NMP1L3356, Relief Requests Associated with Pump Periodic Verification Tests for the Fifth Ten-Year Inservice Test Interval
| ML20282A331 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 10/08/2020 |
| From: | David Gudger Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NMP1L3356 | |
| Download: ML20282A331 (10) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com 10 CFR 50.55a NMP1L3356 October 8, 2020 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Nine Mile Point Nuclear Station, Unit 1 Renewed Facility Operating License No. DPR-63 NRC Docket No. 50-220
Subject:
Relief Requests Associated with Pump Periodic Verification Tests for the Fifth Ten-Year Inservice Test Interval In accordance with 10 CFR 50.55a, "Codes and Standards," Exelon Generation Company, LLC (Exelon) requests your review and approval of the attached relief requests associated with the Inservice Testing (IST) Program for Nine Mile Point Nuclear Station, Unit 1 (NMP1).
The IST Program for the fifth Ten-Year interval began on January 1, 2019, and adopted the 2012 Edition of the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (OM Code). This edition of the OM Code includes a revised definition for the pump periodic verification test (PPVT) that requires testing at the pumps highest design basis accident flow rate. Currently, the NMP1 plant design does not include the configuration necessary to meet the new testing requirement for the Core Spray and the Containment Spray systems. The basis of these two relief requests is that compliance with the Code requirement results in hardship or unusual difficulty with no compensating increase in the level of quality and safety.
The first performance of the PPVT for the Core Spray and Containment Spray systems is due 6/30/2021, which is 24 months plus 6 months of grace from when the new testing requirement became required. Therefore, Exelon requests NRC review and approval of these relief requests by June 30, 2021.
Attachments 1 and 2 to this request provide the RRs for the identified pumps in the Containment Spray and Core Spray systems. NRC guidance for requesting approval for use of an alternative to ASME OM Code PPVT requirements is not specifically provided in NUREG-1482, Revision 3, Guidelines for Inservice Testing at Nuclear Power Plants.
However, Section 5.10 of this NUREG does provide guidance for obtaining approval of an alternative to ASME OM Code Comprehensive Pump Testing Requirements. Since the
Submittal of Inservice Testing Relief Requests Docket No. 50-220 October 8, 2020 Page 2 PPVT and the Comprehensive Pump Tests (CPTs) are similar, the guidance in NUREG-1482 for requesting an alternative for CPT requirements was considered in the RRs for the PPVT.
There are no regulatory commitments contained in this request.
If you have any questions concerning this letter, please contact Mr. David Neff at (267) 533-1132.
Respectfully, David T. Gudger Senior Manager - Licensing Exelon Generation Company, LLC Attachments:
- 1) Relief Request CTNSP-PR-01, Rev. 0 (Unit 1) - Containment Spray Pumps
- 2) Relief Request CS-PR-01, Rev. 0, Core Spray Pumps cc: USNRC Region I, Regional Administrator w/attachments USNRC Senior Resident Inspector, NMP w/attachments USNRC Project Manager, NMP w/attachments A. L. Peterson, NYSERDA w/attachments
Attachment 1 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CTNSP-PR-01, Rev. 0 (Unit 1) - Containment Spray Pumps
- 1. ASME Code Component(s) Affected The following Containment Spray Pumps are affected:
Component Description Class Group PMP-80-03 Containment Spray Pump # 121 2 B PMP-80-04 Containment Spray Pump # 111 2 B PMP-80-23 Containment Spray Pump # 122 2 B PMP-80-24 Containment Spray Pump # 112 2 B
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 V, Pump Periodic Verification Test Program (PPVT),
requires the Owner to perform a pump periodic verification test at least once every two years.
Mandatory Appendix V, V-2000, Definitions, defines the pump periodic verification test as a test that verifies a pump can meet the required (differential or discharge) pressure as applicable, at its highest design basis accident flow rate.
