RS-15-107, Response to NRC Request for Additional Information, Set 48, Dated April 2, 2015

Response to NRC Request for Additional Information, Set 48, Dated April 2, 2015

ML15103A687
Person / Time
Site:	Byron, Braidwood
Issue date:	04/13/2015
From:	Gallagher M Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-15-107
Download: ML15103A687 (23)

Text

Michael P. Gallagher Vice President. License Renewal Exelon Generation Exelon Nuclear 200 Exelon Way Kennett Square, PA 19348 610 765 5958 Office 610 765 5956 Fax www.exelor1corp.com michaelp.gallagher@exeloncorp.com 10 CFR 50 10 CFR 51 10 CFR 54 RS-15-107 April 13, 2015 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Braidwood Station, Units 1 and 2 Facility Operating License Nos. NPF-72 and NPF-77 NRC Docket Nos. STN 50-456 and STN 50-457 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455

Subject:

Response to NRC Request for Additional Information, Set 48, dated April 2, 2015, related to the Braidwood Station, Units 1 and 2, and Byron Station, Units 1 and 2, License Renewal Application

References:

1. Letter from Michael P. Gallagher, Exelon Generation Company LLC (Exelon) to NRC Document Control Desk, dated May 29, 2013, "Application for Renewed Operating Licenses"

2. Letter from Lindsay R. Robinson, US NRC to Michael P. Gallagher, Exelon, dated May 19, 2014 "Request for Additional Information for the Review of the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, License Renewal Application - Aging Management, Set 24 (TAC NOS. MF1879, MF1880, MF1881, AND MF1882)"

3. Letter from Michael P. Gallagher, Exelon Generation Company LLC (Exelon) to NRC Document Control Desk, dated June 9, 2014, "Responses to NRC Requests for Additional Information, Set 24, dated May 19, 2014, related to the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2 License Renewal Application"

4. Letter from Lindsay R. Robinson, US NRC to Michael P. Gallagher, Exelon, dated October 10, 2014, "Request for Additional Information for the Review of the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, License

April 13, 2015 U.S. Nuclear Regulatory Commission Page 2 Renewal Application, Set 42 (TAC NOS. MF1879, MF1880, MF1881, and MF1882)"

5. Letter from Michael P. Gallagher, Exelon to NRC Document Control Desk, dated October 31, 2014, "Response to NRC Request for Additional Information, Set 42, dated October 10, 2014, related to the Braidwood Station, Units 1 and 2, and Byron Station, Units 1 and 2, License Renewal Application"

6. Letter from Michael P. Gallagher, Exelon, to NRC Document Control Desk, dated November 22, 2014, "Supplemental Commitment related to the October 31, 2014 Response to NRC Request for Additional Information, Set 42, dated October 10, 2014, related to the Braidwood Station, Units 1 and 2, and Byron Station, Units 1 and 2, License Renewal Application"

7. Letter from Lindsay R. Robinson, US NRC to Michael P. Gallagher, Exelon, dated January 22, 2015, "Request for Additional Information for the Review of the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, License Renewal Application, Set 45 (TAC NOS. MF1879, MF1880, MF1881, and MF1882)"

8. Letter from Michael P. Gallagher, Exelon, to NRC Document Control Desk, dated February 23, 2015, "Response to NRC Request for Additional Information, Set 45, dated January 22, 2015, related to the Braidwood Station, Units 1 and 2, and Byron Station, Units 1 and 2, License Renewal Application"

9. Letter from John W . Daily, US NRC to Michael P. Gallagher, Exelon, dated April 2, 2015, "Request for Additional Information for the Review of the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, License Renewal Application - Set 48 (TAC NOS. MF1879, MF1880, MF1881, and MF1882)"

In Reference 1, Exelon Generation Company, LLC (Exelon) submitted the License Renewal Application (LRA) for the Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2 (BBS). In References 2 through 8, the NRC Staff and Exelon exchanged information supporting the Staff's review of the adequacy of the Flux Thimble Tube Inspection aging management program for BBS for license renewal.

In Reference 9, the Staff requested additional information to complete its review associated with the Flux Thimble Tube Inspection aging management program, specifically related to the program at Braidwood Station, Units 1 and 2.

Enclosure A to this letter provides the response to this request for additional information.

Enclosure B contains updates to sections of the LRA (except for the License Renewal Commitment List) affected by the response.

Enclosure C provides an update to the License Renewal Commitment List (LRA Appendix A, Section A.5) associated with the response.

There are no other new or revised regulatory commitments contained in this letter.

April 13, 2015 U.S. Nuclear Regulatory Commission Page 3 If you have any questions, please contact Mr. Al Fulvio, Manager, Exelon License Renewal, at 610-765-5936.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on ~ f-/ J- Z'/J-Respectfully,

~~

Vice President - License Renewal Projects Exelon Generation Company, LLC

Enclosures:

A. Byron and Braidwood Stations, Units 1 and 2, License Renewal Application Response to Request for Additional Information RAI B.2.24-1c B. Byron and Braidwood Stations, Units 1 and 2, License Renewal Application Updates Associated with the Response to RAI B.2.24-1 c C. Byron and Braidwood Stations, Units 1 and 2, License Renewal Commitment List Update cc: Regional Administrator- NRC Region Ill NRC Project Manager (Safety Review), NRR-DLR NRC Project Manager (Environmental Review), NRR-DLR NRC Senior Resident Inspector, Braidwood Station NRC Senior Resident Inspector, Byron Station NRC Project Manager, NRR-DORL-Braidwood and Byron Stations Illinois Emergency Management Agency - Division of Nuclear Safety

RS-15-107 Enclosure A Page 1 of 9 Enclosure A Byron and Braidwood Stations, Units 1 and 2, License Renewal Application Response to Request for Additional Information RAI B.2.24-1c

RS-15-107 Enclosure A Page 2 of 9 RAI B.2.24-1c, Flux Thimble Tube Inspection follow-up Applicability: Braidwood Station (Braidwood), Units 1 and 2 Note: This RAI is composed of three sections (1-3), each of which deals with a background, issue, and request.

