ML20036D962

Nine Mile Point Nuclear Station, Peach Bottom Atomic Power Station, & Quad Cities Nuclear Power Station - Proposed Alternative to Extend Reactor Pressure Vessel Safety Relief Valve Testing Frequency

ML20036D962
Person / Time
Site:	Dresden, Peach Bottom, Nine Mile Point, Clinton, Quad Cities
Issue date:	02/04/2020
From:	Rafferty-Czincila S Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML20036D962 (39)

Text

Exelon Generation@

February 04, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461 Dresden Nuclear Power Station, Units 2 and 3 200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249 Nine Mile Point Nuclear Station, Unit 2 Renewed Facility Operating License No. NPF-69 NRC Docket No. 50-410 Peach Bottom Atomic Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278 Quad Cities Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR 29 and DPR 30 NRC Docket Nos. 50-254 and 50-265 10 CFR 50.55a

Subject:

Proposed Alternative to Extend Reactor Pressure Vessel Safety Relief Valve Testing Frequency In accordance with 10 CFR 50.55a, "Codes and standards," paragraph (z)(1), Exelon Generation Company, LLC (Exelon), hereby requests NRC approval of a proposed relief request associated with the lnservice Testing (IST) Program for the cited Exelon Nuclear Power Plants (NPPs). This request proposes to extend the Safety Relief Valve (SRV) IST Program testing frequency to 48 months for group one of one valves and to eight years for the other grouped valves. The basis for these relief requests is that implementation of the Exelon SRV Best Practices Maintenance program has resulted in the SRVs' maintaining their set point within tolerance over an eight-year period. The proposed alternative provides an acceptable level of quality and safety, equivalent to compliance with ASME Section Ill requirements.

Exelon requests your review and approval of this fleet relief request by February 04, 2021.

There are no regulatory commitments contained in this letter.

Proposed Alternative to Safety Relief Valve Testing Frequency February 04, 2020 Page 2 If you have any questions, please contact Mr. David Neff at (267) 533-1132.

Respectfully,

Attachment:

Relief Requests to Extend SRV Testing Frequency cc:

Regional Administrator - NRG Region I Regional Administrator - NRG Region Ill NRC Senior Resident Inspector - Clinton Power Station NRC Senior Resident Inspector-Dresden Nuclear Power Station NRC Senior Resident Inspector - Nine Mile Point Nuclear Station NRC Senior Resident Inspector - Peach Bottom Atomic Power Station NRC Senior Resident Inspector - Quad Cities Nuclear Power Station NRC Project Manager - Exelon Fleet NRC Project Manager - Clinton Power Station NRC Project Manager - Dresden Nuclear Power Station NRC Project Manager - Nine Mile Point Nuclear Station NRC Project Manager - Peach Bottom Atomic Power Station NRC Project Manager - Quad Cities Nuclear Power Station Illinois Emergency Management Agency - Department of Nuclear Safety R. R. Janati - Bureau of Radiation Protection, Commonwealth of Pennsylvania A L. Peterson - NYSERDA

ATTACHMENT Relief Requests Associated with the SRV Testing 8-Year Interval Relief Request No.

2205 RV-020 MSS-VR-02 01A-VRR-5 RV-08 RV-09 Description Clinton Power Station, SRV Testing 8-Year Test Interval Dresden Nuclear Power Station, Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval Nine Mile Point Nuclear Station U/2, SRV Testing 8-Year Test Interval Peach Bottom Atomic Power Station, SRV Testing 8-Year Test Interval Quad Cities Nuclear Power Station, Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval Quad Cities Nuclear Power Station, SRV Testing 8-Year Test Interval

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Clinton Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RR 2205 - Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

1.

ASME Code Component(s) Affected Component Description Class Category 1821-F041A Main Steam Line Safety/Relief Valve 1

c 1821-F041B Main Steam Line Safety/Relief Valve 1

c 1821-F041C Main Steam Line Safety/Relief Valve 1

c 1821-F041D Main Steam Line Safety/Relief Valve 1

c 1821-F041F Main Steam Line Safety/Relief Valve 1

c 1821-F041G Main Steam Line Safety/Relief Valve 1

c 1821-F041L Main Steam Line Safety/Relief Valve 1

c 1821-F047A Main Steam Line Safety/Relief Valve 1

c 1821-F047B Main Steam Line Safety/Relief Valve 1

c 1821-F047C Main Steam Line Safety/Relief Valve 1

c 1821-F047D Main Steam Line Safety/Relief Valve 1

c 1821-F047F Main Steam Line Safety/Relief Valve 1

c 1821-F051B Main Steam Line Safety/Relief Valve 1

c 1821-F051C Main Steam Line Safety/Relief Valve 1

c 1821-F051D Main Steam Line Safety/Relief Valve 1

c 1821-F051G Main Steam Line Safety/Relief Valve 1

c

2.

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2012 Edition with no addenda.

3.

Applicable Code Requirement

Division 1, Mandatory Appendix I, lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, paragraph 1-1320, Test Frequencies, Class 1 Pressure Relief Valves, subparagraph (a) 5-Year Test Interval, which states:

"Class 1 pressure relief valves shall be tested at least once every 5 yr, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20%

of the valves from each valve group shall be tested within any 24-mo interval.

This 20% shall consist of valves that have not been tested during the current 5-yr Page 1 of 6

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Clinton Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RR 2205 - Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval interval, if they exist. The test interval for any installed valve shall not exceed 5 yr. The 5-yr test interval shall begin from the date of the as-left set pressure test for each valve."

4.

Reason for Request

Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(1), an alternative is proposed to SRV testing requirements of the ASME OM-2012 Code. The basis of the request is that an SRV set pressure performance assessment supports conclusion that the proposed alternative would provide an acceptable level of quality and safety.

At Clinton Power Station (CPS) there are 16 Dikkers Model G-471 Main Steam SRVs installed on the Main Steam lines inside the Primary Containment. These valves are classified into the same IST program valve group. Mandatory Appendix I, paragraph 1-1320 requires the installed SRVs be pressure tested within five years from the date of the as-left set pressure test for each valve. As discussed in the NRC-approved CPS Relief Request 2202 (Reference 1) and the submitted Relief Request 2202 (Reference 2), ASME Code Case OMN-17 is being utilized to extend the l-1320(a), five-year test interval to six years, along with the potential use of a six-month grace period. CPS is currently operating on a 24-month refueling cycle. This relief request allowed CPS to go from testing all of the 16 SRVs over two refueling outages, to testing the 16 SRVs over three refueling outages, potentially reducing the number of SRVs being tested over three refueling outages by seven SRVs. The CPS SRVs have continued to show reliable set pressure test performance as described in Section 5 below.

A performance assessment of the CPS Dikkers Model G-471 SRVs concluded that there is reasonable assurance that each SRV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval. Extending the SRV test interval from six to eight years will further reduce the number of valves required to be tested every outage, thereby reducing occupational radiological exposures.

5.

Proposed Alternative and Basis for Use As an alternative to the Code-required 5-year test interval per Mandatory Appendix I, paragraph l-1320(a), CPS has been utilizing NRC-approved Relief Request MSS-VR-01 (Reference 1 ). This Relief Request allows CPS to establish a six-year test interval for the subject Class 1 SRVs provided CPS adheres to the additional requirements stipulated within ASME Code Case OMN-

17.

Page 2of6

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Clinton Power Station Proposed Alternative in Accordance with 1 O CFR 50.55a(z)(1 ),

RR 2205 - Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval Exelon proposes that the subject SRVs be tested at least once every eight years from the date of the as-left set pressure test for each valve. Exelon proposes that relief be granted to allow for the utilization of ASME Code Case OMN-17, with two modifications. The first change extends the OMN-17 testing interval from 6 years to 8 years, with an allowed six-month grace period to coincide with the combined certification testing and refueling outage time periods, and with the interval not to exceed 8.5 years. The second change increases the minimum number of SRVs from each valve group to be tested from '20% within any 24-month interval' to '40% within any 48-month interval' with the 40% population made up of SRVs which have not been tested during the previous 96-month interval, if they exist. The additional requirements stipulated within ASME Code Case OMN-17 will be retained.

At CPS, Exelon implemented an SRV Best Practices Maintenance program in 2010 and incorporated several enhancements between 2010 and 2014 that resulted in improved SRV set point drift performance. Improvements to this program continued after 2014 to further increase the SRV reliability. Exelon recently performed an assessment pertaining to the performance of the CPS Dikkers SRVs. The SRV set point drift performance of the CPS SRVs has steadily improved due to this enhanced maintenance program. This assessment concluded that there is reasonable assurance that each SRV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval which is two years longer than the current Code Case OMN-17, six-year allowed test interval.

