PNO-I-06-014, A: Calvert Cliffs Update of Preliminary Notification on Shutdown Greater than 72 Hours Due to Trip from Closure of Main Turbine Governor and Intercept Valves
| ML063240221 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 11/20/2006 |
| From: | Brian Mcdermott Reactor Projects Branch 1 |
| To: | |
| McDermott, B J, RGN-I/DRP/610-337-5233 | |
| References | |
| PNO-I-06-014A | |
| Download: ML063240221 (2) | |
DCS No.: 05000318111606 Date: November 20, 2006 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-I-06-014A 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 Constellation Generation Group, LLC Licensee Emergency Classification Calvert Cliffs Unit 2 Notification of Unusual Event Lusby, MD Alert Docket: 50-318 Site Area Emergency General Emergency X Not Applicable
SUBJECT:
UPDATE - SHUTDOWN GREATER THAN 72 HOURS DUE TO REACTOR/TURBINE TRIP FROM THE UNEXPECTED CLOSURE OF MAIN TURBINE GOVERNOR AND INTERCEPT VALVES On November 16, 2006, at 12:18 a.m., Calvert Cliffs Unit 2 experienced an automatic reactor trip from full power due to the unexpected closure of main turbine valves during a maintenance activity. Closure of the turbine valves resulted in a reactor trip on high reactor coolant system (RCS) pressure. All control rods fully inserted in response to the reactor trip. One power operated relief valve (PORV), which opened to control RCS pressure, remained open for longer than expected (approximately 90 seconds). The resulting RCS depressurization caused a safety injection actuation signal (SIAS) and safety-related equipment responded as expected.
Operators implemented emergency operating procedures, stabilized the plant in hot shutdown, and initiated a plant cooldown.
Cold shutdown conditions were established as of 1:25 a.m., on November 17. During the shutdown, plant workers replaced the pressurizer PORV that malfunctioned and the quench tank rupture disk. One pressurizer safety valve was also replaced due to suspected seat leakage. Plant staff and the NRC inspectors completed physical inspections of the PORV and relief valve tail pipes, associated supports, and the quench tank. No significant equipment problems were identified. The licensee's preliminary investigation found that the initiating event (turbine valve closure with no direct reactor trip) was caused by an electrical maintenance tagout that was not adequately reviewed for operational impacts. The plant response to the trip was as expected, with the exception of the pressurizer PORV that did not immediately close when its pilot solenoid was de-energized. A detailed evaluation and inspection of the PORV will be performed by the licensee as part of followup actions for this event. The results of their evaluation will be provided to the NRC as part of the required Licensee Event Report for the trip. After completing post-maintenance tests and establishing corrective actions to prevent recurrence of this event, licensee personnel began preparations for a reactor startup.
Routine NRC inspection followup is planned for this event. The State of Maryland will be informed. The information in this updated preliminary notification has been reviewed with the Calvert Cliffs Director of Licensing, and is current as of 2:30 p.m. EST on Monday, November 20, 2006.
ADAMS Accession Number: ML063240221 CONTACT: Brian McDermott Arthur Burritt (610) 337-5233 (610) 337-5069
2 DISTRIBUTION: (PN Recipient List)
OWFN TWFN LST Chairman Klein IRO PDR Comm. Lyons NMSS Comm. Jazcko ACRS Comm. McGaffigan Jr. OIG Comm. Merrifield RES OIP NSIR OCA OGC OPA EDO OE NRR SECY Regional Offices By Fax:
DOT:Trans INPO NSAC RI Resident Office Licensee: Constellation Generation Group, LLC (Calvert Cliffs)
ADAMS Accession Number: ML063240221 SUNSI Review Complete: BJM (Reviewers Initials)
DOCUMENT NAME: C:\FileNet\ML063240221.wpd After declaring this document An Official Agency Record it will be released to the Public.
To receive a copy of this document, indicate in the box: "C" = Copy without attachment/enclosure "E" = Copy with attachment/enclosure "N" = No copy OFFICE RI/DRP RI/DRP RI/ORA RI/DRP RI/DRP NAME ABurritt/ARB NMcNamara/MM for DScrenci/DPS BMcDermott/BJM DLew/DCL DATE 11/20/06 11/20/06 11/20/06 11/20/06 11/20/06 OFFICIAL RECORD COPY Region I Form 83 (Rev. July 2, 2003)