ML17311B077
| ML17311B077 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde |
| Issue date: | 07/26/1995 |
| From: | Huey F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML17311B075 | List: |
| References | |
| 50-528-95-12, 50-529-95-12, 50-530-95-12, NUDOCS 9508010068 | |
| Download: ML17311B077 (68) | |
See also: IR 05000521/2007001
Text
ENCLOSURE 2
U.S.
NUCLEAR REGULATORY COMMISSION
REGION IV
Inspection
Report:
50-52S/95-12
50-529/95-12
50-530/95-12
Licenses:
NPF-51
Licensee:
Arizona Public Service
Company
P.O.
Box 53999
Phoenix,
Facility Name:
Palo Verde Nuclear Generating Station,
Units 1, 2,
and
3
Inspection At:
Haricopa County,
AZ
Inspection
Conducted:
May 21 through July 1,
1995
Inspectors:
K. Johnston,
Senior Resident
Inspector
J.
Kramer, Resident
Inspector
A. MacDougall, Resident
Inspector
D. Garcia,
Resident
Inspector
D. Acker,
Senior Project Inspector
B. Olson,
Project Inspector
Approved:
.
R.
Huey, Acting
C ie
,
Reac
rane
F
ate
Ins ection
Summar
Areas
Ins ected
Units
1
2
and
3
Routine,
announced
inspection of onsite
response
to plant events,
operational
safety,
maintenance
and surveillance
activities, onsite engineering,
and followup items.
Results
Units
1
2
and
3
Generations
Operations
performance
during the inspection period
was generally
good,
as
evidenced
by:
~
Implementation of revised
Emergency Operating
Procedures,
which were
seen
as
a significant improvement
(Section 3.5).
95080i0068
950727
ADOCK 05000528
A
~
Good operations
management
assessment
of a Unit .1 reactor trip
(Section 2.1).
~
Excellent communications
and coordination
between operations
and
maintenance
personnel
in addressing
an emergency
diesel
generator
problem which placed Unit 2 in
a Technical Specification
shutdown action
statement
(Section 2.2).
~
One noted exception
involved operator failure to question indication
that
a Unit
1 emergency
diesel
generator
was not operating at 60 hertz
(Section 3.7).
Haintenance
Surveillance
Maintenance
performance
during the period
was mixed.
A number of maintenance
related
issues
surfaced
at the end of the Unit
1 refueling outage.
Examples
of inspector identified concerns
included:
~
Inappropriate
use of nonseismically qualified scaffolding in Units
1
and
2 (Section
3. 1).
Inadequate
evaluation
and resolution of observed
problems with the
Unit
1 auxiliary feedwater turbine governor valve (Section 4. 1).
Two examples of field work performed without appropriate
reference
to
the applicable
work instruction, involving modification of the Unit 3
fuel pool storage
racks
(Section 4.5),
and surveillance testing of
safety injection system
(Section 5.1).
The latter example
resulted
in
a test procedure violation which could have invalidated the
test results.
En ineerin
and Technical
Su
ort
The licensee
took prompt action in response
to an industry event database
entry on Target
Rock solenoid
operated
valves which might impact valves
installed at Palo Verde (Section 6.4).
However,
in some other instances
of problems
encountered
at Palo Verde,
although the licensee
took appropriate
actions for its
own equipment,
they had
not appropriately explored the generic implications of the deficiencies.
Examples
included problems with cracked
Valcor solenoid operated
valve bodies
(Section 6.2), auxiliary feedwater turbine governor valve packing problems
(Section 4.1),
and the potential for an auxiliary feedwater turbine trip
during
an excess
steam
demand
event
(Section 6.3).
Although the licensee
had initiated
a comprehensive
program for thermal
monitoring of environmentally qualified equipment,
in response
to
a previously
identified weakness,
appropriate
interim action
had not been
taken to verify
4
that field temperatures
were not significantly different from those required
by the qualification reports
(Section
6. I).
Mana ement Oversi ht
The inspectors
noted excellent
management
involvement in the resolution of an
emergency diesel
generator
problem which placed Unit 2 in
a Technical
Specification
shutdown action statement
(Section 2.2),
the evaluation of
scaffolding deficiencies
(Section 3.1),
and the followup of a Unit
1 reactor
trip (Section
2. 1).
However, licensee
management
did not provide appropriate
oversight for the
evaluation
and resolution of Unit
1 auxiliary feedwater turbine governor
problems
(Section 4. 1).
As
a result,
the conclusions of the evaluation
were
not well supported.
Summar
of Ins ection Findin s:
~
One noncited violation was identified (Section 3.1)
~
One violation was identified involving failure to comply with a
surveillance test procedure
(Section
5. 1)
~
One violation was closed
(Section
7. I)
~
Three unresolved
items were closed
(Sections 8.2,
9. 1,
and 9.2)
~
One deviation
was closed
(Section 9.3)
~
One followup item was closed
(Section 8. 1)
Attachments:
1.
Persons
Contacted
and Exit Meeting
2.
List of Acronyms
l
I'i
DETAILS
1
PLANT STATUS
1.1
Unit
1
Unit
1 started
the inspection period in Mode
3 with a reactor coolant
system
(RCS)
heatup
in progress
following a refueling outage.
On May 25, the unit
commenced
a startup
and
was synchronized
to the grid on May 27.
On May 30,
the unit experienced
a reactor trip on low steam generator
level
from
65 percent
power after to
a feedwater isolation valve closed during
maintenance
(Section 2.1).
On May 31, the unit commenced reactor startup
and
synchronized
to the grid the following day.
The unit increased
power to
100
percent
and operated
throughout the inspection period at essentially
100
percent
power.
1.2
Unit 2
Unit 2 started
and
ended
the inspection
period at
100 percent
power.
1.3
Unit 3
Unit 3 started
the inspection period at
100 percent
power.
On June
4, reactor
power was reduced to 85 percent to repair tube leaks identified on Feedwater
Heat Exchanger
11A.
On June 8, following repairs, .the unit returned to
100
percent
power for the remainder of the inspection period.
2 ONSITE RESPONSE
TO EVENTS (93702)
2. 1
Reactor Tri
Followin
Isolation Valve Closure - Unit
1
On May 30, at 10:22 p.m., Unit
1 tripped from 65 percent
power on
a low steam
generator
(SG) level in
SG 12,
The low SG level resulted
from inadvertent
closure of feedwater isolation valve SGB-137.
Plant
systems
responded
as
designed,
and the trip was uncomplicated.
Electrical maintenance
electricians
were in the process of replacing
a coil
for a solenoid operated
valve associated
with the hydraulics for the actuator
of Valve SGB-137 prior to the reactor trip.
The electricians
were attempting
to terminate
the coil leads for solenoid operated
Valve
D onto
a terminal
block.
Subsequent
licensee
troubleshooting
determined that the electricians
had disturbed
a loose termination for solenoid
operated
valve Coil A, which
was terminated
in the
same junction box.
As
a result,
the coil lost power and
actuated
Valve SGB-137.
The terminal block for solenoid coil
A used
a compression
screw that was
loose.
