ML20237L249
| ML20237L249 | |
| Person / Time | |
|---|---|
| Site: | Millstone, Cook, Zion, 05000000, Trojan |
| Issue date: | 08/24/1987 |
| From: | Novak T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Sheron B NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML20237L250 | List: |
| References | |
| AEOD-E709, NUDOCS 8708280020 | |
| Download: ML20237L249 (1) | |
Text
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AUG 2 41987 MEMORANDUM FOR:
Brian W. Sheron, Director DISTRIBUTION:
Division of Reactor and Plant Systems PDR Office of Nuclear Regulatory Research ROAB RF CHsu FROM:
Thomas M. Novak, Director MChi ramal Division of Safety Programs JRosenthal Office for Analysis and Evaluation KBlack of Operational Data MWilliams TNovak FROM:
AUXILIARY FEEDWATER PUMP TRIPS CAUSED BY VBenaroya LOW SUCTION PRESSURE Enclosed is an Engineering Evaluation Report on the above subject recently completed by this office.
Our review indicates that the low suction pressure trips of the AFW pumps were attributed to pressure oscillations or fluctuations in the suction lines, which created a momentary pressure drop despite sufficient available suction head. The momentary low pressure was sensed and actuated the pressure trips of the pumps. The operational conditions which contributed to the occurrence of pressure oscillations or fluctuations appear not to have been fully considered in the design of the pump low suction pressure protection systems.
The low suction pressure trips constitutes a common mode failure that can potentially render the AFW system inoperable and the plant would lose its redundancy in core heat removal capacity.
Although removal of the trip function from pumps can prevent spurious low pressure trip from occurring, the pumps would be susceptible to irreparable damage, during sustained low suction pressure conditions, without the low suction pressure trip protection.
In view of these potential deficiency and safety concern, it is suggested that RES review this potential problem in the ongoing program GI-124. The review should include the adequacy of safety design basis for the AFW system in the design of pump protection systems, and the impact of trip removal from pump on system reliability and availability.
If you have questions or comments, please do not hesitate to contact me or Chuck Hsu (x24443) of my staff. We shall be happy to meet with you or your staff to discuss this matter.
Original Signed By Thomas M. Novak Thomas M. Novak, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
Enclosure:
As stated 8708280020 870824 cc:
E. Jordan PDR ORG NEXD l
C. Heltemes PDR OFC
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