ML053250415

Preliminary Issue List

ML053250415
Person / Time
Site:	Palo Verde
Issue date:	11/15/2005
From:	NRC Region 4
To:
References
FOIA/PA-2004-0307
Download: ML053250415 (2)

Text

- A-cr - T5$S w Wt Preliminary Issue List Palo Verde Nuclear Generating Station Augmented Inspection Team NOTE: This is NOT an all-inclusive list.

• A single phase to ground fault resulted in loss of offsite power and three unit trip

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• Auxiliary Relay, Liberty Transmission Line Fault Detection/Protection System Failure

• inadequate design resulted in single failure vulnerability

• additional single failure design issues identified and corrected to extent practical

• licensee also did not appear to make resolution of this issue a startup issue until the concern was raised by the AIT

• Unit 1 Atmospheric Dump Valve 185 Failure

• control room operator distraction with minimal impact on event response

• apparent cause being determined

• Unit 1 Letdown Heat Exchanger Isolation Failure

• licensee performance deficiency associated with understanding implications of temporary modification installed in plant

• little impact on control room response to event

• some potential impact on fire response being reviewed by AIT

• Unit 1 and 3 General Electric Magne Blast Circuit Breaker Failures

• complicated event recovery efforts by delaying the return of offsite power to ESF buses

• licensee determined apparent cause as "breaker not cycled frequently enough"

• AIT challenged licensee on apparent cause, raised concern regarding current functionality of breakers

• resident staff following as potential operability issue

• Unit 2 Train "A' Emergency Diesel Generator Failure

• resulted in a loss of power to Train "A" ESF busses following loss of offsite power

• apparent cause was diode failure in exciter rectifier circuit

• Unit 2, Train uE" Positive Displacement Charging Pump Trip

• operator error resulted in suction line isolation and protective trip of pump

• AIT identified that auxiliary operator was delayed approximately 10 minutes at the RCA access point even after the operator explained he was on a time critical mission

• when RCA access delay was discussed with licensee, AIT determined that the licensee was unaware of delay .

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• Unit 3 Bypass Valve/Control Cabinet Malfunctions

• good operator actions minimized impact on plant, was operator distraction

• potential design modification issue being reviewed by AIT as apparent cause

• Unit 3 Reactor Coolant Pump Lube Oil Lift Pump Breaker Thermal Overload Trip

• no impact on trip but some minor impacts on recovery

• potential design issue associated with set point of thermal overloads

• Unit 3 Low Pressure Safety Injection System In-leakage (Check Valve V217)

• little impact on event, operator distraction to take manual actions to prevent over pressurization

• apparent cause was Borg-Warner check valve leakage, potential maintenance issue

• Unit 3 Variable Over Power Trip - Reactor Coolant Pump Speed Increase to 67 Hz

• licensee investigating potential impacts on plant equipment

• AIT raised questions about hydraulic affects, if any

• Technical Support Center Emergency Diesel Generator Failure

• apparent cause was test switch out of position

• maintenance personnel failed to use restoration procedure six days prior to event following testing

• some impact on emergency response organization which needed to use alternate TSC

• Procedure Issue Associated with Minimum Amperage for Reactor Coolant Pumps

• complicated recovery efforts by delaying RCP restoration

• appears minimum amperage basis involved NPSH limits

• high voltage in switchyard resulted in low amperage I.

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• Emergency Response Organization Notification Issues

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• some delay in notification occurred but little impact

• apparent cause associated with procedure adequacy and communication failures

• Initial Notification of State and Local Official Issues

• Unit 1 and Unit 3 did meet their guidelines on timeliness of initial notification

• little overall impact because Unit 2 Alert Notification was timely

• apparent cause being reviewed

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