The licensee
repaired
the loose termination
and performed
a subsequent
inspection of the terminations for other valves with similar terminal blocks.
This inspection
included the other feedwater isolation valves
and the main
steam isolation valves.
The inspector
observed
excellent
involvement
by plant management
in the post-
trip review.
Management
took
a cautious
approach
to identifying the cause of
I
I
I
the trip and appropriate
actions
in assessing
the potential
impact
on other
equipment.
2.2
Entr
Into Technical
S ecification
TS 3.0.3 Followin
an
Emer enc
Diesel
Generator
S urious Actuation
On June
13, at approximately Il:20 a.m., control
room operators
received
a
high priority trouble
and engine trip alarm for the Train
B EOG,
and
an
automatic start of the Train
B spray
pond
pump
and the Train
B
EOG building
essential
fans.
Control
room operators
investigated
the alarms
and determined
that the Train
B
EOG had not received
a valid start signal.
The licensee
declared
the Train
B
and
began troubleshooting activities.
Control
room operators
subsequently
performed the surveillance test
(ST)
procedure
used to demonstrate
operability of the remaining sources of AC power
when
one
EDG was declared
as required
by TS. 3.8. 1. 1.
The
procedure
required
the licensee
to declare
both trains of a safety-related
component
inoperable if the Train A component
was unavailable while the
Train
B
EDG was inoperable.
The inspector
noted that these
requirements
were
more restrictive than the requirements
of TS 3.8. 1. 1.
During performance of the
ST, control
room operators
noted that the Train
A
essential
cooling water
(ECW)
pump,
the Train A auxiliary feedwater
(AfW)
pump,
and the Train A hydrogen
recombiner
(HR) were out of service for
maintenance
when the Train
B
EOG was declared
The shift
supervisor
subsequently
declared
both trains of FCW,
HR and
and entered
and Action b of TS 3.7. 1.2,
as required
by the
surveillance
procedure.
The most restrictive action statement
required the
plant to be in hot standby within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
The inspector
noted good
involvement
by o'perations
management
in the review of the
TS and
requirements.
The inspector
asked
the shift supervisor
and the shift technical
advisor
when
they planned to commence
a plant shutdown to ensure that the plant was safely
shutdown within the 6-hour time limit.
The operators
determined that it would
take approximately
3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> to perform
a controlled shutdown,
and planned to
start
a shutdown at 2:30 p.m.
The inspector
concluded that the shift
supervisor's
actions to initiate
a planned
shutdown
were appropriate.
The licensee
restored all the Train
A equipment at approximately
2 p.m.
and
exited
and 3.7.4.
The inspector
observed
good coordination
between
operations
and maintenance
to promptly restore
the Train A components.
The licensee
determined that
a faulted
speed
probe for the Train
B
EOG sent
an
erroneous
signal
to the start circuitry that the'engine
was running which
caused
the essential
fans
and spray
pond
pump to start.
The
EOG subsequently
received
a trip signal
due to actual
low lube oil and cooling water
temperatures
because
the engine
was not running.
The licensee
found
a crack
in the
amphenol
connector for the
speed
probe that caused
an electrical
short
in the circuit.
The licensee initiated
a condition report/disposition
request
(CRDR) to determine
the cause of the failure and to identify appropriate
corrective actions.
The inspector
observed
good troubleshooting efforts
and
agreed with the licensee's
conclusion that the
speed
probe failure initiated
I
I
I
the event
and would not have prevented
the
EDG from starting during
an
emergency.
3 OPERATIONAL SAFETY VERIFICATION
(71707)
3. 1
Control of Scaffoldin
Around Safet
Related
E ui ment
During walkdowns of the Unit 2 auxiliary building and the Unit
support structure
on May 25, the inspectors
identified four instances
where
scaffolding in areas
with seismically qualified equipment
had tags
which
indicated that the scaffolding
had not been erected
to seismic criteria.
The
examples
were
as follows:
~
Both Unit
1
AFW pump rooms
had scaffolding erected
to support
modifications to the turbine driven
AFW pump steam drains.
~
Unit 2
ECW pump Train
B room had scaffolding erected
to support
evaluation of the seismic qualification of the
ECW process
radiation
monitors
and associated
piping.
~
Unit 2 120-foot elevation hallway had scaffolding erected.
The inspectors notified the Unit
1 shift supervisor
(SS)
and the Unit 2
control
room supervisor
(CRS).
The inspector
was promptly called
by the Civil
Engineering
Team
and informed that
CRDR 9-5-560
had
been initiated
and
that walkdowns of scaffolding in all units would be performed.
The licensee
subsequently
found that scaffolding
had
been erected
in the Units
1
and
3
ECW
Train
B pump rooms which was tagged
as nonseismically qualified.
The inspector
was informed the following day by the Site Shift Manager
(SSM)
that the Operations
Director had established
an investigation
team.
The
licensee
determined
that in all but two instances,
the scaffolding
had
been
erected
to seismic criteria established
in licensee
Procedure
The
two exceptions
were scaffolding in the Unit
1
AFW rooms
and the Unit 3
ECW
Train
8 pump room.
The scaffolding
was modified to meet the procedure
specifications.
In addition, licensee civil engineers
performed calculations
of the as-found conditions of the scaffolding
and determined that it would not
have
damaged
seismically qualified equipment during
a seismic event.
The inspector
reviewed the evaluation
and agreed with the licensee
that the
incorrectly installed scaffolding
had minimal safety significance.
Therefore,
the failure to follow the seismic criteria for installing the scaffolding
constitutes
a violation of minor significance
and is being treated
as
a
Noncited Violation, consistent
with Section
IV of the
3. 1. 1 Corrective Actions
The licensee
performed
a cause
evaluation
and identified several
areas of
concern:
~
In some instances,
the carpenters
erecting
the scaffolding
had applied
the seismic criteria of the component
to be worked on to the
I
I,[
f
In the case of the scaffolding in the
ECW pump rooms,
work
was to be performed
on the non-seismically qualified process
radiation
monitors
(RU3).
However,
the scaffolding
was erected
in close proximity
to seismically qualified
ECW equipment.
~
In the case of the Unit
1
AFW rooms,
the scaffolding
had
been erected
during the refueling outage
when the
AFW system
was not required to be
The modification work order,
which included the scaffolding,
was being tracked
by the control
room as
a mode
change
hold.
However,
after the modifications
had
been
completed
and outage
management
emphasized
work order closeout during plant restart to support
mode
transitions,
the carpenters
closed
the step in the initial work order to
remove the scaffolding
and opened
a
new work order to remove the
~
Individuals from Nuclear Assurance
Maintenance
had
used the
and operations auxiliary operators
(AO) had routinely
toured the
rooms prior to the identification of concerns
by the
inspector.
Licensee
management
expectations
for both groups
was that
they should
have identified the scaffolding deficiencies.
~
The licensee identified several
seismic tag deficiencies.
Although the scaffolding issues
appeared
to be isolated to the practices of
one crew,
the licensee
conducted
a "stand-down" with all carpenters
to discuss
the findings and to clarify expectations.
