ML12104A118

Response to NRC Requests for Additional Information, Dated April 5, 2012, Related to License Renewal Application

ML12104A118
Person / Time
Site:	Limerick
Issue date:	04/13/2012
From:	Gallagher M Exelon Generation Co, Exelon Nuclear
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
TAC ME6555, TAC ME6556
Download: ML12104A118 (16)

Text

Michael P. Gallagher Telephone 610-765.5958 Vice President Fax 610-765.5658 Nuclear License Renewal www.exeloncorp.com michaelp.gallagher@exeloncorp.com Exelon Nuclear 200 Exelon Way Kennett Square. PA 19348 10 CFR 50 10CFR51 10 CFR 54 April 13, 2012 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 Limerick Generating Station, Units 1 and 2 Facility Operating License Nos. NPF-39 and NPF-85 NRC Docket Nos. 50-352 and 50-353

Subject:

Response to NRC Requests for Additional Information, dated April 5, 2012, related to the Limerick Generating Station License Renewal Application

Reference:

1. Exelon Generation Company, LLC letter from Michael P. Gallagher to NRC Document Control Desk, "Application for Renewed Operating Licenses", dated June 22, 2011

2. Letter from Robert F. Kuntz (NRC) to Michael P. Gallagher (Exelon),

"Requests for Additional Information for the review of the Limerick Generating Station, Units 1 and 2, License Renewal Application (TAC Nos. ME6555, ME6556)", dated April 5, 2012 In the Reference 1 letter, Exelon Generation Company, LLC (Exelon) submitted the License Renewal Application (LRA) for the Limerick Generating Station, Units 1 and 2 (LGS). In the Reference 2 letter, the NRC requested additional information to support the staffs' review of the LRA.

Enclosed are the responses to these requests for additional information.

If you have any questions, please contact Mr. AI Fulvio, Manager, Exelon License Renewal, at 610-765-5936.

u.s. Nuclear Regulatory Commission April 13, 2012 Page 2 I declare under penalty of perjury that the foregoing is true and correct.

Executed on 4-/3 - ;l01 z..

Respectfully,

~~

Michael P. Gallagher Vice President - License Renewal Projects Exelon Generation Company, LLC

Enclosures:

A: Responses to Requests for Additional Information B: Updates to affected LGS LRA sections C: LGS License Renewal Commitment List Changes cc: Regional Administrator - NRC Region I NRC Project Manager (Safety Review), NRR-DLR NRC Project Manager (Environmental Review), NRR-DLR NRC Project Manager, NRR- DORL Limerick Generating Station NRC Senior Resident Inspector, Limerick Generating Station R. R. Janati, Commonwealth of Pennsylvania

Enclosure A Page 1 of 5 Enclosure A Responses to Requests for Additional Information related to various sections of the LGS License Renewal Application (LRA)

RAI 3.5.2.3.2-1.1 RAI B.2.1.7-2.1 RAI B.2.1.13-2.1

Enclosure A Page 2 of 5 RAI 3.5.2.3.2-1.1

Background

In the response to RAI 3.5.2.3.2-1, PVC roofing scuppers being managed for cracking were added to the Structures Monitoring program. In the response to RAI 3.5.2.3.11-1, fiberglass metal components (permanent drywell shielding) being managed for rips and tears were added to the Structures Monitoring program.

Issue LRA Section B.2.1.35, Structures Monitoring, "Program Description," does not include polymeric components being managed for cracking, rips, and tears. In addition, Enhancement No. 2 lists newly added components; however, roofing scuppers and fiberglass metal components (permanent drywell shielding) were not included in the list when the aging management review (AMR) tables were updated.

Request Confirm that the Structures Monitoring program will manage polymeric components within the scope of the program for cracking, rips and tears and that the roofing scuppers and fiberglass metal components (permanent drywell shielding) are within the scope of the Structures Monitoring program. Revise the Structures Monitoring program as necessary to address these items.

