ML16148A832
| ML16148A832 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/23/1993 |
| From: | Harmon P, Lesser M, George Macdonald, Poertner K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML16148A831 | List: |
| References | |
| 50-269-93-23, 50-270-93-23, 50-287-93-23, 72-0004-93-23, 72-4-93-23, NUDOCS 9310150100 | |
| Download: ML16148A832 (13) | |
See also: IR 05000269/1993023
Text
SREGj
UNITED STATES
0 oNUCLEAR
REGULATORY COMMISSION
REGION II
101 MARIETTA STREET, N.W., SUITE 2900
ATLANTA, GEORGIA 30323-0199
Report Nos. 50-269/93-23, 50-270/93-23, and 50-287/93-23
Licensee: Duke Power Company
422 South Church Street
Charlotte, NC 28242-0001
Docket Nos.: 50-269, 50-270, 50-287 and 72-4
License Nos.: DPR-38, DPR-47 DPR-55 and SNM-2503
Facility Name: Oconee Nuclear Station
Inspection Conducted:
ugus 23 - 28, 1 3
Lead Inspector:
.
c-3
P. Harmon, enior Reside t Inspector Date Sighed
- A3I,
Inspectors:
G. MacD nald, Reac or Insp t r
Date Signed
6
K. Poertner, Resid t Inspkc or
Date Signed
Approved by:
M. S. Lesser, Section Chief
Date Signed
Projects Section 3A
Division of Reactor Projects
SUMMARY
Scope:
This special inspection was performed to evaluate the
circumstances surrounding the Unit 1 Reactor Trip on August 23,
1993 following loss of the 1DIA 125 Volt DC panelboard. The
inspectors reviewed the sequence of events, plant response,
operator response, maintenance and testing activities and the
effectiveness of the licensee's Significant Event Investigation
Team.
Results:
1.
The cause of the loss of DC power and reactor trip was due
to reversed power leads associated with the redundant diode
power supply to panelboard 1DIA.
2.
The Main Feedwater System did not respond properly following
the trip due to an incorrect pump speed control circuit card
which had previously been installed. This prevented the
Main Feedwater pump from developing adequate pressure to
feed the steam generator.
9310150100 930924
PDR ADOCK 05000269
0
REPORT DETAILS
1.
Persons Contacted
Licensee Employees
- H. Barron, Station Manager
S. Benesole, Safety Review Manager
D. Coyle, Systems Engineering Manager
- J. Davis, Safety Assurance Manager
T. Coutu, Operations Support Manager
B. Dolan, Manager, Mechanical/Nuclear Engineering
W. Foster, Superintendent, Mechanical Maintenance
- J. Hampton, Vice President, Oconee Site
D. Hubbard, Component Engineering Manager
C. Little, Superintendent, Instrument and Electrical (I&E)
- M. Patrick, Regulatory Compliance Manager
B. Peele, Engineering Manager
S. Perry, Regulatory Compliance
- G. Rothenberger, Operations Superintendent
- R. Sweigart, Work Control Superintendent
Other licensee employees contacted included technicians, operators,
mechanics, security force members, and staff engineers.
NRC Resident Inspectors
- P. Harmon
- W. Poertner
L. Keller
NRC Personnel
- G. MacDonald
- M. Lesser
- Attended exit interview.
2.
Introduction
a.
Background
DC power at each Oconee unit is provided to the DC loads from four
125 vdc panelboards. Major loads from each panelboard include 125
vdc Control Power, and a 120 vac Static Invertor for vital
instrument power. Each panelboard receives power through a dual
set of isolating transfer diodes, referred to as Normal and
Backup. Either set of diodes will provide full power to the
panelboard. The diode set which provides power is automatically
determined by the highest voltage present. The Normal supply for
each of the Unit 1 panelboards is from the Unit 1 battery bus, and
2
the Backup is supplied from the Unit 2 battery bus. Each diode
pair has an input and an output breaker provided for isolation and
testing of the diodes.
On the day of the Unit 1 trip, all three Oconee Units were at 100
percent power with no major problems and no Technical
Specification (TS) Limiting Conditions for Operations (LCOs) in
effect. A scheduled surveillance test was underway to test the
isolating transfer diodes' ability to transfer and provide power
when the Normal diode pair's input breaker was manually opened.
When the test was performed, the Backup diode pair did not provide
power, and the 125 vdc panelboard was lost along with its
attendant loads.
b.