In addition,
the licensee
has
initiated actions to clarify expectations
for Nuclear Assurance
personnel
and
AOs.
The inspector
concluded that the licensee
conducted
a timely and thorough
investigation of the issue
and that the corrective actions
were appropriate.
3.2
Radiolo ical Controlled Area Mat Lifted B
Wind
On May 22, during
a plant walkdown of the Unit 3 yard radiological controlled
area,
the inspectors
observed
a large rubber mat
become airborne
as
a result
of a sudden burst of wind.
The mat traveled
15 to 30 feet
and landed
on
an
adjacent radiological controlled boundary fence.
The inspector
noted that the
area
was unattended
and notified Radiation Protection
personnel.
The mat was
a rubber sheeting material,
approximately
90 by 90 feet in length,
used
as
a temporary chemical
cleaning
berm.
The berm was originally setup
by
contracting
personnel
for steam generator
chemical
cleaning which had
been
performed during the Unit 3 refueling outage
in April 1994.
The contractor
was in the process
of dismantling the
and
was awaiting
a radiological
survey of the berm before it was removed.
They had dismantled portions of the
berm which were holding the mats
down.
The inspector estimated
that the
berm was within 100 feet of the essential
t
The mat had
been carried north
and
away from the spray ponds.
However,
the inspector
concluded that the licensee
had not been sufficiently
i
sensitive
to the potential that the mat could have
been carried into the spray
ponds.
The inspector discussed
the potential of the mat landing in the spray
pond
with the contracting supervisor
and the system engineer.
They stated that
during setup
and tear
down periods, it had
been
expected
that the berm area
was not to be left unattended.
The system engineer
discussed
barriers that
are set in place to prevent material
from entering the spray
ponds
and the
procedure for controlling potential
tornado
borne missiles
in the outside
areas.
In response
to the inspector's
concerns,
the licensee's
project manager for
the steam generator
chemical
cleaning project conducted
meetings with the
contractor which had set
up the
berm area.
The licensee
discussed
its
expectations
regarding
coverage
oF tear-down activities 'and the necessity for
ensuring that potential
hazards
are secured.
The inspector
found these
actions to be appropriate.
3.3
Loose Electrical
Connections
on Safet -Related
E ui ment in the Auxiliar
~Bui1 din
On May 19, the inspector identified loose connections
on conduit pull boxes
and motor-operated
valves in the Unit 3 west mechanical
room.
The
inspector
also identified three conduit pull boxes that
had incorrectly
installed gaskets
and three junctions
boxes with missing screws
in the Unit I
auxiliary building.
The licensee
determined that these conditions did not
impact operability of the associated
safety related
equipment
because
any
moisture that entered
the system would go into the junction box and not the
end device (e.g.,
motors, transmitters,
solenoids,
etc.).
However,
the
licensee
concluded that these conditions did not meet the specifications for
installed conduit,
and initiated work requests
to correct the deficiencies.
The inspector
concluded that although the loose electrical
connections
in
Unit 3 and the material deficiencies identified in Unit I were not operability
concerns,
they were indications of poor material condition
and inattention to
detail.
The licensee
decided to discuss
these
problems with electricians
and
emphasize
the need to perform detailed
walkdowns after
an outage to identify
and correct these
types of deficiencies.
The inspector
concluded that the
licensee's
response
was appropriate.
3.3.1
(HELB) Analysis
The inspector
reviewed the licensee's
analysis of a
HELB in the auxiliary
building to verify that the loose electrical
connections
did not adversely
impact the operation of safety related
equipment during this event.
The
inspector
noted that the licensee
calculated
a peak pressure
in the mechanical
room of 'less
than
3 psig from this event.
The inspector
reviewed
the environmental qualification (Eg) program manual
and noted that the
licensee
had done
a study concerning
the sealing
requirements
for electrical
connections
exposed
to
a
HELB environment
and determined that for accident
0
4
I
pressures
less
than
3 psig the connections
do not need to be sealed
to
preclude moisture intrusion provided:
~
The conduit
and junction box systems
connected
to the equipment
were
designed
to facilitate condensate
drainage;
and,
~
The integrity of the equipment
enclosure
was maintained
in accordance
with the tested
equipment configuration (e.g.,
use of proper cover
and cover screw/o-ring
and gasket configuration).
The inspector
noted that the study included actual tests
on various types of
electrical
enclosures
to support
the conclusions.
The inspector
concluded
that the licensee's
study supported its determination that the loose
electrical
connections
in the auxiliary building were not safety significant.
The inspector
conducted
walkdown of the mechanical
rooms in the
Unit
1 auxiliary building to determine if the electrical junction boxes
had
weep holes to provide for condensate
drainage,
and if the covers for the
electrical
devices
(e.g.,
motors, transmitters,
solenoids,
etc)
were
appropriately
secured
and sealed.
The inspector verified that the covers for
the electrical
devices
were properly installed
and that all the safety-related
junction boxes
had
weep holes to allow for condensate
drainage.
The inspector also noted that
Eg engineering
was conducting field
verifications of the installation of electrical
conduit in the auxiliary
building to verify the assumptions
used
in the
HELB analysis.
The inspector
concluded that
Eg engineering
had conducted
a thorough, detailed evaluation of
the effect of a
HELB on the electrical
components
in the auxiliary building
and that the licensee's
actions to conduct field verifications were prudent.
3.4
Leakin
Air Re ulator for Atmos heric
Dum
Valve - Unit
1
On June
4, the inspector
noted
a buzzing noise
from an air regulator
associated
with the pneumatic operator for Unit
1 atmospheric
dump Valve
(ADV)
SGB-179.
18C technicians
subsequently
investigated
the noise
and determined
that the air regulator
appeared
to have
a leak past its diaphragm.
The
declared
ADV SGB-179 inoperable
and II C technicians
replaced
the air
regulator.
Operators
then satisfactorily performed
a post-maintenance
pressure
drop test
on the air system for the
ADV and declared
the
ADV
The licensee initiated
CRDR 1-5-0145 to determine
the cause of the leaking air
regu'lator.
The evaluation
had not been
completed at the
end of the
inspection.
The inspector will review the licensee's
evaluation
when it is
completed.
3.5
Emer
enc
0 eration
Procedure
Trainin
The licensee
implemented its revised
emergency
operating
procedures
(EOP) at
the
end of the inspection period.
The
EOPs were revised to be consistent
with
Combustion
Engineering
owner's
group guidance
(CEN 152).
The inspector
observed
portions of the "high intensity team" training conducted for each
l
1
~
I,
-10-
crew in preparation for the implementation of the
EOPs.
The inspector
observed
one crew respond to
a steam line break event
and
tube rupture event.
The inspector
noted that the
enhanced
crew performance
and allowed for
greater flexibility in responding
to events.
As
an example,
during the steam
generator
tube rupture event,
the crew was able to isolate the faulted steam
generator within 14 minutes
From the start of the event.
In contrast,
during
the March
1993 Unit 2 steam generator
tube rupture event,
operators
isolated
the steam generator
in approximately three hours,
in part due to restrictions
in the
used at the time.