Exelon Response The PVC roofing scuppers and the permanent drywell shielding encased in Alpha Maritex (fiberglass) material are within the scope of and managed by the Structures Monitoring program.

LRA Section B.2.1.35, Structures Monitoring, Program Description is revised to include fiberglass fabric for the permanent drywell shielding blankets and PVC roof scuppers.

Enhancement 2 for the Structures Monitoring program is revised in LRA Sections A.2.1.35, B.2.1.35 and in Table A.5 commitment 35 to include permanent drywell shielding and roof scupper components.

LRA Sections A.2.1.35 and B.2.1.35 are revised as shown in Enclosure B.

LRA Table A.5, commitment 35 is revised to include permanent drywell shielding and roof scuppers as shown in Enclosure C.

RAI B.2.1.7-2.1

Background

The response to RAI B.2.1.7-2, provided by letter dated February 15, 2012, stated that the Boiling Water Reactor (BWR) Stress Corrosion Cracking Program includes BWR piping and piping welds made of austenitic stainless steel and nickel alloy regardless of American Society

Enclosure A Page 3 of 5 of Mechanical Engineers (ASME) Code classification, consistent with the Generic Aging Lessons Learned (GALL) Report. The response also stated that determination of program scope included screening of all BWR piping and piping welds made of austenitic stainless steel that are four inches or greater in nominal diameter containing reactor coolant at a temperature greater than 93 °C (200 °F) during power operation, regardless of ASME Code classification.

The response further stated that this screening identified only ASME Code Class 1 piping as within the scope of the BWR Stress Corrosion Cracking Program.

In comparison, the revised Update Final Safety Analysis (UFSAR) supplement (LRA Section A.2.1.7) provided in the response states that the BWR Stress Corrosion Cracking aging management program is an existing augmented Inservice Inspection Program that manages intergranular stress corrosion cracking (IGSCC) in reactor coolant pressure boundary piping and piping components made of stainless steel and nickel based alloy, regardless of code classification, as delineated in NUREG-0313, Revision 2, and NRC Generic Letter 88-01 and its Supplement 1.

Issues The revision to the UFSAR supplement, which includes the reactor coolant pressure boundary piping, is in apparent conflict with the program description provided in response to RAI B.2.1.7-2, which indicates that the scope of program includes all relevant piping regardless of ASME Code classification.

Request Justify why the revision to the UFSAR supplement (LRA Section A.2.1.7) includes reactor coolant pressure boundary piping, inconsistent with the response indicating that the scope of program includes relevant piping and piping welds regardless of ASME Code classification.

Alternatively, revise the UFSAR supplement (LRA Section A.2.1.7) to include relevant piping and piping welds without a reference to reactor coolant pressure boundary piping and piping welds, consistent with the program description provided in the response to RAI B.2.1.7-2.

Exelon Response The UFSAR supplement (LRA Section A.2.1.7) is revised as shown in Enclosure B to include relevant piping and piping welds without a reference to reactor coolant pressure boundary piping and piping components, consistent with the program description provided in the Exelon response to RAI B.2.1.7-2.

RAI B.2.1.13-2.1

Background

The response to RAI B.2.1.13-2, dated February 15, 2012, stated that the loss of material due to cavitation erosion in the reactor enclosure cooling water system piping will be managed by the Closed Treated Water Systems program, which includes an enhancement for periodic condition monitoring using non-destructive examination. The staff notes that LRA Section B.2.1.13 states that the enhancement includes condition and performance monitoring to verify the effectiveness of the water chemistry control at mitigating aging effects. In addition, the staff notes that LRA Section B.2.1.13 describes the Closed Treated Water Systems program as a

Enclosure A Page 4 of 5 mitigation program that includes water treatment to modify the chemical composition of the water such that the function of the equipment is maintained and such that the effects of corrosion are minimized.