This assessment reviewed As-Left/As-Found set pressure data going back to 2002 and identified: 1) The valves' set pressure drift up or down, and 2) The absolute set pressure change between tests. Based on the time between the As-lett and As-Found set pressure test of each SRV, the set pressure drift was then linearly extrapolated to determine whether the SRV's set pressure would still be within the site's required +/- 3.0% tolerance following an eight-year period. An evaluation concluded that use of a linear extrapolation method provided the best mathematical approach.

Since 2015, 12 CPS valves were removed and as-found tested, and, using the linear extrapolation method, all 12 valves were projected to have lift set points within the +/- 3.0% set pressure tolerance for more than eight years. Table 1 summarizes the setpoint drift projection, in years of service, predicting when each SRV would exceed the+/- 3.0% set pressure tolerance for SRVs removed and tested since 2015.

Page 3 of 6

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Clinton Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RR 2205 - Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval The improved valve performance can be attributed to both the utilization of ASME Code Case OMN-17 which requires that all valves be disassembled and inspected prior to As-Left testing and installation, and the implementation of an Exelon SRV Best Practices Maintenance program. This program is comprised of methods and philosophies concerning maintenance, inspection and techniques which uses the SRV manufacturer's recommended maintenance practices and enhancements identified by Exelon that have been broadly termed "Best Practices." This includes as-left testing for setpoint and seat leakage. Exelon SRV Best Practices are developed from the application of the EPRl/NMAC Safety and Relief Valve Testing and Maintenance Guide (Reference 3) and from Exelon Operational Experience (OE). The Exelon SRV Best Practices have been implemented through Exelon's oversight of the valve vendor's test and rebuild processes.

The Code Case OMN-17 includes a requirement that at least 20% of the SRVs be tested every 24 months, with these 20% made up of SRVs which have not been tested during the previous 72-month interval, if they exist. Testing of a minimum number of SRVs from each valve group within any 24-month interval is intended to have some SRVs tested throughout the six-year interval that would allow for more timely discovery of performance issues than would happen if all the testing was scheduled at the end of the six-year interval. This relief request proposes to revise the 20% and 24-month testing requirements to a '48-month interval' with at least a minimum of 40% of the SRVs to be tested every 48 months, with these 40% made up of SRVs which have not been tested during the previous 96-month interval, if they exist. The '40% sample size testing within any 48-month interval' continues to meet the intent of this OM N-17 requirement.

CPS will continue to implement all other requirements contained within ASME Code Case OMN-17. During outages when there is only a partial complement of SRVs replaced, those SRVs removed shall be As-Found tested prior to resumption of electrical generation. For each SRV that fails to meet the CPS set pressure acceptance criteria tolerance, two additional SRVs shall be tested. If either of these two additional SRVs are found to not meet their CPS set pressure acceptance criteria, then all remaining SRVs within the same group shall be tested.

CPS shall also continue to disassemble and inspect each subject SRV following As-Found set pressure testing to verify that parts are free of defects resulting from time-related degradation or service-induced wear. Each valve shall also be disassembled and inspected prior to As-Left testing and installation to the requirements provided above as well as all other requirements stipulated in ASME OM Code Case OMN-17.

Page 4 of 6

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Clinton Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RR 2205 - Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval Extending the test interval from six to eight years and revising the intervening outage testing sample size and frequency are viewed acceptable based upon past performance and a mathematical evaluation which shows that the CPS Dikkers SRVs are capable of maintaining their set point within tolerance over an eight-year period. This proposed relief request will also contribute to the principals of maintaining radiation dose As Low As Reasonably Achievable (ALARA).

Using recent dose measurements associated with CPS SRVs' removal and replacement, the average radiological exposure incurred per valve has been 0.65 Rem. Extending the OMN-17 SRV testing interval from six to eight years would allow extending the schedule for testing of the 16 SRVs from three to four refueling outages, potentially providing a reduction of three SRVs tested every ten years with a potential radiological exposure savings of approximately 1.95 Rem.

Based on the application of the Exelon SRV Best Practices Maintenance program, the past performance of the SRVs at CPS and a mathematical evaluation of valve performance, there is reasonable assurance that each SRV will remain within the set point tolerance over the extended eight-year testing interval. This proposal provides an alternative which would maintain an acceptable level of valve operational readiness, provide an acceptable level of quality and safety pursuant to 10 CFR 50.55a(z)(1) and provide for reduced occupational radiological exposure.

Table 1 SRV Setpoint Performance Projection Year As-Projection to Exceeding+/- 3% Setpoint Tolerance (Years)

Found For Each SRV Removed and Tested Tested 1

2 3

4 5

2015 10.0 17.1 21.0 46.5 72.2 2017 11.5 19.9 21.2 22.7 23.6

6.

Duration of Proposed Alternative 6

192.3 24.8 This proposed alternative will be utilized for the remainder of the current IST interval.

Page 5of6

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Clinton Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RR 2205 - Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

7.

Precedent None

8.

References

1. Letter from S. J. Campbell, (USNRC Branch Chief) to M. J. Pacilio (Exelon Generation Company, LLC), "Clinton Power Station, Unit No. 1 -

Safety Evaluation of Relief Request Nos. 2201, 2202, and 3201, for Third 10-Year lnservice Testing Interval", dated June 10, 2010, (Accession Number ML101340691)

2. Exelon letter to the NRC, "Relief Requests Associated with the Fourth lnservice Testing Interval," dated May 23, 2019 (ADAMS Accession No. ML19143A305)

3. Electric Power Research Institute I Nuclear Maintenance Applications Center (EPRl/NMAC) Safety and Relief Valve Testing and Maintenance Guide, Revision of TR-105872, Technical Report 3002005362, August 2015 Page 6of6

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Dresden Nuclear Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 },

RV-02D - Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval

1.

ASME Code Component(s) Affected Component Description Class Category 2-0203-3A 3A Target Rock Relief/Safety Valve 1

c 3-0203-3A 3A Target Rock Relief/Safety Valve 1

c

2.

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2004 through 2006 Addenda.

3.

Applicable Code Requirement

Division 1, Mandatory Appendix I, lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, paragraph 1-1320, Test Frequencies, Class 1 Pressure Relief Valves, subparagraph (a) 5-Year Test Interval, which states:

"Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20% of the valves from each valve group shall be tested within any 24-month interval. This 20% shall consist of valves that have not been tested during the current 5-year interval, if they exist. The test interval for any individual valve shall not exceed 5 years."

4.

Reason for Request

Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(1), an alternative is proposed to MSRV testing requirements of the ASME OM-2004 Edition of the Code, through 2006 addenda. The basis of the request is that an MSRV set pressure performance assessment supports the conclusion that the proposed alternative would provide an acceptable level of quality and safety.

At Dresden Nuclear Power Station (DNPS), Units 2 and 3, there is a single Target Rock 3-Stage, Model 67F MSRV installed on each unit's Main Steam lines inside the drywell. This valve is classified into the same lnservice Test (IST) program valve group (i.e., group one of one on a unit). Per the requirements of ASME OM Code, Mandatory Appendix I, section l-1320(a), this valve is assigned a five-year testing interval and is required to be tested every outage in order to comply with the additional requirements that a minimum of 20% of the valves in each group are tested every 24 months. DNPS, Units 2 and Page 1 of 5

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Dresden Nuclear Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV-020 - Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval 3 are currently operating on 24-month refueling cycles. The DNPS, Units 2 and 3 MSRVs have continued to show reliable set pressure test performance as described in Section 5 below.

A performance assessment of the DNPS Units 2 and 3 Target Rock MSRVs concluded that there is reasonable assurance that each MSRV will retain the set pressure within the required drift tolerances after extending the test interval from the current 24-month interval to a proposed 48-month interval. Extending the MSRV test interval from 24 to 48 months will permit testing the MSRV every other refueling outage and a corresponding reduction in occupational radiological dose incurred during the MSRV removal, testing and re-installation maintenance activities.

5.

Proposed Alternative and Basis for Use Exelon proposes that the ASME OM Code, Mandatory Appendix I, section l-1320(a) minimum testing interval for the group 1 of 1 MSRVs be extended from 24 months to 48 months from the date of the as-left set pressure test for each valve.