4. Reason for Request
Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(2), an alternative is proposed to the pump test requirements of the ASME OM-2012 Code. With the adoption of the ASME OM-2012 Code on January 1, 2019, for Nine Mile Point Nuclear Station, Unit 1 (NMP1), a new requirement was added to perform periodic verification testing at the pumps highest design basis accident flow rate. The current system design does not include the capability to test the pumps at these conditions, except for spraying torus water into the drywell and torus airspace. The basis of the request is that compliance with the Code requirements results in hardship or unusual difficulty with no compensating increase in the level of quality and safety.
The Containment Spray System (CNTSS) at NMP1 is an engineered safeguards system designed to prevent overheating and overpressurization of the containment, reduce drywell airborne fission product concentrations, and control the pressure suppression chamber water temperature following a design basis Loss of Coolant Accident (LOCA).
The system is designed to provide heat removal capabilities for Reactor Pressure Vessel 1
Attachment 1 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CTNSP-PR-01, Rev. 0 (Unit 1) - Containment Spray Pumps (RPV) leaks up to and including the design basis accident, the double-ended break of a reactor recirculation line, without core spray system operation.
The CNTSS is designed with two redundant loops as described by the diagram provided in the NMP1 Updated Final Safety Analysis Report (UFSAR), Figure VII-3. Each loop includes two redundant trains and consists of two suction headers, two CNTSS pumps, two heat exchangers and the associated CNTSS raw water pumps, a common test return line, and associated piping and control valves. The primary loop (Loop 11) contains CNTSS pumps # 111 and # 112 and provides water to the primary or inner drywell sparger and torus sparger. The secondary loop (Loop 12) contains CNTSS pumps # 121 and
- 122 and provides water to the secondary or outer drywell sparger and torus sparger.
The torus sparger is common to both loops. Each of the two loops are cross-connected through the test return lines such that each of the loops can provide flow for both the primary loop and secondary loop spargers. Each loop takes suction from the torus and sprays water into the drywell and torus airspaces using the drywell and torus spargers.
A permanent test return line is provided to permit surveillance testing of the CNTSS pumps without injecting torus water into the drywell or torus airspaces. The test return line connects to a common header downstream of each of the CNTSS pumps and discharges into the Torus. The suctions for the CNTSS pumps are solely connected to the torus and only have the capability to pump water to the Drywell and Torus spargers or torus via the test return line.
The highest required design basis accident flow rate for the CNTSS system is 3600 gpm.
The CNTSS mode for one-pump operation requires 3600 gpm to meet accident conditions. The CNTSS test return line is designed to conduct routine system testing at a flowrate of approximately 2900 gpm. This is 80.5% of the highest design basis accident flow rate. This design allows for testing at a representative point on the pumps performance curve to allow for demonstrating pump performance but not at the highest design basis accident flow rate.
In order to test the CNTSS pumps with the current system piping design and meet the new PPVT requirement highest design basis accident flow rate, the CNTSS pumps must use the normal system flow path and discharge water into the drywell or torus airspace. This would result in spraying electrical equipment in the Drywell with water and spread radioactive contamination which would be detrimental to the long-term integrity of the equipment in the drywell and torus and increase radiation levels thereby increasing worker radiation dose.
Compliance to the new PPVT at the highest design basis accident flow rate would require an extensive system redesign and modification that would include installation of additional or larger diameter piping and isolation valves, new hydraulic and seismic evaluations and likely new supports and snubbers. It has been estimated that such a modification to the CNTSS to install test return piping would very likely involve significant cost, in excess of
$2.9 million, and extended outage time to install. Such a major system modification is costly and burdensome with no compensating increase in the level of quality or safety.
Performing these modifications to the CNTSS by enlarging the test return piping and 2
Attachment 1 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CTNSP-PR-01, Rev. 0 (Unit 1) - Containment Spray Pumps components to achieve design basis accident flow rates are not warranted since there will be no improvement in the ability to detect pump degradation. Testing for the PPVT at an alternate flow rate is proposed and would provide a reasonable assurance of pump operational readiness and an acceptable level of quality and safety
5. Proposed Alternative and Basis for Use
All the CNTSS pumps have been and will continue to be tested using quarterly and comprehensive test methods in accordance with the ASME OM Code paragraph ISTB-5200, Vertical Line Shaft Centrifugal Pumps. Pump flow testing of the CNTSS pumps is conducted with pump suction from the torus and returning back to the torus through common test return piping. This CNTSS pump operability and performance testing is currently being performed in accordance with the NMP1 Technical Specifications Surveillance Requirement 4.3.7 and the NMP1 Inservice Testing Program.
