05000373/LER-2003-001
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3732003001R00 - NRC Website | |
PLANT AND SYSTEM IDENTIFICATION
General Electric - Boiling Water Reactor, 3489 Megawatts Thermal Rated Core Power
A. CONDITION PRIOR TO EVENT
Unit(s): 1 � Event Date: 4/9/03 � Event Time: 1742 Reactor Mode(s): 1 � Power Level(s): 100 Mode(s) Name: Run
B. DESCRIPTION OF EVENT
On April 7, 2003, Unit 1 Division 2 125 VDC (DC)DJ] battery terminal voltage was observed to be oscillating by 1-2 VDC, and current was oscillating by approximately 30 amps. The Division 2 125 VDC system remained operable, because battery terminal voltage stayed above the Technical Specification (TS) Surveillance Requirement (SR) 3.8.4.1 limit of 128 VDC, and the TS SR 3.8.4.6 requirement to supply the required amperage for various system voltages at specified times were not challenged.
Troubleshooting determined that repairs to the battery charger were required, which would include replacing the charger sensing, amplifier and firing modules.
A temporary non-class 1E battery charger would be used during the maintenance activity, which would render the Division 2 125 VDC electrical power distribution subsystem inoperable. An estimated 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> was needed to complete the repairs.
TS 3.8.4 Condition A allows the Division 1 or 2 125 VDC electrical power subsystem to be inoperable for two hours. If operability cannot be restored, then Required Action E.1 requires the unit to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Required Action E.2 requires the unit to be in Mode 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />. TS 3.8.7 Condition B allows Division 1 or 2 125 VDC electrical power subsystem to be inoperable for two hours. If operability cannot be restored, then Required Action D.1 requires the unit to be in Mode 3 in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and Required Action D.2 requires the unit to be in Mode 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
To repair the battery charger without placing the unit in a shutdown transient, a one-time relief from TS 3.8.4, Required Action A.1 and TS 3.8.7 Required Action B.1 was requested to extend the Completion Time an additional 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. This request was verbally transmitted to members of the NRC staff on April 9, 2003, at 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br />, with approval being verbally granted at 1358 hours0.0157 days <br />0.377 hours <br />0.00225 weeks <br />5.16719e-4 months <br />.
Repair of the Unit 1 Division 2 battery charger was initiated at 1742 hours0.0202 days <br />0.484 hours <br />0.00288 weeks <br />6.62831e-4 months <br /> on April 9, 2003. Following completion of the proposed work, post maintenance testing (PMT) was completed acceptably, and the charger was reconnected to the DC bus. Upon picking up the load of the DC bus, voltage and current fluctuations resumed, although at a reduced level. An operability review was conducted, and because TS SR 3.8.4.1 and 3.8.4.6 were not challenged by the oscillations, the Unit 1 Division 2 125 VDC system was declared operable at 0407 hours0.00471 days <br />0.113 hours <br />6.729497e-4 weeks <br />1.548635e-4 months <br /> on April 10, 2003.
The Unit 1 Division 2 125 VDC electrical power distribution subsystem was inoperable for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 25 minutes. Since this was in excess of the two hours allowed by the TS Required Actions identified above, this event is reportable under 10 CFR 50.73(a)(2)(i)(B) as an operation or condition prohibited by the plant's Technical Specifications.
On April 11, 2003, a written Request for Notice of Enforcement Discretion was submitted to the Commission.
C. CAUSE OF EVENT
Following the repairs performed on April 9, 2003, the voltage and current oscillations were reduced. On April 28, 2003, the 125 VDC feed to fire protection inverter 1FPOlE was isolated and the oscillations stopped.
Troubleshooting of 1FPOlE continues.
D. SAFETY ANALYSIS
The safety significance of allowing continued operation for 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> and 25 minutes with an inoperable 125 VDC battery charger and electrical power distribution system was minimal. The redundant Division 1 and Division 3 subsystems of Class 1E 125 VDC power were operable throughout the event.
E. CORRECTIVE ACTIONS
The DC feed to 1FPOlE has been removed. Troubleshooting of the 1FPOlE continues.
F. PREVIOUS OCCURRENCES
A review of Licensee Event Reports over the previous 10 years found no previous or similar occurrences.
G. COMPONENT FAILURE DATA
Troubleshooting of 1FPOlE is in progress.