At DNPS, Units 2 and 3, Exelon implemented an SRV Best Practices Maintenance program in 2010 and incorporated several enhancements between 2010 and 2014 that resulted in improved MSRV set point drift performance.

Improvements to this program continued after 2014 to further increase the MSRV reliability. Exelon recently performed an assessment pertaining to the performance of the DNPS, Units 2 and 3, Target Rock MSRVs. The MSRV set point drift performance of the DNPS, Units 2 and 3, MS RVs has steadily improved due to this enhanced maintenance program. This assessment concluded that there is reasonable assurance that each MSRV will retain the set pressure within the required drift tolerances after extending the test interval from the current 24-month interval to a proposed 48-month interval.

This assessment reviewed As-Left/As-Found set pressure data going back to 1998 and identified: 1) Whether the valves' set pressure drifted up or down, and

2) The absolute set pressure change between tests. Based on the time between the As-Left and As-Found set pressure test of each MSRV, the set pressure drift was then linearly extrapolated to determine whether the MSRV's set pressure would still be within the site's required+/- 3.0% tolerance following a 48-month period. An evaluation concluded that use of linear extrapolation provides the best mathematical approach.

Since 2014, five DNPS, Units 2 and 3, valves were removed and as-found tested, and, using the linear extrapolation method, four of the five valves were projected to have lift set points within the+/- 3.0% set pressure tolerance for more Page 2 of 5

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Dresden Nuclear Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV-020 - Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval than 48-months. Table 1 summarizes the set pressure test performance, in years of service, predicting when each MSRV would exceed the +/- 3.0% set pressure tolerance for MSRVs removed and tested since 2014. An evaluation of the one valve that did not meet the 48-month set point tolerance criteria was performed and the table note provides a summary identifying the cause for the set point drift, how the Exelon SRV Best Practices Maintenance program addresses the cause, and the corrective actions performed.

Today's improved valve performance can be attributed to implementation of an Exelon MSRV Best Practices Maintenance program which requires that all valves be disassembled and inspected prior to As-Left testing and installation. This program is comprised of methods and philosophies concerning maintenance, inspection and techniques which uses the MSRV manufacturer's recommended maintenance practices and enhancements identified by Exelon that have been broadly termed "Best Practices". Exelon MSRV Best Practices are developed from the application of the EPRl/NMAC Safety and Relief Valve Testing and Maintenance Guide (Reference 1) and from Exelon Operational Experience (OE). The Exelon MSRV Best Practices have been implemented through Exelon's oversight of the valve vendor's test and rebuild processes.

DNPS will continue to disassemble and inspect each subject MSRV following As-Found set pressure testing to verify that parts are free of defects resulting from time-related degradation or service-induced wear. Each valve shall also be disassembled and inspected prior to As-Left testing and installation in accordance with the Exelon MSRV Best Practices Maintenance program.

Extending the test interval from 24 months to 48 months is viewed as acceptable based upon past performance and a mathematical evaluation which shows that the DNPS Target Rock MSRVs are capable of maintaining their set point within tolerance over a 48-month period. This proposed relief request will also contribute to the principals of maintaining radiation dose As Low As Reasonably Achievable (ALARA).

Using recent dose measurements associated with DNPS, Units 2 and 3, MSRVs removal and replacement, the average radiological exposure incurred per valve has been 0.52 Rem. Extending the MSRV testing interval from 24 to 48 months would allow extending the schedule for testing of the MSRV on each unit from every refueling outage to every-other refueling outage, potentially providing a reduction of two MSRVs tested every ten years per unit. This can result in a potential radiological exposure savings of approximately 2 Rem for the station over a ten-year IST interval.

Based on the application of the Exelon SRV Best Practices Maintenance program, the past performance of the MSRVs at DNPS and a mathematical evaluation of valve performance, there is reasonable assurance that each MSRV Page 3 of 5

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Dresden Nuclear Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RV-020 - Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval will remain within the set point tolerance over the extended 48-month testing interval. This proposal provides an alternative which would maintain an acceptable level of valve operational readiness, provide an acceptable level of quality and safety pursuant to 10 CFR 50.55a(z)(1) and provide for reduced occupational radiological exposure.

Table 1 MSRV Setpoint Performance Projection Note:

Year As-Found Tested 2014 2015 2016 2017 2018 Setpoint Performance Projection in Years 3.01 9.4 112.0 4.01 4.4

1. This valve was disassembled, inspected and tested in 2011 before being re-installed in 2012 and was then removed in 2014 and as-found tested. The 2011 maintenance and testing occurred prior the Exelon SRV Maintenance Best Practices in 2014. Consequently, the 2014 as-found test results were out of tolerance high. This same valve was then disassembled, inspected and tested in 2014 before being re-installed in 2015 and was then removed in 2017 and as-found tested. The as-found test results in 2014 for this specific valve showed improvement in the setpoint performance projection to just above the 48-month setpoint performance criteria. The relatively low setpoint performance projection for several of the DNPS Target Rock MSRVs, compared to other experience at other Exelon nuclear power plants was reviewed as part of Dresden's evaluation. Efforts are continuing to be made towards reducing the effects of the vibrational wear at DNPS. The Exelon SRV Maintenance Best Practices were completed during the valve refurbishment in 2014 and 2017 and continued increased valve performance is expected.

6.

Duration of Proposed Alternative This proposed alternative will be utilized for the remainder of the current IST interval.

7.

Precedents None Page 4 of 5

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Dresden Nuclear Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RV-020 - Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval

8.

References

1. Electric Power Research Institute I Nuclear Maintenance Applications Center (EPRl/NMAC) Safety and Relief Valve Testing and Maintenance Guide, Revision of TR-105872, Technical Report 3002005362, August 2015 Page 5 of 5

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

1.

Unit 2, ASME Code Component(s) Affected Component Description Class Category 2MSS*PSV120 MAIN STEAM SRV 1

c 2MSS*PSV121 MAIN STEAM SRV (ADS)#

1 c

2MSS*PSV122 MAIN STEAM SRV 1

c 2MSS*PSV123 MAIN STEAM SRV 1

c 2MSS*PSV124 MAIN STEAM SRV 1

c 2MSS*PSV125 MAIN STEAM SRV 1

c 2MSS*PSV126 MAIN STEAM SRV (ADS) 1 c

2MSS*PSV127 MAIN STEAM SRV (ADS) 1 c

2MSS*PSV128 MAIN STEAM SRV 1

c 2MSS*PSV129 MAIN STEAM SRV (ADS) 1 c

2MSS*PSV130 MAIN STEAM SRV (ADS) 1 c

2MSS*PSV131 MAIN STEAM SRV 1

c 2MSS*PSV132 MAIN STEAM SRV 1

c 2MSS*PSV133 MAIN STEAM SRV 1

c 2MSS*PSV134 MAIN STEAM SRV (ADS) 1 c

2MSS*PSV135 MAIN STEAM SRV 1

c 2MSS*PSV136 MAIN STEAM SRV 1

c 2MSS*PSV137 MAIN STEAM SRV (ADS) 1 c

Note: # - Valve Includes Automatic Depressurization System (ADS) function

2.

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2012 Edition with no addenda.

3.

Applicable Code Requirement

Division 1, Mandatory Appendix I, lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, paragraph 1-1320, Test Frequencies, Class 1 Pressure Relief Valves, subparagraph (a) 5-Year Test Interval, which states:

Page 1 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval "Class 1 pressure relief valves shall be tested at least once every 5 yr, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20%

of the valves from each valve group shall be tested within any 24-mo interval.

This 20% shall consist of valves that have not been tested during the current 5-yr interval, if they exist. The test interval for any installed valve shall not exceed 5 yr. The 5-yr test interval shall begin from the date of the as-left set pressure test for each valve."

4.

Reason for Request

Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(1), an alternative is proposed to SRV testing requirements of the ASME OM-2012 Code. The basis of the request is that an SRV set pressure performance assessment supports the conclusion that the proposed alternative would provide an acceptable level of quality and safety.

At Nine Mile Point Nuclear Station (NMPNS), Unit 2, there are 18 Dikkers Model G-471 Main Steam SRVs installed on the Main Steam lines inside the drywell.

