05000260/LER-2001-001

LER-2001-001,

Event date:
Report date:
2602001001R00 - NRC Website

NAME

Ted G Achorn, BFN Licensing Supervisor TELEPHONE NUMBER (Include Area Code) (256) 729-3612 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

NPRDS

' — .F.:

TO NPRDS

X AA SHV G080 Y SUPPLEMENTAL REPORT EXPECTED 114) EXPECTED

SUBMISSION

DATE (15)

YES

(If yes, complete EXPECTED SUBMISSION DATE). X

NO

ABSTRACT (Limit to 1400 spaces, � i.e., approximately 15 single-spaced typewritten lines) � (16) On April 3, 2001 2351 CDT, during a refueling outage, Unit 2 received a reactor scram signal due to a west scram discharge volume high water level signal. All expected alarms and actuations were received. All control rods [AA] were initially in the "full in" position, therefore, no control rod movement occurred. The applicable immediate and subsequent actions specified in Abnormal Operating Instruction 2-A0I-100-1 were carried out.

The cause of the scram was the Scram Discharge Volume (SDV) exceeding the high level setpoint due to scram outlet valve leakby and the SDV vent and drain valves being shut to support plant maintenance. The leaking scram outlet valves have been repaired and the SDV vent and drain valves returned to service.

TVA is reporting this event in accordance with 10 CFR 50.73 (a)(2)(iv) as an event that resulted in a automatic actuation of an engineered safety feature, including the reactor protection system.

FACILITY NAME (1) DOCKET LER NUMBER (6) PAGE (3) Browns Ferry Nuclear Plant - Unit 2 05000260

I. PLANT CONDITIONS

Prior to the event , Unit 2 was in a refueling outage. � Unit 3 was at 100 percent power. Unit 1 was shutdown and defueled.

II. DESCRIPTION OF EVENT

A. Event:

On April 3, 2001, during a Unit 2 refueling outage, the water level in the scram discharge volume (SDV) [AA] instrument volume started to rise. This level increase occurred following the removal of a clearance for maintenance and was due to leakage through eight scram outlet valves. The applicable annunciators alarmed and at 2351 an automatic reactor scram occurred due to high SDV level. All expected alarms and actuations were received. All control rods were already fully inserted, therefore, no control rod motion occurred.

The immediate and subsequent actions specified in Abnormal Operating Instruction 2-A0I-100-1 were carried out without exception.

B. Inoperable Structures, Components, or Systems that Contributed to the Event:

None.

C. Dates and Approximate Times of Major Occurrences:

April 3, 2001, at 0743 hours0.0086 days <br />0.206 hours <br />0.00123 weeks <br />2.827115e-4 months <br /> CDT � Initiated clearance that shut SDV vent and drain valves.

April 3, 2001, at 2338 hours0.0271 days <br />0.649 hours <br />0.00387 weeks <br />8.89609e-4 months <br /> CDT Received west SDV level rod block.

April 3, 2001, at 2351 hours0.0272 days <br />0.653 hours <br />0.00389 weeks <br />8.945555e-4 months <br /> CDT Received reactor scram due to west SDV high water level.

April 4, 2001, at 0006 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> CDT Placed SDV high level bypass switch in bypass and reset the scram per Abnormal Operating Instruction A01-100-1.

April 4, 2001, at 0622 hours0.0072 days <br />0.173 hours <br />0.00103 weeks <br />2.36671e-4 months <br /> CDT A eight-hour non-emergency report was made to the NRC pursuit of 10 CFR 50.72 (b) (3) (iv) (B).

D. Other Systems or Secondary Functions Affected:

None.

E. Method of Discovery:

Operators received alarms indicating west SDV was nearing high level.

FACILITY NAME (1) DOCKET LER NUMBER (6) PAGE (3) Browns Ferry Nuclear Plant - Unit 2 05000260

F. Operator Actions:

Operations personnel responded to the event in accordance with applicable plant procedures.

G. Safety System Response:

All required safety systems operated as designed.

III. CAUSE OF THE EVENT

A. Immediate Cause:

West scram discharge volume high water level resulted in receipt of a reactor scram signal.

B. Root Cause:

The cause of the event was leakage through eight scram outlet valves while maintenance isolation prevented opening of the SDV vent and drain valves to allow draining.

C. Contributing Factors:

• An equipment clearance requiring the SDV vent and drain valves to be closed precluded draining of the SDV.

IV. ANALYSIS OF THE EVENT

On April 3, 2001, at 0743 hours0.0086 days <br />0.206 hours <br />0.00123 weeks <br />2.827115e-4 months <br />, a clearance was issued to allow packing replacement of the vent valves for both of Unit 2 SDVs. This maintenance required isolating the control air to both SDV vent valves and all scram outlet valves. In addition, a clearance was issued to repair an air line leak downstream of the SDV vent and drain valves. This clearance isolated control air to the vent and drain valves for both Unit 2 SDVs.

The vent and drain valves fail closed on loss of control air. This condition precluded draining of any water that may enter the SDV.

On April 3, 2001, at 1831 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.966955e-4 months <br />, maintenance was completed on the SDV vent valves. The return to normal alignment called for reopening the 185 scram outlet valves. Leaking scram outlet valves introduced water into the SDV. Since the SDV drain and vent valves remained closed to support other maintenance, there was no method to drain the SDV allowing level to rise to the SDV high level scram setpoint.

The cause of this event was leaking scram outlet valves allowing the SDV to fill to the high level scram setpoint. Contributing to this event was an equipment clearance leaving the SDV vent and drain valves closed precluding draining of the SDV.

V. ASSESSMENT OF SAFETY CONSEQUENCES

• The evaluation of plant system and component responses to the event concluded that responses were as designed and within the time-frames expected. The normal shutdown decay heat removal path was not affected during this event.

FACILITY NAME 11) DOCKET LER NUMBER (61 PAGE (3) Browns Ferry Nuclear Plant - Unit 2 05000260 There were no equipment failures during or following the scram. In addition, there was no radioactive material released and no actual or potential safety consequences as a result of this event. Therefore, this event did not adversely affect the safety of plant personnel or the public.

VI. � CORRECTIVE ACTIONS

A. Immediate Corrective Actions:

Operators carried out the requirements specified in the appropriate instructions.

B. Corrective Action to Prevent Recurrence:

Maintenance has repaired the leaking scram outlet valves.

Operations will coordinate with outage scheduling to ensure that future activities that require isolation of the SDV vent and drain valves will occur when the scram outlet valves remain shut. 1

A. Failed Components:

Scam outlet valves. General Electric Part Number 729E244P001.

B. Previous Similar Events:

None.

C. Additional Information:

None D. Safety System Functional Failure:

This event did not result in a safety system functional failure in accordance with NEI 99-02.

VIII. COMMITMENTS

None.

1TVA does not consider this corrective action a regulatory tracked in TVA's Corrective Action Program.

commitment. The completion of this item will be