The inspector
observed
good trainer performance
in that they closely observed
crew performance
and performed detailed
and critical post-scenario
reviews.
The inspector also interviewed several
crews following the training and found
that they were consistently
pleased
with the
new EOPs.
They found the
procedures
to be easier to use
and allowed them to concentrate
on plant
performance.
3.6
Walkdown of EDGs - Units
1 and
2
On June 8, the inspector
performed
a walkdown of the Units
1 and
2
EDGs.
The
inspector
noted that the housekeeping
of the Unit
1
EDGs was adequate
and that
the housekeeping
of the Unit 2
EDGs has greatly improved, especially
in the
area of the auxiliary skid.
The inspector
noted that starting air cross-tie
Valve DGN-V238 in Unit
1 on
the Train
A EDG was not in its normal position
as indicated
by plant
procedures.
The valve had
been
opened to keep both starting air receivers
pressurized
during air dryer maintenance.
The change of the valve's
normal
position was not documented.
The inspector discussed
the valve position with
the system engineer
and determined that the valve was in the nonsafety-related
portion of the system
and that there
was
no safety significance in leaving the
valve in the open position.
The inspector
informed the Unit
1 operations
department
leader
about the
position of DGH-V238 and the inspectors
concern for the conFiguration control
of the valve.
The operations
department
leader
agreed that there
was
a
configuration control weakness
and attached
a caution tag to the valve to
ensure it was returned to the desired position
upon completion of the
maintenance.
The inspector
concluded that the licensee's
response
was
appropriate.
3.7
EDG Governor Control
Fre uenc
- Unit
1
On May 23,
the inspector
observed
that the Unit
1 Train A EDG was providing
the only source of power to the vital 4160 volt bus,
due to insulator repair
on the associated
startup transformer.
The inspector
noted that the
EDG was
operating
in the isochronous
mode at 60.8 hertz,
and questioned
the operators
about the
EDG frequency
because
the
EDG usually operates
at 60.0 hertz.
The
inspector
was concerned
that the operators
had not questioned
the
frequency
and were unable to effectively respond
to the inspector's
concern
that the observed
indication
may represent.
a problem or an unfavorable trend.
'i
J
1
I
i
li
,
I
-11-
The inspector
noted that
a similar concern
was raised
in February,
1995
(NRC
Inspection
Report 50-528/95-03;
50-529/95-03;
50-530/95-03),
when operators
did not demonstrate
a questioning attitude
when they noted,
but failed to
investigate,
an off-normal indication in safety injection line pressures.
The
inspector
also noted that the licensee
procedures
being used to operate
the
"Emergency Diesel
Generator A," and 410P-lPBOl,
"4. 16kV Class
1E Power (PB)," did not specify that the
EDG should
be operated
at
60 hertz.
The inspector
informed the
EDG system engineer
about the inspector's
observation
and questioned
the performance of the woodward governor.
The
engineer
investigated
the
EDG performance
and responded
that the governor
was
performing
as designed.
The inspector evaluated
the engineer's
conclusion,
agreed that the
EDG was performing
as designed,
and concluded
that the
engineer
had responded
quickly and thoroughly to the inspector's
concern.
The inspector
informed the operations
department
leader
about the
observations
and the licensed
operator
response.
The operations
department
leader
agreed with the inspector's
concern,
and issued
a
memo to all licensed
operators
emphasizing
management's
expectation for control board
awareness
and
for the operators
to monitor and question
any abnormal
indication.
In
addition,
the operations
department
leader
issued
an instruction
change
request
to change
the 4.16kV Class
1E Power procedure
in all three units to
provide guidance
on
EDG frequency control.
The inspector
concluded that the
operations
department
leader's
corrective actions
were appropriate.
4
MAINTENANCE OBSERVATIONS
(62703)
4. 1
S stem Governor Valve
Unit
1
On May
13
and
May 15, the Unit
1 steam driven
AFW pump turbine tripped
on
during uncoupled
runs performed
as pa'rt of postmaintenance
testing.
The postmaintenance
testing
was performed following the replacement
of the
valve stem
and packing.
The licensee
observed that the governor valve failed
to properly respond
to control signals,
resulting in the overspeed trips.
The
inspectors
observed
mechanical
maintenance
engineers
disassemble
the governor
valve,
interviewed maintenance
personnel,
reviewed the licensee's
evaluation
of cause,
and assessed
the licensee's
planned corrective actions.
The licensee
determined that the overspeed trip was caused
by binding of the
governor valve stem,
which prevented
the valve from stroking freely.
The
licensee
determined
that the binding resulted
from deficiencies
in the inner
packing of the governor valve.
The licensee
speculated
that the stuffing box
had not been
adequately filled, resulting in broken carbon
spacers
and cocked
stainless
steel
washers.
The licensee
concluded that the improper assembly
was
caused
by inattention to detail
by the mechanical
maintenance
technicians.
The inspector
concluded that the licensee
had not been rigorous in its cause
eva'luation,
and
had not performed sufficient review to determine that packing
deficiencies
caused
the valve to stick.
Additionally, the inspector
concluded
that weak work instructions
were
a significant contributor to the packing
deficiencies,
and that there
had
been prior opportunities to enhance
the work
instructions.
0
-12-
4.1.1
As-found Condition
The stuffing box for the governor valve contained
the inboard
and outboard
valve packing assembly.
The assembly
provided
a labyrinth seal with the
combination of carbon
spacers
and stainless
steel flat washers,
followed by
the guide bushing
and the retaining ring.
Prior to disassembling
the governor valve,
mechanics
attempted to move the
valve stem.
With the stem in
a horizontal orientation
(as installed),
they
could not move the stem.
With the stem in a vertical orientation,
the stem
could
be moved easily.
Mechanical
maintenance
personnel
subsequently
disassembled
the governor valve stuffing box on May 17,
and found several
of
the carbon
spacers
broken in half, chipped
and pulverized.
In addition,
the
number of sets of carbon
spacers
and steel
washers
removed
was determined to
be one set less
than the
amount
needed
to completely fill the stuffing box.
The licensee
measured
the stuffing box and determined that
22 sets
plus
one
extra washer
was required to completely fill the stuffing box.
The licensee
repacked
the stuffing box accordingly,
and noted
a gap of 0.025 inches
between
the guide bushing
and the retaining ring.
This gap
was determined to be
acceptable.
The postmaintenance
test
was repeated
and the governor valve
responded
appropriately.
4.1.2
Licensee's
Apparent
Cause
Determination
The licensee
determined that the governor valve had failed due to the stuffing
box not being completely full.
This allowed the packing assembly to have too
much free play and the licensee
speculated
that this allowed the steel
washers
to become
cocked.
Additionally, when force was applied to the valve stem,
the
cocked steel
washers
placed additional friction on the carbon spacers,
causing
the carbon
spacers
to break.
The licensee
concluded that this would have
explained
why the valve stem locked
up in the horizontal orientation
and not
the vertical orientation.
Additionally, one mechanical
maintenance
engineer
noted that during
a past
packing job he had cocked
one of the washers.