These valves are classified into the same lnservice Test (IST) program valve group. Mandatory Appendix I, paragraph 1-1320 requires the installed SRVs be pressure tested within five years from the date of the as-left set pressure test for each valve. As discussed in the NRC approved NMPNS, Unit 2 Relief Request MSS-VR-01 (Reference 1), ASME Code Case OMN-17 is being utilized to extend the 1-1320(a), five-year test interval to six years, along with the potential use of a six-month grace period. NMPNS, Unit 2 is currently operating on a 24-month refueling cycle. This relief request allowed NMPNS, Unit 2 to go from testing all the SRVs over two refueling outages, to testing all the SRVs over three refueling outages, potentially reducing the number of SRVs being tested over three refueling outages by six SRVs. The NMPNS, Unit 2 SRVs have continued to show reliable set pressure test performance as described in Section 5 below.

A performance assessment of the NMPNS Unit 2 Dikkers Model G-471 SRVs concluded that there is reasonable assurance that each SRV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval. Extending the SRV test interval from six to eight years will further reduce the number of valves required to be tested every outage, thereby reducing occupational radiological exposures.

Page 2 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

5.

Proposed Alternative and Basis for Use As an alternative to the Code-required five-year test interval per Mandatory Appendix I, paragraph l-1320(a), NMPNS Unit 2 has been utilizing NRC approved Relief Request MSS-VR-01 (Reference 1 ). This Relief Request allows NMPNS Unit 2 to establish a six-year test interval for the subject Class 1 SRVs provided NMPNS Unit 2 adheres to the additional requirements stipulated within ASME Code Case OMN-17.

Exelon proposes that the subject SRVs be tested at least once every eight years from the date of the as-left set pressure test for each valve. Exelon proposes that relief be granted to allow for the utilization of ASME Code Case OMN-17, with two modifications. The first change extends the OMN-17 testing interval from six years to eight years, with an allowed six-month grace period to coincide with the combined certification testing and refueling outage time periods, and with the interval not to exceed 8.5 years. The second change increases the minimum number of SRVs from each valve group to be tested from '20% within any 24-month interval' to '40% within any 48-month interval' with the 40%

population made up of SRVs which have not been tested during the current 96-month interval, if they exist. The additional requirements stipulated within ASME Code Case OMN-17 will be retained.

At NMPNS Unit 2, Exelon implemented an SRV Best Practices Maintenance program in 2015 and included several enhancements from the previous Exelon program that had been identified between 2010 and 2014. Improvements to this program increased the SRV reliability. Exelon recently performed an assessment pertaining to the performance of the NMPNS, Unit 2 Dikkers SRVs.

The SRV set point drift performance of the NMPNS Unit 2 SRVs has steadily improved due to this enhanced maintenance program. This assessment concluded that there is reasonable assurance that each SRV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval which is two years longer than the current Code Case OMN-17, six-year allowed test interval.

This assessment reviewed As-Left/As-Found set pressure data going back to 1998 and identified: 1) Whether the valves' set pressure drifted up or down, and

2) The absolute set pressure change between tests. Based on the time between the As-Left and As-Found set pressure test of each SRV, the set pressure drift was then linearly extrapolated to determine whether the SRV's set pressure would still be within the site's required+/- 3.0% tolerance following an eight-year period. An evaluation concluded that use of linear extrapolation provides the best mathematical approach.

Page 3 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval Since 2014, 18 NMPNS Unit 2 valves were removed and as-found tested, and, using the linear extrapolation method, 16 valves were projected to have lift set points within the+/- 3.0% set pressure tolerance for more than eight years.

Table 1 summarizes the setpoint drift projection, in years of service, predicting when each SRV would exceed the+/- 3.0% set pressure tolerance for SRVs removed and tested since 2014. An evaluation of the two valves that did not meet the eight-year set point tolerance criteria was performed and the table notes provide a summary identifying the cause for the set point drift, how the Exelon SRV Best Practices Maintenance program addresses the cause, and the corrective actions performed.

The improved valve performance can be attributed to both the utilization of ASME Code Case OMN-17 which requires that all valves be disassembled and inspected prior to As-Left testing and installation, and the implementation of an Exelon SRV Best Practices Maintenance program. This program is comprised of methods and philosophies concerning maintenance, inspection and techniques which uses the SRV manufacturer's recommended maintenance practices and enhancements identified by Exelon that have been broadly termed "Best Practices." This includes as-left testing for setpoint and seat leakage. Exelon SRV Best Practices are developed from the application of the EPRl/NMAC Safety and Relief Valve Testing and Maintenance Guide (Reference 2) and from Exelon Operational Experience (OE). The Exelon SRV Best Practices have been implemented through Exelon's oversight of the valve vendor's test and rebuild processes.

The Code Case OMN-17 includes a requirement that at least 20% of the SRVs be tested every 24 months, with these 20% made up of SRVs which have not been tested during the current 72-month interval, if they exist. Testing of a minimum number of SRVs from each valve group within any 24-month interval is intended to have some SRVs tested throughout the six-year interval that would allow for more timely discovery of performance issues than would happen if all the testing was scheduled at the end of the six-year interval. This relief request proposes to revise the 20% and 24-month testing requirements to a '48-month interval' with at least a minimum of 40% of the SRVs to be tested every 48 months, with these 40% made up of SRVs which have not been tested during the current 96-month interval, if they exist. The '40% sample size testing within any 48-month interval' continues to meet the intent of this OMN-17 requirement.

NMPNS will continue to implement all other requirements contained within ASME Code Case OMN-17. During outages when there is only a partial complement of SRVs replaced, those SRVs removed shall be As-Found tested prior to resumption of electrical generation. For each SRV that fails to meet the NMPNS set pressure acceptance criteria tolerance, two additional SRVs shall be tested.

Page 4of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval If either of these two additional SRVs are found to not meet their NMPNS set pressure acceptance criteria, then all remaining SRVs within the same group shall be tested.

NMPNS shall also continue to disassemble and inspect each subject SRV following As-Found set pressure testing to verify that parts are free of defects resulting from time-related degradation or service-induced wear. Each valve shall be disassembled and inspected prior to As-Left testing and installation to the requirements provided above as well as all other requirements stipulated in ASME OM Code Case OMN-17.

Extending the test interval from six to eight years and revising the intervening outage testing sample size and frequency are viewed acceptable based upon past performance and a mathematical evaluation which shows that the NMPNS Dikkers SRVs are capable of maintaining their set point within tolerance over an eight-year period. This proposed relief request will also contribute to the principals of maintaining radiation dose As Low As Reasonably Achievable (ALARA).

Using recent dose measurements as~ociated with NMPNS, Unit 2 SRVs' removal and replacement, the average radiological exposure incurred per valve has been 0.5 Rem. Extending the OMN-17 SRV testing interval from six to eight years would allow extending the schedule of testing of the 18 SRVs from three to four refueling outages, potentially providing a reduction of three SRVs tested every ten years with a potential radiological exposure savings of approximately 1.5 Rem.

Based on the application of the Exelon SRV Best Practices Maintenance program, the past performance of the SRVs at NMPNS and a mathematical evaluation of valve performance, there is reasonable assurance that each SRV will remain within the set point tolerance over the extended eight-year testing interval. This proposal provides an alternative which would maintain an acceptable level of valve operational readiness, provide an acceptable level of quality and safety pursuant to 10 CFR 50.55a(z)(1) and provide for reduced occupational radiological exposure.

Page 5of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1},

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval Year As-Found Tested 2014 2016 2018 Notes:

Table 1 SRV Setpoint Performance Projection Projection to Exceeding+/- 3% Setpoint Tolerance (Years)

For Each SRV Removed and Tested 1

2 3

4 5

4.71 10.0 19.4 20.6 27.9 6.1 2 8.3 13.6 15.0 32.9 9.9 10.1 18.2 32.0 39.4 6

48.9 52.3 107.6 1 This valve was disassembled, inspected and tested before being re-installed in 2010 and was then removed in 2014 and as-found tested. The 2010 maintenance and testing occurred prior to the addition of a seat leak tightness test that was added to the Exelon SRV Maintenance Best Practices in 2015 for NMP2. Consequently, the 2014 as-found test results were out of tolerance low with elevated seat leakage. The Exelon SRV Maintenance Best Practices were completed during the valve refurbishment and increased valve performance is expected. (Reference 4. 72, valve 160964 Cell T242, and EC text).

2 This valve was disassembled, inspected and tested before being re-installed in 201 O and was then removed in 2016 and as-found tested. The 2010 maintenance and testing occurred prior to the addition of a seat leak tightness test that was added to the Exelon SRV Maintenance Best Practices in 2015 for NMP2. Consequently, the 2014 as-found test results were out of tolerance low with elevated seat leakage. The Exelon SRV Maintenance Best Practices were completed during the valve refurbishment and increased valve performance is expected. (Reference 6.15 valve 160968 cell T282 and EC)

Page 6of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station Unit 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

MSS-VR Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

6.