The response to RAI B.2.1.13-2 also stated that loss of material due to cavitation erosion was not considered an applicable aging effect, and that cavitation erosion is a design or operating deficiency that is addressed during the current term of operation by the corrective action program. The staff notes that the design or operating deficiency, which is causing the cavitation erosion in the reactor enclosure cooling water system was not corrected, but instead was addressed by implementing periodic monitoring of the loss of material. The response stated that a recurring task was initiated to periodically monitor this piping for cavitation erosion, with an initial frequency of 4 years, and once a trend has been established, the inspection frequency will be re-evaluated and adjusted accordingly. The staff notes that these aspects are not reflected in the program enhancement, which does not address monitoring and trending and does not describe reevaluating the initial 4-year inspection frequency after a trend has developed.

Issue The loss of material due to cavitation erosion does not appear to be adequately managed by the Closed Treated Water Systems program, because the program minimizes the effects of corrosion through water chemistry controls, and the loss of material due to cavitation erosion is not related to water chemistry control. In addition, although the program enhancement includes condition monitoring activities using non-destructive examinations, the stated purpose of the enhancement is to verify the effectiveness of water chemistry control, and the enhancement does not discuss the initial 4-year inspection frequency or the trending activities to adjust the inspection frequency.

In addition, since the loss of material is caused by a design/operating deficiency, it was not clear to the staff whether variations in operating conditions can affect the cavitation erosion rate, and if so, whether the parameters monitored or inspected program element needs to monitor temperatures, flow rates, or other parameters in establishing the cavitation erosion trend.

Request Provide a detailed description of the proposed aging management program to manage loss of material due to cavitation erosion in reactor enclosure cooling water system piping. Include a discussion of enhancements to the appropriate program elements of an existing AMP or a discussion of all ten program elements for a plant-specific AMP. Also include a discussion of any monitoring activities, (e.g., temperatures, flow rates), that may need to be trended in order to establish the cavitation erosion rate.

Exelon Response The loss of material due to cavitation erosion in the reactor enclosure cooling water piping to the 2A Reactor Water Cleanup System (RWCU) non-regenerative heat exchanger has been addressed for the current operating term in the LGS Corrective Action Program. The degradation is at an elbow located immediately downstream of a normally throttled valve and was initially identified by observation of noise and vibration. The valve was replaced in 2007 as part of maintenance activities and no noise or vibration has been observed since valve replacement, indicating that cavitation erosion was no longer occurring in the piping elbow.

However, the condition monitoring activities described in Exelons response to Item 1 of

Enclosure A Page 5 of 5 RAI B.2.1.13-2 will continue to remain in place to verify that the loss of material due to cavitation erosion has been arrested.

The Closed Treated Water Systems program (B.2.1.13) will be used to manage the loss of material due to cavitation erosion in the reactor enclosure cooling water piping to the 2A Reactor Water Cleanup System (RWCU) non-regenerative heat exchanger. This program includes water treatment and chemical testing activities for the management of aging effects in closed treated water systems. It also includes periodic condition monitoring activities which verify the effectiveness of water chemistry control at mitigating aging effects. A components susceptibility to cavitation erosion is not affected by water treatment or chemical testing activities. However, the periodic condition monitoring activities of the program are effective in validating that the loss of material due to cavitation erosion has been arrested or is not a significant aging effect.

Parameters Monitored or Inspected (Element 3), Detection of Aging Effects (Element 4), and Monitoring and Trending (Element 5) of the Closed Treated Water Systems program (B.2.1.13) are enhanced to include the condition monitoring activities for cavitation erosion in the reactor enclosure cooling water piping to the 2A Reactor Water Cleanup System (RWCU) non-regenerative heat exchanger as described above and in Exelons response to Item 1 of RAI B.2.1.13-2. An enhancement to Element 5 for monitoring and trending of system operating parameters (e.g., pressures, temperatures, flow rates) is not required. Valve replacement is expected to have eliminated the operational parameters that created the system conditions conducive to cavitation erosion. However, the loss of material in the piping where cavitation erosion had occurred will be monitored periodically and trended to ensure that cavitation erosion has been arrested. The initial inspection frequency of 4 years has been established in an engineering evaluation. Once a trend has been established, the inspection frequency will be re-evaluated and adjusted as necessary.