Background 1:

In its response dated February 23, 2015, the applicant stated that historical flux thimble tube wear experienced at Braidwood is bounded by industry operating experience for which the GALL Report AMP was evaluated. The applicant further stated that a plant-specific AMP is not necessary, since its plant-specific condition and age-related operating experience is bounded by the conditions and operating experience for which GALL Report AMP XI.M37 was evaluated.

In its RAI response dated October 31, 2014, the applicant stated that widespread inability to obtain flux thimble tube eddy current data occurred suddenly at Braidwood Station, Units 1 and 2 and involved flux thimble tubes of various in-service times. The applicant also stated that while Byron, Units 1 and 2 and Braidwood, Units 1 and 2 have the same basic flux thimble tube design (i.e., dimensions), the Byron Units have not had significant difficulty completing eddy current examinations.

In its October 31, 2014 response, the applicant stated that causal factors which include moisture and lubricant could account for the difficulties getting eddy current data, and it would consider activities to mitigate this issue. In its response dated February 23, 2015, the applicant stated that moisture and lubricant were not likely the causal factors and that deformation of the flux thimble tubes such that the internal dimension of the tubes is affected could prevent the eddy current probe from being fully inserted. The applicant also stated that deformation could occur because of mishandling, and is unlikely to result in deformation of all 58 flux thimble tubes. The applicant concluded that the most logical scenario is that the eddy current testing equipment or testing process is the likely cause of the recent issues related to obtaining eddy current testing data.

Issue 1:

The staff noted from the applicants responses that its program failed to obtain useful data from most of its flux thimble tubes during the recent outage inspections since 2012, due to restrictions inside the flux thimble tubes. The staff is concerned that the applicant has yet to identify the root cause and, as a result, is not able to implement effective corrective actions to resolve the problem.

The staff performed an industry operating experience search and did not note occurrences of widespread issues with inability to get eddy current data. In addition, since the 1980s when flux thimble tube wear became an issue, industrys use of chrome plated replacement tubes has greatly reduced wear rates which does not seem to be the case with the chrome plated replacement flux thimble tubes at Braidwood. The staff is also concerned that the increasing trend in the numbers of uninspectable flux thimble tubes, unique to Braidwood, may be due to an age-related deformation of the tubes (i.e., reduction in inside diameter).

RS-15-107 Enclosure A Page 3 of 9 Request 1:

(a) Provide technical justification that the operating experience for which the GALL Report AMP was evaluated is applicable to the plant-specific operating experience at Braidwood, considering the high wear rates, and multiple issues with eddy current examinations.

(b) Explain if higher than normal wear rates have been observed with chrome plated replacement tubes.

(c) Provide root cause analysis and corrective actions related to the inability to obtain useful inspection data.

(d) Explain if there is a new age-related mechanism in addition to wear that is causing obstruction of eddy current probe insertion.

(e) If the applicants operating experience is unique and not bounded by the operating experience for which the GALL Report AMP XI.M37 was evaluated, explain why a plant-specific AMP is not required to manage the aging effects during the period of extended operation (PEO).

Background 2:

In the LRA, the applicant described its program as an existing program which is consistent with the GALL Report AMP XI.M37, Flux Thimble Tube Inspection. In its February 23, 2015, response to the staffs follow-up RAI, the applicant described its program elements as will be consistent with the GALL Report AMP XI.M37 program elements.

Issue 2:

The staff reviewed the applicants claim of program consistency by comparing the applicants program with the GALL program. The staff noted that several program elements in the applicants program are not consistent with those of the GALL program. Specifically, the applicants program failed to obtain useful data from most of its flux thimble tubes during the recent outage inspections since 2012, and proposes an enhancement to replace its tubes every three cycles if flux thimble tube inspection data cannot be obtained. Based on the applicants existing operating experience, there is a possibility that the issues with the eddy current examinations will recur during the PEO. Based on this, the applicant will be replacing the flux thimble tubes at an acceptable frequency instead of inspecting them. In such a case, the applicants program would have exceptions to the following elements of the GALL AMP:

Element 3. Parameters Monitored/Inspected. GALL Guidance recommends that flux thimble tube wall thickness is monitored to detect loss of material from the flux thimble tubes. The applicants program would not be able to monitor material loss, or wear.

Element 4. Detection of Aging Effects. GALL Guidance recommends an inspection methodology (such as eddy current testing) used to detect loss of material. The applicants program would not be able to detect the aging effect of wear.

Element 5. Monitoring and Trending. GALL Guidance recommends that flux thimble tube wall thickness measurements are trended and wear rates are calculated and projected based on plant-specific data. The applicants program would not be able to provide trending and monitoring.

Request 2:

Identify all of the programs exceptions to GALL Report AMP XI.M37, Flux Thimble Tube Inspection when flux thimble tube inspection data cannot be obtained. Discuss how the

RS-15-107 Enclosure A Page 4 of 9 proposed enhancement, to replace tubes at an acceptable frequency, will address the exceptions. Revise the program accordingly.

