ML20248B926

Special Rept PIR 2-M89-0232:on 890902,momentary Lifting of Two Pressurizer PORVs Occurred.Mixing of RCS After Pump Starts Could Have Caused Unexpected Pressure Decrease. Operators Discussed Hazards Re Starting of Pump

ML20248B926
Person / Time
Site:	Mcguire
Issue date:	10/02/1989
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
PIR-2-M89-0232, PIR-2-M89-232, NUDOCS 8910030330
Download: ML20248B926 (2)

Text

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, October.2, 1989 i

U.S.-Nuclear.. Regulatory Commission Document Control Desk

-Washington, DC- 20555

Subject:

.McGuire Nuclear Station, Unit 2 ~

Docket No. 50-370 -

Pressurizer.PORV Cycling Special Report-

>J- Gentlemen:

' Pursuant to Technical Specification (T.S.) 6.9.2 as specified by T.S. 3.4.9.3.c,

. find attached a special report concerning the cycling of PORVs 2NC-32 and 2NC-34.-

-LIf you have.any questions, please contact S.E. LeRoy at (704) 373-6233.

..Very truly yours, J

1 Hal B. Tucker SEL/462-

-Attachment' xc: 'Mr. S.D. Ebneter, Administrator Mr. P.K. Van Doorn U.S. Nuclear Regulatory Commission NRC Senior Resident Inspector Region II McGuire Nuclear Station 1C1 Marietta St., NW, Suite 2900 Atlanta, Georgia' 30323 i

Mr. Darl Hood, Project Manager INPO Records Center

-Office of Nuclear Reactor Regulation Suite 1300 U.S. Nuclear Regulatory Commission 1100 Circle 75 Parkway Washington, DC -'20555 Atlanta, Georgia 30339

%F ' I 8910030330 89100~2 PDR ADOCK 05000370 S PDC

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• 1 ' Document Control Desk Docket No. 50-370

( October 2, 1989 i

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Attachment Duke Power Company McGuire Nuclear Station Pressurizer PORV Cycling Special Report (PIR 2-M89-0232)

On September 2,1989 at 0400 with Unit 2 in Mode 5 during Reactor Coolant (NC) system fill and vent operations following a refueling outage, a momentary lifting of two pressurizer PORVs occurred. Following the initial 20 second NC pump run, the NC system was vented and considered water solid, with most of the air vented from the steam generator tubes, vessel head, and the pressurizer. Preparations were made to perform a simultaneous one minute run of all four NC pumps. Operator A was to start the NC pumps on 30 second intervals and monitor pump parameters.

Operator B was to monitor NC system pressure and respond to the expected decrease and subsequent increase in pressure.

NC system pressure decreased as expected on the first pump start, but continued to decrease when the second and third pumps were started. Operator B adjusted charging and letdown attempting to maintain NC pump seal differential pressure (D/P) greater than 200 psid to allow the last pump to start. Shortly after the last pump started, NC system pressure began to rapid)y increase. Operator B adjusted charging and letdown in an attempt to contro! the pressure increase. NC system pressure was beginning to stabilize when Operator A received an alarm indicating PORV 2NC-34 had actuated. He immediately verified system pressure was stable and that all PORVs were closed. After completion of the one minute run, all four NC pumps were stopped. Further examination of the alarm typer eevealed PORVs 2NC-34 and 2NC-32 had momentarily opened.

At the time of the incident, initial NC system conditions were at 97 degree-F and 350 psig. During the NC pump starts, NC system pressure dropped 75 to 100 psig and then rapidly recovered. Attempts to stabilize pressure appeared to have held NC system pressure at approximately 385 psig when an indication was received that PORV 2NC-34 had opened. NC system pressure was verified to be under control and maintained between 300 to 350 psig with all PORVs closed.

There was a long delay of four to eight hours after running the individual 20 second runs that could have led to temperature stagnations in the idle NC Fystem loops. The mixing of the NC system after the pump starts could have caused the unexpected pressure decrease. The lack of experience of Operator B in solid water operating conditions could have delayed his reaction to the subsequent pressure increase.

All operators involved in the incident discussed the transient and the hazards associated with starting the NC pumps under solid operating conditions. Two hours following the incident all four NC pumps were started and run for 10 minutes with no pressure control problems.

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