Event Summary
On August 23, at 11:17 a.m., Oconee Unit 1 tripped from 100
percent power. The trip was initiated during a maintenance
surveillance of the Unit 1 DC panelboards' isolating diodes. When
the IDIA panelboard's supply was shifted to the backup source, the
panelboard deenergized, causing a loss of the DC loads fed from
IDIA. The turbine electrohydraulic control system and several
turbine supervisory instruments were deenergized, causing a
turbine generator trip and a subsequent reactor trip. The control
room operator's response to this trip was complicated by the loss
of several related power supplies. The main feedwater pumps did
not respond properly to the trip, and Emergency Feedwater was
automatically initiated when steam generator levels decreased to
the automatic initiation setpoint. Operators were able to
stabilize the plant at hot shutdown with systems within normal
parameters.
Several complications occurred due to the loss of DC control power
from the 1DIA panel board. These included the loss of main feeder
bus #1 and the Reactor Coolant Pump (RCP) supply bus 1TA not
automatically transferring to the Startup Transformer CT1. The two
RCPs on bus 1TA lost power and coasted down with their pump
breakers remaining closed. Several minutes later, when power to
the pump buses was restored, the RCPs attempted to restart.
Additionally, numerous control room instruments and alarms were
lost, adding additional confusion to the incident.
The event investigation found that a maintenance related error was
the principal cause of the trip. The leads to the backup supply's
isolating diodes for the IDIA circuit had been inadvertently
reversed during a breaker replacement evolution in May 1993. As a
result, the diodes' input polarities were reversed, and the diodes
did not conduct current. When the normal power supply was
deenergized as part of the surveillance test, the backup supply
did not provide power to the IDIA panelboard.
0II
3
The inability of the Main Feedwater Pumps (MFWP) to supply
feedwater to the steam generators was also found to be maintenance
related. A printed circuit card was replaced in the MFWP control
circuit during the previous refueling outage. The new card was
installed to replace a malfunctioning card in the circuit and was
not properly modified by removing an integration limiter which is
part of the basic card as a shelf item. As a result, MFWP speed
did not increase to a high enough value to force water into the
generators at the higher, shutdown pressures. As the water levels
in the SGs decreased, the motor driven Emergency Feedwater pumps
were automatically initiated when level dropped below 20 inches
for 30 seconds and valves 1FDW-315 and 1FDW-316 automatically
opened to supply emergency feedwater to the steam generators.
3.
Sequence of Events on August 23, 1993
1100 I&E Technicians started performing surveillance test
IP/0/A/3000/6, Peak Inverse Voltage Test, on the isolating diodes
for the IDIA 125 vdc Panelboard. (This 125 vdc panelboard
receives normal supply from Unit 1 Battery Bus 1DCA via an
isolating transfer diode. A backup supply, with its own isolating
transfer diodes, is fed from Unit 2 Battery Bus 2DCA, with an
auctioneering circuit which will select the highest potential from
the two available diode pairs.)
1115 Technicians checked the availability of power from the backup
source prior to opening the normal isolating diodes' input
breaker. This check consisted of verifying the backup breaker
position, and verifying no voltage drop across the breaker.
1117 Technicians opened the input breaker to the Unit 1 diodes. The
following occurred:
-
Power lost to lDIA (feeds IKVIA static invertor, D.C.
control power for breaker control, and EHC control power.
among other loads).
-
Power lost to static invertor 1KVIA (feeds Inadequate Core
Cooling Monitor train A, RPS Channel A, ES channel A among
others).
-
Main Turbine trip due to loss of Electrohydraulic Control
(EHC) power.
-
Reactor trip due to turbine trip.
-
Station auxiliary loads transferred from IT (Auxiliary
Transformer) to CT-1 (Startup Transformer).
-
Reactor Coolant pump bus 1TA did not fast transfer to the
Startup Transformer due to loss of DC control power. With
4
the Auxiliary transformer deenergized, the two RCPs (1A1 and
181) on bus ITA coasted down and stopped.
-
Power lost to the Radiation Monitor (RIA) monitor in the
control room (no cause determined at time of this report).
1118 Operators responded to trip as follows:
Verified that the Main Feedwater system was responding to
the reactor trip and the Feedwater startup valves were
opening to control Steam Generator (SG) level to the no-load
setpoint of 25 inches. The Main Feedwater pump speed
increased automatically to overcome the increased SG
pressure, but did not provide enough speed and discharge
pressure to overcome SG pressure. (This was later
determined to be caused by installation of an incorrect
printed circuit card which limited pump speed).
