ML19208D413

LER 79-112/01T-0:on 790912,Tech Spec Upper Level Limit for Refueling Water Storage Tank Was Exceeded & Was Less than FSAR Vol Requirement.Caused by Incorrect Station Curve,Based on Usable Vol as Opposed to Contained Vol

ML19208D413
Person / Time
Site:	North Anna
Issue date:	09/26/1979
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19208D410	List: ML19208D409 ML19208D413
References
LER-79-112-01T, LER-79-112-1T, NUDOCS 7909280398
Download: ML19208D413 (2)

Text

NRC FORM 366 U. S. NUCLE AR REGULATORY COMMISSION (7-771 LICENSEE EVENT REPORT CON TROL BLOCK: l l l l l l l (PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 1 6 lO lil l Vl Al ? l Al S 1 @lIS 0l 0l -l 0lLICENSE 14 0l 0l 0l 0l - 0l Ol@l huMBER 2S 26 4 1 Il 1l 1 @l51 L Al T Sdl@

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719 k 0l9l2l6l7 9h 14 75 RE POP T D ATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h o 2 l During Mode 1 operation, the Technical Specification unner level linit for the o 3 l RWST was exceeded when the station curve for the tank was discovered to be inenrrect.I o 4 l Also, the Technical Specification RWST limits were found to be less than the vol-o s required by the FSAR for post accident containment depressurization. Si ice suf ficiend o 6 water was available for post accident requirements. the health and safety of the 1 0 7 general public were not affected by this event. Reportable pursuant to l 0 s l T. S . 6.9 .1. 8. f . 80 l

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43 44 Sl 4] 2l Q@ 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS i o The station curve for the RWST was incorrect because it was based on usable volume I j, ji l as opposed to co*.tained volume and the Technical Specificatic RWST limits wera I

, , ; below the volume required by the FSAR because the limits we .e never changed followine l

, 3 l modifications to correct pump NPSH. A safety analysis was performed and a Technical i, j4; j Specification change was submitted to raise the RWST limits. The station curve for 7 8 3 tne te n volume was also correcte . so ST S  % POWER OTHER STATUS DISCOV RY DISCOVERY DESCRIPTION i s l Ej@ l 0l 8l ggl 10 NA 44 l l45Cl@l46 Review of Emergency Procedure 80 7 8 9 12 11 ACTIVI TY CONTENT RELE ASED OF RELE ASE AYOUNT OF ACTIVITY LOCATION OF RELEASE 7

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PERSONNEL EXPO $URES NUVPER TYPE DESCRIPTION lilil l IOl@lZl@l l PERSONNE L INJURIES NUVaER DESCRIPTION

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NAME OF PREPARER R PHONE: MnP"' 5151

Virginia Electric and Pows r Company North Anna Power Station, Unit #1

Attachment:

Page 1 of 1 Docket No. 50-338 Report No. LER 79-112/0lT-0 Description of Event During Mode 1 operation, the Technical Specification upper level limit for the Refueling Water Storage Tank (RWST) was exceeded. This event was discovered while reviewing the emergency procedure for a loss of coolant accident (LOCA).

The amount of water required by the FSAR to be pumped into the containment by the quench spray pumps following a LOCA was determined to be greater than the Technical Specification requirements for contained water volume of the RWST.

The physical layout of the RWST was reviewed to determine the amount of usable volume of borated water in the RWST for quench spray purp operation. The res nlts of this review determined that the station curve was incorrect in that it was based on usable volume as opposed to contained volume. With the station curve corrected to show contained volume, the RWST level was greater than the maximum level limit of the Technical Specifications 3.1.2.8 and 3.5.5. No significant occurrence took place as a result of this event.

Probable Consequences c2 Event This event did not a'.fect the public health or safety. The RWST level was maintsined higher than the Technical Specification limit; however, the Tech-nical Specificatior. limit was less than the FSAR required volume for post accident containme.it depressurization. Sufficient water was available for post accident requirements. Unit 2 is similarly affected.

Cause of Event The cause of the high level in the RWST was that the Technical Specification limit is based on a contained volume and the station curve, which was used to fill the tank, was based on a usable volume. Tha difference is approximately 17,000 gallons. The cause of the Technical Specification RWST limit being less than the FSAR volume required for post accident containment depressuri-zation, was that the licits were not changed following station modification to correct the NPSH of certain safety grade pumps.

Immediate Corrective Action The RWST level was lowered to the upper Technical Specification limit of 464,000 gallons of contained voltae. This allowed a volume of 445,000 gallons of borated water in the RWST which could be expended into the containment following an accident. A safety analysis was performed to evaluate the re-duced amount of water available. The FSAR value of 456,000 gallons required was based on the core rating of 2910 MWT. Using the Technical Specification limit of 2775 MWT, the safety analysis showed that the usable volume of 445,000 gallons was sufficient. A Technical Specification change was submitted to raise the RWST limits and the station curve for the RWST volume was corrected.

Scheduled Corrective Action This is considered an isolated incident and no further corrective action is planned.

Actions Taken to Prevent Recurrences No further actions are required.

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