05000305/LER-2005-004

LER-2005-004,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
Initial Reporting
3052005004R02 - NRC Website

FACILITY NAME (1) DOCKET NUMBER (2)� LER NUMBER (6 PAGE (3)

Event Description

On March 15, 2005 with the plant in Refueling Shutdown Mode, station personnel determined that the Kewaunee plant design for protection against internal flooding would not ensure that required safety-related equipment would be protected from the failure of non-safety related piping [PSP] in the turbine building [NM].

High water level in the turbine building would result in water flowing into certain Engineered Safety Features (ESF) equipment rooms. The ESF equipment rooms are separated from the remainder of the turbine building by non-water-tight doors and the plant floor drain system. The ESF equipment rooms contain the auxiliary feedwater (AFW) [BA], emergency diesel generators (EDG) [EK] [DG], and both 480 volt [ED] and 4160 volt [EB] ESF switchgear [SWGR]. The water could reach levels that may result in failure of certain ESF and plant safe shutdown equipment.

Documentation that considers specific flooding events from postulated failures of plant equipment exists, however, a complete internal plant flooding analysis was not developed during or subsequent to the plant's original design. Information describing the plant's design for internal flooding was limited.

Event Analysis and Safety Significance This event is being reported under 10 CFR 50.73(a)(2)(ii)(B), any event or condition that resulted in the plant being in an unanalyzed condition, and 10 CFR 50.73(a)(2)(v)(A), any event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to shut down the reactor and maintain it in a safe shutdown condition. This event was initially reported on March 15, 2005 as a 10 CFR 50.72 non-emergency event under criterion (b)(3)(ii)(B), unanalyzed condition, and criterion (b)(3)(v)(A), safe shutdown capability (reference Event Notification EN 414496).

This LER is not associated with an event resulting in actual flooding of any portion of the plant. However, flooding or excessive steam releases as a result of random or seismically induced failures of non-Class 1 systems in the turbine building could impact the safety-related function of the AFW pumps, the EDGs, the 480 volt ESF buses [BU], and the 4160 volt ESF buses. Based on the Significance Determination Process, this condition was characterized as Yellow.

This report involves a safety system functional failure.

Cause

A summary of the causes for this event are as follows:

1) Design basis documentation regarding flooding, HELB, seismic, and tornado protection lacked detail and was difficult to retrieve. This made it difficult for the plant staff to identify the actual flooding design basis requirements and determine what actions were required to maintain compliance with them.

2) Some processes related to maintaining the design basis were weak and were inconsistent with industry standards.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMBER (6 PAGE (3) 3) The plant staff lacked a thorough knowledge of the design basis and fully effective processes for determining the significance of problems and prioritizing their resolution.

4) The plant staff evaluation and resolution of identified and potential problems lacked rigor.

5) The PRA submitted for Kewaunee's IPE was flawed with respect to flooding risk.

Corrective Actions

1. The design and licensing basis for internal flooding to support current and future flooding design was compiled.

2. Seismic qualification of selected piping and components was completed.

3. Design modifications to protect Class 1 plant systems and components as defined in the Kewaunee USAR were completed. This included:

• Installation of flood barriers at the doors to rooms containing auxiliary feedwater pumps, 480 volt safeguards buses, the safe shutdown panel, emergency diesel generators 1A and 1B, and 4160 volt safeguard buses 1-5 and 1-6.

• Installation of check valves in selected floor drain lines connecting the turbine building and rooms containing Class 1 equipment.

• Installation of circuitry which trips the circulating water pumps on high water level in the turbine building basement.

• Rerouting of AFW lubricating oil cooler drain lines to the turbine building to prevent flooding in the AFW pump rooms.

4.IIn a letter dated November 14, 2005 (Letter from W. R. Matthews (Dominion Energy Kewaunee) to NRC, Kewaunee Power Station Update on Improvement Initiatives (ADAMS Accession No.

ML053190099), an update was provided on initiatives that were initially committed to on March 18, 2005 and identified additional improvement actions intended to address the conditions identified in this LER.

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