ML20214F540

Revised Special Rept:On 860602,while Placing Valves 2NC-32 & 34 in Low Pressure Mode,Porv Setpoint Reduced to 400 Psig. Cause Unidentified.Valve Controlling Circuit Recalibr

ML20214F540
Person / Time
Site:	Catawba
Issue date:	11/13/1986
From:	Tucker H DUKE POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8611250342
Download: ML20214F540 (2)

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DUKE POWER GOMPAST P.O. Box 33100 CIIAHLOTTE, N.C. 28242 IIAL H. TUCKER Tener< owe

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November 13, 1986 Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 l

Atlanta, Georgia 30323 l

Re: Catawba Nuclear Station, Unit 2 Docket No. 50-414

Dear Dr. Grace:

Pursuant to Technical Specification 3.4.9.3, Action Statement c, please find attached a Revision to the Special Report which was submitted July 2, 1986, concerning the automatic opening of a pressurizer power-operated relief valve.

Very truly yours,

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Hal B. Tucker RWO/47/slb Attachment xc: Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C.

20555 NRC Resident Inspector Catawba Nuclear Station 8611250342 861113 PDR ADOCK 05000414 S

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SPECIAL REPORT LIFTED VALVE 2NC-34 (NC PORV)

Circumstances Initiating The Transient:

On June 2, 1986 during performance of controlling procedure for unit shutdown (OP/2/A/6100/02), step 2.61 placed valves 2NC-32 and 2NC-34 (pressurizer PORV's) in the low pressure (L/P) mode. This reduced the lift setpoint of the PORV's to 400 psig. 2NC-32 was placed in the L/P mode without incident. When 2NC-34 was placed in the L/P mode, it immediately lifted. The Operator at the controls immediately closed 2NC-34 by placing the valve in the " normal" wode. Pressure gauges being used during depressurization ranged in values from 380 to 360 psig. Computer indication for B loop was 379 psig. Further depressurization commenced and 2NC-34 was again placed in L/P mode. Again the PORY lifted, so it was returned to

" normal" mode. On the third attempt, with Reactor Coolant System pressure at 320 psig, 2NC-34 was placed in L/P mode without incident.

Effect of PORV On The Transient:

No real transient existed for the PORV to mitigate.

Reactor Coolant pressure was lowered to 320 psig and the PORV no longer lifted.

Corrective Action To Prevent Recurrence:

The valve's controlling circuit was thoroughly checked out, recalibrated and no problems were identified. The valve lifted at the correct pressures in the L/P mode. No further actuations of 2NC-34 have occurred to date.

The checkout and recalibration of the circuit should prevent recurrence.

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