Continued
steaming of the SGs caused levels in the SGs levels to
decrease further.
-
Controlled Makeup Control Valve 1HP-26 to control RCS
makeup.
Started High Pressure Injection (HPI) Pump 1B and noted that
the 1A HPI pump had no indicating light, but had normal
running amps. HPI pump 1A could not be stopped.
-
Noted the Condenser Circulating Water (CCW) gravity flow
valves opening.
1124
I&E Technicians performing the surveillance reclosed the normal
isolating diodes' input breaker, reenergizing iDIA. This
restoration of DC control power caused several additional events:
RCP bus 1TA transferred to the startup transformer,
restoring power to the 1A1 and 181 RCPs.
-
RCPs 1A1 and 181 started to roll.
-
High starting current on 1Al and 181 RCPs was noted by the
operator.
-
High (long term) current tripped the RCP breakers approxi
mately 7 seconds after trying to restart the RCPs. RCPs 1A1
and 181 stopped.
-
1KVIA power fuse blows, and the breaker to the 1KVIA Static
Invertor opens.
1131 Steam Generator levels reached 20 inches, initiating the dryout
protection feature and starting the motor driven emergency
feedwater pumps. (The dryout protection feature is not a Technical
5
Specification required feature, but was available during this
event).
1132 Emergency Feedwater (EFW) flow rates reached 500 gpm, operators
took manual control of valves 1FDW-315 and 1FDW-316, the EFW level
control valves, to raise SG levels slowly. Both valves go shut
(Valves do not have a bumpless transfer feature). Operators
reopened the valves in Manual mode of operation.
1133 Operators attempted to place the 1FDW 315/316 valves back in
Automatic, but both valves shut. Operators regain Manual control
(Operators did not realize that placing valves in manual reset the
automatic level control associated with the SG dryout start
feature). Operators concerned that Automatic control of 1FDW
315/316 was not working properly.
1135 SG levels returned to normal.
Operators were controlling the
plant within normal post-trip conditions. Forced circulation was
in effect with two RCPs running. Trip review and event
investigation begins.
4.
Event Investigation and Findings
a.
Trip Report and Significant Event Investigation Team (SEIT) Team
Response
Shortly after the trip, licensee management decided to ask for an
independent review of the event by their Significant Event
Investigation Team (SEIT). A SEIT was formed and dispatched to
the Oconee site. Individual team members began arriving at
approximately 7:00 p.m. on August 23.
The team conducted
interviews and witnessed the licensee's trip review process. The
SEIT team concurred in the plant staff's trip review and readiness
for restart. The SEIT team's report contained items to be
resolved prior to startup, recommendations which should be
considered for subsequent corrective actions, and items to be
reviewed without specific recommendations. Each of the team's
issues to be resolved prior to restart were adequately addressed.
The inspectors observed the SEIT team's participation in the event
review and trip review. The team's recommendations appeared to be
reasonable and conservative, and included appropriate items for
further review. Final disposition or resolution of the team's
recommendations will be addressed by the Oconee staff in the
Licensee Event Report (LER) covering this event. The resident
inspectors will review resolution of these items during review of
the LER.
The trip report identified the root cause of the trip, event and
system anomalies, and ensured appropriate corrective actions were
initiated. For the instances identified where maintenance errors
had resulted in a loss of configuration control in the isolating
6
transfer devices and the feed pump control circuits, the licensee
determined that the same devices on the other two units were
properly configured.
b.
Cause of the Trip_
The trip was caused by a deenergized 125 vdc panelboard, and loss
of loads associated with that panelboard. The electrohydraulic
control circuitry powered from the panelboard deenergized and
tripped the turbine. The reactor tripped as designed when the
turbine tripped. The panelboard was deenergized during a
surveillance test which required the backup power supply to
function. A maintenance error had previously reversed the leads
to blocking diodes supplying the panelboard. When the normal
supply was deenergized as part of the test, the backup source did
not automatically supply the panelboard. This item is discussed
further in paragraph 6.
5.
Plant and System Response
a.
Feedwater System Response
Following a reactor trip, the Main Feedwater System (MFW) is
designed to provide feedwater and bring SG levels to 25 inches.
Due to installation of an incorrect printed circuit card in the
MFW pump control circuit, pump speed did not increase to a point
high enough to bring feedwater pressure above steam generator
pressure. Steam pressure increases from approximately 850 psig at
full power to approximately 1000 psig at hot shutdown. The feed
pump circuit problem is discussed further in paragraph 6.b.
b.