This was discovered
when
he
noted that there
were washers
and spacers left over when the stuffing box was
full.
This observation
supported
the licensee's
conclusions that
a cocked
washer
may have contributed to the inadequately full stuffing box.
The licensee
determined
that inattention to detail
by mechanical
maintenance
personnel
was the apparent
cause of the failure to completely fill the
stuffing box.
l
vl
li
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4.1.3
Licensee's
Planned
Corrective Actions
The inspector
reviewed the licensee's
proposed corrective actions
described
in
the
CROR,
The licensee
planned to implement the following corrective actions
prior to the next refueling outage:
~
Enhancements
to the master work instructions
and preventative
maintenance
(PH) tasks to include more quantitative instructions
on
packing the valve.
~
Additional training for proper assembly of the governor valve stuffing
box using
a mockup of the governor valve.
4.1.4
Inspector's
Review of Cause
Determination
The inspector questioned
the state of the carbon
spacers
found in the past
when disassembling
the governor valve.
Both the mechanical
maintenance
engineer
and the maintenance
technicians
stated that it was
common to find
broken carbon
spacers
during valve disassembly.
However, they noted that it
had never caused
the valve stem to bind.
The inspector questioned
whether
the
discovery of broken carbon
spacers
had ever been evaluated.
The licensee
determined that it had not.
The technicians
also stated that the carbon
spacers
could be easily chipped or
broken
when the packing
was assembled.
The threads
on the
end of the valve
stem
may contain tiny burrs that
may chip the inside diameter of the spacer
during installation or removal.
Whi'le the installation
and removal of the
spacers
could have resulted
in some chipping,
the inspector determined
that this would not explain the amount of breakage
observed
during
a typical
disassembly.
The inspector
considered
that the licensee
had not been
appropriately sensitive
to previously observed
spacer deficiencies.
The inspector
reviewed the
PH task work order which controlled the original
replacement
of the valve stem
and packing,
and
compared it with the
instruction provided in the vendor technical
manual
(VTH).
Both contained
instructions for repacking
the stuffing box assembly.
The work instructions
in the
PH task,
which duplicated
the
VTH instructions,
stated
in part:
"Starting with a carbon
spacer,
alternate
stacking the carbon
spacer
and
flat washer until the stuffing box is full and the guide bushing
and
retaining ring can
be installed.
Use additional
washers
to finish
filling the stuffing box.
The complete stack should not be tight,
some
play is required".
The inspector questioned
the mechanical
eng-'neer
as to what the required
amount of play was
and what does it mean
when the stuffing box was full.
The
engineer
stated that it was
common maintenance
practice to fill the stuffing
box until no further carbon
spacers
(0. 125 inch thick) could
be added,
and
then fill the remaining
space with additional
washers
(0.062 inch thick).
As noted previously,
the proper as-left gap
was 0.025 inches.
Using this
value,
the inspector determined
that the as-found
gap with one spacer
and
two
f)
I
0
-14-
washers
missing would be approximately I/4 inch.
The inspector questioned
whether
a I/4 gap could
be
seen
by the mechanics
as providing
a full stuffing
box meeting the ".
. .not tight,
some play.
. ." criteria.
The mechanical
maintenance
team leader concluded that it would have
been too loose.
However,
the team leader
noted that the gap could have
been
measured
between
the last
washer
and the bushing.
During the
Hay reassembly it was noted that the
shoulder
appeared
to have
eroded
which allowed the bushing to set
lower in the stuffing box, reducing the clearance
between
the bushing
and last
washer.
This also
increased
the gap between
the bushing
and the
snap ring.
The licensee
discussed
the various
ways to measure
the stuffing box gap with
the vendor.
The vendor noted that the total
gap established
was the critical
dimension.
The inspector
concluded,
however, that
had the mechanics
measured
the gap between
the bushing
and the last washer,
and not considered
the gap
between
the bushing
and the snap ring, they could have reasonably
concluded
that the stuffing box was full with some play.
The technicians
stated that they were confident that they had packed
the
stuffing box in accordance
with the work instructions.
After the technicians
assembled
the valve, they checked for valve freedom of movement,
as required
by the work instructions.
However,
the technicians
pointed out that there
was
no quantitative
acceptance
criteria for the valve's length of stroke.
If a
spacer
had
been
cocked, it would have
been possible for the stem to have
some
movement.
The inspector considered
that valve stroke length
was
a significant
parameter
which should
have
been
included in the work instructions.
4. 1.5
Evaluation of Licensee's
Cause
Evaluation
Process
The inspector
noted that the licensee
considered this problem to be
an
"Adverse" condition,
as identified by its
CRDR process.
The event
was
determined
to not be "Significant," primarily due to the fact that it was
discovered
during postmaintenance
testing
and not while the
pump was
considered
Consistent with its program,
mechanical
maintenance
did
not perform
a formal root cause
evaluation,
and planned only to identify an
"apparent
cause."
The inspector
noted that while the classification of "adverse"
was consistent
with licensee
procedures, it did not appear to be prudent,
in that the
licensee
has experienced
a significant history of AFW turbine overspeed
events.
Additionally, there
have
been several
recent industry events
highlighting concerns
with the governor valve stem
and its packing.
Given
these
events
and the risk-significance of the turbine driven
AFW pump at Palo
Yerde,
the inspector
considered
that it would have
been prudent to have
performed
an in-depth root cause
evaluation.
The inspector
met with licensee
maintenance
personnel
and management
several
times during the inspection period,
and noted that maintenance
personnel
seemed
to be learning
new information from each other.
In addition,
the
inspector consistently
found
new and sometimes conflicting information during
followup inspection.
It also
appeared
that plant management
had
a greater
expectation of the cause
evaluation
than those.-at
the working level
and that
these
expectations
had not been well communicated.
r
i'
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The inspector concluded that,
although the evidence
appeared
to qualitatively
support
the licensee's
conclusion that the stuffing box had
been
inadequately
packed,
these
conclusions
were not supported
by rigorous quantitative
evaluation,
such
as using mockups with a spare governor valve, or specific
measurement
of how much space
was necessary
to allow a washer to cock.
At the exit meeting,
the Director of Maintenance
agreed with the inspector
that communications
could
be improved and that
a more rigorous root cause
evaluation
should
have
been performed.
The licensee
also agreed
to assess
the
adequacy of the
CRDR process
which lead the engineers
to only conduct
an
apparent
cause
evaluation.
4.2
Leakin
Safet
In'ection
S stem Check Valve - Unit
1
On May 18,
a high pressure
safety injection (HPSI) system
check valve in
Unit 1, SIA-V113, failed
a postmaintenance
reverse
flow seat
leakage test.
SIA-V113 was
a 3-inch Borg Warner swing check valve
and functioned
as the
inside containment isolation valve for the
HPSI injection line to reactor
coolant
Loop 2B.
The reverse
flow seat
leakage test
was required after the
valve was disassembled
and inspected
on April 13.
The licensee
subsequently
disassembled
SIA-V113 to determine
the cause of the
excessive
seat
leakage.