Background 3:

In its response dated February 23, 2015, the applicant stated multiple times that No flux thimble tube has been replaced due to age-related degradation in less than four (4) cycles, and that None of the 116 flux thimble tubes were required to be replaced due to age-related degradation in less than four (4) refueling cycles.

In its response, the applicant also stated multiple times that plant-specific historical wear rates were used to project tube wear and were applicable. The applicant further stated that industry operating experience indicates that flux thimble tube wear decreases over the flux thimble tube service life. In addition, the applicant provided an enhancement to its AMP to replace flux thimble tubes every three cycles when inspection data cannot be obtained.

Issue 3:

In Table 2, on Page 13 of its response, the applicant indicated that three tubes had to be replaced after only one cycle of service due to wear, which the staff considers to be age-related.

This appears to contradict the applicants statement that No flux thimble tube has been replaced due to age-related degradation in less than four (4) cycles.

The applicants justification for the enhancement does not consider worst case wear scenarios.

For example, it had experienced higher than expected wear rates but does not consider high wear rates in consecutive cycles. The applicant cited industry operating experience that wear rates decrease following high wear in earlier cycles. The staff noted that the applicant also experienced an increase in wear rates following cycles of low wear rates.

In addition, during its review of industry operating experience, the staff noted that there is industry operating experience which indicates that high wear rates may be sustained in multiple cycles. Specifically, the staff noted that a similar plant encountered multiple tube failures prior to the completion of three cycles of operation (LER-272/1981-028). A three-cycle replacement period appears to be inadequate.

Request 3:

a) Explain why initial wear resulting in replacement of three flux thimble tubes after one cycle is not flow related wear and will not recur.

b) Explain why replacing flux thimble tubes every three cycles when examination data are not obtained is adequate, in light of the plant-specific high wear rates, and industry operating experience which indicates that high wear rates could continue into subsequent cycles and result in tube failures in less than three cycles.

RS-15-107 Enclosure A Page 5 of 9 Exelon Response:

Introduction - Latest Testing Results Flux thimble tube eddy current testing was performed during the Braidwood Station, Unit 1 Spring 2015 Refueling Outage in the week of March 30. Full-length eddy current data was obtained on all 58 flux thimble tubes.

In Exelon Letter RS-15-071, dated February 23, 2015, response to RAI B.2.1-24-1b Request 4, it was reported that the most likely cause of the eddy current testing difficulties was due to eddy current testing equipment or testing process issues. The completion of the recent eddy current testing of the Braidwood Unit 1 flux thimble tubes confirmed this to be the case.

This recent eddy current test was performed utilizing three improvements to the eddy current test equipment and process which resulted in successful testing. The three improvements are:

1. The flux thimble tubes were not wet cleaned. This eliminated the possibility of residual moisture contributing to increased internal tube friction.

2. Dry gauging of the flux thimble tubes was performed prior to performing eddy current testing. The gauging process consists of the insertion of a dummy probe to ensure clear passage through the flux thimble tube. A dummy probe is a neutron detector cable without the neutron detector attached. Multiple dry gauging passes, as required, were performed until the technicians felt normal flux thimble tube friction.

3. Data was collected with a slightly smaller eddy current probe (0.182 inches verses 0.188 inches). The smaller probe provides additional clearance and therefore, less resistance when inserting the probe in the flux tube.

The highest measured wear was 68% wall loss on one flux thimble tube that was capped during the previous outage. This previously capped flux thimble tube was replaced since the wear is greater than the 60% measured wall loss criteria. The measured wear of the other flux thimble tubes ranged from no detectable defect to 46% wall loss this refueling outage. Based on the plant-specific wear rates and the WCAP projection methodology, the maximum flux thimble tube wear at the next refueling outage, Fall 2016, is projected to be 48% wall loss, justifying the operation of all flux thimble tubes until the next scheduled eddy current test during the next refueling outage. The detected wear was consistent with previous operating experience.

Collection of eddy current data on all 58 flux thimble tubes provides objective evidence that the past difficulties experienced during flux thimble tube eddy current testing are resolved. Eddy current testing will be performed for each flux thimble tube every refueling outage until sufficient data has been accumulated to establish a plant-specific frequency to ensure no flux thimble tube is predicted to incur wear that exceeds 80% before the next inspection in accordance with Enhancement 1 of Commitment 24 submitted in Exelon letter RS-15-071, dated February 23, 2015.

Due to the similarity between Unit 1 and Unit 2, it can be concluded these actions will be effective on Unit 2, therefore there is reasonable assurance that both Unit 1 and 2 will be within the guidelines of the NUREG-1801, XI.M37, Flux Thimble Tube Inspection Aging Management Program prior to entering the period of extended operation.

RS-15-107 Enclosure A Page 6 of 9 Response to Request 1 (a) The high wear rates referenced in the Request are bounded by the operating experience for which the GALL Report AMP was evaluated. GALL Report AMP XI.M37 is based on the requirements established in NRC IE Bulletin 88-09, which was developed in response to industry operating experience of flux thimble tube thinning in Westinghouse reactors due to flow-induced wear. This industry operating experience was summarized in NRC Information Notice 87-44. In response to these documents, the Westinghouse Owners Group developed WCAP-12866. WCAP-12866 analyzed industry operating experience and developed a model to predict wear growth as well as guidance for an effective program to manage flow-induced wear of flux thimble tubes. Industry operating experience described in Information Notice 87-44 and WCAP-12866 includes examples of single cycle wear in excess of 27%. For example, Supplement 1 of Information Notice 87-44 identifies a nuclear station where indications approaching 40% through-wall loss had developed over a single cycle of operation. Furthermore, Braidwood plant-specific operating experience shows that, overall, the flux thimble tube wear growth aligns with the wear trends predicted in WCAP-12866, as described in the response to Request 2 in Exelon Letter RS-15-071.

