 4I5 44,

Enclosure 3 PG&E Letter DCL-04-070 RETYPED TECHNICAL SPECIFICATION PAGE 5.0-16

Programs and Manuals 5.5 5.5 Programs and Manuals 5.5.9 Steam Generator (SG) Tube Surveillance Program (continued)

7) Axial cracks in tubes returned to service using W* shall have the upper crack tip below the BWT by at least the NDE measurement uncertainty, and below the top of tube sheet (TTS) by at least the NDE measurement uncertainty and crack growth allowance, such that at the end of the subsequent operating cycle the entire crack remains below the tubesheet secondary face.

8) Resolvable, single axial indications (multiple indications must return to the null point between individual cracks) within the flexible W* length can be left in service. Alternate RPC coils or an ultrasonic test (UT) inspection can be used to demonstrate return to null point between multiple axial indications or the absence of circumferential involvement between axial indications.

9) Tubes with inclined axial indications less than 2.0 inches long (including the crack growth allowance) having inclination angles relative to the tube axis of < 45 degrees minus the NDE uncertainty, ANDEcA, on the measurement of the crack angle can be left in service. Tubes with two or more parallel (overlapping elevation), inclined axial cracks shall be plugged or repaired. For application of the 2.0-inch limit, an inclined indication is an axial crack that is visually inclined on the RCP C-scan, such that an angular measurement is required, and the measured angle exceeds the measurement uncertainty of ANDECA.

10) Circumferential, volumetric, and axial indications with inclination angles greater than (45 degrees - ANDECA) within the flexible W*

length shall be plugged or repaired.

11) Any type of combination of the tube degradation below the W*

length is acceptable.

I) Tube Repair refers to a process that establishes tube serviceability.

Tube repair of defective tubes will be performed by installation of the leak-limiting sleeve as described in Westinghouse Report WCAP-15919-P, Revision 01.

2. The SG tube integrity shall be determined after completing the corresponding actions (plug or repair all tubes exceeding the plugging or repair limit) required by Table 5.5.9-2.

e. Reports The contents and frequency of reports concerning the SG tube surveillance program shall be in accordance with Specification 5.6.10.

DIABLO CANYON - UNITS 1 & 2 5.0-16 Unit 1-Amendment No. 435442, Unit 2 - Amendment No. 435 442,