Emergency Feedwater (EFW) Response
The EFW system would not normally actuate to provide water to the
SGs following a reactor trip. Since main feedwater did not
respond properly and control levels at 25 inches, SG levels
decreased below approximately 20 inches for 30 seconds, and the
motor driven EFW pumps started. The start signal for the motor
driven EFW pumps was a SG Dryout signal. This signal is not
considered an emergency start signal, but is a backup to the "Both
Feed Pumps Tripped" signal which is considered an emergency start.
Since the MFW pumps did not trip in this instance, EFW operation
was different than operators had experienced or trained for.
Operators typically take Manual control of EFW control valves FDW
315 and FDW 316, throttle them to minimize the thermal transient
on the SGs, and return the valves to Automatic when levels reach
the control point, 30 inches. Since the Emergency start is sealed
in by the MFW pumps being tripped, automatic control is still
available and will control to the SG level setpoint. When the
Dryout protection signal initiated the start of the motor-driven
EFW pumps, the operators took manual control, and the valves
immediately shut. Taking the valves to Manual resets the
7
actuation signal following a Dryout Protection start, and sends a
zero position signal to the valves. Operators reopened the valves
and fed the SGs to approximately 25 inches. The valves were then
placed in Automatic, and the valves were reclosed. Since the
operators were not aware of the different actuation and control
circuitry for the valves in the "Dryout Protection" mode, they
assumed the valves were malfunctioning. The valves were returned
to Manual, and the operators maintained SG levels. In conclusion
the EFW System responded properly although not as expected by
operators.
c.
Reactor Coolant Pump Response
When the reactor tripped, 125 vdc control power was not available
to fast transfer the RCPs on bus 1TA to their alternate power
supply. When power on the ITA bus was lost, the pumps slowed
down, but did not trip from the bus. The undervoltage protection
scheme does not sense reduced voltage or hertz on the bus, but
instead "anticipates" low voltage by monitoring breaker position
of the normal and startup feeder breakers to the 1TA (1TB bus for
pumps 1A2 and 1B2) pump supply bus. The undervoltage condition is
sensed by both breakers being open for 2 seconds. Since DC power
to the 2 second time delay circuit was lost, the undervoltage
circuit did not actuate and open the RCP breakers. Consequently,
the 1A1 and 1BI RCPs remained connected to a dead bus.
Approximately 7 minutes after the reactor trip and RCP coastdown,
technicians restored power to the deenergized 1DIA panelboard.
This also restored power to the 125 vdc control circuit. The 125
vdc control circuit then performed the fast transfer of the ITA
power supply to the startup transformer, reenergizing the two idle
RCPs. The 1A1 and 181 RCPs began to roll, even though a normal
pump start interlock had not been satisfied. The interlock, Oil
Lift Pump running for at least 2 minutes and oil pressure normal,
is only designed for preventing closure of the pump breakers. Due
to the high starting current applied to start two pumps
simultaneously, the RCPs tripped within approximately 7 seconds on
overcurrent. Operators witnessed this series of events, and
confirmed that high starting current and RCS flow indicated that
the pumps had indeed started, but then tripped. Prior to
restarting these pumps for the subsequent plant startup, the
licensee conferred with the manufacturer, Westinghouse, on the
possibility of pump damage due to starting without proper oil
pressure from the oil lift pumps. Westinghouse recommended
additional monitoring of pump vibration, but concluded that damage
should not have occurred. The pumps were later started with no
problems indicated.
d.
Loss of Radiation Monitors (RIAs)
When the reactor tripped and station power transferred to the
startup transformer, the process radiation monitors for the steam
line and condenser air ejectors were lost. These monitors provide
8
crucial information relative to operators determining whether a SG
tube rupture has occurred. The loss of the monitors was origi
nally thought to be part of the instruments directly affected by
the IDIA panelboard power loss. Later investigation revealed that
the RIAs should have been unaffected by the 125 vdc power loss.
The RIAs for Unit 3 had also been lost during the previous Unit 3
trip on January 26, 1993. The licensee had initiated a Problem
Investigation Process (PIP 93-375) on the Unit 3 event. Since the
RIAs use the plant computer for signal processing, the licensee
believes that the momentary power drop when the plant auxiliary
power shifts to the startup transformer may cause a computer
related problem in the RIAs. This is still under investigation by
the licensee's corrective action program. After the Unit I trip
resulted in the loss of RIAs, operators were notified of the
possibility of RIA loss during future plant trips.