The licensee
determined that the bonnet
assembly
was
installed too high which resulted
in the valve disc not being centered
in the
valve seat.
On May 22, the licensee
aligned the valve disc
and seat,
and
SIA-V113 passed
the postmaintenance
seat
leakage test.
The licensee initiated
a
CRDR to determine
the cause of the leakage
and to identify appropriate
corrective actions.
The inspector
reviewed the model
maintenance
procedure for disassembly
and
reassembly of Borg Warner check valves,
reviewed the
VTM, and
had several
discussions
with the check valve engineer.
The purpose of this inspection
was
to determine if the model
maintenance
procedure
was adequate
to detect
and
correct
a check valve alignment problem.
4.2. 1
Vertical Alignment Determination
The inspector
noted that the check valve maintenance
procedure
required the
mechanics
to measure
and record the distance
from the top of the seat
retaining ring to the valve body prior removing the check valve internals.
This measurement
was recorded
as the as-found
Dimension
A.
When the valve was
reassembled,
the procedure
required the mechanics
to thread the seat retainer
into the valve body until the as-left Dimension
A was .the
same
as the
as-found
Dimension
A.
The inspector
noted that using this procedure
ensured
that the valve disc was reinstalled
in the
same vertical location
on the valve
seat.
The inspector
noted that Appendix 0 of the procedure
included instructions for
determining if the valve disc was centered
on the valve seat.
Using these
instructions
the mechanics
could measure
the distance
from the top of the
valve body to the center of the valve seat
and the distance
from the top of
the valve bonnet to the center of the valve disc,
and then calculate
an
'(
I,l
-16-
as-left Dimension
A that would ensure
the valve disc was centered
in the valve
seat.
The licensee
was required to perform the alignment
check in Appendix
D if the
results of previous
seat
leakage
tests
were higher than normal, or if there
were abnormal
wear marks
on the valve seat during the check valve inspection.
The licensee
did not perform the Appendix
D alignment
check
prior to
reassembling
SIA-V113 because
the last reverse
flow test
was well within the
acceptance
criteria and there
were not any abnormal
wear indications
on the
valve disc
and seat.
The inspector
concluded that the licensee
had complied with the applicable
check valve maintenance
procedure.
The inspector also concluded that, prior
to the observed
valve leakage
problem,
and based
on the licensee's
previous
trouble-free experience
with these
va'ives
and existing vendor manual
guidance,
the procedure
requirements
For ensuring
proper valve assembly
appeared
to have
been reasonable.
However,
based
on the observed
problem,
the inspector
concluded that additional
procedure
guidance
to ensure
proper valve assembly
was warranted.
4.2.2
Corrective Actions
The licensee
determined that differences
in measuring
the Dimension
A
contributed to the valve bonnet for SIA-V113 being set higher than other
similar check valves.
The licensee
subsequently
disassembled
SIA-Yll3 and
calculated
a new Dimension
A using Appendix D.
The licensee
reassembled
the
valve
and set the vertical alignment using the
new Dimension
A and the valve
successfully
passed
the reverse
flow test.
The licensee initiated
an evaluation of whether Appendix
D should
be performed
to verify the proper vertical alignment of the check valves
as part of every
check valve inspection.
The licensee
also planned to disassemble
a spare
and determine
an optimum method to measure
the dimensions
used to
center
the valve disc
and seat.
The inspector
concluded that these corrective actions
were appropriate.
However,
the inspector
was concerned
that the licensee's initial corrective
actions did not include
an appropriate
acceptance
criteria for when the
vertical alignment of the valve would be adjusted
based
on the calculated
Dimension
A using Appendix D.
The inspector discussed
this concern with the
check valve engineer
who agreed
to include
an action to quantify this
acceptance
criteria.
The inspector
concluded that the licensee's
response
was
appropriate.
4.3
Instrumentation
and Controls
I8C
Technicians
Workin
on Wron
Valve-
Unit I
On March 23,
1995, while in containment
to perform work on pressurizer
spray
Valve 100E,
an
I8C technician
tightened
a jam nut on the booster relay for the
valve, resulting in spurious closure of the valve.
Since
spray Valve 100F was
the valve in service maintaining
RCS pressure,
its closure
caused
RCS pressure
to increase
to 2274 psia.
Operators
had
been maintaining the spray valve open
with pressurizer
heaters
on to provide boric acid equalization
between
the
1
I
I
-17-
and the pressurizer.
Operators
were alerted to the condition by a control
room alarm
and stabilized
RCS pressure
by turning off pressurizer
heaters.
The
I&C technicians
returned to the control
room and were questioned
by the
operators
as to what work they had performed
and whether it could have
impacted
Valve lOOF.
The
I&C technicians
stated that they had tightened
the
jam nut and recognized that
an associated
adjustment
screw
may have turned
with the nut.
I&C technicians
returned
to containment
and readjusted
the jam
nut, restoring the operation of the spray valve.
After the event,
the
initiated
CRDR 1-5-133.
The inspector discussed
this work with the
I&C department
leader,
section
leader
and
team leader.
They noted that there
was
an open work order for the
spray valve covering the proper adjustment of the booster relay.
They stated
that the technicians
had not anticipated that tightening the jam nut would
have turned the adjustment
screw.
However,
they concluded that it would have
been appropriate for the technicians
to inform the control
room prior to
performing the adjustment
and they subsequently
counselled
the technicians.
I&C management
also discussed
lessons
learned
from this event with I&C
personnel.
The inspector
found these
actions to be appropriate.
4.'4
Wron
Tor ue Values
Used
on Unit
1
and
2
S ra
Valves
During the Unit
1 refueling outage,
the actuators
of both
RCS spray valves
were replaced with larger actuators.
In addition, the body to bonnet gaskets
were replaced.
The gasket for RCS spray Valve RCE-PV-100E
began to leak
as
RCS pressure
was increased
during the Unit restart.
Mechanical
maintenance
increased
the body to bonnet bolt torque
by
10 percent
in an attempt to stop
the leakage.
When the leakage failed to stop,
the licensee
discovered that
the bolt torque
used
was significantly lower than the appropriate
torque value
for valves
in this service.
The licensee
took concurrent actions to perform calculations to determine
appropriate
torque values
and to contact the vendor,
The
initial torque value
had
been
130 ft-lbs.
The licensee initially calculated
a
torque value of 345 ft-lbs.
The vendor subsequently
recommended
a torque
value of 540 ft-lbs.
The licensee
applied its calculated
torque values to
both Unit
1 spr ay valves.
In addition,
the licensee
entered
both Units
2
and
3 containment buildings with the units at full power to retorque
the spray
valve body-to-bonnet bolts.
They noted bolt movement
in the Unit 2 valves,
which had
been modified during
a February
1995 refueling outage.
However,
no
bolt movement
was noted in Unit 3.
4.4. 1
Cause
Review
The licensee
determined that the following factors contributed to the
inadequate
torque of the Units
1 and
2 spray valve body to bonnet bolts:
~
The licensee
index for the Fisher Controls
VTMs referenced
the wrong
manual for the spray valves.
