ML12025A159
| ML12025A159 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 03/13/2012 |
| From: | Doug Broaddus Plant Licensing Branch II |
| To: | James Shea Tennessee Valley Authority |
| Lingam S | |
| References | |
| TAC ME5982, TAC ME5983 | |
| Download: ML12025A159 (7) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 13, 2012 Mr. Joseph W. Shea Manager, Corporate Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801
SUBJECT:
SEOUOYAH NUCLEAR PLANT, UNITS 1 AND 2 - SAFETY EVALUATION OF RELIEF REOUEST NO. RP-01, REVISION 1 FOR THE THIRD 10-YEAR INSERVICE TESTING PROGRAM INTERVAL (TAC NOS. MES982 AND MES983)
Dear Mr. Shea:
By letter dated April 1, 2011 (Agencywide Documents Access and Management System Accession No. ML 1109S0682), Tennessee Valley Authority (TVA), the licensee, submitted Relief Request No. RP-01, Revision 1 for the Sequoyah Nuclear Plant (SON), Units 1 and 2. The licensee requested relief for four essential raw cooling water screen wash pumps, from certain flow measurement requirements noted in the American Society of Mechanical Engineers Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code). Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) SO.SSa(f)(6)(i), TVA requested relief and to use alternative requirements for preservice and inservice testing items on the basis that the code requirement is impractical.
The proposed alternatives as described above will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR SO.SSa(f)(6)(i>>, the U.S. Nuclear Regulatory Commission authorizes the use of the alternative requirements for preservice and inservice testing items.
All other requirements of the ASME OM Code for which relief has not been specifically requested and approved remain applicable. If you have any questions, please feel free to contact the SON Project Manager, Siva P. Lingam, at (301) 41S-1S64.
Sincerely, f"~/1'ck£ ~.
Douglas A. Broaddus, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. SO-327 and SO-328
Enclosure:
Safety Evaluation cc w/encl: Distribution via listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST NO. RP-01, REVISION 1 FOR THE THIRD 10-YEAR INSERVICE TESTING PROGRAM INTERVAL TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT. UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
By a letter dated April 1, 2011 (Agencywide Documents Access and Management System Accession No. ML110950682), Tennessee Valley Authority (TVA, the licensee) submitted Relief Request No. RP-01, Revision 1 to the U.S. Nuclear Regulatory Commission (NRC) for the third 1O-year inservice testing (1ST) program interval for Sequoyah Nuclear Plant (SQN), Units 1 and 2.
The licensee requested relief for four essential raw cooling water (ERCW) screen wash pumps, from certain flow measurement requirements noted in the American Society of Mechanical Engineers (ASME) Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code).
Specifically, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(f)(6)(i), the licensee requested relief and to use alternative requirements for 1ST items (Relief Request No.
RP-01, Revision 1) on the basis that the code requirement is impractical.
2.0 REGULATORY EVALUATION
Paragraph (f), "Inservice Testing Requirements," of 10 CFR 50.55a requires, in part, that 1ST of certain ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with the specified ASME Code and applicable addenda incorporated by reference in the regulations.
Exceptions are allowed where alternatives have been authorized or relief has been requested by the licensee and granted by the NRC pursuant to paragraphs (a)(3)(i), (a)(3)(ii), or (f)(6)(i) of 10 CFR 50.55a.
In proposing alternatives or requesting relief, the licensee must demonstrate that: (1) the proposed alternatives provide an acceptable level of quality and safety (10 CFR 50.55a(a)(3)(i>>;
(2) compliance would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety (10 CFR 50.55a(a)(3)(ii>>; or (3) conformance is impractical for the facility (10 CFR 50.55a(f)(6)(i>>. Section 50.55a allows the NRC to authorize alternatives and to grant relief from ASME OM Code requirements upon making necessary findings.
-2 The SON Units 1 and 2 third 1O-year 1ST program interval began on June 1, 2006. The applicable ASME OM Code edition and addenda for the SON Units 1 and 2 third 10-year 1ST program intervals is the 2001 edition through 2003 addenda.
3.0 TECHNICAL EVALUATION
3.1 Licensee's Relief Request RP-01, Revision 1 Section IST8-5210(a) of the ASME OM Code, "Preservice Testing," (Vertical Line Shaft Centrifugal Pumps) states:
In systems where resistance can be varied, flow rate and differential pressure shall be measured at a minimum of five points. If practicable, these points shall be from pump minimum flow to at least pump design flow.
A pump curve shall be established based upon the measured points. At least one point shall be designated as the reference point(s). Data taken at the reference point will be used to compare the results of inservice tests.
