PNO-I-03-027, Dual Unit Reactor Scram Due to Electrical Grid Disturbance
| ML032591206 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 09/16/2003 |
| From: | NRC Region 1 |
| To: | |
| References | |
| PNO-I-03-027 | |
| Download: ML032591206 (5) | |
DCS No.:05000277278030915 Date: September 16, 2003 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-I-03-027 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically all that is known by the Region I staff on this date.
Facility: Licensee Emergency Classification:
Exelon Nuclear X Notification of Unusual Event Peach Bottom Atomic Power Station Units 2 & 3 Alert Delta, PA Site Area Emergency General Emergency Not Applicable Docket Nos.: 05000277; 05000278 License No.: DPR-44; DPR-56
SUBJECT:
DUAL UNIT REACTOR SCRAM DUE TO ELECTRICAL GRID DISTURBANCE On September 15, 2003, Region I responded to events associated with electrical grid transients that caused Peach Bottom Units 2 and 3 to scram. On September 15, at approximately 1:32 a.m.,
far from the site, breakers on the grid did not properly function to isolate a lightning strike and caused a low voltage condition on both offsite power sources to Peach Bottom. All four emergency diesel generators (EDG) immediately started and loaded all plant safety buses. Voltage returned to normal on offsite power source in approximately one minute.
The power interruption to the safety buses resulted in an automatic reactor scram and main steam isolation valves closure on both units at approximately 1:33 a.m. All control rods inserted. The high pressure coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems automatically started to control reactor water level. Safety relief valves (SRV) automatically opened to control reactor pressure. One SRV in Unit 3 initially stuck open, challenging the operators until it closed at about 400 psi reactor pressure. Operators controlled reactor pressure using SRVs, HPCI, and RCIC. At 2:30 a.m., the E-2 emergency diesel generator tripped on low jacket coolant pressure. The emergency diesel generator trip affected a 4 KV safety bus on each unit, which were subsequently transferred back to offsite power. Following the trip of the E-2 emergency diesel generator, Exelon declared an Unusual Event, based on the shift managers discretion because of degrading plant conditions. At approximately 7:40 a.m. Exelon restored safety and non-safety electrical buses to their normal configuration. At 10:46 a.m. Exelon terminated the Unusual Event. The operators were challenged, somewhat by a number of equipment problems, but were successful in placing the plant in safe condition.
Unit 2 and Unit 3 were placed in a cold shutdown condition at 4:25 a.m. and 1:20 p.m.
respectively, on September 16, 2003.
2 Resident and regional inspectors responded to the event and observed activities in the control room and Technical Support Center. Several inspectors will remain on-site this week evaluating the licensees response and investigation. NRC Region I Incident Response Center (IRC) was activated in the Monitoring Phase of Normal Mode until 6 p.m. 9/15. Headquarters and Region IV IRC also monitored site activities. The facts of this PN were verified with Exelon management.
The Region I Public Affairs is prepared to respond to media inquiries.
The Commonwealth of Pennsylvania and State of Maryland have been informed.
Contact:
Dr. Mohamed Shanbaky (610) 337-5209
3 DISTRIBUTIONS:
BY E-MAIL:
OWFN TWFN LST Chairman Diaz IRO PDR Comm. McGaffigan Jr. NMSS Comm. Merrifield OIG OIP RES OCA OGC EDO OE NRR SECY Regional Offices BY FAX:
DOT:Trans INPO NSAC RI Resident Office Licensee: ___________________________
(Reactor Licensees)
DOCUMENT NAME: G:\BRANCH4\Peach Bottom\PN 9-16-03 Grid Disturbance.wpd OFFIC RI/DRP RI/ORA RI/ORA RI/DRP E
NAME MBuckley/MS RBores/RJB DScrenci/NAS BHolian/BEH for for DATE 09/16/03 09/16/03 09/16/03 09/16/03 Region I Form 83 (Rev. July 2, 2003)