ML20010B005

Forwards LER 81-114/03L-0.Detailed Event Analysis Encl

ML20010B005
Person / Time
Site:	McGuire
Issue date:	08/07/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20010B006	List: ML20010B005 ML20010B009
References
NUDOCS 8108130211
Download: ML20010B005 (3)

Text

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DUKE POWER COMPANY 3 . ,. 3 g . p g , j .; ' '

POWER DUII. DING ' \ ~/ 4 432 SouTIt Cnuncu STnEET, CHANI.OTTE, N. C. asa4a n

1 i ' m p) P \ bb WIW AM O. PARMER, J R. August 7, 1981 Vice Persiotut : Ttttpoiost:AntA704 SttAnn PacDuCTion 373-4083 Mr. James P. 0'Reilly, Director U. S. Nuclear Regulatory Commission Region 11 101 Marietta Street, Suite 3100 gh@,, /O s Atlanta, Georgia 30303 /\\ '

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Re: McGuire Nuclear Station Unit 1 Docket No. 50-369 M l,,,p c3;.

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Dear Mr. O'Reilly:

A Please find attacned Reportable Occurrence Report RO-369/81-114. This report concerns Technical Specification 3.7.1.2, "At least three independent steam generator auxiliary feedwater pumps and associated flow paths shall be operable . . . ." This incident was considered to be of no significance with respect to the health and safety of the public.

V y truly yours, JAA 0. ' r William O. Parker, Jr'.

PBN:scs Attachment cc: Director Mr. Bill Lavallee Office of Management and Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Commission P. O. Box 10412 Washington, D. C. 20555 Palo Alto, California-.94303-.

Ms. M. J. Graham NRC Resident Inspector McGuire Nuclear Station 8108130211 810907 4/ 7 DR ADOCK 0500 6 ,

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DUKE POWER COMPANY MCGUIRE NUCLEAR STATION' REPORTABLE OCCURRENCE Report Number: 81-114 Report Date: August 7, 1981 Occurrence Date: July 8, 1031 Facility: McGuire Nuclear Station, Unit 1, Cornelius, North Carolic; Identification of Occurrence:

The turbine driven auxiliary feedwater pump was declared inoperable due to a slow operating time for two steam supply valves.

Condition Prior to Occurrence: Mode 3, Hot Standby

. Description of Occurrence:

The two steam supply valves provide steam to the auxiliary feedwater pump turbine.

During the valves' periodic test, it was discovered that they would not cycle within the required time limit (50 seconds). Since all auxiliar*, feedwater pumps are required in Mode 3, this incident is reportable pursuant ta Technical Specifi-cation 3.7.1.2.

Apparent Cause of' Occurrence:

The two valves use air pressure to close and a spring to open. Apparently the orifice which bleeds off air pressure (to open the valve), was too small. This resulted in a long opening time for the valves.

Analysis of Occurrence:

When the two valves were originally installed and tested, stroke times were well within the accepted limits. There was a problem with water hammer, however, because they were opening too quickly. To correct this, the system was slightly redesigned, and a smaller orifice was used to bleed air off them more slowly. It was hoped that if the air bled slowly, then the valve would open at a corrasponi-ingly slow rate. Instead, the air bled slowly, with no corresponding valve move-ment. When a threshold air pressure was reached to break the plug loose from the seat, the valve would quickly stroke open. The threshold at which opening occurred was very dependent on system conditions during valve closure, i.e. system pressure, temperature, flowrate, temperature cycles, etc. It was decided that the orifice should be increased to its original size. The system redesign should eliminate any of the previous water hammer problems.-

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>\; o Report Number 81-114 Page Two Safety Analysis:

There were no incidents during this time which required use of the auxiliary feedwater pumps. Even if they had been required, both motor driven auxiliary feedwater pumps were available the entire time. In addition, since the two-

= valves did eventually open, the turbine driven auxiliary feedwater pump was available for long-term cooling. Therefore, this incident had t. effect on the health and safety of the public.

Corrective Action:

The orifice, which controls the air bleed off rate, was replaced with a' larger size. The valves were retested and returned to operable status on July 23, 1981.

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