As for the multiple issues with eddy current examinations, as explained in the Introduction above, the issues with eddy current examinations were associated with eddy current test equipment and process issues, not a known or new age-related degradation mechanism.

Therefore, the operating experience for which the GALL Report AMP was evaluated is applicable to the plant-specific operating experience at Braidwood.

(b) A review of the flux thimble tube procurement records by the station and the flux thimble tube supplier indicates that chrome plated flux thimble tubes have not been supplied to Braidwood Station. Therefore, there is no wear data for chrome plated flux thimble tubes at Braidwood Station.

(c) In Exelon Letter RS-15-071, dated February 23, 2015, response to RAI B.2.1-24-1b Request 4, it was reported that the most likely cause of the eddy current testing difficulties was due to eddy current testing equipment or testing process issues. The completion of the recent eddy current testing of the Braidwood Unit 1 flux thimble tubes confirmed this to be the case.

This recent eddy current test was performed utilizing three improvements to the eddy current test equipment and process which resulted in successful testing. The three improvements are:

1. The flux thimble tubes were not wet cleaned. This eliminated the possibility of residual moisture contributing to increased internal tube friction.

2. Dry gauging of the flux thimble tubes was performed prior to performing eddy current testing. The gauging process consists of the insertion of a dummy probe to ensure clear passage through the flux thimble tube. A dummy probe is a neutron detector cable without the neutron detector attached. Multiple dry gauging passes, as required, were performed until the technicians felt normal tube friction.

3. Data was collected with a slightly smaller eddy current probe (0.182 inches verses 0.188 inches). The smaller probe provides additional clearance and therefore, less resistance when inserting the probe in the flux tube.

RS-15-107 Enclosure A Page 7 of 9 The above corrective actions were effective as demonstrated by the collection of full-length eddy current data on all 58 flux thimble tubes.

(d) The ability to perform flux mapping, the ability to insert and retract the flux thimble tubes during refueling outages, and the collection of eddy current data on all 58 flux thimble tubes during the Unit 1 Spring 2015 Refueling Outage provides reasonable assurance that the flux thimble tubes are not deforming and a new age-related degradation mechanism causing obstruction is not occurring.

(e) As discussed in the Response to Request 1(a) above, the flux thimble tube wear operating experience at Braidwood is not unique. The widespread issues with obtaining eddy current data are unique to Braidwood, but are due to the eddy current test equipment and process issues, not an age-related degradation mechanism. Since the widespread issue with obtaining eddy current data is not age-related degradation, the age-related operating experience at Braidwood is bounded by the age-related operating experience for which GALL Report AMP XI.M37 was evaluated. Therefore, a plant-specific aging management program is not needed. To address the potential of eddy current data collection issues recurring in the future, an exception to GALL Report AMP XI.M37 is taken as described in the Response to Request 2, below.

Response to Request 2 To address the potential of eddy current data collection issues recurring in the future, the following exception is being applied to Element 3, Parameters Monitored/Inspected, Element 4, Detection of Aging Effects, and Element 5, Monitoring and Trending:

Braidwood Flux Thimble Tube Inspection program operating experience indicates that there have been instances in which useable data could not be obtained for most of its flux thimble tubes during routine flux thimble tube eddy current testing. Although there is confidence that future eddy current testing will be successful, there is a possibility that the issues with the eddy current testing could recur during the period of extended operation. Therefore, there is the possibility that flux thimble tubes will be replaced on a two (2) cycle frequency rather than the inspections and trending recommended in NUREG-1801, Chapter XI.M37 (Braidwood only).

The justification for the above exception is that the Braidwood Flux Thimble Tube Inspection program is enhanced to require flux thimble tubes be replaced every two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the program.

The Element 3 recommendation that flux thimble tube wall thickness is monitored to detect loss of material, the Element 4 recommendation to use an inspection methodology such as eddy current testing to detect loss of material, and the Element 5 recommendation that flux thimble tube wall thickness measurements are trended and wear rates are calculated and projected based on plant-specific data are not applicable for a component that is replaced on a two (2) cycle frequency due to the limited amount of time the flux thimble tube remains in service.

Based on plant specific operating experience, a two (2) cycle replacement frequency will provide reasonable assurance that flux thimble tubes will be replaced prior to age-related degradation progressing to the point where flux thimble tube integrity is challenged.

RS-15-107 Enclosure A Page 8 of 9 See Enclosure B for revisions to LRA Table 3.1.1, Table 3.1.2-1, and Appendix B, Section B.2.1.24.

Response to Request 3 a) The wear resulting in the replacement of three (3) flux thimble tubes described in the Exelon Letter RS-15-071 response to Request 2 was determined to be event driven rather than age-related based on the relatively short period of time over which the wear occurred and on the fact that these wear rates have not re-occurred. As stated in the Exelon Letter RS-15-071 response to Request 2, the wear occurred during the initial cycle of plant operation and the replacement flux thimble tubes remained in service for at least 15 cycles.

Since the initial cycle wear rates were not repeated, an additional wear contributor to the normal flow-induced wear must have been present at these thimble locations, resulting in the event driven wear.

