ML19332D547

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LER 85-003-03:on 890907,determined That Situation Could Arise Where Water Level Would Rise to 264 Ft Before Next Required Surveillance Interval.Cause Not Determined.Dike to Be constructed.W/891122 Ltr
ML19332D547
Person / Time
Site: North Anna Dominion icon.png
Issue date: 11/22/1989
From: Kane G
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-85-003, LER-85-3, N-85-003C, N-85-3C, NUDOCS 8912040130
Download: ML19332D547 (3)


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a VIRGlNI A ELECTRIC AND POWER' COMP ANY NORTH ANN A POWER ST ATION i P. o. BO A 402 MINERAL, VIRGINI A 23117 November 22, 1989 .

U. S. Nuclear, Regulatory Commission . Serial No. N-85-003C Attention:- Document Control Desk. N0/DEQ: nih. '

Washington, D.C. 20555 Docket No. 50-338 50-339 License No. NPF-4 NPF-7

Dear' Sirs:

The Virginia Electric and Power Company hereby submits the following updated Licensee Event Report applicable to North Anna Unite 1 and 2. This Licensee; Event Report has been updated to include an additional situation that could arise-under extreme rainfall conditions and to update the permanent corrective actions being taken.

Report No. LER 85-003-03

'This report has been reviewed by the Station Nuclear Safety and Operating a Committee and will be forwarded to Safety Evaluation and Control for their review.

Very Truly Yours, G . rm.a Station Manager Enclosures E '

cc: U. S. Nuclear Regulatory Commission

, 101 Marietta Street, N.W.

Suite 2900

Atlanta, Georgia 30323 Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station Oi hhbhff39

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.' LICENSEE EVENT REPORT (LERI ESTIMATED SU7, DEN PER F ESPONtf TO COMPLY FATH THl$

Po'%ENTs'%*A#D,',fo'fsDEN f'TLArL T' ' "L'RECW"Di AND REPORTS MANAGEMENT BRAlvCH tP430). U S. NUCLE AR PAPEHWO K RE T t'ON DJ t'3 .' O #C OF MANAGEMENT AND BUDGET W A$HINGTDN, DC 20bO3 8 ACJLITY NAME (il DOCEET NUMSER (23 FAGE G SNORTH ANNA POWER STATION, UNITS 1 AND 2 o l5 l 0 l0 l 0 l313 l8 1 l0Fl012 1' it'TLE 441 FLOODING POTENTIAL NOT PREVIOUSLY EVALUATED-UPDATED TO REVISE CORRECTIVE ACTION EVENT DAf t (Si Lim NUMRER 166 REPORT DATE (71 OTHER 7 ACILITits INVOLVED 186 MONTH DAY YEAR vtAR %Y , 707,$ MONYM DAY TEAR ' Acturv h Awas Doca T huusEntsi NORTH ANNA, UNIT 2 0 l 6 l 010 l o 131319 7 0l3 1l 9 8 5 8l5 0l0l3 0l3 1l1 2l2 8l9 o gs r o goio n i i OPE RATING THis REPORT IS SueMITTED PUR$UANT TO THE ALOUIREMENTS OF 10 CFR l ten.c4 ene or mor of in foneamfl Cia "00 ' * ' to no2w 1 to 40em son.H2He n. tim g to naswHiHo so w.Hu 1 so.23i. Hum n.75m Hoi 110l0 to 4oe=Hm _

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A recent review of the North Anna Main Dam and other hydro structures

,. revealed that previous studies had failed to identify the Unit 3 & 4

1. construction area as a potential flood path to the Unit 1 & 2 Turbine Building. Partial flooding of the Turbine Building is addressed by the  !

UFSAR. Current procedures provide guidance for action to be taken in response to rising lake level.

However, on September 7, 1989, it was determined that due to the current surveillance interval required by Technical Specification 3/4.7.6, a l

situation could arise, under Design Basis rainfall' conditions, where the L water level is measured below 255 feet and.would rise to 264 feet prior to j- the next required surveillance interval.

I As a corrective action, a Justification for Continued Operation was J

l written and administrative controls were implemented to require surveillance of the water level at an increased frequency. As a permanent corrective 1 action a flood control dike will be constructed to protect safety related electrical equipment from flood damage.

l LC Form 366 (68st

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." 88100 Nem 3B04 U.S. NUCLE A 4 [E!UL1 TORY COMMISSIO88

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LICCNSEE EVENT REPORT (LER) TEXT CONTINUATION areRovto ove no m-oioa EXPIRES 4?31/M

's FACILITY anaME Of . DOC 8tET 8suenett.4 (21 Lin tuuhe8EP (Si Pact (3)

YEAR SQ' MAL

$7 NORTH ANNA POWER STATION, UNITS'l & 2 o l5 jo l0 l0 l3 l3 J 8 8] 5 --

0 l0 l3 --

0l3 0l2 OF 0 l2 uxv .w- ==. . ==.4 w ac r.= amm im A recent review of the North Anna Main Dam and other hydro structures -

revealed that previous studies had failed to identify the Unit 3 8. 4 I construction. area as a potential flood path to the Unit 1 & 2 Turbine building. Partial flooding of the Turbine building is addressed by the UFSAR. The normal Lake Anna water level is 250 feet above mean sea level (msl). Finished ground grade elevation for the station is 271 feet. The Turbine Building basement elevation is 254 feet. The Unit 2 end of the Turbine building faces the Unit 3 & 4 restored construction site area which has a nominal elevation of 250 feet. Dike VI protects the Unit 3 & 4-construction area from Lake Anna flooding up to 255 feet. The original FSAR-estimated . lake flood level was 254.5 feet. In June 1976 a revised analysis indicated a still-water probable maximum flood level of 264.2 feet could exist at the station site. The height of Dike VI had not been identified as insufficient until a recent study.

During a probable maximum flood, Dike VI would not protect the Unit 3 &

4 restored contruction site from flooding. Further, Unit 2 Turbine Building does not have a water tight wall (cinder block with doors sealed by steel plating). on the westside facing the restored area. The UFSAR evaluation addresses flooding the Turbine Building to 255' 11" during a maximum flood event, without safety related equipment damage. If no additional action is taken to pump-the Turbine Building the possibility exists that the water level in the Turbine Building could exceed the height of the water tight walls which are designed to protect the Service and Auxiliary Buildings to the 257 foot level.

A significant length of time will exist between the first indication of rising lake level and possible Servics Building flooding and will allow adequate corrective measures to be implemented. Existing procedures provide guidance on lake level control with the operation of dam gates, shutdown of both units during unusually high lake level, minimizing Turbine Building flooding and implementing the Emergency Plan if safety related equipment could be affected by flooding.

However, on September 7, 1989, it was determined that due to the current surveillance interval required by Technical Specification 3/4.7.6, a situation could arise, under Design Basis rainfall conditions, where the water level is me asured below 255 feet and would rise to 264 feet prior to the next required surveillance interval.

As a corrective action, a Justification for Continued Operation was I i

written and administrative controls were implemented to require surveillance of the water level at an increased frequency. As a permanent corrective action a flood control dike will be constructed around the end of the Unit 2 Turbine and Service Buildings. The construction of the flood dike will be completed in 1989. In the interim, the already implemented compensatory measures (see above paragraph) will be continued.

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