PNO-I-14-002, A - UPDATE- Millstone Dual Unit Trip with Loss of Offsite Power
| ML14153A180 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/02/2014 |
| From: | Raymond Mckinley NRC/RGN-I/DRP/PB5 |
| To: | |
| Raymond R. McKinley | |
| References | |
| PNO-I-14-002A | |
| Download: ML14153A180 (3) | |
Date: June 2, 2014 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE - PNO-I-14-002A This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. Some of the information may not yet be fully verified or evaluated by the Region I staff.
Facility Licensee Emergency Classification Dominion Nuclear Connecticut, Inc. __ Notification of Unusual Event Millstone Power Station, Units 2 and 3 ___ Alert Waterford, CT ___ Site Area Emergency Docket Nos. 50-336, 50-423 ___ General Emergency License Nos. DPR-65, NPF-49 _X Not Applicable
SUBJECT:
UPDATE - MILLSTONE POWER STATION UNITS 2 AND 3: UNUSUAL EVENT DECLARED DUE TO LOSS OF OFFSITE POWER AND DUAL REACTOR TRIPS AND NRC PLANS TO DISPATCH A SPECIAL INSPECTION TEAM This Preliminary Notification updates information discussed in PNO-I-14-002, which discussed a Notification of Unusual Event (NOUE) declaration at Millstone Power Station due to loss of offsite power (LOOP) and dual reactor trips.
On May 25, 2014, at 7:02 a.m. EST, Millstone Power Station Unit 2 and 3 experienced a Dual Unit trip due to LOOP. At 7:15 a.m., Millstone declared an NOUE due to a LOOP. The LOOP was due to a localized issue in the Millstone switchyard and the surrounding areas were not affected by the power loss. The Region 1 Incident Response Center entered monitoring mode at 7:49 a.m. and exited at 3:02 p.m. on May 25, 2014. Dominion exited the NOUE at 2:14 p.m.
on May 25, 2014. Both units are currently in a safe and stable condition.
Millstone Unit 2 responded normally. Unit 2 emergency diesel generators (EDGs) started and supplied power to all safety buses and all safety systems responded as designed. Millstone Unit 3 experienced an unexpected loss of non-safety instrument air following the LOOP, which complicated the recovery actions. The normal reactor coolant system letdown flow path was not able to be established and this resulted in the rupture of the pressurizer relief tank rupture disk inside containment. The relief valve on the volume control tank lifted when restoring normal letdown. This caused the primary drains transfer tank to overflow into the auxiliary building.
This overflow path was isolated, and the normal letdown was subsequently restored. Both Unit 3 EDGs started and supplied power to all safety buses and all safety systems responded as designed. Off-site power was restored as of 12:56 p.m. on May 25, 2014. The NRC resident inspectors responded to the site and continue to closely follow Dominions actions. NRC oversight is being conducted through the NRCs baseline inspection program currently, and will be supplemented with a reactive inspection that will begin June 2, 2014.
After evaluating the causes of the event and assessing equipment condition, Dominion restarted Unit 2 on May 27, 2014, and Unit 3 on June 2, 2014.
The Region will dispatch a Special Inspection Team on June 2, 2014, to review and assess the equipment issues and station response to the event (see Press Release dated June 2, 2014).
2 State officials have been informed. Region I Public Affairs is prepared to respond to media inquiries.
The information presented herein has been discussed with Dominion Management and is current as of June 2, 2014, at 11:00 a.m.
This preliminary notification is issued for information only and no further notification by the staff is anticipated.
ADAMS Accession Number: ML14153A180 CONTACT: Raymond McKinley, Projects Branch 5 (610) 337-5150 Raymond.McKinley@nrc.gov
ML14153A180 Non-Sensitive Publicly Available SUNSI Review Sensitive Non-Publicly Available OFFICE RI/DRP RI/DRP RI/PAO RI/SLO RI/ORA NAME RMcKinley/RRM HNieh/HKN DScrenci/NAS for NMcNamara/DBT for WDean/DCL for DATE 5/30/14 5/30/14 5/30/14 5/30/14 6/2/14