The referenced
VTM covered
a similar valve
body model, rated for 600 psi,service,
which required only 130 ft-lbs
The licensee
concluded that
an error was-made
when the
VTM
(Ij
-18-
index was created.
They speculated
that
a note in the vendor drawing
for the valve contributed to confusion in that it indicated the valve
weight of 600 lbs.
~
Fisher Controls identified during its discussions
with the licensee that
the spray valves
were
4 inch bodies with 3 inch ends.
The vendor
drawing did not indicate this fact.
The licensee
subsequently
found
that
a purchase
specification did confirm that the spray valves
were
4-inch bodies.
The vendor
body to bonnet torque specification for
4-inch bodies
was
540 ft-lbs versus
404 ft-lbs for 3-inch valves.
Licensee
work records
indicated that prior to the development of the
VTN
index,
the valves
had
been
torqued to 404 ft-lbs.
~
Fisher Controls identified that the
540 ft-lbs specified for the 4-inch
valves
was
a maximum torque value to use in problem valves.
The
licensee
confirmed this with its
own calculations
in that torque values
this high could produce
high bonnet stresses.
The licensee
determined
that optimum bolt torque would be between
350
and
405 ft-lbs.
~
A chance to identify these
problems
was missed during the Unit 2 outage.
One of the Unit 2 spray valves
had initially leaked after having
been
torqued to
130 ft-lbs.
It was subsequently
torqued to 143 ft-lbs and
stopped
leaking.
t
The inspector discussed
the licensee's
findings with maintenance
engineering
and found them to be appropriate.
4.4.2
Safety Significance of As-Found Condition
The licensee identified that Unit 2 had operated
for greater
than
30 days with
the low spray valve body to bonnet bolt torques.
They performed
an as-found
condition calculation to determine
whether there
had
been sufficient preload
on the bolts to prevent cyclic stresses
during all operational
conditions.
The calculation,
which considered
temperature,
pressure,
and seismic
influence,
determined that while a substantial
amount of preload could be
lost, sufficient joint compression
remained.
Additionally, the licensee
evaluated
the potential for loss of gasket
crush to determine
the potential
maximum body to bonnet
leakage.
They calculated that the maximum leak would
be
a fraction of the makeup capacity for one charging
pump.
The inspector
reviewed the
scope of the calculations
and the calculation
assumptions
and found that they were appropriate.
4.4.3
Corrective Actions
The licensee initiated plans to re-torque all bolts to 375 ft-lbs.
This was
completed
in Units I and
3 with plans to torque Unit 2 bolts in early July.
The licensee initiated
an action to revise the
VTH and appropriate
drawings to
reflect the results of its investigation.
In addition, the licensee
had
asked
the vendor to clarify its conclusion that the torque values for the spray
valves
as indicated
in the
VTN were
maximum values.
This was not clear in the
I
'
0
-19-
VTH and could have
an impact
on the torque applications for other valves.
The
inspector will follow the licensee's
evaluation during routine inspection.
The inspector
found that although the licensee
had initially missed
the
opportunity to identify these
problems in Unit 2, the subsequent
corrective
actions
were appropriate.
The licensee's
review of the issue
and the response
to deficiencies
were thorough
and prompt.
'I
4.5
S ent Fuel
Pool
S acer
Removal - Unit 3
On June
13, the inspectors
observed refueling
and maintenance
services
(RAHS)
personnel
remove spent
fuel rack blocking plates
from the spent
fuel pool.
This design
change
would modify the current checkerboard
mode of storage
to
a
different storage
mode to allow for more fuel assembly
storage
space.
The inspector
noted that the work package
was not present
at the work site.
The inspector questioned
one of the
RAHS personnel
and
was told that the work
package
was back in the
RAHS office.
The inspector
went to the office to
review the work package.
The inspector
noted that the work was being
performed in accordance
with the work instructions
however,
not having the
work package
in the field could lead to procedure
noncompliance
problems.
The team leader stated that the inspector's
observation
did not meet
management's
expectations.
The inspector
reviewed the "Principles of
Haintenance"
issued
by management
and noted that, principle number
2 states,
"maintain the work document/procedure
at the work site.
. ."
The inspector
noted that
a previous
example of work being performed without the work package
in the field was documented
in
NRC Inspection
Report 50-528/95-10;
50-529/95-10;
50-530/9510,
Section 4.2.
The inspector
was concerned
that
these
examples
may indicate
a need to emphasize
management's
expectations
for
the use of work packages
in the field.
The inspector
noted that the licensee
had initiated
an evaluation of
procedures
to determine
the need to emphasize
management
expectations
or to
provide appropriate
guidance for the use of work orders
in the field.
The
licensee
planned to present
these
expectations
to all maintenance
personnel.
The inspector
concluded that the licensee's
response
was appropriate.
4.6
Heat
Exchan er Leak
Re air
Unit 3
On June
6, the inspector
observed
mechanical
maintenance
technicians
repair
tube leaks identified on Feedwater
Heat Exchanger
IA.
The inspector
noted
that the technician did not have
an oxygen monitor inside the heat
exchanger.
Sometime later,
another technician obtained
the oxygen monitor and gave it to
the technician working inside the heat exchanger.
The inspector
reviewed the procedure
for confined
space entry
and its
requirements
for an oxygen monitor and discussed
the requirements
with the
maintenance
team leader responsible
for the job.
The maintenance
team leader
stated
that there
was
no immediate threat or danger to the technician
inside
the heat
exchanger
since there
was continuous ventilation provided
by
a
portable blower, but he was unsure of the requirement
to have
an oxygen
monitor.
i
O
1
-20-
The inspector discussed
the concerns with nuclear
assurance
and the
maintenance
section
leader.
The oxygen monitor was not required
because
the
heat exchanger
was classified
as
a non-permit required confined
space
area,
however,
the maintenance
team leader
was unsure of the
classification.
The inspector
concluded that although the oxygen monitor was
not needed
in this case, it was apparent
that th'e confined
space
requirements
were not well understood
by the acting
team leader
when challenged
by the
inspector.
The licensee
discussed
requirements
concerning confined
space
areas
with all of the maintenance
crews.
The inspector
concluded that the
licensee's
response
was appropriate.
5
SURVEILLANCE OBSERVATION
(61726)
5. 1
Safet
In 'ection
S stem
Check Valve Leaka
e Testin
- Unit
1
On Hay 23, the inspector
observed
the licensee
perform portions of
Surveillance
Test 73ST-9SI03,
"Leak Test of SI/RCS Pressure
Isolation Valves".
The purpose of the test
was to satisfy surveillance
Requirement 4.4.5.2.2 of
Technical Specifications
by verifying that SI/RCS check valve leakage
was
within limits.
The inspector
noted that the licensee
did not perform the procedure
as
written.
Specifically, the licensee did not install the drain rigs in
accordance
with the procedure
and did not drain the water from the 3-inch
upstream of check Valves SIA-V523 and SIB-V533,
as directed
by the
procedure.
Instead,
the licensee
installed the drain rigs with a loop seal
to
keep the headers full.