Each CNTSS loop is designed to provide for full-flow conditions. Data on flows and pressures at various points in the flow lines for each CNTSS pump was obtained during testing and was used to create the field validated pump performance curves. These tests show that each CNTSS pump is able to meet the design basis accident flow conditions.
Data on the pump flow rates and pressures at various points for each CNTSS loop are routinely obtained for comparison with the previously established normal conditions in accordance with the IST program. Subsequent retesting and re-baselining of the pump performance test acceptance criteria is performed following major maintenance of the CNTSS pumps in accordance with ISTB-3300, Reference Values. Testing of the CNTSS pumps at a flow rate of approximately 2900 gpm utilizing the existing test return line flow path provides for substantial flow testing in a stable region of the pump curve. Testing over the last 20 years has shown no signs of mechanical or hydraulic degradation as indicated by consistent performance of the CTNSS pumps within ASME OM Code acceptance criteria.
A review of completed maintenance and Inservice Testing results during the last 20 years for the CNTSS pumps concluded the pumps have only required minor maintenance and have retained their operational readiness with no signs of mechanical or hydraulic degradation. Additional pump performance monitoring conducted for the CNTSS pumps includes pump-motor bearing temperature monitoring, vibration monitoring, and periodic sampling of the lube oil. Performance monitoring of the CNTSS pumps indicates the pumps remain capable of meeting their design function and have no indication of degradation. If measured parameters are found to be outside the normal operating range or determined to be trending toward an unacceptable degraded state, then appropriate actions are taken. These actions include monitoring additional parameters, review of specific information to identify cause, and potential removal of the pump from service to perform necessary maintenance. Continued testing in a stable flow range combined with the additional pump performance monitoring provides reliable performance monitoring beyond those requirements prescribed in the Code that reliably validates the ability of each pump to meet the design basis accident flow rates. The testing is effective for detecting mechanical and hydraulic degradation as required by Subsection ISTB.
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Attachment 1 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CTNSP-PR-01, Rev. 0 (Unit 1) - Containment Spray Pumps Relief is requested pursuant to 10 CFR 50.55a(z)(2) based on the determination that compliance with the Code required PPVT pump test requirements cannot be achieved without major system modifications. Such a significant change to the system is a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The proposed alternative provides reasonable assurance of pump operational readiness and provides an acceptable level of quality and safety.
6. Duration of Proposed Alternative
This request, upon approval, will be applied to the NMP1 fifth 10-year interval, which began on January 1, 2019, and is scheduled to end on December 31, 2028.
- 7. Precedent
- 1. Letter from J. Dana (U.S. Nuclear Regulatory Commission) to D. Moul (NextEra),"
Seabrook Station, Unit No. 1 - Relief from the Requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (EPID L-2019-LLR-0042)," dated March 17, 2020 (ML20073E434).
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Attachment 2 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CS-PR-01, Rev. 0, Core Spray System Pumps
- 1. ASME Code Component(s) Affected The following Core Spray System Pumps are affected:
Component Description Class Group PMP-81-03 Core Spray System Pump # 121 2 B PMP-81-23 Core Spray System Pump # 111 2 B PMP-81-51 Core Spray System Topping Pump # 121 2 B PMP-81-50 Core Spray System Topping Pump # 111 2 B
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 V, Pump Periodic Verification Test Program (PPVT),
requires the Owner to perform a pump periodic verification test at least once every two years.
Mandatory Appendix V, V-2000, Definitions, defines the pump periodic verification test as a test that verifies a pump can meet the required (differential or discharge) pressure as applicable, at its highest design basis accident flow rate.