Enclosure B Page 1 of 6 Enclosure B LGS License Renewal Application Updates Notes:

• Updated LRA Sections and Tables are provided in the same order as the RAI responses contained in Enclosure A.

• To facilitate understanding, portions of the original LRA have been repeated in this Enclosure, with revisions indicated.

• Existing LRA text is shown in normal font. Changes are highlighted with bold italics for inserted text and strikethroughs for deleted text.

Enclosure B Page 2 of 6 Consistent with the response to RAI 3.5.2.3.2-1.1 provided in Enclosure A of this letter, LRA Section A.2.1.35 and Section B.2.1.35 are revised as shown below:

A.2.1.35 Structures Monitoring The Structures Monitoring program is an existing program that was developed to implement the requirements of 10 CFR 50.65 and is based on NUMARC 93-01, Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants, and Regulatory Guide 1.160, Monitoring the Effectiveness of Maintenance at Nuclear Power Plants. The program includes elements of the Masonry Walls (A.2.1.34) program. The program relies on periodic visual inspections to monitor the condition of structures and structural components, structural bolting, component supports, and masonry block walls. The inspections are conducted on a frequency not to exceed 5 years.

The Structures Monitoring aging management program will be enhanced to:

2. Add the following components and commodities:

a. Pipe, electrical, and equipment component support members

b. Pipe whip restraints and jet impingement shields

c. Panels, Racks, and other enclosures

d. Sliding surfaces

e. Sump and Pool liners

f. Electrical cable trays and conduits

g. Electrical duct banks

h. Tube tracks

i. Doors

j. Penetration seals

k. Blowout panels

l. Permanent drywell shielding

m. Roof scuppers B.2.1.35 Structures Monitoring Program Description The Structures Monitoring program is an existing condition monitoring program that was developed to implement the requirements of 10 CFR 50.65 and is based on NUMARC 93-01, Industry Guideline for Monitoring the Effectiveness of Maintenance at Nuclear Power Plants, and Regulator Guide 1.160, Monitoring the Effectiveness of Maintenance at Nuclear Power Plants. The program includes elements of the Masonry Walls (B.2.1.34) program. As a result, the program elements incorporate the requirements of NRC IEB 80-11, Masonry Wall Design, and the guidance in NRC IN 87-67, Lessons Learned from Regional Inspections of Licensee Actions in Response

Enclosure B Page 3 of 6 to IE Bulletin 80-11. The structures and structural components are inspected by qualified personnel in accordance with station procedures which will be enhanced for consistency with ACI 349.3R-02. Concrete structures are inspected for indications of deterioration and distress including evidence of leaching, loss of material, cracking, and a loss of bond, as defined in ACI 201.1R, Guide for Making a Condition Survey of Existing Buildings. Steel components are inspected for loss of material due to corrosion. Masonry walls are inspected for cracking and loss of material. Elastomers will be are monitored for hardening, shrinkage and a loss of sealing. PVC roof scuppers are monitored for cracking. The fiberglass fabric of the permanent drywell shielding blankets will be monitored for rips and tears. Environments include air-outdoor, air-indoor (uncontrolled), treated water, raw water, water-flowing, and ground water and soil.

The program also includes provisions for periodic testing and assessment of ground water chemistry and inspection of accessible below grade concrete structures. A de-watering system is not relied upon to control settlement and porous concrete was not used in the design of the LGS foundations.