Duration of Proposed Alternative This proposed alternative will be utilized for the remainder of the current IST interval.

7.

Precedent None

8.

References

1. Letter from J. G. Danna, (USNRC Chief Plant Licensing Branch I) to B. C.

Hanson (Exelon Generation Company, LLC), "Nine Mile Point Nuclear Station, Units 1 and 2 - Relief From the Requirements of ASME Code (EPID L-2017-LLR-0145 Through EPID L-2017-LLR-0152, dated November 13, 2018, (Accession Number ML18275A139)

2. Electric Power Research Institute I Nuclear Maintenance Applications Center (EPRl/NMAC) Safety and Relief Valve Testing and Maintenance Guide, Revision of TR-105872, Technical Report 3002005362, August 2015 Page 7 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

1.

ASME Code Component(s) Affected Component Description Class Category RV-2-02-071A Main Steam Safety Relief Valve 1

c RV-2-02-071 B Main Steam Safety Relief Valve 1

c RV-2-02-071C Main Steam Safety Relief Valve 1

c RV-2-02-071 D Main Steam Safety Relief Valve 1

c RV-2-02-071 E Main Steam Safety Relief Valve 1

c RV-2-02-071 F Main Steam Safety Relief Valve 1

c RV-2-02-071G Main Steam Safety Relief Valve 1

c RV-2-02-071 H Main Steam Safety Relief Valve 1

c RV-2-02-071J Main Steam Safety Relief Valve 1

c RV-2-02-071 K Main Steam Safety Relief Valve 1

c RV-2-02-071 L Main Steam Safety Relief Valve 1

c RV-3-02-071 A Main Steam Safety Relief Valve 1

c RV-3-02-0718 Main Steam Safety Relief Valve 1

c RV-3-02-071C Main Steam Safety Relief Valve 1

c RV-3-02-071 D Main Steam Safety Relief Valve 1

c RV-3-02-071 E Main Steam Safety Relief Valve 1

c RV-3-02-071 F Main Steam Safety Relief Valve 1

c RV-3-02-071G Main Steam Safety Relief Valve 1

c RV-3-02-071 H Main Steam Safety Relief Valve 1

c RV-3-02-071J Main Steam Safety Relief Valve 1

c RV-3-02-071 K Main Steam Safety Relief Valve 1

c RV-3-02-071L Main Steam Safety Relief Valve 1

c

2.

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2012 Edition with no addenda.

3.

Applicable Code Requirement

Division 1, Mandatory Appendix I, lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, paragraph 1-1320, Test Frequencies, Page 1 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval Class 1 Pressure Relief Valves, subparagraph (a) 5-Year Test Interval, which states:

"Class 1 pressure relief valves shall be tested at least once every 5 yr., starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20%

of the valves from each valve group shall be tested within any 24-mo interval.

This 20% shall consist of valves that have not been tested during the current 5-yr interval, if they exist. The test interval for any installed valve shall not exceed 5 yr. The 5-yr test interval shall begin from the date of the as-left set pressure test for each valve."

4.

Reason for Request

Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(1 ), an alternative is proposed to SRV testing requirements of the ASME OM-2012 Code. The basis of the request is that an SRV set pressure performance assessment supports the conclusion that the proposed alternative would provide an acceptable level of quality and safety.

At Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3, there are 11 Target Rock Models73-67F and 74 -67F (3-stage) Main Steam SRVs installed on each unit's Main Steam lines inside the drywell. These valves are classified into the same lnservice Test (IST) program valve group. Mandatory Appendix I, paragraph 1-1320 requires the installed SRVs be pressure tested within five years from the date of the as-left set pressure test for each valve. As discussed in the NRC-approved PBAPS, Units 2 and 3 Relief Request 01A-VRR-3 (Reference 1 ),

ASME Code Case OMN-17 is being utilized to extend the l-1320(a), five-year test interval to six years, along with the potential use of a six-month grace period.

PBAPS, Units 2 and 3 are currently operating on 24-month refueling cycles. This relief request allowed PBAPS, Units 2 and 3 to go from testing all the SRVs on each unit over two refueling outages, to testing all the SRVs on each unit over three refueling outages, potentially reducing the number of SRVs being tested over three refueling outages by six SRVs per unit. The PBAPS, Units 2 and 3 SRVs have continued to show reliable set pressure test performance as described in Section 5 below.

A performance assessment of the PBAPS Units 2 and 3 Target Rock SRVs concluded that there is reasonable assurance that each SRV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval. Extending the SRV Page 2 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval test interval from six to eight years will further reduce the number of valves required to be tested every outage, thereby reducing occupational radiological exposures.

5.

Proposed Alternative and Basis for Use As an alternative to the Code-required 5-year test interval per Mandatory Appendix I, paragraph l-1320(a), PBAPS Units 2 and 3 has been utilizing NRC-approved Relief Request 01A-VRR-3 (Reference 1 ). This Relief Request allows PBAPS Units 2 and 3 to establish a six-year test interval for the subject Class 1 SRVs provided each PBAPS unit adheres to the additional requirements stipulated within ASME Code Case OMN-17.

Exelon proposes that the subject SRVs be tested at least once every eight years from the date of the as-left set pressure test for each valve. Exelon proposes that relief be granted to allow for the utilization of ASME Code Case OMN-17, with two modifications. The first change extends the OMN-17 testing interval from six years to eight years, with an allowed six-month grace period to coincide with the combined certification testing and refueling outage time periods, and with the interval not to exceed 8.5 years. The second change increases the minimum number of SRVs from each valve group to be tested from '20% within any 24-month interval' to '40% within any 48-month interval' with the 40%

population made up of SRVs which have not been tested during the previous 96-month interval, if they exist. The additional requirements stipulated within ASME Code Case OMN-17 will be retained.

At PBAPS Units 2 and 3, Exelon implemented an SRV Best Practices Maintenance program in 2010 and incorporated several enhancements between 201 O and 2014 that resulted in improved SRV set point drift performance.

Improvements to this program continued after 2014 to further increase the SRV reliability. Exelon recently performed an assessment pertaining to the performance of each unit's Target Rock SRVs. The SRV set point drift performance of each unit's SRVs has steadily improved due to this enhanced maintenance program. This assessment concluded that there is reasonable assurance that each SRV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval which is two years longer than the current Code Case OMN-17, six-year allowed test interval.

This assessment reviewed As-Left/As-Found set pressure data going back to 2011 and identified: 1) Whether the valves' set pressure drifted up or down, and

2) The absolute set pressure change between tests. Based on the time between Page 3 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval the As-Left and As-Found set pressure test of each SRV, the set pressure drift was then linearly extrapolated to determine whether the SRV's set pressure would still be within the site's required +/- 3.0% tolerance following an eight-year period. An evaluation concluded that the use of a linear extrapolation method provided the best mathematical approach.

Since 2014, 21 PBAPS Unit 2 and Unit 3, valves were removed and as-found tested, and, using the linear extrapolation method, 20 valves were projected to have lift set points within the+/- 3.0% set pressure tolerance for more than eight years. Table 1 summarizes the setpoint drift projection, in years of service, predicting when each SRV would exceed the +/- 3.0% set pressure tolerance for SRVs removed and tested since 2014. An evaluation of the one valve that did not meet the eight-year set point tolerance criteria was performed and the table notes provide a summary identifying the cause for the set point drift, how the Exelon SRV Best Practices Maintenance program addresses the cause, and the corrective actions performed.

The improved valve performance can be attributed to both the utilization of ASME Code Case OMN-17 which requires that all valves be disassembled and inspected prior to As-Left testing and installation, and the implementation of an Exelon SRV Best Practices Maintenance program. This program is comprised of methods and philosophies concerning maintenance, inspection and techniques which uses the SRV manufacturer's recommended maintenance practices and enhancements identified by Exelon that have been broadly termed "Best Practices." This includes as-left testing for setpoint and seat leakage. Exelon SRV Best Practices are developed from the application of the EPRl/NMAC Safety and Relief Valve Testing and Maintenance Guide (Reference 2) and from Exelon Operational Experience (OE). The Exelon SRV Best Practices have been implemented through Exelon's oversight of the valve vendor's test and rebuild processes.