4. Reason for Request
Pursuant to 10 CFR 50.55a, Codes and standards, paragraph (z)(2), an alternative is proposed to the pump test requirements of the ASME OM-2012 Code. With the adoption of the ASME OM-2012 Code on January 1, 2019, for Nine Mile Point Nuclear Station, Unit 1 (NMP1), a new requirement was added to perform periodic verification testing at the pumps highest design basis accident flow rate. The current system design does not include the capability to test the pumps at these conditions, except for injection to the reactor pressure vessel (RPV) with water from the Torus. The basis of the request is that compliance with the Code requirements results in hardship or unusual difficulty with no compensating increase in the level of quality and safety.
The Core Spray System (CSS) pumps at NMP1 take suction from the Torus (Suppression Pool) and spray water into the reactor vessel on top of the fuel assemblies to cool the core in the event of a Loss of Coolant Accident (LOCA). The CSS consists of two independent "systems" (loops). A diagram is provided in the NMP1 Updated Final Safety Analysis Report (UFSAR), Figure VII-1. Each loop contains redundant pump sets with each set of pumps comprised of a CSS pump and CSS topping pump.
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Attachment 2 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CS-PR-01, Rev. 0, Core Spray System Pumps The CSS, in conjunction with the Automatic Depressurization System (ADS), is the standby emergency core cooling system for removal of decay heat from the reactor fuel assemblies in the event of a LOCA. For a large break LOCA, the CSS provides the required core cooling without assistance.
For a small break LOCA, the RPV is depressurized by the ADS to allow the low-pressure CSS to operate. For a CSS loop to achieve its design basis flow rate, one CSS pump set (consisting of a single CSS pump and its associated CSS topping pump) must start and one inside isolation valve must open within the specified time requirements.
A permanent test return line is provided to permit surveillance testing of the CSS pumps without injecting torus water into the RPV. The test return line connects to the CSS piping between the CSS topping pump and the outboard reactor coolant isolation valve and discharges into the Torus. In addition, for RPV injection testing purposes, one CSS pump set in each loop can be aligned to take suction from the Condensate Storage Tanks (CSTs). This permits core spray injection tests into the RPV during outages using clean demineralized water from the CSTs rather than torus water. The CSS pump sets with this capability are the CSS pump sets # 112 and # 122. The suctions for the other CSS pump sets, in each loop (i.e., CSS pump sets # 111 and # 121) are not connected to the CST and only have the capability of RPV injection with torus water.
The highest required design basis accident flow rate for the CSS system is 4540 gpm for each CSS pump set. The NMP1 CSS test return lines for the CSS pumps sets # 111 and
- 121 are designed to conduct routine system testing at a flowrate of approximately 3000 gpm per CSS pump set. This is 66% of the highest design basis accident flow rate.
This design allows for testing at a representative point on the pumps performance curve to allow for demonstrating pump performance, but not at the highest design basis accident flow rate.
In order to test the CSS pump sets # 111 and # 121 with the current system design and meet the new PPVT required highest design basis accident flow rate (i.e., 4540 gpm at 0 psig RPV pressure), the CSS pumps would need to take suction from the Torus and discharge water directly into the RPV. The torus water has lower quality water compared to RPV water. Injecting torus quality water into the RPV using the # 111 or the # 121 CSS pump sets to conduct the full flow test would introduce contaminants (e.g., rust from the uncoated Torus) into the RPV. Introduction of these contaminants into the RPV and Reactor Coolant System (RCS) is contrary to existing NRC, industry and Exelon guidelines for reactor coolant chemistry controls. These controls are necessary to maintain the long-term integrity of the fuel cladding, the RPV and the RCS piping.
