Event Notification Report for March 07, 2002

POTENTIAL LOSS OF SAFE SHUTDOWN CAPABILITY


"At Oconee, TS 3.4.9 requires a minimum of 126 kW of Pressurizer heaters to be operable and capable of being powered from an emergency power supply. These heaters are needed to compensate for ambient heat loss from the Pressurizer in order to maintain single phase RCS natural circulation flow during various design basis events.

In addition, TS 3.10.1 requires that the Standby Shutdown Facility (SSF) be operable for certain emergency conditions. One subsystem of the SSF is the Auxiliary Service Water (ASW) system. This system supplies a back-up emergency feedwater supply to any or all of the three Oconee Units.

The Bases for TS 3.10.1 document that, in order to maintain single phase RCS natural circulation flow, an adequate number of Pressurizer heaters must be OPERABLE and capable of being powered from the SSF power supply.

On March 7, 2002, Oconee Nuclear Site Engineering personnel concluded that heat transfer losses from the Reactor Coolant System Pressurizer to the reactor building environment exceeded the value previously used in system calculations and analyses. This conclusion was based on recent analysis of operational data on all three Oconee Units. There are two results of this conclusion:

1.Engineering concluded that the TS 3.4.9 requirement for a
minimum of 126 kW of heater capacity is nonconservative.
Operations personnel were notified. The operable capacity
greatly exceeds the minimum so current compliance with the
intent of TS 3.4.9 is not considered an issue.

2.Engineering recommended to Operations that the SSF-ASW system be
declared inoperable because the existing heater capacity powered
from the SSF is less than the minimum needed to fully
compensate for the ambient heat losses as calculated from the
recent analysis.

Event:

At 1400 hours on March 7, 2002, Oconee Operations accepted the Engineering recommendation and conservatively declared the Standby Shutdown Facility (SSF) ASW system inoperable and entered TS 3.10.1, Condition A, which has a 7 day completion time. The SSF-ASW was declared inoperable due to the discovery by site Engineering that heat transfer losses from the Pressurizer to the reactor building environment exceeded the capacity of Pressurizer heaters powered from the SSF power source.

At the time of the discovery, there was no analysis to justify that single phase natural circulation could be maintained during all SSF design scenarios using the new loss values as inputs. Therefore Engineering concluded that there was a potential that two phase cooling might occur. At this time, the judgment of Engineering personnel is that two phase cooling would be adequate to protect the affected unit from any core damage, but two phase cooling is outside the TS basis documented for TS 3.10.1.

Analyses are in progress to support a revision of applicable Abnormal Procedure to provide interim compensatory guidance to Operators. It is expected that this guidance will allow the Operator to avoid two phase flow.

Oconee personnel will evaluate more permanent corrective actions after additional analyses are completed.

This event is conservatively being reported under 10 CFR 50.72(b)(3)(v) as a condition that, at time of discovery, could have prevented the fulfillment of the safety function of the SSF ASW system to maintain a safe shutdown condition.

The NRC Resident was notified at 1900 hours."

PLANNED LOSS OF POWER TO EOF DUE TO MAINTENANCE

"During performance of planned maintenance, the Emergency Operation Facility (EOF) will be de-energized. These maintenance activities, including electrical isolation and restoration are expected to last approximately 8 hours. Contingency plans for emergency situations have been established.

"This event is reportable per 10CFR50.72(b)(3)(xiii) since this constitutes a loss of an emergency response facility for the duration of the evolution.

"The NRC Resident was previously notified that this activity was scheduled to occur and will be informed of this ENS notification."

* * * UPDATE ON 3/7/02 @ 2231 BY WEEKLEY TO GOULD * * *

Power restored at 20:34 CT. Notified RDO(Loveless).

C-3 STEAM GENERATOR CLASSIFICATION BECAUSE GREATER THAN 1% OF THE INSPECTED TUBES WERE DISCOVERED TO BE DEFECTIVE

"At 0700 EST on March 7, 2002, with Watts Bar Unit 1 in Mode 6, steam generator inspections were being performed in accordance with Technical Specification (TS) 5.7.2.12, 'Steam Generator (SG) Tube Surveillance Program.' The results of the inspections performed on SG Number 4 indicated that greater than 1% of the inspected tubes were defective. Based on TS 5.7.2,12, this determination results in the classification of C-3. The current inspection results do not meet the criteria specified for steam generator tube degradation in Revision 2 of NUREG 1022, Event Reporting Guidelines 10 CFR 50.72 and 50.73. However, for classification C-3, WBN TS 5.9.9, 'SG Tube Inspection Report', requires that the results of the inspection be reported under 10 CFR 50.72. At this time, the submittal of a Licensee Event Report in accordance with 10 CFR 50.73 is not planned."

The NRC Resident has been notified.