Inspection frequency for the in-scope structures will not exceed 5 years, with provisions for more frequent inspections when conditions are observed that have a potential to impact an intended function. Unacceptable conditions, when found, are evaluated or corrected in accordance with the corrective action program.

Enhancements Prior to the period of extended operation, the following enhancements will be implemented in the following program elements:

2. Add the following components and commodities:

a. Pipe, electrical, and equipment component support members

b. Pipe whip restraints and jet impingement shields

c. Panels, Racks, and other enclosures

d. Sliding surfaces

e. Sump and Pool liners

f. Electrical cable trays and conduits

g. Electrical duct banks

h. Tube tracks

i. Doors

j. Penetration seals

k. Blowout panels

l. Permanent drywell shielding

m. Roof scuppers Program Element Affected: Scope of Program (Element 1)

Enclosure B Page 4 of 6 Consistent with the response to RAI B.2.1.7-2.1 provided in Enclosure A of this letter, LRA Section A.2.1.7 is revised as shown below:

A.2.1.7 BWR Stress Corrosion Cracking The BWR Stress Corrosion Cracking aging management program is an existing augmented Inservice Inspection program that manages intergranular stress corrosion cracking (IGSCC) in relevant piping and piping welds reactor coolant pressure boundary piping and piping components made of stainless steel and nickel based alloy, regardless of code classification, as delineated in NUREG-0313, Revision 2, and NRC Generic Letter 88-01 and its Supplement 1. The program includes preventive measures to mitigate IGSCC, and inspection and flaw evaluation to monitor IGSCC and its effects. The schedule and extent of the inspections are performed in accordance with the NRC staff-approved BWRVIP-75-A report for normal water chemistry conditions.

Enclosure B Page 5 of 6 Consistent with the response to RAI B.2.1.13-2.1 provided in Enclosure A of this letter, LRA Sections A.2.1.13 and B.2.1.13 are revised as shown below:

A.2.1.13 Closed Treated Water Systems The Closed Treated Water Systems program is an existing mitigation program that includes (a) nitrite-based water treatment, including pH control and the use of corrosion inhibitors for carbon steel and copper alloys, to modify the chemical composition of the water such that the function of the equipment is maintained and such that the effects of corrosion are minimized; and (b) chemical testing of the water to ensure that the water treatment program maintains the water chemistry within acceptable guidelines. The Closed Treated Water Systems program manages the loss of material and the reduction of heat transfer in piping, piping components, piping elements, tanks, and heat exchangers exposed to a closed treated water environment.

The Closed Treated Water Systems aging management program will be enhanced to:

1. Perform condition monitoring and performance monitoring, including periodic testing and opportunistic and periodic NDE, to verify the effectiveness of water chemistry control to mitigate aging effects. A representative sample of piping and components will be selected based on likelihood of corrosion and inspected at an interval not to exceed once in 10 years during the period of extended operation.

2. Perform condition monitoring for the loss of material due to cavitation erosion in the reactor enclosure cooling water piping to the 2A Reactor Water Cleanup System (RWCU) non-regenerative heat exchanger. An initial inspection frequency of 4 years has been established. The inspection frequency will be re-evaluated and adjusted as necessary based on trend data.

This These enhancements will be implemented prior to the period of extended operation.

B.2.1.13 Closed Treated Water Systems Program Description The Closed Treated Water Systems program is an existing mitigation program that includes (a) nitrite-based water treatment, including pH control and the use of corrosion inhibitors for carbon steel and copper alloys, to modify the chemical composition of the water such that the function of the equipment is maintained and such that the effects of corrosion are minimized; and (b) chemical testing of the water to ensure that the water treatment program maintains the water chemistry within acceptable guidelines. The Closed Treated Water Systems program manages the loss of material and the reduction of heat transfer in piping, piping components, piping elements, tanks, and heat exchangers exposed to a closed treated water environment.

