05000424/LER-2004-002
| Docket Number(S)Seouential Revisionmonth Day Year Year Month Day Yearnumber Number Vegp - Unit 2 05000425Property "Site" (as page type) with input value "Docket Number(S)Seouential Revisionmonth Day Year Year Month Day Yearnumber Number Vegp - Unit 2 05000425" contains invalid characters or is incomplete and therefore can cause unexpected results during a query or annotation process. | |
| Event date: | 04-22-2004 |
|---|---|
| Report date: | 06-17-2004 |
| 4242004002R00 - NRC Website | |
FACILITY NAME (1) DOCKET LER NUMBER (6 PAGE (3)
A. REQUIREMENT FOR REPORT
This report is required per 10 CFR 50.73 (a)(2)(i)(B). The units operated in a condition prohibited by the Technical Specification (TS) when the control room air intake radioactive gas monitors were inoperable for a period of time greater than that allowed by the action requirements.
B. UNIT STATUS AT TIME OF EVENT
At the time of this event, Unit 1 was in Mode 1 (Power Operations) at 100% of rated thermal power.
Unit 2 was in Mode 6 (Refueling) at 0% of rated thermal power. Other than that described herein, there was no inoperable equipment that contributed to the occurrence of this event.
C. DESCRIPTION OF EVENT
On the morning of April 22, 2004, a Unit Shift Supervisor (USS) shift turnover walkdown was in progress in the Unit 1 control room. At 0540 EDT, the USS found the Control Room Normal HVAC Outside Air Damper, AHV-12153, closed. The pressure differential between control room air and the outside atmosphere was checked and found to be zero. This condition stops flow past the control room air intake radioactive gas monitors, rendering them inoperable. After verifying that there was no valid reason for maintaining AHV-12153 closed, it was re-opened at 0548 EDT, restoring the control room differential pressure.
A review of the Integrated Plant Computer (IPC) records found that the AHV-12153 was closed on April 21, 2004, at 1242 EDT. This represented a total of 17 hours1.967593e-4 days <br />0.00472 hours <br />2.810847e-5 weeks <br />6.4685e-6 months <br /> and 6 minutes that the damper was closed and the control room air intake radioactive gas monitors were inoperable. TS 3.3.7 requires the control room emergency filtration system (CREFS) to be placed in the emergency operating mode if the control room air intake radioactive gas monitors are inoperable for more than one hour. Because the one hour time was exceeded and CREFS was not placed in the emergency operating mode, the units operated in a condition prohibited by the TS.
D. CAUSE OF EVENT
On April 21, 2004, switchgear 2AB05 was being cleaned per the generic switchgear cleaning procedure 27731-C, "480 Volt Switchgear Cubicle / Transformer Maintenance." This procedure required the cell switch for switchgear breaker 04 to be cycled five times. Although the switchgear itself was de-energized, cycling the switch allowed the de-energizing of two solenoid valves that must remain energized to maintain AHV-12153 open. Furthermore, it takes manual action to re open the damper after cell switch cycling, but the procedure does not take steps to ensure the damper FACILITY NAME (1) DOCKET LER NUMBER (6 PAGE (3) is re-opened. In addition, the Operations dept. electrical switchgear notes, used to assist plant operators in determining what is affected by clearances, had no information regarding loss of power to the damper due to exercising the cell switch. Therefore, the cause of this event was a failure of the work planning process to recognize that operation of the cell switch in the de-energized switchgear would have an effect on an operating component.
E. ANALYSIS OF EVENT
During this event, AHV-12153 was closed while Unit 2 was in Mode 6 with no fuel movement or core alterations in progress, and Unit 1 was in Mode 1. The primary means of actuating the CREFS via a safety injection signal was still operable. Furthermore, no such event occurred during the 17+ hours involved. Based on these considerations, there was no adverse effect on plant safety or on the health and safety of the public as a result of this event.
The event does not represent a safety system functional failure.
F. CORRECTIVE ACTIONS
1) The switchgear cleaning procedure, 27731-C, will be revised by October 29, 2004 to address actions to be taken when operating cell switches that effect dampers for the four CREFS units.
2) By September 21, 2004, appropriate information will be added to the Operations department electrical switchgear notes, for the affected switchgear, to assist in future work planning.
G. ADDITIONAL INFORMATION
1) Failed Components:
None 2) Previous Similar Events:
There have been no previous similar events in the last three years.
3) Energy Industry Identification System Code:
Control Room Emergency Filtration System — VI Plant Effluent Radiation Monitoring System — IL Integrated Plant Computer System — ID 480 Volt AC Switchgear System - ED