ML20203D628

Special Rept:While Venting Reactor Vessel Head,Operator Noticed That RCS Low.Operator Increased Letdown Flow to Decrease Nc Sys Pressure.Porv Actuated for 2 S.Operator Counseled to Pay Attention to Parameters During Evolutions

ML20203D628
Person / Time
Site:	Catawba
Issue date:	04/09/1986
From:	Tucker H DUKE POWER CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8604220221
Download: ML20203D628 (2)

Text

F

% i

. 4 DUKE POWElt Goxiwxy P.O.150X 33180 CIIAlt!.OTTE, N.C. 28242 HAL II. TUCKER

.. ._. p.\\ .h TEI.EPuowE no.o mmi.

, j, , g April 9, 1986 Dr. J. Nelson Grace, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 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 Special Report concerning the automatic opening of a pressurizer power-operated relief valve.

Very truly yours, J

A&L Hal B. Tucker RWO: sib Attachment ec: Director Office of Inspection and Enforcement  ;

U. S. Nuclear Regulatory Commission  !

Washington, D. C. 20555  !

1 NRC Resident Inspector l Catawba Nuclear Station i l

1 8604220221 860409 4 l PDR ALOCK 0500 s _

J ekk o t =;;-

d

, -o SPECIAL REPORT Lifted Valve 2NC32 (NC PORV)

Circumstances Initiating The Transient:

While in the process of venting the reactor vessel head, it was noticed by the operator that reactor coolant (NC) system was low. Pressure was approximately 260 psig and should have been 325 psig. He then made the necessary adjustments to NC system letdown flow to slowly increase NC system pressure.

Approximately five minutes later, pressure had increased to 301 psig and was still slowly rising. Seven minutes after this, valve 2NC32 lifted.

This condition alarmed the appropriate annunciator. The operator immediately increased letdown flow to decrease NC system pressure to 325 psig.

The PORV actuated for approximately 2 seconds. Maximum NC system pressure was 399 psig. The PORV actuated because while the operator was slowly increasing NC system pressure, other operations personnel were venting the Reactor Vessel head. The bubble was being compressed and vented at the same time. When it was completely vented (This occurred within five minutes of the PORV actuation), it caused a more solid water condition.

This resulted in a rapid pressure increase to 399 psig.

Effect Of PORV On The Transient:

The PORV and the operator's actions alleviated the condition. NC system pressure was lowered to 325 psig.

Corrective Action To Prevent Recurrence:

e Operator was counseled to pay proper attention to parameters when evolutions are in progress.

e Shift Supervisors will review this event to ensure other shifts understand the circumstances surrounding the event.