6.
Review of Maintenance Activities
a.
Maintenance/Surveillance On Isolating Transfer Diode Cabinet 1ADA
The inspectors reviewed the troubleshooting plans for the transfer
of diode 1ADA. The licensee troubleshooting consisted of
performing procedure IP/O/A/3000/006 to attempt to reproduce the
failure. IP/O/A/3000/006 contained a check of the diode cabinet
circuit breakers and diodes. Troubleshooting concentrated on the
circuit breakers in the diode cabinets because of previous
problems encountered with these breakers. The licensee did not
have a written troubleshooting plan to systematically assess the
diode cabinet power supply components and all diode cabinet
components. The vendor manual/drawings were not initially present
at the job site. The inspectors reviewed the vendor manual for
the diode cabinets and noted that it contained a troubleshooting
section. Once the licensee determined that the diode cabinet
circuit breakers were acceptable, additional planning was required
to develop testing to locate the problem. A comprehensive and
systematic planning effort prior to beginning troubleshooting
could have reduced the time to correct the problem and the time
the unit was in an LCO for troubleshooting.
The inspectors witnessed the licensee's troubleshooting efforts on
the diode cabinet. The licensee determined the cause of the
failed diode cabinet power supply and completed the repairs within
the time allowed by the plant technical specifications. Temporary
modification TM1091 was implemented to reverse the DC power leads
inside diode cabinet 1ADA and restore proper polarity to the unit
2 diode power supply. The inspectors witnessed the testing of
diode cabinet 1ADA after the temporary modification was complete.
The test results were satisfactory. The remaining diode cabinets
were tested to verify that both power sources were operable. All
power supplies to the diode cabinets were operable.
9
The licensee determined that the Unit 2 powersupply circuit
breaker leads had been reversed on the circuit breaker in DC Motor
Control Center 2DCA Compartment 3A. During circuit breaker
testing, the circuit breaker in 2DCA Compartment 3A was found to
be cracked and was replaced under Work Order 9204935901 on May 18,
1992.
Licensee Maintenance Directive 4.4.13 original revision, "ONS I&E
Configuration Control Work Practices" Step 5.3.1, requires that a
"Component Out Of Normal Sheet" be completed when station I&E
equipment is placed in an out of normal state. Lifting electrical
leads was listed as an example requiring the use of the "Out Of
Normal Sheet."
The inspectors reviewed Work Order 9204935901 and noted that the
2DCA Compartment 3A circuit breaker shunt trip leads were listed
on the "Out Of Normal Sheet."
The circuit breaker line and load
side DC power cables were not listed on the "Out Of Normal Sheet."
Step 10.3 of procedure IP/0/A/3011/013 required that the line and
load side cables be marked and disconnected. A procedure step
completion signoff was required by the performer for Step 10.3.
Step 10.21 of IP/O/A/3011/013 required that the breaker cables be
connected as marked in Step 10.3. Step 10.21 required a
completion signoff by the performer and a verifier. From the
review of the work package, it appeared that one individual marked
and disconnected the breaker power cables and two different
individuals reterminated the cables. The convention for marking
leads could not be determined by the inspectors.
The post maintenance testing for Work Order 9204935901 consisted
of performing circuit breaker overcurrent testing in accordance
with IP/0/A/3011/013. The only control mechanism for maintaining
configuration control was the marking of the breaker leads. The
inspectors examined the circuit breaker power cables in 2DCA
Compartment 3A and found no cable markings. The incorrect
connection of 2DCA Compartment 3A circuit breaker rendered the
Unit 2 DC supply to diode cabinet 1ADA inoperable.
Review of Work Order 9204935901 indicated that the 2DCA
Compartment 3A circuit breaker power cables were not adequately
controlled to ensure proper termination by a different individual.
The "Out Of Normal Sheet" was not utilized to control the
configuration of the circuit breaker power cables. This item is
identified as an example of Violation 50-269,270,93-23-01: Failure
to Follow Procedures to Maintain Configuration Control.
b.
Maintenance/Surveillance on Unit 1 Main Feedwater Pump Speed
Controls
On December 28, 1992, the main feedwater pump speed control
proportional plus integral module failed its time specification
during surveillance testing. The installed controller module was
10
a Bailey Meter Company Type 6620255A-9. Procedure IP/0/B/0325/003
calibration data sheet required a Type 6620255A-9 controller which
did not have a speed limiter. Work Order 51316L installed a new
Type 6620255A-10 controller which contained a speed limiter.
