05000220/LER-2008-001

LER-2008-001, Loss of Offsite Power due to an Equipment Malfunction

Nine Mile Point Unit 1
Event date:	05-13-2008
Report date:	07-07-2008
Reporting criterion:	10 CFR 50.73(a)(2)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident 10 CFR 50.73(a)(2)(iv)(A), System Actuation
2202008001R00 - NRC Website

A. PRE-EVENT PLANT CONDITIONS:

On May 13, 2008, Nine Mile Point Unit 1 (NMP1) was in the power operating condition at approximately 100% steady state reactor power.

At 0637 hours0.00737 days <br />0.177 hours <br />0.00105 weeks <br />2.423785e-4 months <br />, NMP1 removed one of two 115 kV offsite power lines (Line 1) from service for planned maintenance.

B. EVENT:

At 0806 hours0.00933 days <br />0.224 hours <br />0.00133 weeks <br />3.06683e-4 months <br />, the unit experienced a Loss of Offsite Power (LOOP) when Line 4, which is a shared line with James A. Fitzpatrick Nuclear Power Plant, was lost. Line 4 is the second of two offsite power lines. The LOOP caused the loss of two 4160 V vital buses and subsequent start of the emergency diesel generators to carry emergency loads. The loss of these vital buses caused the operating Spent Fuel Pool (SFP) cooling pump to trip, as designed. Also, the LOOP caused the loss of a third 4160 V bus, which resulted in the trip of one of five Reactor Recirculation pumps as designed. The loss of Reactor Recirculation pump resulted in reduction of reactor thermal power to 90%. Upon the loss of the Reactor Recirculation pump and the SFP cooling pump, operators entered applicable Special Operating Procedures (SOPs).

Reactor recirculation flow was stabilized and SFP cooling was restored. Operators also commenced recovery of Line 1, which had been removed from service for planned maintenance. At 0825 hours0.00955 days <br />0.229 hours <br />0.00136 weeks <br />3.139125e-4 months <br />, the Shift Manager declared an Unusual Event (UE) and the required notifications were made. At 0843 hours0.00976 days <br />0.234 hours <br />0.00139 weeks <br />3.207615e-4 months <br />, Line 1 was restored to service. At 1022 hours0.0118 days <br />0.284 hours <br />0.00169 weeks <br />3.88871e-4 months <br />, the UE was terminated and the required notifications were made.

Line 4 was restored to service on May 16, 2008, at 0515 hours0.00596 days <br />0.143 hours <br />8.515212e-4 weeks <br />1.959575e-4 months <br />.

THE EVENT:

115 kV offsite power Line 1 ( taken out of service for planned maintenance) 115 Kv offsite power Line 4 (failed)

D. DATES AND APPROXIMATE TIMES OF MAJOR OCCURRENCES:

May 13, 2008, 0637: Removed Line 1 from service for planned maintenance May 13, 2008, 0806: Lost Line 4 May 13, 2008, 0825: Declared a UE May 13, 2008, 0843: Restored Line 1 to service May 13, 2008, 1022: Terminated the UE May 16, 2008, 0515: Restored Line 4 to service

E. OTHER SYSTEMS OR SECONDARY FUNCTIONS AFFECTED:

Other than those described under section B above, no other systems or secondary functions were affected.

F. METHOD OF DISCOVERY' This event was immediately apparent by control room indications and annunciations.

G. MAJOR OPERATOR ACTION:

In response to the LOOP, trip of a Reactor Recirculation pump, and trip of the operating SFP cooling pump, the operators entered applicable Special Operating Procedures and took appropriate corrective actions to stabilize reactor recirculation flow and to restore SFP cooling.

At 0825 hours0.00955 days <br />0.229 hours <br />0.00136 weeks <br />3.139125e-4 months <br />, the Shift Manager declared a UE and made required notifications.

The operators commenced recovery of Line 1, which had been removed from service for planned maintenance. At 0843 hours0.00976 days <br />0.234 hours <br />0.00139 weeks <br />3.207615e-4 months <br />, Line 1 was restored to service.

H. SAFETY SYSTEM RESPONSES:

The LOOP resulted in the loss of two 4160 V vital buses and the subsequent start of emergency diesel generators to carry the emergency loads.

II. CAUSE OF EVENT:

The event is a NUREG-1022 Cause Code C, "External Cause.

The apparent cause of this event is an equipment malfunction associated with the James A.

Fitzpatrick Nuclear Power Plant's switchyard.

NMP Condition Report 2008-4077 applies to this LER.

III. ANALYSIS OF THE EVENT:

This event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) because of the automatic start of Division 1 and 2 Emergency Diesel Generators. The event is also reportable in accordance with 10 CFR 50.73(a)(2)(v)(D) because of loss of both 115 kV offsite power sources.

The loss of both 115 kV offsite power lines is described in the Updated Final Safety Analysis Report (UFSAR).Section IX.B.1.2 describes failure modes for the 115 kV offsite power system. Actual system response was in accordance with the expected response described in the UFSAR.

The trip of a reactor recirculation pump had a minimal effect on safety. UFSAR Section XV.B.3.7 analysis bounds this transient and concludes that the Minimum Critical Power Ratio was not challenged. Reactor power responded as expected for the trip of the reactor recirculation pump.

The trip of the operating SFP cooling pump resulted in the SFP temperature rising to 87 degrees F (a 2 degrees increase), well below the maximum limit of 140 degrees F.

When Line 1 was taken out of service for planned maintenance, the risk was assessed and managed in accordance with the site integrated risk management procedure.

IV. CORRECTIVE ACTIONS:

A. ACTION TAKEN TO RETURN AFFECTED SYSTEMS TO PRE-EVENT NORMAL STATUS:

On May 13, 2008, at 0843 hours0.00976 days <br />0.234 hours <br />0.00139 weeks <br />3.207615e-4 months <br />, Line 1, which had been removed from service for planned maintenance, was restored to service. On May 16, 2008, at 0515 hours0.00596 days <br />0.143 hours <br />8.515212e-4 weeks <br />1.959575e-4 months <br />, Line 4 was restored to service after completion of corrective action at the James A. Fitzpatrick Nuclear Power Plant.

B. ACTION TAKEN OR PLANNED TO PREVENT RECURRENCE:

Nine Mile Point Nuclear Station will review the James A. Fitzpatrick Nuclear Power Plant's causal analysis for extent of condition pertinent to NMP1 and NMP2.

A. FAILED COMPONENTS:

There were no failed components at NMP1 that initiated or contributed to this event.

B. PREVIOUS LERs ON SIMILAR EVENTS:

The following events occurred at Nine Mile Point Nuclear Station:

08/14/2003, Nine Mile Point Unit 1 scram due to a loss of offsite power during the Northeast Blackout (LER 2003-02) 08/14/2003, Nine Mile Point Unit 2 scram due to a foss of offsite power during the Northeast Blackout (LER 2003-02) C. THE ENERGY INDUSTRY IDENTIFICATION SYSTEM (EIIS) COMPONENT FUNCTION

THIS LER:

COMPONENT IEEE 803 FUNCTION IEEE 805 SYSTEM

IDENTIFIER IDENTIFICATION

115 kv offsite power line NA FK Switchgear SWGR EA Emergency Diesel Generator DG EK Reactor Recirculation Pump P AD Emergency Power Distribution Buses BU EB Spent Fuel Pool Cooling Pump P DA Switchyard NA FK

D. SPECIAL COMMENTS:

None