ML102160340
| ML102160340 | |
| Person / Time | |
|---|---|
| Site: | Watts Bar  |
| Issue date: | 07/30/2010 |
| From: | Krich R Tennessee Valley Authority |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| TAC ME4204 | |
| Download: ML102160340 (8) | |
Text
Tennessee Valley Authority rIVIA 1101 Market Street, LP 3R Chattanooga, Tennessee 37402-2801 R. M. Krich Vice President Nuclear Licensing July 30, 2010 10 CFR 50.4 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390
Subject:
Response to Request for Additional Information Regarding Relief Request PV-02, Revision 1 (TAC No. ME4204)
Reference:
- 1. Letter from NRC to TVA, "Watts Bar Nuclear Plant, Unit 1 - Request for Additional Information Regarding Relief Request PV-02, Revision 1 (TAC No. ME4204), dated July 15, 2010
- 2. Letter from TVA to NRC, "American Society of Mechanical Engineers Request for Relief PV-02, Revision 1,," dated July 1, 2010 provides the Tennessee Valley Authority's (TVA's) response to the NRC's Request for Additional Information (RAI) (Reference 1) regarding relief request PV-02, Revision 1. This response is due by July 30, 2010. Enclosure 2 provides a corrected relief request as described in the response to RAI No. 1. This corrected version of relief request PV-02, Revision 1, supersedes the version submitted in Reference 2.
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U.S. Nuclear Regulatory Commission Page 2 July 30, 2010 There are no commitments associated with this submittal. If you have any questions about this change, please contact Kevin Casey at (423) 751-8523.
Respectfully, R. M. Krich Enclosures
- 1. Response to Request for Additional Information Regarding Relief Request PV-02, Revision 1
- 2. Corrected Version of Relief Request PV-02, Revision 1 cc: (Enclosure):
NRC Regional Administrator - Region II NRC Resident Inspector - Watts Bar Nuclear Plant
Enclosure 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING RELIEF REQUEST PV-02, REVISION I NRC Request for Additional Information (RAI) #1 Relief is being requested from measuring the pump flow rate during preservice or IST of the essential raw cooling water (ERCW) screen wash pumps. Please explain why you are not asking for relief from ISTB-5223(b) for the comprehensive pump test.
Response #1 This was in error. Relief request PV-02, Revision 1 should have included ISTB-5223(b).
This omission has been entered in TVA's Corrective Action Program. A corrected version of PV-02, Revision 1 which includes ISTB-5223(b) is attached for NRC review and approval. The revisions, including the addition of ISTB-5223(b), to PV-02 are shown in bold italic text. This corrected version supersedes the version submitted July 1, 2010.
NRC RAI #2 You state that preservice test data for differential pressure and vibration data will be evaluated to verify it represents acceptable pump operation. Please explain how this will be done.
Response #2 The new ERCW Screen Wash Pump bowl assembly will be tested at the vendor's facility before shipment to the Watts Bar Nuclear Plant. This test data is adjusted to account for the pump column (in order to represent the fully assembled pump configuration). Then a vendor pump curve will be developed and provided to the plant before installation of the pump.
The preservice pump test will be performed by setting the throttle valves full open (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.
This data will be evaluated to verify it represents acceptable pump operation as follows.
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 requirements established in the ERCW Screen Wash Pump design specification, design criteria, and system description (i.e., pump performance should achieve 350 feet Total Developed Head at 270 gallons per minute).
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If the pump hydraulic data meets the design requirements with some margin to provide for future degradation and the vibration data analysis is acceptable then the pump will be considered to be operating acceptably.
Visual examination of screen wash spray nozzle performance provides additional positive verification the pump is operating acceptably and is capable of performing its safety related function.
NRC RAI #3 Please explain how the preservice tests were performed for the currently installed ERCW screen wash pumps, and why the test method(s) used for them cannot be used for the new ERCW screen wash pumps.
Response #3 The code of record for Inservice Testing (IST) during the preservice test period was American Society of Mechanical Engineers, "Code for Operation and Maintenance of Nuclear Power Plants (ASME OM Code), 1987 Edition through 1988 Addenda. In this edition/addenda of the Code, the preservice test requirement is essentially the same as the quarterly inservice test requirements. ASME OM Code, 1987 Edition through 1988 Addenda, Part 6, "4.1 Preservice Testing," states, "Each pump shall be tested during the preservice test period as required by this part. This testing shall be conducted under conditions aslnear as practicable to those expected during subsequent inservice testing...". ASME OM Code, 1987 Edition through 1988 Addenda, Part 6, "5 Testing Methods," does not prescribe different methods for preservice testing versus inservice testing.
These ERCW screen was pumps were startup tested per Component Test Procedure CSI-1-067-0468-M02-000 on August 8, 1993. This test measured the discharge pressure at normal operating conditions. No flow measurement was obtained. Vibration data, pump speed, and electrical data (voltage and current) was also obtained. The Pre-Operational T1est Program declared this pump to be acceptable for use.