Licensee personnel obtained the spare module by referencing the
MMIS number. The MMIS data indicated that part number 6620255A-10
was issued. It appeared that licensee personnel did not compare
the part number of the old controller to the part number of the.
new controller. The part number on the calibration data sheet in
IP/0/B/0325/003 was also not compared with the part number of the
new module. The vendor manual clearly explained that the type
6620255A-9 module did not contain a speed limiter while the type
6620255A-10 contained a speed limiter. It appeared that the
licensee relied solely on the MMIS data to identify the correct
replacement module.
The inspectors reviewed the post installation calibration checks
performed after the installation of the type 6620255A-10 module.
The calibration checks did not input test values which could have
detected the presence of a limiter card.
Subsequent to the trip the licensee verified that the feedwater
speed controllers for Units 2 and 3 did not contain speed limiter
cards in their proportional plus integral modules. The inspectors
reviewed WR 93028973 for Unit 2 and WR 93028974 for Unit 3 which
verified that the speed controllers for Units 2 and 3 did not have
limiter cards.
There have been previous instances where incorrect Bailey modules
were installed in the integrated control system. LER 287/90-01
Revision 2, reported that on January 19, 1990, an incorrect relay
module was discovered in the Integrated Control System. The I&E
procedures contained no requirements to compare or otherwise
ensure exact replacements. On April 25, 1990, a memorandum was
issued to all I&E Technicians, Supervisors, and General
Supervisors in response to LER 287/90-01. The memorandum
indicated that the MMIS number could not be relied on solely to
ensure correct part replacements. The memorandum required that
new and old part numbers should be compared and that the part
numbers on the new part and the calibration data sheet should be
compared. The licensee developed Maintenance Directive 4.4.13,
"ONS I&E Configuration Control Work Practices", on February 25,
1993, to maintain I&E configuration control.
Despite the
memorandum, the procedure, and the management directive, licensee
personnel still did not follow procedures and failed to maintain
configuration control.
This item is identified as another example
of Violation 50-269,270,287/93-23-01: Failure to Follow Procedures
to Maintain Configuration Control.
The inspectors observed that the licensee's MMIS database
contained several different Bailey controller part numbers under
11
the same MMIS number (stock number). This represents a problem to
personnel required to maintain configuration control of the ICS.
7.
CONCLUSIONS
a.
Root Cause of the Trip
The root cause of the event is considered to be maintenance errors
during work 4ctivities conducted during the previous refueling
outage for Unit 2. These errors resulted in the loss of
configuration control of a power supply to safety related DC
panelboard IDIA. In addition to the maintenance errors, lack of a
rigorous post-maintenance testing program prevented prompt
identification of the errors at the time they were made. Instead,
the errors went undetected until the failed device was challenged.
b.
Maintenance-related errors
The maintenance practices detailed in this report indicate
weaknesses in the Maintenance Program at Oconee. This event and
several similar events precipitated by maintenance activities have
unnecessarily challenged the safety systems and operators.
C.
Post-maintenance testing inadequacies
Post-maintenance testing in the instances detailed was inadequate.
The purpose of testing after a maintenance activity such as
lifting and relanding leads should determine that the activity was
properly performed. A lack of a rigorous approach to testing is
indicated by this and several similar events at Oconee.
d.
Evaluation of Operator Response
The Operations shift personnel performed well during the
transient. They adequately verified the post-trip parameters, and
maintained the plant at stable shutdown conditions. The
complexity of a losslof 125 vdc panelboard concurrent with the
trip introduced several anomalous indications and events the
operators were not familiar with. Adherence to procedures and
knowledge of the plant and systems were demonstrated during this
event. A lack of adequate training and familiarity was indicated
in the operation of the Emergency Feedwater System in the dryout
protection mode.
8.
Exit Interview
The inspection scope and findings were summarized on August 27, 1993,
with those persons indicated in paragraph 1. The inspectors described
the areas inspected and discussed in detail the inspection findings.
The licensee did not identify as proprietary any of the material
provided to or reviewed by the inspectors during this inspection.
12
Item Number
Description/Reference Paragraph
VIO 50-269,270/93-23-01
Failure to Follow Procedures
to Maintain Configuration Control, two
examples(paragraphs 6.a and 6.b).
0