Some additional wear contributors that could have added to the normal flow-induced wear include the unique flow conditions experienced during plant start-up testing, construction/manufacturing issues (burrs, sharp edges, or machine shavings/foreign material) associated with the interfacing components, and flux thimble tube installation issues. Based on the replacement flux thimble tubes remaining in service for at least 15 cycles, there is reasonable assurance that these event driven wear rates will not recur. In addition, the short, two (2) cycle replacement frequency of the flux thimble tubes, if useful eddy current testing is not obtained, will provide reasonable assurance that the integrity of the flux thimble tubes is maintained during the period of extended operation. During the recent Braidwood Station, Unit 1, Spring 2015 Refueling Outage, the detected wear was consistent with previous plant-specific and industry operating experience.

b) Justification for a three (3) cycle replacement frequency if eddy current data is not obtained was provided in Exelon Letter RS-15-071 response to Request 2. The key points of the justification were; no flux thimble tube has been replaced due to age-related degradation in less than four (4) cycles and there have been only three (3) instances of replacement at four (4) cycles due to age-related wear, flux thimble tubes replaced in three (3) cycles or less were replaced due to issues other than flow induced wear, single cycle wear of 27% or greater is rare, consecutive cycles with wear of 27% or greater does not occur, and overall wear of the Braidwood flux thimble tubes does not follow a linear trend but rather follows the exponentially decreasing trend predicted in WCAP-12866.

The industry operating experience reported in LER-272/1981-028 was considered in the development of WCAP-12866, which provided industry guidance concerning thimble tube wear. The subject event occurred over 25 years ago, prior to the requirement to perform periodic flux thimble tube eddy current testing and trending of flux thimble tube wear. As stated in NRC Bulletin 88-09, the amount of vibration the thimble tubes experience is determined by such plant-specific factors as the gap distance from the lower core plate to the fuel assembly instrument tube, the amount of clearance between the thimble tube and the guide or instrument tube, the axial component of the local fluid velocity, the thickness of

RS-15-107 Enclosure A Page 9 of 9 the thimble tube and the moment of inertia of the thimble tube. The Braidwood design is different than the subject plant design (e.g., gap between thimble tube OD and instrument column ID for the subject plant is larger than at Braidwood, the subject plant was a downflow plant when the event occurred whereas, Braidwood units are upflow plants, and the core flow per assembly is different between the subject plant and the Braidwood units, as described in WCAP-12866 Table 5, Plant Categorization). The differences in design between the subject plant and the Braidwood units would make the use of the historical plant-specific flux thimble tube wear data more relevant than the operating experience reported under LER-272/1981-028.

Although the plant-specific historical operating experience supporting a three (3) cycle replacement frequency, if eddy current data is not obtained, is considered more relevant than the industry operating experience reported under LER-272/1981-028, the enhancement to the Braidwood Station Flux Thimble Tube Inspection Program is revised to replace a flux thimble tube after two (2) cycles of service or remove the flux thimble tube from service if eddy current data is not obtained, to account for any additional future uncertainty. This increased replacement frequency will ensure the integrity of the flux thimble tubes is maintained during the period of extended operation.

See Enclosure B for revisions to LRA Table 3.1.1, Table 3.1.2-1, Appendix A, Section A.2.1.24 and Appendix B, Section B.2.1.24. See Enclosure C for revisions to the License Renewal Commitment List, LRA Appendix A, Section A.5.

RS-15-107 Enclosure B Page 1 of 8 Enclosure B Byron and Braidwood Stations, Units 1 and 2, License Renewal Application Updates Associated with the Response to:

RAI B.2.24-1c Note: To facilitate understanding, portions of the original LRA have been repeated in this Enclosure, with revisions indicated. Existing LRA text, as modified by subsequent submittals, is shown in normal font. Changes are highlighted with bolded italics for inserted text and strikethroughs for deleted text.

RS-15-107 Enclosure B Page 2 of 8 As a result of the response provided in Enclosure A of this letter, LRA Table 3.1.1, Item 3.1.1-54, page 3.1-37, is revised as shown below. Additions are indicated with bolded italics.

Table 3.1.1 Summary of Aging Management Evaluations for the Reactor Vessel, Internals, and Reactor Coolant System Item Component Aging Aging Management Further Evaluation Discussion Number Effect/Mechanism Programs Recommended 3.1.1-54 Stainless steel bottom Loss of material due Chapter XI.M16A, PWR No Consistent with NUREG-1801 with mounted instrument to wear Vessel Internals, and exceptions. The Flux Thimble Tube system flux thimble tubes Chapter XI.M37, "Flux Inspection (B.2.1.24) program and PWR (with or without chrome Thimble Tube Inspection" Vessel Internals (B.2.1.7) program will be plating) exposed to used to manage loss of material of reactor coolant and stainless steel bottom mounted instrument neutron flux system flux thimble tubes exposed to reactor coolant and neutron flux in the Reactor Coolant System.

Exceptions apply to the NUREG-1801 recommendations for PWR Vessel Internals (B.2.1.7) program implementation.

Exceptions apply to the NUREG-1801 recommendations for Flux Thimble Tube Inspection (B.2.1.24) program implementation at Braidwood only.

RS-15-107 Enclosure B Page 3 of 8 As a result of the response provided in Enclosure A of this letter, LRA Table 3.1.2-1, pages 3.1-52 and 3.1-69, are revised as shown below. Additions are indicated with bolded italics and deletions indicated by strikethroughs.

