ML19256A406
| ML19256A406 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/29/1978 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19256A405 | List: |
| References | |
| NCR-962, NUDOCS 7901050184 | |
| Download: ML19256A406 (1) | |
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ENCLOSURE SEQUOYAH NUCLEAR PLANT - UNITS 1 AND 2 HIGH-PRESSURE FIRE PROTECTION PUMP FAILURES NCR 962 FINAL REPORT Description of Deficiency.
The deficiency is the separation of the impeller from the pump shaf ts af ter a period of use.
In several astances, the high-pressure fire protection (HPFP) pumps and motors have been heavily damaged following separation of the impeller from the shaft.
Safety Implications If this deficiency had remained uncorrected, the possibility exists that coincident, multiple HPFP pump failures may have led to the inability of the plant to combat potential fires in safety-related areas.
If fires occurred in safety-related areas that could not be controlled, equipment necessary for safe shutdown of the plant may have been damaged or destroyed.
Corrective Action Upon discovery of the deficiency, pressure signature tests were performed on the pumps to aid in determining the cause of the pump failures.
The tests revealed a slight momentary pressure spike during HPFP coastdown before the upstream backflow check valve closed.
However, this pressure spike was not significant enough to create a hazard to the equipment.
The separation of the impeller was apparently due to the method of attaching the impeller to the pump shaft.
The impellers were initially attached by means of a lock collet construction which permitted them to come loose due to a shock on the impeller.
The pumps are being repaired by reattaching thc* impellers by the thrust ring construction method which will prevent the impeller from becoming loose from the pump shaf t in future operation.
Pumps of similar design and manufacture used on safety systems will be checked for water hammer before being placed into service on any other of TVA's nuclear facilities.
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