05000373/LER-2003-002, Regarding 1A and 0 Diesel Generators Inoperable Simultaneously Due to Inadvertent Partial C02 Actuation
| ML031750595 | |
| Person / Time | |
|---|---|
| Site: | LaSalle  |
| Issue date: | 06/16/2003 |
| From: | Landahl S Exelon Generation Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| LER-03-002-00 | |
| Download: ML031750595 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 3732003002R00 - NRC Website | |
text
ExelnM Exelon Generation Company, LLC www.exeloncorp.com Nuclear LaSalle County Station 2601 North 21 Road Marseilles, IL 61341-9757 June 16, 2003 10 CFR 50.73 United States Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 LaSalle County Station, Unit 1 Facility Operating License No. NPF-1 I NRC Docket No. 50-373
Subject:
Licensee Event Report In accordance with 10 CFR 50.73(a)(2)(v)(D), Exelon Generation Company, (EGC), LLC, is submitting Licensee Event Report Number 03-002-00, Docket No. 050-373.
Should you have any questions concerning this letter, please contact Mr. Glen Kaegi, Regulatory Assurance Manager, at (815) 415-2800.
Respecffully, Susan Landahl Plant Manager LaSalle County Station
Attachment:
Licensee Event Report cc:
Regional Administrator - NRC Region IlIl NRC Senior Resident Inspector - LaSalle County Station
Abstract
At 1848 hours0.0214 days <br />0.513 hours <br />0.00306 weeks <br />7.03164e-4 months <br /> on April 23, 2003, while the 1A Diesel Generator DG) was inoperable for surveillance testing, a partial C02 suppression system actuation occurred for the 0 DG room when a non-licensed operator attempted to blow some dust off of a circuit board in the local C02 fire suppression cabinet.
The partial actuation closed several dampers in the 0 DG ventilation support system, which rendered the 0 DG inoperable.
No C02 was discharged.
Technical Specification 3.8.1 allows two DGs to be inoperable on the same unit for two hours.
If operability cannot be restored, the unit must be placed 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 in Mode 4 in 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.
The 1A DG was restored to operability at 1923 hours0.0223 days <br />0.534 hours <br />0.00318 weeks <br />7.317015e-4 months <br />.
The 0 and 1A DGs were simultaneously inoperable for 29 minutes.
The safety significance of the event was minimal, because normal AC power was available to ESF loads throughout the event, and the 0 DG would have started and loaded on a loss of offsite power.
The cause of the event was foreign material on the horizontal surface of the Zone 1 circuit board in the suppression cabinet.
Corrective actions
include revising the appropriate procedures to remove foreign material from the cabinet during periodic surveillances.
NRC FORM 366 (7-2001)
(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Forn 366A)
Once it was confirmed that there was no C02 in the DG Rooms, the non-licensed operators entered the 1A DG Room and placed the DG control switch in STANDBY.
The 1A DG was restored to an operable status at 1952.
The 0 and the 1A DG were inoperable simultaneously for a total of 64 minutes.
This event was determined to be reportable under 10 CFR 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 OF 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 C02 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 DG C02 suppression system to determine the reason for the intermittent alarms that caused the operator to open the local C02 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 1A 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 DG 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 DG would have carried its design load long enough for the 1A DG to be returned to an operable status.
This was not 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 C02 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 C02 control panels (AT# 155441-18).
(If more space is required, use additional copies of NRC Form 366A)
- 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.
G.
COMPONENT FAILURE DATA
This section is not applicable, since no components failed in this event.7-2001)