Table 3.1.2-1 Reactor Coolant System (Continued)

Component Intended Material Environment Aging Effect Aging Management NUREG-1801 Table 1 Item Notes Type Function Requiring Programs Item Management Bottom mounted Pressure Boundary Stainless Steel Air with Borated Water None None IV.E.RP-05 3.1.1-107 A instrument system: Leakage (External) flux thimble tubes Reactor Coolant and Cracking PWR Vessel Internals IV.B2.RP-301 3.1.1-53 D Neutron Flux (B.2.1.7)

Water Chemistry (B.2.1.2) IV.B2.RP-301 3.1.1-53 C Cumulative Fatigue TLAA IV.C2.R-223 3.1.1-9 A, 1 Damage Loss of Material Water Chemistry (B.2.1.2) IV.B2.RP-24 3.1.1-87 A Flux Thimble Tube IV.B2.RP-284 3.1.1-54 A-Inspection (B.2.1.24)

B, 5 PWR Vessel Internals IV.B2.RP-284 3.1.1-54 B (B.2.1.7)

Plant Specific Notes:

5. The exception to the Flux Thimble Tube Inspection (B.2.1.24) program applies to Braidwood only.

RS-15-107 Enclosure B Page 4 of 8 As a result of the response provided in Enclosure A of this letter, LRA Appendix A, Section A.2.1.24, page A-28, is revised as shown below. Additions are indicated with bolded italics and deletions indicated by strikethroughs.

A.2.1.24 Flux Thimble Tube Inspection The Flux Thimble Tube Inspection aging management program is an existing condition monitoring program that manages the loss of material in flux thimble tubes due to wear (i.e., wall thinning). Flux thimble tubes, which provide a path for the in-core neutron flux monitoring system detectors, establish part of the reactor coolant pressure boundary and are subject to flow-induced fretting which causes wear. The program uses the non-destructive examination methodology of eddy current testing to periodically inspect the full length of all flux thimble tubes, which encompasses the path from the reactor vessel instrument nozzle to the fuel assembly instrument guide.

The results of the periodic eddy current testing are evaluated and trended to determine if corrective actions are required or if the inspection frequency needs to be changed to ensure reactor coolant pressure boundary integrity is maintained. Corrective actions include flux thimble tube limited repositioning (one-time), replacement, or isolation (removal from service).

The Flux Thimble Tube Inspection program implements the recommendations of NRC IE Bulletin 88-09, Thimble Tube Thinning in Westinghouse Reactors. This existing aging management program will continue to be implemented during the period of extended operation.

The Flux Thimble Tube Inspection aging management program will be enhanced as follows:

1. For Braidwood Units 1 and 2: Perform corrective actions to re-establish periodic eddy current testing of the flux thimble tubes prior to the period of extended operation to ensure that wall thickness is monitored to detect loss of material from the flux thimble tubes. Once periodic eddy current testing is re-established, eddy current testing will be performed for each flux thimble tube every refueling outage until sufficient data has been accumulated to establish a plant-specific eddy current testing frequency such that no flux thimble tube is predicted to incur wear that exceeds 80% before the next inspection. Flux thimble wall thickness measurements will be trended and wear rates will be calculated based on plant-specific data. Wall thickness will be projected using plant-specific data in accordance with the WCAP-12866, Bottom Mounted Instrumentation Flux Thimble Wear, methodology.

2. For Braidwood Unit 1:

a. The 17 Braidwood Station, Unit 1 flux thimble tubes that exhibited indications of wear during eddy current testing performed during A1R15 Refueling Outage (Fall 2010), will be replaced or removed from service during A1R18 Refueling Outage (Spring 2015), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program. (Flux thimble tubes 1 (J-8), 8 (K-6), 9 (H-11), 12 (E-9), 14 (H-4), 18 (L-11), 19 (L-

RS-15-107 Enclosure B Page 5 of 8 5), 21 (E-11), 23 (D-10), 36 (J-14), 37 (P-9), 41 (N-4), 44 (R-8), 45 (N-13),

48 (P-4), 54 (A-11), 55 (N-14))

b. The remaining Braidwood Station, Unit 1 flux thimble tubes, not replaced during A1R18, will be replaced or removed from service during A1R19 Refueling Outage (Fall 2016), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program.

c. Following A1R19, any Braidwood Station, Unit 1 flux thimble tube will be replaced every three (3) two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the Flux Thimble Tube Inspection program.

3. For Braidwood Unit 2:

a. The 29 Braidwood Station, Unit 2 flux thimble tubes that exhibited indications of wear during eddy current testing performed during A2R15 Refueling Outage (Spring 2011) and not replaced during A2R17 Refueling Outage (Spring 2014), will be replaced or removed from service during A2R18 Refueling Outage (Fall 2015), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program. (Flux thimble tubes 1 (J-8), 4 (H-6), 5 (F-8), 6 (J-10), 7 (F-7), 9 (H-11), 10 (L-8), 11 (G-5),

18 (L-11), 22 (K-12), 23 (D-10), 24 (H-13), 25 (N-8), 26 (H-3), 27 (C-8), 29 (N-6), 32 (L-13), 33 (C-5), 34 (H-2), 36 (J-14), 37 (P-9), 40 (F-14), 41 (N-4),

42 (D-3), 45 (N-13), 46 (J-1), 50 (R-6), 52 (L-15), 56 (N-2))

b. The remaining Braidwood Station, Unit 2 flux thimble tubes, not replaced during A2R17 or A2R18, will be replaced or removed from service during A2R19 Refueling Outage (Spring 2017), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program.

c. Following A2R19, any Braidwood Station, Unit 2 flux thimble tube will be replaced every three (3) two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the Flux Thimble Tube Inspection program.

These enhancements will be implemented in accordance with the schedule specified in the enhancement.