A pump curve need not be established for pumps in systems where the resistance cannot be varied.
Section IST8-5221 (b) of the ASME OM Code, "Group A Test Procedure," (I nservice Testing)
(Vertical Line Shaft Centrifugal Pumps), states:
The resistance of the system shall be varied until the flow rate equals the reference point. The differential pressure shall then be determined and compared to its reference value. Alternatively, the flow rate shall be varied until the differential pressure equals the reference point and the flow rate determined and compared to the reference flow rate value.
Section IST8-5223(b) of the ASME OM Code, "Comprehensive Test Procedure," (Inservice Testing) (Vertical Line Shaft Centrifugal Pumps), states:
The resistance of the system shall be varied until the flow rate equals the reference point. The differential pressure shall then be determined and compared to its reference value. Alternatively, the flow rate shall be varied until the differential pressure equals the reference point and the flow rate determined and compared to the reference flow rate value.
The licensee requested relief from the above code paragraphs for the following pumps:
0-PMP-067-0470-A ERCW Screen Wash Pump 0-PMP-067-0477-B ERCW Screen Wash Pump 0-PMP-067 -0482-8 ERCW Screen Wash Pump 0-PMP-067 -0487-A ERCW Screen Wash Pump These ERCW screen wash pumps are vertical line shaft centrifugal pumps.
-3 3.2 Licensee's Basis for Relief Request RP-01, Revision 1 The licensee notes the following:
No in-line instrumentation exists to measure flow and the physical configuration of the ERCW screen wash pumps and piping does not allow the use of portable flow measuring equipment such as ultrasonic flow meters. Piping from the discharge of the screen wash pumps is open-ended to the spray nozzles at the traveling screen and is relatively short with multiple elbows, reducers, and valves in different planes. The physical configuration of this piping system is such that no portion of the piping meets the requirements for adequate installation of a permanent flow measuring device or the utilization of a portable flow measuring device capable of providing accurate flow rate measurements. Therefore, measured flow readings from an installed device may not be repeatable or representative of actual pump flow. Significant system modifications, such as piping rerouting and pipe support redeSign, would be required to obtain a configuration that would provide reliable flow readings.
Flow is not the critical parameter for these pumps. The nature of their operation is to ensure that sufficient pressure is maintained at the spray nozzles during flushing operations of the traveling water screens to ensure that sufficient force is exerted on the debris accumulated on the screen to remove it. This can be verified by testing the effectiveness of the flushing operation.
The preservice, Group A, and comprehensive tests will be performed by setting the system resistance to the same point for each test with the throttle valves full open. Flow will not be measured. The remaining variable that could affect system resistance is the spray nozzles. The condition of the spray nozzles will be inspected during each test performance with corrective actions initiated as necessary, thus providing assurance that the spray nozzle condition will not affect flow rate. Maintenance history was reviewed for spray nozzle plugging and it was determined that nozzle plugging was infrequent. The spray nozzles are inspected by operations personnel during spray operation with corrective maintenance initiated as required. With system resistance maintained constant for each test, pump degradation would be identified through changes in differential pressure.
Differential pressure is calculated using inlet (based upon lake level or suction pressure) and discharge pressure. The pumps can be trended for degradation based on differential pressure at this point. Vibration readings will also be taken at this reference pOint. The pumps will be tested in this manner for the preservice, the quarterly Group A, and the biennial comprehensive tests.
Instrument accuracy and acceptance criteria for pump differential pressure and vibration will meet the requirements of Table ISTB-3500-1, "Required Instrument Accuracy," and Table ISTB-5200-1, "Vertical Line Shaft and
-4 Centrifugal Pumps Test Acceptance Criteria," respectively, for the appropriate test type.
Preservice test data for differential pressure and vibration data will be evaluated to verify if it represents acceptable pump operation and will be used as reference values for subsequent quarterly Group A and biennial comprehensive tests.
For a new ERCW screen wash pump, the bowl assembly will be tested at the vendor's facility prior to shipment to SON. This test data is adjusted to account for the pump column (in order to represent the fully assembled pump configuration). A vendor pump curve will then be developed and provided to SON prior to pump installation.
The preservice pump test for a new ERCW screen wash pump will be performed by setting the throttle valves full open (the same position as the Group A and comprehensive tests) and measuring pump differential pressure and vibration. Flow will not be measured. In addition, the condition of the screen spray nozzles will be inspected to verify that the spray covers the screen spray area and the spray force is sufficient to remove any debris present.