Compliance to the new PPVT at the highest design basis accident flow rate, while maintaining proper reactor coolant chemistry controls, would require an extensive system redesign and modification that would include installation of additional or larger diameter piping and isolation valves, new hydraulic and seismic evaluations and likely new supports and snubbers. It has been estimated that such a modification to the CSS to install test return piping would very likely involve significant cost, in excess of $2.9 million, and extended outage time to install. Such a major system modification is costly and 2
Attachment 2 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CS-PR-01, Rev. 0, Core Spray System Pumps burdensome with no compensating increase in the level of quality or safety. Performing these modifications to the CSS by enlarging the test return piping and components to achieve design basis accident flow rates is not warranted since there will be no improvement in the ability to detect pump degradation. Testing for the PPVT at an alternate flow rate is proposed and would provide a reasonable assurance of pump operational readiness and an acceptable level of quality and safety
5. Proposed Alternative and Basis for Use
All the CSS pump sets have been and will continue to be tested using quarterly utilizing comprehensive test methods in accordance with the ASME OM Code paragraph ISTB-5200, Vertical Line Shaft Centrifugal Pumps for the CSS pumps and paragraph ISTB-5100, Centrifugal Pumps (Except Vertical Line Shaft Centrifugal Pumps), for the CSS topping pumps. Pump flow testing of CSS pump sets # 111 and # 121 is conducted with pump suction from the Torus with water return to the Torus. This CSS pump operability and performance testing is currently being performed in accordance with the NMP1 Technical Specifications Surveillance Requirement 4.1.4 and the Inservice Testing Program.
Each CSS loop was designed for full flow rated conditions. Data on flows and pressures at various points in the flow lines for each CSS pump was obtained during testing and was used to create the field validated pump performance curves. These tests showed that each CSS pump set was able to meet the design basis accident flow conditions.
Data on the pump set flow rates and pressures at various points for each CSS loop are routinely obtained for comparison with the previously established normal conditions in accordance with the IST program. Testing and baselining of the pump performance test acceptance criteria is reperformed following major maintenance of the CSS pumps in accordance with ISTB-3300, Reference Values. Testing of the CSS pumps at a flow rate of approximately 2900 gpm utilizing the existing test return line flow path provides for substantial flow testing in a stable region of the pump curve. Testing over the last 20 years has shown no signs of mechanical or hydraulic degradation as indicated by consistent performance of the CSS pumps within ASME OM Code acceptance criteria.
A review of the completed maintenance and the Inservice Testing results during the last 20 years for the CSS pumps and topping pumps concluded the pumps have only required minor maintenance and the pumps have retained their operational readiness with no signs of mechanical or hydraulic degradation. Additional pump performance monitoring conducted for the CSS pumps includes pump-motor bearing temperature monitoring, vibration monitoring, and periodic sampling of the lube oil. Performance monitoring of the CSS pumps indicates the pumps remain capable of meeting their design function and have no indication of degradation. If measured parameters are found to be outside the normal operating range or determined to be trending toward an unacceptable degraded state, then appropriate actions are taken. These actions include monitoring additional parameters, review of specific information to identify cause, and potential removal of the pump from service to perform necessary maintenance. Continued testing in a stable flow range combined with the additional pump performance monitoring provides reliable 3
Attachment 2 EXELON GENERATION COMPANY, LLC IST PROGRAM - RELIEF REQUEST Nine Mile Point Nuclear Station, Unit 1 Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
CS-PR-01, Rev. 0, Core Spray System Pumps performance monitoring beyond those requirements prescribed in the Code that reliably validates the ability of each pump to meet the design basis accident flow rates. The testing is effective for detecting mechanical and hydraulic degradation as required by Subsection ISTB.
Relief is requested pursuant to 10 CFR 50.55a(z)(2) based on the determination that compliance with the Code required PPVT pump test requirements cannot be achieved without major system modifications. Such a significant change to the system is a hardship or unusual difficulty without a compensating increase in the level of quality and safety.
The proposed alternative provides reasonable assurance of pump operational readiness and provides an acceptable level of quality and safety.
6. Duration of Proposed Alternative
This request, upon approval, will be applied to the NMP1, fifth 10-year interval, which began on January 1, 2019, and is scheduled to end on December 31, 2028.
- 7. Precedent
- 1. Letter from J. Dana (U.S. Nuclear Regulatory Commission) to D. Moul (NextEra),"
Seabrook Station, Unit No. 1 - Relief from the Requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (EPID L-2019-LLR-0042)," dated March 17, 2020 (ML20073E434).
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