RS-15-107 Enclosure B Page 6 of 8 As a result of the response provided in Enclosure A of this letter, the NUREG-1801 Consistency section of LRA Appendix B, Section B.2.1.24, page B-153, is revised as shown below. Additions are indicated with bolded italics; deletions are shown with strikethroughs.

B.2.1.24 Flux Thimble Tube Inspection NUREG-1801 Consistency The Flux Thimble Tube Inspection aging management program is will be consistent with the ten elements of aging management program XI.M37, Flux Thimble Tube Inspection, specified in NUREG-1801, with the following exception.

Exceptions to NUREG-1801 None.

1. Braidwood Flux Thimble Tube Inspection program operating experience indicates that there have been instances in which useable data could not be obtained for most of its flux thimble tubes during routine flux thimble tube eddy current testing. Although there is confidence that future eddy current testing will be successful, there is a possibility that the issues with the eddy current testing could recur during the period of extended operation. Therefore, there is the possibility that flux thimble tubes will be replaced on a two (2) cycle frequency rather than the inspections and trending recommended in NUREG-1801, Chapter XI.M37 (Braidwood only). Program Elements Affected: Parameters Monitored/Inspected (Element 3), Detection of Aging Effects (Element 4), Monitoring and Trending (Element 5)

Justification for Exception The Braidwood Flux Thimble Tube Inspection program is enhanced to require flux thimble tubes be replaced every two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the program. The Element 3 recommendation that flux thimble tube wall thickness is monitored to detect loss of material, the Element 4 recommendation to use an inspection methodology such as eddy current testing to detect loss of material, and the Element 5 recommendation that flux thimble tube wall thickness measurements are trended and wear rates are calculated and projected based on plant-specific data are not applicable for a component that is replaced on a two (2) cycle frequency due to the limited amount of time the flux thimble tube remains in service. Based on plant specific operating experience, a two (2) cycle replacement frequency will provide reasonable assurance that flux thimble tubes will be replaced prior to age-related degradation progressing to the point where flux thimble tube integrity is challenged.

RS-15-107 Enclosure B Page 7 of 8 Enhancements The following enhancements will be implemented in the following program elements:

1. For Braidwood Units 1 and 2: Perform corrective actions to re-establish periodic eddy current testing of the flux thimble tubes prior to the period of extended operation to ensure that wall thickness is monitored to detect loss of material from the flux thimble tubes. Once periodic eddy current testing is re-established, eddy current testing will be performed for each flux thimble tube every refueling outage until sufficient data has been accumulated to establish a plant-specific eddy current testing frequency to ensure that no flux thimble tube is predicted to incur wear that exceeds 80% before the next inspection. Flux thimble tube wall thickness measurements will be trended and wear rates will be calculated based on plant-specific data. Wall thickness will be projected using plant-specific data in accordance with the WCAP-12866, Bottom Mounted Instrumentation Flux Thimble Wear, methodology.

Program Element Affected: Parameters Monitored/Inspected (Element 3),

Detection of Aging Effects (Element 4), Monitoring and Trending (Element 5), and Corrective Actions (Element 7)

2. For Braidwood Unit 1:

a. The 17 Braidwood Station, Unit 1 flux thimble tubes that exhibited indications of wear during eddy current testing performed during A1R15 Refueling Outage (Fall 2010), will be replaced or removed from service during A1R18 Refueling Outage (Spring 2015), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program. (Flux thimble tubes 1 (J-8), 8 (K-6), 9 (H-11), 12 (E-9), 14 (H-4), 18 (L-11), 19 (L-5), 21 (E-11), 23 (D-10), 36 (J-14), 37 (P-9), 41 (N-4), 44 (R-8), 45 (N-13), 48 (P-4), 54 (A-11), 55 (N-14))

b. The remaining Braidwood Station, Unit 1 flux thimble tubes, not replaced during A1R18, will be replaced or removed from service during A1R19 Refueling Outage (Fall 2016), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program.

c. Following A1R19, any Braidwood Station, Unit 1 flux thimble tube will be replaced every three (3) two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the Flux Thimble Tube Inspection program.

Program Element Affected: Corrective Actions (Element 7)

RS-15-107 Enclosure B Page 8 of 8

3. For Braidwood Unit 2:

a. The 29 Braidwood Station, Unit 2 flux thimble tubes that exhibited indications of wear during eddy current testing performed during A2R15 Refueling Outage (Spring 2011) and not replaced during A2R17 Refueling Outage (Spring 2014), will be replaced or removed from service during A2R18 Refueling Outage (Fall 2015), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program. (Flux thimble tubes 1 (J-8), 4 (H-6), 5 (F-8), 6 (J-10), 7 (F-7), 9 (H-11), 10 (L-8), 11 (G-5),

18 (L-11), 22 (K-12), 23 (D-10), 24 (H-13), 25 (N-8), 26 (H-3), 27 (C-8), 29 (N-6), 32 (L-13), 33 (C-5), 34 (H-2), 36 (J-14), 37 (P-9), 40 (F-14), 41 (N-4),

42 (D-3), 45 (N-13), 46 (J-1), 50 (R-6), 52 (L-15), 56 (N-2))

b. The remaining Braidwood Station, Unit 2 flux thimble tubes, not replaced during A2R17 or A2R18, will be replaced or removed from service during A2R19 Refueling Outage (Spring 2017), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program.

c. Following A2R19, any Braidwood Station, Unit 2 flux thimble tube will be replaced every three (3) two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the Flux Thimble Tube Inspection program.