The Code Case OMN-17 includes a requirement that at least 20% of the SRVs be tested every 24 months, with these 20% made up of SRVs which have not been tested during the previous 72-month interval, if they exist. Testing of a minimum number of SRVs from each valve group within any 24-month interval is intended to have some SRVs tested throughout the six-year interval that would allow for more timely discovery of performance issues than would happen if all the testing was scheduled at the end of the six-year interval. This relief request proposes to revise the 20% and 24-month testing requirements to a '48-month interval' with at least a minimum of 40% of the SRVs to be tested every 48 months, with these 40% made up of SRVs which have not been tested during the previous 96-month interval, if they exist. The '40% sample size testing within any 48-month interval' continues to meet the intent of this OMN-17 requirement.

Page 4of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval PBAPS will continue to implement all other requirements contained within ASME Code Case OMN-17. During outages when there is only a partial complement of SRVs replaced, those SRVs removed shall be As-Found tested prior to resumption of electrical generation. For each SRV that fails to meet the PBAPS set pressure acceptance criteria tolerance, two additional SRVs shall be tested.

If either of these two additional SRVs are found to not meet their PBAPS set pressure acceptance criteria, then all remaining SRVs within the same group shall be tested.

PBAPS shall also continue to disassemble and inspect each subject SRV following As-Found set pressure testing to verify that parts are free of defects resulting from time-related degradation or service-induced wear. Each valve shall also be disassembled and inspected prior to As-Left testing and installation to the requirements provided above as well as all other requirements stipulated in ASME OM Code Case OMN-17.

Extending the test interval from six to eight years and revising the intervening outage testing sample size and frequency are viewed acceptable based upon past performance and a mathematical evaluation which shows that the PBAPS Units 2 and 3 SRVs are capable of maintaining their set point within tolerance over an eight-year period. This proposed relief request to the testing requirements will also contribute to the principals of maintaining radiation dose As Low As Reasonably Achievable (ALARA).

Using recent dose measurements associated with PBAPS, Units 2 and 3 SRVs removal and replacement, the average radiological exposure incurred per valve has been approximately 1.25 Rem. Extending the OMN-17 SRV testing interval from six to eight years would allow extending the schedule of testing of the 11 SRVs on each unit from three to four refueling outages, potentially providing a reduction of two SRVs tested every ten years per unit. This can result in a potential radiological exposure savings of approximately 5 Rem for the station over a ten-year IST interval.

Based on the application of the Exelon SRV Best Practices Maintenance program, the past performance of the SRVs at PBAPS and a mathematical evaluation of valve performance, there is reasonable assurance that each SRV will remain within the set point tolerance over the extended eight-year testing interval. This proposal provides an alternative which would maintain an acceptable level of valve operational readiness, provide an acceptable level of quality and safety pursuant to 10 CFR 50.55a(z)(1) and provide for reduced occupational radiological exposure.

Page 5 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval Table 1 SRV Setpoint Performance Projection Year As-Projection to Exceeding+/- 3% Setpoint Tolerance (Years)

Found For Each SRV Removed and Tested Tested 1

2 3

4 5

2014 U2 8.1 8.6 11.1 12.6 N/A 2015 U3 36.6 70.1 164.5 N/A N/A 2016 U2 8.7 11.7 37.5 122.2 N/A 2017 U3 11.8 14.2 22.5 37.8 82.7 2018 U2 7.991 10.8 15.3 19.1 48.1 Notes:

1 This valve was disassembled, inspected and tested before being re-installed in 2012 and was then removed in 2018 and as-found tested. The 2012 maintenance and testing occurred prior to the refinement of the upgraded lapping, pilot abutment and preload gap settings optimization techniques which were added to the Exelon SRV Maintenance Best Practices procedures in 2014. Consequently, the 2018 as-found test results were out-of-tolerance low. The Exelon SRV Maintenance Best Practices will be completed during the valve refurbishment prior to re-installation and increased valve performance is expected.

6.

Duration of Proposed Alternative This proposed alternative will be utilized for the remainder of current IST interval.

7.

Precedent None Page 6 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Peach Bottom Atomic Power Station, Units 2 and 3 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

01A-VRR-5 Reactor Pressure Vessel Safety Relief Valve (SRV) Testing 8-Year Test Interval

8.

References

1. Letter from J. G. Danna, (USN RC Chief Plant Licensing Branch) to B. C.

Hanson (Exelon Generation Company, LLC), "Peach Bottom Atomic Power Station, Units 2 and 3-Safety Evaluation of Relief Request 01A-VRR-3 Regarding the Fifth 10-Year Interval of the lnservice Testing Program (EPID L-2017-LLR-0096), dated February 7, 2018, (Accession Number ML18036A156)

2. Electric Power Research Institute I Nuclear Maintenance Applications Center (EPRl/NMAC) Safety and Relief Valve Testing and Maintenance Guide, Revision of TR-105872, Technical Report 3002005362, August 2015 Page 7 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RV Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval

1.

ASME Code Component(s) Affected Component Description Class Category 1-0203-003A MS-3A Safety/Relief Valve (Target Rock}

1 c

2-0203-003A MS-3A Safety/Relief Valve (Target Rock) 1 c

2.

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2004 through 2006 Addenda.

3.

Applicable Code Requirement

Division 1, Mandatory Appendix I, lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, paragraph 1-1320, Test Frequencies, Class 1 Pressure Relief Valves, subparagraph (a) 5-Year Test Interval, which states:

"Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20% of the valves from each valve group shall be tested within any 24month interval. This 20% shall consist of valves that have not been tested during the current 5-year interval, if they exist. The test interval for any individual valve shall not exceed 5 years."

4.

Reason for Request

Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(1), an alternative is proposed to MSRV testing requirements of the ASME OM-2004 Edition of the Code, through 2006 addenda. The basis of the request is that an MSRV set pressure performance assessment supports that the proposed alternative would provide an acceptable level of quality and safety.

At Quad Cities Nuclear Power Station (QCNPS), Units 1 and 2, there is a single Target Rock 3 Stage, Model 74-67F MSRV installed on each unit's Main Steam lines inside the drywell. This valve is classified into the same lnservice Test (IST) program valve group (i.e., group one of one on a unit). Per the requirements of ASME OM Code, Mandatory Appendix I, section l-1320(a), this valve is assigned a five-year testing interval and is required to be tested every outage in order to comply with the additional requirements that a minimum of 20% of the valves in each group are tested every 24 months. QCNPS, Units 1 Page 1of4

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval and 2 are currently operating on 24-month refueling cycles. The QCNPS, Units 1 and 2 MSRVs have continued to show reliable set pressure test performance as described in Section 5 below.

A performance assessment of the QCNPS Units 1 and 2 Target Rock MSRVs concluded that there is reasonable assurance that each MSRV will retain the set pressure within the required drift tolerances after extending the test interval from the current 24-month interval to a proposed 48-month interval. Extending the MSRV test interval from 24 to 48 months will permit testing the MSRV every other refueling outage and a corresponding reduction in occupational radiological dose incurred during the MSRV removal, testing and re-installation maintenance activities.

5.

Proposed Alternative and Basis for Use Exelon proposes that the ASME OM Code, Mandatory Appendix I, section l-1320(a) minimum testing interval for the group 1 of 1 MSRVs be extended from 24-months to 48-months from the date of the as-left set pressure test for each valve.

At QCNPS, Units 1 and 2, Exelon implemented an SRV Best Practices Maintenance program in 2010 and incorporated several enhancements between 2010 and 2014 that resulted in improved MSRV set point drift performance.

Improvements to this program continued after 2014 to further increase the MSRV reliability. Exelon recently performed an assessment pertaining to the performance of the QCNPS, Units 1 and 2, Target Rock MSRVs. The MSRV set point drift performance of the QCNPS, Units 1 and 2, MSRVs has steadily improved due to this enhanced maintenance program. This assessment concluded that there is reasonable assurance that each MSRV will retain the set pressure within the required drift tolerances after extending the test interval from the current 24-month interval to a proposed 48-month interval.

This assessment reviewed As-Left/As-Found set pressure data going back to 1998 and identified: 1) Whether the valves' set pressure drifted up or down, and

2) The absolute set pressure change between tests. Based on the time between the As-Left and As-Found set pressure test of each MSRV, the set pressure drift was then linearly extrapolated to determine whether the MSRV's set pressure would still be within the site's required+/- 3.0% tolerance following a 48-month period. An evaluation concluded that use of linear extrapolation provides the best mathematical approach.

