ML20210H940
| ML20210H940 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 03/18/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| REF-PT21-86, REF-PT21-86-170-000, REF-PT21-86-222-000 NCR-1249, PT21-86-170, PT21-86-170-000, PT21-86-222, PT21-86-222-000, NUDOCS 8604030264 | |
| Download: ML20210H940 (2) | |
Text
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA TENNESSEE 37401 SN 157B Lookout Place March 18, 1986 h
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's U.S. Nuclear Regulatory Comission h
Region II Attn:
Dr. J. Nelson Grace, Regional Administrator p
101 Marietta Street, NW, Suite 2900
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Atlanta, Georgia 30323 M
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNIT 1 - EXCESSIVE VIBRATIONS OF ERCW PUMP / MOTOR -
NCR 1249 - THIRD REVISED FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector F. S. Centre 11 on August 19, 1980 in accordance with 10 CFR 50.55(e).
This was followed by our interim reports dated September 17 and December 2, 1980, our final report dated February 4, 1981, and our revised final reports dated September 8,1981 and August 6,1982.
Enclosed is our third revised final report. The reason for this revision is to correct the statement in the last
. paragraph concerning the units and method of measurement of the vibration levels. Inspection report 438,439/83-09 noted these discrepancies and requested correction. We consider 10 CFR Part 21 applicable to this
~
deficiency.
If you have any questions, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours.
TENNESSEE VALLEY AUTHORITY
. L. Gridley Manager of Licensing Enclosure cc:
Mr. James Taylor,~ Director (Enclosure)
Office of Inspection and Enforcement U.S. Nuclear Regulatory Comission Washington, D.C.
20555 Records Center (Enclosure)
Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 8604030264 B60318 gDR ADOCK 0 ] 4g
\\\\
An Equal Opportunity Employer gg
ENCLOSURE BELLEFONTE NUCLEAR PLANT UNIT 1 EXCESSIVE VIBRATIONS OF ERCW PUNP/ MOTOR NCR 1249 l
THIRD REVISED FINAL REPORT i
Description of Deficiency Excessive vibrations have been observed in essential raw cooling water (ERCW) pump / motor assemblies for unit 1 pumps 1A-1A and 1A-2A while running. TVA and Weir Pumps Limited have agreed that the vibration experienced on the ERCW pumps was because of resonant amplification caused by the operating speed being too close to the natural frequency of the pumps.
The fundamental cause of the problem was that pump design resulted in natural frequencies too near the running speed. A contributing factor also appeared to be the fact that the floor under the pumps was reworked.
Safety Implications Excessive vibrations could lead to-failure of the pump and/or motor resulting in failure of the pump to perform its intended function of providing raw cooling water to the plant. This would result in loss of the cooling of safety-related equipment and would have affected adversely the safety of operations of the plant.
Corrective Action The solution to the vibration problem proposed by the pump vendor consists of shif ting the natural frequency away from the running speed by adding mass to the motors. TVA has evaluated the solution propcsed by Weir and determined it to be offective.
The permanent addition of weight to the motors has been seismically requalified. The seismic qualification of the ERCW pumps was verified by a Weir Pumps Report (Report No. TECH /LPD/NV/737/81, Revision 0, dated May 1981). This report was based on the original analysos performed by Mcdonald Engineering and presently included as an addendum to it.
The report concludes that 2500 pounds of additional weight could be added to the pumps without altering their seismic qualification. TVA has added approximately 1700 pounds to'the IA-1A pump and approximately 2100 pounds to the IA-2A pump. The vibration levels for each motor are now less than three mils (measured from peak to peak displacement). This is within acceptable limits. Modifications, if required, to other ERCW pumps will be considered separately when they become operational.
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