The IST Preservice Test was performed on September 27, 1995 by use of the quarterly inservice test'with no acceptance criteria established for the initial test. Once data (i.e.,
lake level/discharge pressure which are used to calculate Total Developed Head and vibration) was obtained from the initial performance, acceptance criteria were established in accordance with ASME OM Code, Part 6 requirements. Watts Bar Nuclear Plant Unit 1 commercial operation date was May 27, 1996.
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The code of record for the IST Program in the current interval is ASME OM Code, 2001 Edition through 2003 Addenda. In this edition/addenda of the Code, the preservice test requirement is to develop a five point pump curve with one of the points used for subsequent inservice tests. OM Code ISTB-5210(a) states, in part, "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 on the measured points. At least one point shall be designated as the reference points(s). Data taken at the reference point will be used to compare the results of inservice tests...".
The preservice test requirements in the current code edition/addenda are more stringent than the code edition/addenda in effect during the initial preservice test period. The plant design and piping configuration for ERCW Screen Wash Pumps do not include permanent flow instrumentation and do not facilitate installation of temporary flow instrumentation. Therefore, it is not possible to measure the pump flow and therefore, not possible to develop a five point pump curve as required by the ASME OM Code for the preservice pump test.
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Enclosure 2 Tennessee Valley Authority Watts Bar Nuclear Plant, Unit I Second 10-Year Interval CORRECTED REQUEST FOR RELIEF NUMBER PV-02, Revision I Systems/Components For Which Relief Is Requested Code Class 3 Essential Raw Cooling Water Screen Wash Pumps:
- 1-PMP-67-431 -A (reference drawing 1-47W845-1)
- 1-PMP-67-440-B (reference drawing 1-47W845-1)
- 2-PMP-67-437-A (reference drawing 1-47W845-1)
- 2-PMP-67-447-B (reference drawing 1-47W845-1)
Applicable Code Edition and Addenda
For the current, second 10-year inservice testing (IST) interval, the applicable Code edition is the American Society of Mechanical Engineers (ASME), "Code for Operation and Maintenance of Nuclear Power Plants" (ASME OM Code), 2001 Edition through 2003 Addenda. The second interval began on May 27, 2007 and will end on May 26, 2016, which will return the Watts Bar Nuclear Plant (WBN) IST intervals to the original 10-year schedule, as the first interval was extended to 11 years.
Applicable Code Requirement
ASME OM Code, 2001 Edition through 2003 Addenda, ISTB-5210(a), "In systems where resistance can be varied, flow rate and differentialpressure 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 establishedbased upon the measured points. At least one point shall be designatedas 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 establishedfor pumps in systems where the resistance cannot be varied."
ASME OM Code, ISTB-5221(b), "The resistance of the system shall be varied until the flow rate equals the reference point. The differential pressure shall 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."
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ASME OM Code, ISTB-5223(b), "The resistance of the system shall be varied until the flow rate equals the reference point. The differentialpressureshall then be determined and compared to its reference value. Alternatively, the flow rate shall be varied until the differentialpressure equals the reference point and the flow rate determined and compared to the reference flow rate value.
Code Requirement From Which Relief Is Requested Relief is being requested from:
- 1. Measuring flow rate and differential pressure at five points during Preservice Testing and establishment of a pump curve, and
- 2. Measuring the pump flow rate during Preservice or Inservice Testing of the Screen Wash Pumps.
Basis for Relief No in-line instrumentation exists to measure flow and the physical configuration of the pump and piping does not allow the use of portable flow measuring equipment such as ultrasonics. 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.
Therefore, measured flow readings from an installed device may not be repeatable nor representative of actual pump flow. Significant system modifications, such as piping rerouting and 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 verifying the effectiveness of the flushing operation.
Maintenance history was reviewed for spray nozzle plugging and it was determined that nozzle plugging is infrequent. The spray nozzles are inspected by operations personnel during spray operation with corrective maintenance initiated as required.
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Alternative Examinations Testing 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. 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 on lake level or suction pressure) and discharge pressure. The pump will 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,and the quarterly Group A and the biennial Comprehensive inservice tests.
Instrument accuracyand acceptance criteriafor pump differentialpressure and vibration will meet the requirements of Table ISTB-3500-1 and Table ISTB-5200-1, respectively, for the appropriatetest type.
Preservicetest data for differentialpressure and vibration data will be evaluated to verify it represents acceptablepump operationand will be used as reference values for subsequent quarterlyGroup A and Comprehensive inservice tests.
Justification for the Granting of Relief Based upon the above discussion, the alternative test provides an acceptable level of quality and safety. Authorization to implement the proposed alternative is requested in accordance with 10CFR50.55a(3)(i).
Revision 0 of this Relief Request was authorized by letter from Margaret H. Chernoff, Acting Branch Chief Plant Licensing Branch to Karl W. Singer dated March 9, 2007. The attached Safety Evaluation transmitted by this letter authorized the use of Relief Requests PV-01, PV-02, PV-03, and PV-04 for the Second Inservice Interval at WBN.
Implementation Schedule This proposed alternative is requested for the Second Inservice Interval.
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