Since 2014, five QCNPS, Units 1 and 2, valves were removed and as-found tested, and, using the linear extrapolation method, all five valves were projected to have lift set points within the+/- 3.0% set pressure tolerance for more than Page 2 of 4

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station Proposed Alternative in Accordance with 1 O CFR 50.55a(z)(1 ),

RV Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval 48-months. Table 1 summarizes the set pressure test performance, in years of service, predicting when each MSRV would exceed the+/- 3.0% set pressure tolerance for MSRVs removed and tested since 2014.

Today's improved valve performance can be attributed to implementation of an Exelon MSRV Best Practices Maintenance program which requires that all valves be disassembled and inspected prior to As-Left testing and installation. This program is comprised of methods and philosophies concerning maintenance, inspection and techniques which uses the MSRV manufacturer's recommended maintenance practices and enhancements identified by Exelon that have been broadly termed "Best Practices". Exelon MSRV Best Practices are developed from the application of the EPRl/NMAC Safety and Relief Valve Testing and Maintenance Guide (Reference 1) and from Exelon Operational Experience (OE). The Exelon MSRV Best Practices have been implemented through Exelon's oversight of the valve vendor's test and rebuild processes.

QCNPS will continue to disassemble and inspect each subject MSRV following As-Found set pressure testing to verify that parts are free of defects resulting from time-related degradation or service-induced wear. Each valve shall also be disassembled and inspected prior to As-Left testing and installation in accordance with the Exelon MSRV Best Practices Maintenance program.

Extending the test interval from 24-months to 48-months is viewed as acceptable based upon past performance and a mathematical evaluation which shows that the QCNPS Target Rock MSRVs are capable of maintaining their set point within tolerance over a 48-month period. This proposed relief request to the testing requirements will also contribute to the principals of maintaining radiation dose As Low As Reasonably Achievable (ALARA).

Using recent dose measurements associated with QCNPS, Units 1 and 2, MSRVs removal and replacement, the average radiological exposure incurred per valve has been 0.54 Rem. Extending the MSRV testing interval from 24 to 48 months would allow extending the schedule of testing of the MSRV on each unit from every refueling outage to every-other refueling outage, potentially providing a reduction of two MSSVs tested every ten years per unit. This can result in a potential radiological exposure savings of approximately 2 Rem for the station over a ten-year IST interval.

Based on the application of the Exelon SRV Best Practices Maintenance program, the past performance of the MSRVs at QCNPS and a mathematical evaluation of valve performance, there is reasonable assurance that each MSRV will remain within the set point tolerance over the extended 48-month testing interval. This proposal provides an alternative which would maintain an Page 3 of 4

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV Main Steam Relief/Safety Valve (MSRV) "Group of One" Testing Interval acceptable level of valve operational readiness, provides an acceptable level of quality and safety pursuant to 10 CFR 50.55a(z)(1) and provides for reduced occupational radiological exposure.

Table 1 MSSV Setpoint Performance Projection Year As-Found Tested Setpoint Performance Projection in Years 2014 4.4 2015 21.6 2016 18.2 2017 172.2 2018 25.9

6.

Duration of Proposed Alternative This proposed alternative will be utilized for the remainder of the current IST interval.

7.

Precedents None

8.

References

1. Electric Power Research Institute I Nuclear Maintenance Applications Center (EPRl/NMAC) Safety and Relief Valve Testing and Maintenance Guide, Revision of TR-105872, Technical Report 3002005362, August 2015 Page 4 of 4

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval

1.

ASME Code Component(s) Affected Component Description Class Category 1-0203-004A MS-4A Safety Valve 1

c 1-0203-0048 MS-48 Safety Valve 1

c 1-0203-004C MS-4C Safety Valve 1

c 1-0203-004D MS-4D Safety Valve 1

c 1-0203-004E MS-4E Safety Valve 1

c 1-0203-004F MS-4F Safety Valve 1

c 1-0203-004G MS-4G Safety Valve 1

c 1-0203-004H MS-4H Safety Valve 1

c 2-0203-004A MS-4A Safety Valve 1

c 2-0203-0048 MS-48 Safety Valve 1

c 2-0203-004C MS-4C Safety Valve 1

c 2-0203-004D MS-4D Safety Valve 1

c 2-0203-004E MS-4E Safety Valve 1

c 2-0203-004F MS-4F Safety Valve 1

c 2-0203-004G MS-4G Safety Valve 1

c 2-0203-004H MS-4H Safety Valve 1

c

2.

Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code), 2004 through 2006 Addenda.

3.

Applicable Code Requirement

Division 1, Mandatory Appendix I, lnservice Testing of Pressure Relief Devices in Light-Water Reactor Nuclear Power Plants, paragraph 1-1320, Test Frequencies, Class 1 Pressure Relief Valves, subparagraph (a) 5-Year Test Interval, which states:

"Class 1 pressure relief valves shall be tested at least once every 5 years, starting with initial electric power generation. No maximum limit is specified for the number of valves to be tested within each interval; however, a minimum of 20% of the valves from each valve group shall be tested within any 24-month interval. This 20% shall consist of valves that have not been tested during the current 5-year interval, if they exist. The test interval for any individual valve shall not exceed 5 years."

Page 1 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1},

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval

4.

Reason for Request

Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(1}, an alternative is proposed to MSSV testing requirements of the ASME OM-2012 Code. The basis of the request is that an MSSV set pressure performance assessment supports the conclusion that the proposed alternative would provide an acceptable level of quality and safety.

At Quad Cities Nuclear Power Station (QCNPS}, Units 1 and 2, there are eight Dresser Model 37770 MSSVs installed on each unit's Main Steam lines inside the drywell. These valves are classified into the same lnservice Test (IST) program valve group. Mandatory Appendix I, paragraph 1-1320 requires the installed MSSVs be pressure tested within five years from the date of the as-left set pressure test for each valve. As discussed in the NRC approved QCNPS, Units 1 and 2 Relief Request RV-05 (Reference 1), ASME Code Case OMN-17 is being utilized to extend the l-1320(a), five-year test interval to six years, along with the potential use of a six-month grace period. QCNPS, Units 1 and 2 are currently operating on 24 month refueling cycles. This relief request allowed QCNPS Units 1 and 2, to go from testing all the MSSVs on each unit over two refueling outages, to testing all the MSSVs on each unit over three refueling outages, potentially reducing the number of MSSVs being tested over three refueling outages by four MSSVs per unit. The QCNPS, Units 1 and 2 MSSVs have continued to show reliable set pressure test performance as described in Section 5 below.

A performance assessment of the QCNPS Units 1 and 2 Dresser MSSVs concluded that there is reasonable assurance that each MSSV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval. Extending the MSSV test interval from six to eight years will further reduce the number of valves required to be tested every outage, reducing occupational radiological exposures.

5.

Proposed Alternative and Basis for Use As an alternative to the Code-required 5-year test interval per Mandatory Appendix I, paragraph l-1320(a), QCNPS Units 1 and 2 have been utilizing NRC approved Relief Request 01A-VRR-3 (Reference 1 ). This Relief Request allows QCNPS Units 1 and 2 to establish a six-year test interval for the subject Class 1 MSSVs provided each QCNPS unit adheres to the additional requirements stipulated within ASME Code Case OMN-17.

Page 2of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval Exelon proposes that the subject MSSVs be tested at least once every eight years from the date of the as-left set pressure test for each valve. Exelon proposes that relief be granted to allow for the utilization of ASME Code Case OMN-17, with two modifications. The first change extends the OMN-17 testing interval from six years to eight years, with an allowed six-month grace period to coincide with the combined certification testing and refueling outage time periods, and with the interval not to exceed 8.5 years. The second change increases the minimum number of MSSVs from each valve group to be tested from '20% within any 24-month interval' to '40% within any 48-month interval' with the 40%

population made up of MSSVs which have not been tested during the current 96-month interval, if they exist. The additional requirements stipulated within ASME Code Case OMN-17 will be retained.

At QCNPS, Units 1 and 2, Exelon implemented an SRV Best Practices Maintenance program in 2010 and incorporated several enhancements between 2010 and 2014 that resulted in improved MSSV set point drift performance.

