05000373/LER-2003-002
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident |
| Initial Reporting | |
| 3732003002R01 - 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: 4/23/03 � Event Time: 1848 Reactor Mode(s): 1 � Power Level(s): 100 Mode(s) Name: Run
B. DESCRIPTION OF EVENT
At approximately 1700 hours0.0197 days <br />0.472 hours <br />0.00281 weeks <br />6.4685e-4 months <br /> on 4/23/2003, the Unit 1 non-licensed rounds operator observed an intermittent trouble alarm at the Unit 1 Main Fire Panel (1FP04JA) in the Auxiliary Electric Equipment Room (AEER). The alarm was associated with the 0 Diesel Generator (DG)[EK] Carbon Dioxide (CO2)[100 suppression system. The rounds operator informed the Field Supervisor of this condition and continued with his rounds.
At 1815 hours0.021 days <br />0.504 hours <br />0.003 weeks <br />6.906075e-4 months <br />, the 1A DG control switch was placed in MAINTENANCE in preparation for performing a 24-hour run surveillance per surveillance procedure LOS-DG-R1A.
With the lA DG control switch in MAINTENANCE, the IA DC was declared inoperable and the applicable Technical Specification (TS) 3.8.1 time clocks were entered.
In the meantime, the Unit 1 rounds operator had continued with his rounds and at 1830 hours0.0212 days <br />0.508 hours <br />0.00303 weeks <br />6.96315e-4 months <br /> was in the vicinity of the 0 DG room. He decided to inspect the local CO2 fire suppression cabinet to determine if it could be the cause of the intermittent 0 DG CO2 suppression system alarm.
The rounds operator inspected the outside of the control panel and found no unusual indications. He then opened the control panel door to visually inspect the interior of the panel. The operator observed no discoloration on any circuit boards, no loose or broken connections, but he did observe a small amount of dust on the horizontally mounted Zone 1 Circuit Board. At 1848 hours0.0214 days <br />0.513 hours <br />0.00306 weeks <br />7.03164e-4 months <br />, he attempted to remove the dust by blowing on the circuit board, and a 0 DG CO2 suppression system fire alarm and a partial CO2 suppression system actuation occurred immediately.
A fire alarm was received in the control room for CO2 actuation in the 0 DG Room and LOA-FP-101, "Unit 1 Fire Protection System Abnormal' was entered. The fire brigade was dispatched to the scene and confirmed that there was no fire. No CO2 was discharged.
A walkdown identified that several dampers in the 0 DG ventilation support system had closed as a result of the actuation. This made the 0 DG ventilation support system and the 0 DG inoperable, which made both the Division 1 and 2 DGs inoperable at the same time. TS 3.8.1 Condition F allows two required Division 1, 2, or 3 DGg to be inoperable for two hours. If operability Cannot bp reRtored, then Required Action G.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 0.2 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 />.
Once it was confirmed that there was no CO2 in the DG Rooms, the non-licensed operators entered the 1A DG Room and placed the DO control switch in STANDBY. The IA DG was restored to an operable status at 1952. The 0 and the lA DO were inoperable simultaneously for a total of 64 minutes.
This event was determined to be reportable under 10 CPR 50.72(b)(3)(v)(D) and 10 CFR 50.73(a)(2)(v)(D) as an event or condition that could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident. An ENS phone call was made at 0025 on 4/24/03 (EN# 39789).
C. CAUSE OP EVENT
The cause of the event was that dust/foreign material was present on the horizontally mounted Zone 1 Circuit Board, which was disrupted when the operator blew on it. The foreign material shorted across energized points on the Zone 1 Circuit Board, resulting in a partial system actuation and closure of the 0 DG ventilation dampers. The surveillances that are performed annually to verify proper operation of the CO2 systems do not include steps to remove accumulated dust or other foreign materials inside the panel, as the vendor suggests.
Troubleshooting was performed on the 0 DO CO2 suppression system to determine the reason for the intermittent alarms that caused the operator to open the local CO2 fire suppression cabinet. Troubleshooting revealed low voltage on the standby (back-up) batteries, which caused the alarms. The batteries were replaced. The standby batteries are replaced every two years, and were scheduled to be replaced in July 2003.
D. SAFETY ANALYSIS
The safety significance of this event was minimal. Normal AC power was available to Division 1 and 2 loads throughout the event. Had a loss of offsite power occurred, the 0 DG would have started and loaded, and the IA diesel could have been quickly made operable.
At the time of the event, outside air temperature was approximately 61 degrees F, 0 DG room temperature was approximately 75 degrees F, and 0 DO cooling water was fully operable with lake temperatures of approximately 69 degrees F. Of these parameters, cooling water temperature is the most critical to diesel operation.
Given these initial conditions, the 0 DO would have carried its design load long enough for the 1A DO to be returned to an operable status.
This was a Safety System Functional Failure.
E. CORRECTIVE ACTIONS
1. The Zone 1 Circuit Board was replaced with a new one as a precaution. No problems were found with the original board. Complete.
2. Surveillance procedures for the Diesel Generator Room CO2 System Channel Functional Test will be revised to add steps to inspect and remove any accumulation of dust or foreign material from the horizontally mounted circuit boards inside the CO2 control panels (AT# 155441-18).
3. Instrument and Electrical Maintenance personnel will be trained to inspect for and remove foreign material from horizontally mounted circuit boards when performing maintenance inside panels (AT# 155441-19/20).
F. - PREVIOUS OCCURRENCES A review of Licensee Event Reports over the previous three years found no previous or similar occurrences.
a. � COMPONENT FAILURE DATA This section is not applicable, since no components failed in this event.