Enclosure B Page 6 of 6 Enhancements Prior to the period of extended operation, the following enhancements will be implemented in the following program elements:

1. Perform condition monitoring and performance monitoring, including periodic testing and opportunistic and periodic NDE to verify the effectiveness of water chemistry control at mitigating aging effects. A representative sample of piping and components will be selected based on likelihood of corrosion and inspected at an interval not to exceed once in 10 years during the period of extended operation. Program Elements Affected: Parameters Monitored or Inspected (Element 3), Detection of Aging Effects (Element 4)

2. Perform condition monitoring for the loss of material due to cavitation erosion in the reactor enclosure cooling water piping to the 2A Reactor Water Cleanup System (RWCU) non-regenerative heat exchanger. An initial inspection frequency of 4 years has been established. The inspection frequency will be re-evaluated and adjusted as necessary based on trend data. Program Elements Affected: Parameters Monitored or Inspected (Element 3), Detection of Aging Effects (Element 4), Monitoring and Trending (Element 5)

Enclosure C Page 1 of 3 Enclosure C LGS License Renewal Commitment List Changes This Enclosure identifies commitments made in this document and is an update to the LGS 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 LGS LRA Appendix A, Table A.5 License Renewal Commitment List are as a result of the Exelon response to the following RAIs:

RAI 3.5.2.3.2-1.1 RAI B.2.1.13-2.1 Notes:

• Updated LRA Sections and Tables are provided in the same order as the RAI responses contained in Enclosure A.

• To facilitate understanding, portions of the original LRA have been repeated in this Enclosure, with revisions indicated.

• Existing LRA text is shown in normal font. Changes are highlighted with bold italics for inserted text and strikethroughs for deleted text.

Enclosure C Page 2 of 3 Consistent with the response to RAI 3.5.2.3.2-1.1 provided in Enclosure A of the letter, LRA Appendix A.5 is revised as shown below:

A.5 License Renewal Commitment List NO. PROGRAM OR IMPLEMENTATION COMMITMENT SOURCE TOPIC SCHEDULE 35 Structures Monitoring Structures Monitoring is an existing program that will be enhanced to: Program to be enhanced prior Section A.2.1.35 to the period of extended

2. Add the following components and commodities; operation.

a. Pipe, electrical, and equipment component support members Inspection schedule identified

b. Pipe whip restraints and jet impingement shields in commitment.

c. Panels, Racks, and other enclosures

d. Sliding surfaces

e. Sump and Pool liners

f. Electrical cable trays and conduits

g. Electrical duct banks

h. Tube tracks

i. Doors

j. Penetration seals LGS Letter

k. Blowout panels dated 4/13/12

l. Permanent drywell shielding

m. Roof scuppers RAI 3.5.2.3.2-1.1

Enclosure C Page 3 of 3 Consistent with the response to RAI B.2.1.13-2.1 provided in Enclosure A of this letter, LRA Appendix A.5 is revised as shown below:

A.5 License Renewal Commitment List IMPLEMENTATION PROGRAM OR COMMITMENT SOURCE NO. SCHEDULE TOPIC 13 Closed Treated Water Closed Treated Water Systems is an existing program that will be Program to be enhanced prior Section A.2.1.13 Systems enhanced to: to the period of extended operation.

1. Perform condition monitoring and performance monitoring, including periodic testing and opportunistic and periodic Inspection schedule identified NDE, to verify the effectiveness of water chemistry control in commitment.

to mitigate aging effects. A representative sample of piping and components will be selected based on likelihood of corrosion and inspected at an interval not to exceed once in 10 years during the period of extended operation.

2. Perform condition monitoring for the loss of material LGS Letter due to cavitation erosion in the reactor enclosure dated 4/13/12 cooling water piping to the 2A Reactor Water Cleanup System (RWCU) non-regenerative heat exchanger. An initial inspection frequency of 4 years has been RAI B.2.1.13-2.1 established. The inspection frequency will be re-evaluated and adjusted as necessary based on trend data.