05000219/LER-2003-004

LER-2003-004,

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
2192003004R00 - NRC Website

DATE OF DISCOVERY

This event occurred on August 22, 2003.

IDENTIFICATION OF OCCURRENCE

Note: System Identification codes from IEEE 805-1984 are indicated with SI. Component Function Identifiers from ANSI/IEEE 803A-1983 are indicated by CFI.

A spurious actuation of a Moisture Separator (SI - SN), HI-HI Level switch (CFI - LS) tripped the main turbine (CFI - TRB) and scrammed the reactor (CFI - RCT). Actuation of the Reactor Protection System is reportable under 10 CFR 50.73(a)(2)(iv)(A).

CONDITIONS PRIOR TO DISCOVERY

The plant was operating at approximately 100% power at normal reactor pressure, level, and temperature. All safety-related equipment was operable. Plant conditions prior to the Turbine Trip / Scram were stable.

DESCRIPTION OF OCCURRENCE

On August 22, 2003, at 0259 hours0.003 days <br />0.0719 hours <br />4.282407e-4 weeks <br />9.85495e-5 months <br />, annunciators (CFI - ANN) in the Main Control Room indicated a Moisture Separator HI-HI Level alarm. About ten seconds later the main turbine tripped as designed. The reactor then scrammed as designed, due to the anticipatory scram on the turbine stop valve closure.

The turbine trip caused a pressure increase which caused two of five Electromatic Relief Valves (CFI - RV) to open momentarily, three of five Reactor Recirculation Pumps (SI - AD, CFI - P) to trip, and both Isolation Condensers (SI - BL) to actuate. The reactor scram shut down the reactor as designed. Operators manually tripped the two operating Reactor Recirculation pumps, as required by procedure, and stabilized plant conditions.

Although no Technical Specification required the plant to be placed in the Cold Shutdown condition, the trip of all reactor recirculation pumps required cooldown to cold shutdown to recover the plant. Plant cooldown was begun at 0349 hours0.00404 days <br />0.0969 hours <br />5.770503e-4 weeks <br />1.327945e-4 months <br />. Shutdown Cooling (SI - BO) was placed in service at 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br /> and the cold shutdown condition was reached at 1205 hours0.0139 days <br />0.335 hours <br />0.00199 weeks <br />4.585025e-4 months <br />.

NRC FOR/0360A (1-2031) NRC FORM MAUS. NUCLEAR REGULATORY COMMISSION (1-20011 FACILITY NAME (1) DOCKET (2) LER NUMBER (6) PAGE (3)

APPARENT CAUSE

Actuation of the Reactor Protection System was caused by closure of the turbine stop valves when the turbine tripped. The turbine trip was caused by spurious actuation of Moisture Separator Hi-Hi Level switch, LS-4-691.

ANALYSIS OF OCCURRENCE AND SAFETY ASSESSMENT

The safety significance of this event is considered minimal. The plant is designed for this type of transient and responded as designed. Technical specification limits were maintained. There was no radioactive release, nor any effect on the health and safety of the public. Operator performance was satisfactory.

CORRECTIVE ACTIONS

Replaced all four moisture separator Hi-Hi Level Switches.

A root cause of the switch actuation is in progress to determine if additional corrective actions are warranted.