Program Element Affected: Corrective Actions (Element 7)

RS-15-107 Enclosure C Page 1 of 3 Enclosure C Byron and Braidwood Stations, Units 1 and 2, License Renewal Commitment List Update This Enclosure identifies commitments made in this document and is an update to the Byron and Braidwood Station (BBS) LRA Appendix A, Table A.5, License Renewal Commitment List.

Any other actions discussed in the submittal represent intended or planned actions and are described to the NRC for the NRCs information and are not regulatory commitments. Changes to the BBS LRA Appendix A, Table A.5 License Renewal Commitment List are as a result of this submittal.

Notes:

To facilitate understanding, portions of the original License Renewal Commitment List have been repeated in this Enclosure, with revisions indicated.

Existing LRA text, as modified by subsequent submittals, is shown in normal font.

Changes are highlighted with bold italics for inserted text and strikethroughs for deleted text.

RS-15-107 Enclosure C Page 2 of 3 As a result of the response provided in Enclosure A of this letter, LRA Appendix A, Table A.5 License Renewal Commitment List, Item 24 on page A-80, is revised as shown below. The correspondence that led to this commitment modification is listed in the SOURCE column. Any other actions described in this submittal represent intended or planned actions. They are described for the NRCs information and are not regulatory commitments. Additions are indicated with bolded italics; deletions are shown with strikethroughs.

NO. PROGRAM OR IMPLEMENTATION COMMITMENT SOURCE TOPIC SCHEDULE*

24 Flux Thimble Tube Section A.2.1.24 Inspection Flux Thimble Tube Inspection is an existing program that will be Byron: Ongoing enhanced as follows: Exelon letter (Note 3)

Braidwood: Schedule for flux RS-14-336

1. For Braidwood Units 1 and 2  : Perform corrective actions to thimble tube replacement 11/22/2014 re-establish periodic eddy current testing of the flux thimble tubes activities identified in prior to the period of extended operation to ensure that wall commitment. Exelon letter thickness is monitored to detect loss of material from the flux RS-15-071 thimble tubes. Once periodic eddy current testing is re- Corrective actions to re- 02/23/15 established, eddy current testing will be performed for each flux establish periodic eddy current thimble tube every refueling outage until sufficient data has been testing at Braidwood will be Exelon letter accumulated to establish a plant-specific eddy current testing completed either no later than RS-15-107 frequency to ensure that no flux thimble tube is predicted to incur six months prior to the PEO, or 04/13/2015 wear that exceeds 80% before the next inspection. Flux thimble before the end of the last tube wall thickness measurements will be trended and wear refueling outage prior to the rates will be calculated based on plant-specific data. Wall PEO, whichever occurs later.

thickness will be projected using plant-specific data in accordance with the WCAP-12866, Bottom Mounted Braidwood Unit 1:

Instrumentation Flux Thimble Wear, methodology. Commitment 2.a completed during A1R18 in Spring 2015

2. For Braidwood Unit 1 (Note 3):

a. The 17 Braidwood Station, Unit 1 flux thimble tubes that exhibited indications of wear during eddy current testing performed during A1R15 Refueling Outage (Fall 2010), will be replaced or removed from service during A1R18 Refueling Outage (Spring 2015), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program. (Flux thimble tubes 1 (J-8), 8 (K-6), 9 (H-11), 12 (E-9), 14 (H-4), 18 (L-11), 19 (L-5), 21 (E-11), 23 (D-10), 36 (J-14), 37 (P-9), 41 (N-4), 44 (R-8), 45 (N-13), 48 (P-4), 54 (A-11), 55 (N-14))

RS-15-107 Enclosure C Page 3 of 3 NO. PROGRAM OR IMPLEMENTATION COMMITMENT SOURCE TOPIC SCHEDULE*

b. The remaining Braidwood Station, Unit 1 flux thimble tubes, not replaced during A1R18, will be replaced or removed from service during A1R19 Refueling Outage (Fall 2016),

unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program.

c. Following A1R19, any Braidwood Station, Unit 1 flux thimble tube will be replaced every three (3) two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the Flux Thimble Tube Inspection program.

(Note 3)

3. For Braidwood Unit 2  :

a. The 29 Braidwood Station, Unit 2 flux thimble tubes that exhibited indications of wear during eddy current testing performed during A2R15 Refueling Outage (Spring 2011) and not replaced during A2R17 Refueling Outage (Spring 2014), will be replaced or removed from service during A2R18 Refueling Outage (Fall 2015), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program. (Flux thimble tubes 1 (J-8), 4 (H-6), 5 (F-8), 6 (J-10), 7 (F-7), 9 (H-11), 10 (L-8), 11 (G-5), 18 (L-11), 22 (K-12), 23 (D-10), 24 (H-13), 25 (N-8), 26 (H-3), 27 (C-8), 29 (N-6), 32 (L-13), 33 (C-5), 34 (H-2), 36 (J-14), 37 (P-9), 40 (F-14), 41 (N-4), 42 (D-3), 45 (N-13), 46 (J-1), 50 (R-6), 52 (L-15), 56 (N-2))

b. The remaining Braidwood Station, Unit 2 flux thimble tubes, not replaced during A2R17 or A2R18, will be replaced or removed from service during A2R19 Refueling Outage (Spring 2017), unless eddy current data is obtained as required by the Flux Thimble Tube Inspection program.

c. Following A2R19, any Braidwood Station, Unit 2 flux thimble tube will be replaced every three (3) two (2) refueling outages or removed from service if eddy current data is not obtained in accordance with the Flux Thimble Tube Inspection program.