ML051080484
| ML051080484 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/18/2005 |
| From: | Paul Krohn NRC Region 1 |
| To: | |
| Krohn P, RI/DRP/PB6/610-337-5120 | |
| References | |
| FOIA/PA-2005-0208 PNO-I-05-17 | |
| Download: ML051080484 (3) | |
Text
DCS No.: 05000423041705 Date: April 18, 2005 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -- PNO-I-05-17 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 Millstone Unit 3 Power Station Licensee Emergency Classification Waterford, CT Notification of Unusual Event Docket: 50-423 X Alert Site Area Emergency General Emergency Not Applicable
SUBJECT:
ALERT DECLARED AT MILLSTONE 3 DUE TO A MAIN STEAM SAFETY VALVE NOT RESEATING AFTER AN SI ACTUATION ON LOW MAIN STEAM LINE PRESSURE On April 17, 2005, at 8:29 a.m. Millstone Unit 3 experienced a reactor trip from full power. In addition to the reactor trip, one of two trains of the Safety Injection (SI) and Main Steam Isolation (MSI) subsystems actuated. Control room operators manually initiated a full SI and MSI. There were also indications that multiple main steam line safety valves (MSSVs) opened with at least one MSSV that appeared to remain open. As a result, at 8:42 a.m., Dominion Nuclear Connecticut (DNC) declared an Alert due the failure of one MSSV to close. The response of the MSSVs is under further review.
The SI and MSI signals were initially attributed to a sensed low steam line pressure on one of four steam generators. Auxiliary Feedwater (AFW) automatically actuated during the event.
However, the turbine-driven AFW pump initially tripped and was successfully reset locally and restarted. Both motor-driven AFW pumps operated as expected to maintain steam generator levels. Due to the additional inventory added during the SI, the pressurizer filled and an overpressure condition caused pressurizer valves to lift and reseat. Operators responded to these conditions, stabilized the plant in Hot Standby and began a cooldown. Subsequently, the plant entered hot shutdown at 7:03 p.m. and DNC terminated the Alert at 7:05 p.m. The facts of this PN were verified with the Site Vice President - Millstone.
NRC resident inspectors responded to site, the NRC entered "monitoring" mode at 9:53 a.m.,
and activated the RI incident response center. The NRC, including on-site inspectors, monitored DNCs activities to stabilize the plant throughout the event including actions to place the plant in a hot shutdown condition.
DNC has established an event review team to review the root causes, extent of condition, and actions taken to address the event. The NRC staff is assessing event follow up per NRC Management Directive 8.3. Additional NRC inspection is planned to review DNCs actions including their root cause determination, safety system response including any identified equipment issues, and actions taken to mitigate the consequences of the event.
The Region I Public Affairs Office issued a press release and has responded to media inquiries.
DNC issued three press releases during the event. The States of Connecticut and New York have been informed.
ADAMS Accession Number: ML051080484 CONTACT: Paul Krohn (610) 337-5120
DISTRIBUTION: (PN Recipient List)
OWFN TWFN LST Chairman Diaz 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: ________________________
ADAMS Accession Number: ML051080484 SISP Review Complete: PGK (Reviewers Initials)
DOCUMENT NAME: E:\Filenet\ML051080484.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 OFFIC RI/DRP RI/DRP RI/ORA RI/DRP RI/DR E P NAME SBarber/GSB RBores/R DScrenci/D PKrohn/PGK ABlough/AR JB PS B DATE 04/18/05 04/18/05 04/18/05 04/18/05 04/18/05 OFFICIAL RECORD COPY Region I Form 83 (Rev. July 2, 2003)