The measured differential pressure will be plotted on the vendor pump curve to determine the theoretical flow rate. The differential pressure and theoretical flow rate will then be evaluated against the requirements established in the ERCW screen wash pump design specification, design criteria, and system description. If the pump hydraulic data meets the design requirements with some margin to provide for future degradation and the vibration data analysis is acceptable, the pump will be considered to be operating acceptably. Visual examination of screen wash spray nozzle performance provides additional positive verification that the pump is operating acceptably and is capable of performing its safety-related function.
3.3 NRC Staff's Evaluation ASME OM Code, Section ISTB-5210(a) requires that the flow rate and pressure be measured at a minimum of five points, in order to develop a pump curve to establish a reference point, during preservice testing of the ERCW screen wash pumps, 0-PMP-067-0470-A, 0-PMP-067-0477-B, 0-PMP-067 -0482-B, and 0-PMP-067 -0487 -A. Sections ISTB-5221 (b) and ISTB-5223(b) of the ASME OM Code require that the resistance of the ERCW system be varied until the flow rate equals the reference point during Group A and comprehensive pump tests for these screen wash pumps.
The screen wash pumps take suction from the pit directly below the pump deck and are positioned on the deck adjacent to the traveling screens. The discharge piping for each pump is short and open ended containing several elbows, reducers, and valves prior to entering the traveling screen enclosure. No flow instrumentation is installed in the system to measure flow as required by the ASME OM Code. The existing piping configuration will not be feasible for the installation of any
- S-flow measured device that will provide reliable flow readings. Further, the current configuration of the piping does not allow the use of portable flow measuring equipment such as ultrasonic flow meters. To add a reliable and permanent flow measuring device, significant pipe rerouting along with heat trace and the associated pipe support redesign are required. Therefore, the NRC staff finds that compliance with the Code requirements for measuring flow rate for these pumps is impractical.
The purpose of the ERCW screen wash pumps is to clear debris off of the traveling screens with sufficient water flow and pressure. The licensee plans to perform pump inservice and preservice testing as described in Section 3.2 of this technical evaluation. The proposed request by the licensee measures pump vibration and sets system resistance to the same point for each test, with the throttle valves full open, while inspecting the spray nozzles to ensure nozzle clogging does not affect system flow. This provides reasonable assurance of the operational readiness and reliability of these ERCW screen wash pumps.
4.0 CONCLUSION
As set forth above, the NRC staff determined that it is impractical for the licensee to comply with certain requirements of the ASME OM Code for the ERCW screen wash pump testing, and the proposed testing specified above provides reasonable assurance that the ERCW screen wash pumps will remain operationally ready.
Granting relief pursuant to 10 CFR SO.SSa(f)(6)(i) is authorized by law and will not endanger life or property or the common defense and security, and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility. All other ASME OM Code requirements for which relief was not specifically requested and approved in the subject request for relief remain applicable.
This relief is granted for the remainder of the SON Units 1 and 2 third 10-year 1ST interval, which began on June 1, 2006.
Principal Contributor: Robert Wolfgang Date: March 13,2012
March 13,2012 Mr. Joseph W. Shea Manager, Corporate Nuclear Licensing Tennessee Valley Authority 3R Lookout Place 1101 Market Street Chattanooga, TN 37402-2801 SUB~IECT: SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 - SAFETY EVALUATION OF RELIEF REQUEST NO. RP-01, REVISION 1 FOR THE THIRD 10-YEAR INSERVICE TESTING PROGRAM INTERVAL (TAC NOS. ME5982 AND ME5983)
Dear Mr. Shea:
By letter dated April 1, 2011 (Agencywide Documents Access and Management System Accession No. ML110950682), Tennessee Valley Authority (TVA), the licensee, submitted Relief Request No. RP-01, Revision 1 for the Sequoyah Nuclear Plant (SQN), Units 1 and 2. The licensee requested relief for four essential raw cooling water screen wash pumps, from certain flow measurement requirements noted in the American Society of Mechanical Engineers Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code). Pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50.55a(f)(6)(i), TVA requested relief and to use alternative requirements for preservice and inservice testing items on the basis that the code requirement is impractical.
The proposed alternatives as described above will provide an acceptable level of quality and safety. Therefore, pursuant to 10 CFR 50.55a(f)(6)0>>, the U.S. Nuclear Regulatory Commission authorizes the use of the alternative requirements for preservice and inservice testing items.
All other requirements of the ASME OM Code for which relief has not been specifically requested and approved remain applicable. If you have any questions, please feel free to contact the SQN Project Manager, Siva P. Lingam, at (301) 415-1564.
Sincerely, IRA by FSaba forI Douglas A. Broaddus, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-327 and 50-328
Enclosure:
Safety Evaluation cc w/encl: Distribution via Listserv Distribution:
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