05000220/LER-2003-003
| Event date: | |
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| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation |
| 2202003003R00 - NRC Website | |
1. pescriotion of Event On November 13, 2003 at 2149 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.176945e-4 months <br />, with the reactor at approximately 100% power, Emergency Diesel Generator (EDG) 103 automatically initiated due to the momentary loss of offsite 115 kV power source Line 04 and an abnormal plant configuration.
Nine Mile Point Unit 1 (NMP1) receives 115 kV service from two offslte power sources, Une #1 and Une #4. Line #1 and Line #4 provide power to 4160 V emergency power boards (PB) #102 and 0103, respectively. The two offslte sources are connected through a 115 kV reserve bus and a normally dosed, bus sectionalizing motor- operated disconnect switch MD5-8106. The reserve bus, with the closed disconnect switch, allows one offsite power source to feed both emergency PBs. In the event offsite power Is unavailable, each PB can be supplied power from Its associated EDG. EDG 103 (PB #103) and EDG 102 (PB #102) will automatically initiate on a low voltage condition.
On November 13, 2003 at 2149 hours0.0249 days <br />0.597 hours <br />0.00355 weeks <br />8.176945e-4 months <br />, high wind conditions resulted In the momentary loss of Line #4. At the time, failed switch MDS-6106 was open to facilitate required maintenance activities on the switch. As a result, Line #1 was unavailable to provide power to PB #103. Consequently, the loss of Line #4 resulted in a low voltage condition on PB #103 and the automatic Initiation of EDG 103. Also, toss of Line #4 resulted in an undervoltage condition on PH #101, causing the trip of recirculation pump #13, end a subsequent reduction in reactor power.
11. Cause of Event The apparent cause of the event was 1) high wind conditions which resulted in the temporary loss of Line #4, together with 2) the abnormal configuration of reserve bus disconnect switch MOS 6106 (i.e., MOS-6106 was open). Failed switch MDS-6106 was in the open position to facilitate necessary maintenance activities. With MDS-6106 In the closed position, Line #1 would have been available to supply uninterrupted power to PS #103 and EDG 103 would not have automatically initiated.
III. Analysis of Event
The automatic Initiation of EDG 163 Is reportable in accordance with 10 CFR 50.73(2)(2)(1v)(A). The event did not pose a threat to the health and safety of plant personnel or the public based on the following:
Plant systems responded as designed to the loss of Line #4 event.
EDG 103 automatically initiated as designed on a low voltage condition to supply power to PB #103.
Offsite power source Line #1 as well as EDG 102 were operable and available to supply power to redundant emergency PB #102.
NRC FORM MA (1-2031)
IV. Corrective Actions
Immediate actions Included verification that the plant responded properly to the loss of Line #4 event and entry into appropriate operating procedures. Reserve bus disconnect switch MDS-8105 has been repaired. Preventive maintenance procedures will be generated/ revised, as necessary, to enhance reliability of the subject switch.
V. Additional Information
I. Fulled Components: None 2. Previous similar events: None 3. Identification of components referred to in this Licensee Event Report:
Components � IEEE 805 System JD � IEEE $03A Function 115 kV Offsite Power System � FK � N/A Emergency Diesel Generator � EK � DG Reserve Bus � FK � BU Disconnect Switch � FK � DISC Recirculation Pump � AD Power Board � EB � BD