United States of America

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CARBON DIOXIDE RELEASE TO A PLANT VITAL AREA

The plant was operating at 100% power when a release of carbon dioxide (CO2) to a plant vital area occurred. The area was immediately evacuated, and there were no personnel injuries nor any effect on plant safety systems. The CO2 bottles are located in an auxiliary builiding room and are used for a fire suppression system in an adjacent cable spreading room. The release occurred due to improper thread engagement during the performance of a surveillance test procedure on the back-up bank of bottles.

Category: Power Reactor United States of America »

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MINOR FIRE INVOLVING A SAFETY RELATED SYSTEM

The plant was operating at 100% power when a small fire occorred on the exhaust manifold of an emergency diesel generator that had been started for testing. The fire salf-extinguished when the emergency diesel generator was secured. The emergency diesel generator was not damaged, and there were no personnel injuries. The source of the fire was a small lube oil leak on thge exhaust manifold. The plant remained at power throughout the event.

Category: Power Reactor United States of America »

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INES 1

PLANT TRANSIENT INITIALLY CAUSED BY THE LOSS OF CIRCULATING WATER PUMPS DUE TO HIGH MARSH GRASS/DEBRIS CONCENTRATIONS

Salem Unit 1 was operating at 73% power when excessive marsh grass/debris in the Delaware river caused some of the main condenser circulating water pumps to trip off due to high differential pressure. Operators manually initiated a power reduction to 7% power which, upon going below 10%, automatically re-instated the low power trip setpoints of 25%. The operator subsequently withdrew rods to restore RCS (reactor coolant system) temperature to its normal band. This resulted in a power increase to 25% and an automatic reactor trip.

Category: Power Reactor United States of America »

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INES 0

LOSS OF OFF-SITE POWER AND REACTOR SCRAM

Unit was operating at full power when a total loss of off-site power and reactor scram occurred due to the loss of a transformer. The loss of the transformer was due to an electrical failure of its associated current transformer. The event was complicated by the unanticipated loss of some non-safety related systems. However, all three emergency diesel generators started and assumed loads as required, and all safety equipment operated as designed. Off-site power, supplied through Unit 2, was restored to the emergency buses in about one hour.

Category: Power Reactor United States of America »

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MINOR FIRE INVOLVING A SAFETY RELATED SYSTEM

The plant was operating at 100% power when a small fire occurred on the exhaust manifold lagging of an emergency diesel generator that was started for testing. An operator quickly extinguished the fire using a hand held extinguisher. No other systems were affected by the fire and the operators continued to operate the emergency diesel generator until the test was complete. The diesel generator remained operable throughout the event. The source of the fire was minor oil leakage past a flange gasket between the exhaust manifold and the turbogenerator.

Category: Power Reactor United States of America »

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INES 0

EXCESSIVE FEEDWATER REGULATING VALVE OSCILLATIONS CAUSE WATER HAMMER INDUCED VIBRATION OF THE MAIN FEEDWATER PIPING

North Anna unit 2 was operating at 70% power when operators observed fluctuations in feedwater flow. An operator was sent out to investigate and observed severe oscillations on two of three main feedwater pipes. Operators manually tripped the reactor in response to the feedwater piping vibrations. The plant was placed in a stable condition and cooled down utilizing normal procedures. No feedwater line leaks occurred as a result of the event.

Category: Power Reactor United States of America »

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PERRY UNIT 1 MAIN SERVICE WATER PIPE BREAK

The plant was operating at 100 percent power when a break in the main supply header (30 inch/76 cm) of the Plant Service Water System resulted in the flooding of several buildings, including the Auxiliary and Off-Gas Buildings. Operators safely shut down the reactor in response to the event. The leak and the associated flooding was stopped by shutting down and isolating the Plant Service Water System.

Category: Power Reactor United States of America »

INES-event
INES 1

PVNGS 2 STEAM GENERATOR TUBE RUPTURE

Palo Verde Unit 2 was operating at 98 percent power. At 0435, operators noticed a decrease in pressurizer pressure and level. Although additional charging flow was started, pressurizer level and pressure continued to decrease. The operators manually scrammed the reactor at 0447. Safety injection and containment isolation signals automatically initiated. After determining that a steam generator tube rupture existed, operators began to cool down and depressurize the reactor coolant system. The leak rate was estimated to be approximately 15 l/s (240 gal/min.).

Category: Power Reactor United States of America »

INES-event
INES 0

ZION UNIT 2 LOSS OF NSSS CONTROL ROOM ANNUNCIATORS

Zion Unit 2 was operating at 100% power when a blown fuse caused the loss of the ability to silence and reset about half the visual and audible main control board alarm annuniciators. The annunciators that were lost were those that alarm in the event of abnormal conditions or actuations of 1) safeguards components (e.g.containment spray, auxiliary feed, and service water), 2) reactor coolant components (e.g., rod control and reactor coolant pumps), and 3) safeguards buses normally supplied by the emergency diesel generators.

Category: Power Reactor United States of America »

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UNAUTHORIZED INTRUDER INTO PLANT PROTECTED AREA WHILE OPERATING AT 100 PERCENT POWER

On February 7, 1993, a Site Area Emergency was declared at the Thee Mile Island Nuclear plant after an intruder drove his station wagon through a protected area fence and crashed into a turbine building roll-up door. After a 4-hour search, the unarmed intruder was apprehended beneath the Unit 1 main condenser by site security and turned over to the Pennsylvania State Police. The intruder had recently been released from a psychiatric ward of a local hospital.

Category: Power Reactor United States of America »