Improvements to this program continued after 2014 to further increase the MSSV reliability. Exelon recently performed an assessment pertaining to the performance of the QCNPS, Units 1 and 2, Dresser MSSVs. The MSSV set point drift performance of the QCNPS, Units 1 and 2, MSSVs has steadily improved due to this enhanced maintenance program. This assessment concluded that there is reasonable assurance that each MSSV will retain the set pressure within the required drift tolerances after extending the test interval from the current six-year interval to a proposed eight-year interval which is two years longer than the current Code Case OMN-17, six-year allowed test interval.

This assessment reviewed As-Left/As-Found set pressure data going back to 1998 and identified: 1) Whether the valves' set pressure drifted up or down, and

2) The absolute set pressure change between tests. Based on the time between the As-Left and As-Found set pressure test of each MSSV, the set pressure drift was then linearly extrapolated to determine whether the MSSV's set pressure would still be within the site's required+/- 3.0% tolerance following an eight-year period. An evaluation concluded that use of linear extrapolation provides the best mathematical approach.

Since 2014, 13 QCNPS, Units 1 and 2, valves were removed and as-found tested, and, using the linear extrapolation method, ten valves were projected to have lift set points within the +/- 3.0% set pressure tolerance for more than eight years. Table 1 summarizes the setpoint drift projection, in years of service, predicting when each MSSV would exceed the+/- 3.0% set pressure tolerance for MSSVs removed and tested since 2014. An evaluation of the three valves that did not meet the eight-year set point tolerance criteria was performed and the table Page 3 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval notes provide a summary identifying the cause for the set point drift, how the Exelon SRV Best Practices Maintenance program addresses the cause, and the corrective actions performed.

The improved valve performance can be attributed to both the utilization of ASME Code Case OMN-17 which requires that all valves be disassembled and inspected prior to As-Left testing and installation, and the implementation of an Exelon SRV Best Practices Maintenance program. This program is comprised of methods and philosophies concerning maintenance, inspection and techniques which uses the MSSV manufacturer's recommended maintenance practices and enhancements identified by Exelon that have been broadly termed "Best Practices." This includes as-left testing for setpoint and seat leakage. Exelon SRV Best Practices are developed from the application of the EPRl/NMAC Safety and Relief Valve Testing and Maintenance Guide (Reference 2) and from Exelon Operational Experience (OE). The Exelon SRV Best Practices have been implemented through Exelon's oversight of the valve vendor's test and rebuild processes.

The Code Case OMN-17 includes a requirement that at least 20% of the MSSVs be tested every 24 months, with these 20% made up of MSSVs which have not been tested during the current 72-month interval, if they exist. Testing of a minimum number of MSSVs from each valve group within any 24-month inte!Val is intended to have some MSSVs tested throughout the six-year interval that would allow for more timely discovery of performance issues than would happen if all the testing was scheduled at the end of the six-year interval. This relief request proposes to revise the 20% and 24-month testing requirements to a '48-month interval' with at least a minimum of 40% of the MSSVs to be tested every 48 months, with these 40% made up of MSSVs which have not been tested during the current 96-month interval, if they exist. The '40% sample size testing within any 48-month interval' continues to meet the intent of this OMN-17 requirement.

QCNPS will continue to implement all other requirements contained within ASME Code Case OMN-17. During outages when there is only a partial complement of MSSVs replaced, those MSSVs removed shall be As-Found tested prior to resumption of electrical generation. For each MSSV that fails to meet the QCNPS set pressure acceptance criteria tolerance, two additional MSSVs shall be tested. If either of these two additional MSSVs are found to not meet their QCNPS set pressure acceptance criteria, then all remaining MSSVs within the same group shall be tested.

Page 4of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1 ),

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval QCNPS shall also continue to disassemble and inspect each subject MSSV following As-Found set pressure testing to verify that parts are free of defects resulting from time-related degradation or service-induced wear. Each valve shall be disassembled and inspected prior to As-Left testing and installation to the requirements provided above as well as all other requirements stipulated in ASME OM Code Case OMN-17.

Extending the test interval from six to eight years and revising the intervening outage testing sample size and frequency are viewed acceptable based upon past performance and a mathematical evaluation which shows that the QCNPS Dresser MSSVs are capable of maintaining their set point within tolerance over an eight-year period. This proposed relief request to the testing requirements will also contribute to the principals of maintaining radiation dose As Low As Reasonably Achievable (ALARA).

Using recent dose measurements associated with QCNPS, Units 1 and 2, MSSVs removal and replacement, the average radiological exposure incurred per valve has been 0.54 Rem. Extending the OMN-17 MSSV testing interval from six to eight years would allow extending the schedule of testing of the eight MSSVs on each unit from three to four refueling outages, potentially providing a reduction of two MSSVs tested every ten years per unit. This can result in a potential radiological exposure savings of approximately 2 Rem for the station over a ten-year IST interval.

Based on the application of the Exelon SRV Best Practices Maintenance program, the past performance of the MSSVs at QCNPS and a mathematical evaluation of valve performance, there is reasonable assurance that each MSSV will remain within the set point tolerance over the extended eight-year testing interval. This proposal provides an alternative which would maintain an acceptable level of valve operational readiness, provide an acceptable level of quality and safety pursuant to 10 CFR 50.55a(z)(1) and provide for reduced occupational radiological exposure.

Page 5of7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval Table 1 MSSV Setpoint Performance Projection Year As-Found 1

2 3

4 Tested 2014 U2 6.1 1 7.82 9.0 11.6 2015 U1 7.73 15.3 51.8 11.6 2016 U2 104.2 180.4 38 83.4 2017 U1 200+4 139.0 16.7 17.0 2018 U2 12.1 32.8 43.8 22.6 Notes:

1. This valve was disassembled, inspected and tested before being re-installed in 2009 and was then removed in 2014 and as-found tested. The 2009 maintenance and testing occurred prior to procedure steps to replace the original bronze set screws with an approved stainless-steel set screw that were added to the Exelon SRV Maintenance Best Practices in 2014.

Consequently, the 2014 as-found test results were out of tolerance low. The Exelon SRV Maintenance Best Practices were completed during the valve refurbishment and increased valve performance is expected. (6.1, Valve BK6529, Cell AC112)

2. This valve was disassembled, inspected and tested before being re-installed in 2010 and was then removed in 2014 and as-found tested. The 2010 maintenance and testing occurred prior to a refinement of the as-left setpoint adjustment procedure that was added to the Exelon SRV Maintenance Best Practices in 2014. Consequently, the 2014 as-found test results were out-of-tolerance low. The Exelon SRV Maintenance Best Practices were completed during the valve refurbishment and increased valve performance is expected.

(7.8, Valve BL2467, Cell T232)

3. This valve was disassembled, inspected and tested before being re-installed in 201 O and was then removed in 2015 and as-found tested. It appears that this valve was still utilizing the original main spring. The 2010 refurbishment occurred prior to instituting the detailed inspection criteria of the spindle to disk fit-up that was added to the Exelon SRV Maintenance Best Practices in 2014. The main spring no longer met the revised/current height criteria and was also replaced in 2015. Consequently, the 2015 as-found test results were out-of-tolerance high. The Exelon SRV Maintenance Best Practices Page 6 of 7

EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Quad Cities Nuclear Power Station, Units 1 and 2 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(1),

RV Reactor Pressure Vessel Main Steam Safety Valve (MSSV) Testing 8-Year Test Interval were completed during the valve refurbishment and increased valve performance is expected. (7. 7, Valve BL 1132, Cell AL222)

4. This valve retained its setpoint during the 2017 as-found test and there was no drift so the setpoint drift projection is very high. (200+ AL 192, BK7165)

6.

Duration of Proposed Alternative This proposed alternative will be utilized for the remainder of the current IST interval.

7.

Precedent None

8.

References

1. Letter from J. S. Wiebe, (USN RC Acting Chief Plant Licensing Branch 111-2) to M. J. Pacilio (Exelon Generation Company, LLC), "Quad Cities Nuclear Power Station, Units 1 and 2 - Safety Evaluation in Support of Request for Relief Associated with the Fifth 10 Year Interval lnservice Testing Program (TAC Nos. ME7981, ME7982, ME7983, ME7984, ME7985, ME7986, ME7987, ME7988, ME7990, ME7991, ME7992, ME7993, ME7994, and ME7995), dated February 14, 2013, (Accession Number ML13042A348)

2. Electric Power Research Institute I Nuclear Maintenance Applications Center (EPRl/NMAC) Safety and Relief Valve Testing and Maintenance Guide, Revision of TR-105872, Technical Report 3002005362, August 2015 Page 7 of 7