The failure of the licensee
to follow procedures
is
a
violation of TS 6.8.1 (Violation 528/9512-01).
The inspector
informed the
CRS about the observations.
The
CRS discussed
the
procedure
performance with the test director.
The
CRS noted in the
surveillance test log that the test director had chosen
not to perform the
procedure
as written due to difficulty in draining
and subsequently refilling
the header,
which did not include
a vent valve in that section of pipe.
The
CRS noted that the test
was performed for 10 minutes,
no leakage
was noted,
and,
thereFore,
the one
gpm limit was not exceeded.
The inspector questioned
the licensee
about the performance of the
surveillance test.
The licensee initiated
a
CRDR to evaluate
the technical
adequacy of the method
used
by the test director.
Engineering calculated
the
volume of the pipe
and hose,
used
worse
case conditions
by assuming that the
piping was initially empty,
and calculated that to fill the piping and
hose in
a 10-minute period,
the leak rate past the check valves would be 0.66
gpm.
Accordingly the licensee
concluded that the check valve leakage did not exceed
the
TS limit of 1.0 gpm.
The inspector discussed
the performance of the test with the test director
and
reviewed the test director's
statement
about the event.
The inspector
noted
that the test director thought that the procedure
had
been
changed
to place
a
in the drain hose
and
was not aware of the actual
requirements
of
Appendix D.
i
-21-
The licensee
discussed
with the test director the expectation for procedure
use
as well
as the conduct of complete
and accurate
prejob briefings.
In
addition,
the licensee
submitted
an instruction change
request
to revise the
Appendix 0 leak rate testing
method.
The licensee
indicated that the change
would be incorporated prior to the next use of the procedure during the Unit 3
refueling outage.
The inspector
concluded that the safety significance of the failure to follow
the procedure
was low.
However,
the inspector
concluded that the test
director did not refer to the procedure prior to or during performance of the
test
and,
as
a result,
made incorrect assumptions
about the requirements
of
the procedure.
5.2
Other Surveillance
Observations
The inspectors
observed
the following surveillance test
and determined that it
was performed acceptably:
~
EDG A Monthly Surveillance
Test
Unit 3.
6
ONSITE ENGINEERING (37551)
6.1
E
Life of S
G 81owdown Isolation Valves
During
a routine tour of the mechanical
room of the Unit 2
auxiliary building, the inspector
noted that the
blowdown line
sample valves were continuously energized
Valcor solenoid operated
valves
(SOVs),
and were in contact with hot process fluid.
The inspector
noted that
the licensee
had previously identified solenoid valves in similar applications
where the service
temperatures
of the solenoids
were higher than the
temperatures
used
in the
Eg test report
used to qualify the solenoids.
The inspector
asked
the
Eg engineering
group to identify the critical
components
of the Valcor
SOVs, the temperatures
used
in the qualification test
report for these
components,
and the service
temperatures
of these
components.
The licensee
was
aware that these
valves were susceptible
to potential
hot
spots,
but they had not previously compared
actual field conditions to the
assumptions
in the
Eg binder.
In response
to the inspector's
questions,
the
licensee
reviewed the
Eg binder,
determined
the qualified temperatures
of the
critical components,
and took inservice
temperature
readings of these
components.
The licensee
concluded that the service temperatures
of the
much lower than the temperatures
used
in the qualification
report
and that there
was not
a safety concern with the valves.
The inspector
was concerned
that the licenseo
had not yet determined
which
Eg
components
were the most susceptible
to hot spots
from process fluid heating,
and evaluated
these
components
to determine if there
was
a qualification
concern for these
components.
The inspector
reviewed the licensee's
thermal
monitoring program in
NRC Inspection
Report 50-528/95-10
and noted that the
licensee
measured field temperatures
of target rock SOVs
and
Namco limit
switches
in the main steam support structure,
and verified that the qualified
life oF these
components
were appropriate.
f
II
f
"1
I f
~
I
~ ~
tl
-22-
The inspector discussed
this concern with the supervisor of Eg engineering
and
noted that the licensee
had identified five components
that were
a potential
concern during the process
of developing the
scope of the thermal monitoring
program.
The licensee
had previously taken temperature
readings
on two of
these
components,
Target
Rock
SOVs and
Namco limit switches,
because
of actual
performance
problems.
The licensee
revised
the
Eg life of these
two
components
as
a result of these
reviews.
The licensee
evaluated
the Valcor
SOVs in response
to the inspectors
questions.
The licensee
had not measured
service temperatures
to validate the
Eg life of the remaining
two components,
Asco
and Skinner solenoids.
The inspector
asked
the
Eg engineering
supervisor
why they had not performed
a
preliminary assessment
of all the components
susceptible
to hot spots
in the
support structure,
the auxiliary building,
and in the containment
building,
The
Eg supervisor stated
that they planned to monitor the
temperatures
and the Asco and Skinner solenoids later in
1995,
when the formal thermal monitoring program
was
implemented.
The
licensee
made this decision primarily because
there
had
been
no performance
problems with these
components.
The inspector
concluded that the licensee
was shortsighted
.by only using
known
performance
problems
as the criteria for validating the service temperatures
of these
components.
The inspector
based this conclusion
on the fact that the
absence
of known performance
problems
does
not mean that
a component with a
qualified life will perform adequately
during
a design basis
event.
The
inspector
also concluded that the licensee
should
have validated the service
temperatures
used to qualify these
components
as
an interim corrective action,
prior to implementation of the formal thermal monitoring program.
The inspector discussed
this observation with the
Eg section leader
who agreed
with the inspector that
a preliminary assessment
of all the susceptible
components
would have
been appropriate
and committed to measure
the service
temperatures
of a representative
sample of the remaining
components
and
evaluate
the adequacy of its qualified life.
The inspector
concluded that
these
actions
were appropriate.
6.2
Crackin
in
Sam le Valves
In January
1994,
the licensee identified internal
cracks in the bodies of RCS
hot leg sample valves in Unit 2
(NRC Inspection
Report 50-529/94-02).
The two
solenoid operated
sample valves,
supplied
by Valcor, were the inside
and
outside
containment isolation valves for the
RCS hot leg sample line.
The
valves
were removed
and replaced.
The licensee
had contracted with the
Southwest
Research
Institute laboratories
to perform failure analysis
and
metallurgical
inspection.
The valves
are constructed
from a 4-inch block oF stainless
steel
with inlet
and outlet penetration
ports.
The valve internals
are threaded
and seal
welded into an approximate
2-inch diameter,
2-inch deep cylindrical bore.
The
cracks,
identified when the internals
had
been
removed for inspection,
formed
along the
base of the cylindrical bore
and along the inlet port.
The cracks
were not through-wall.
I
1'
~
14 W'
%%A 4r
-23-
The failure analysis
indicated that the cracking
had resulted
from low cycle
The valves
had
seen
approximately
3000 to 5000 cycles of
ambient to 600'F temperature
changes.
The failure analysis
concluded that the
valves would have remained functional for over
20 years
in that service
environment.
The licensee
reviewed industry data
and discussed
the findings with the valve
vendor but did not identify any similar instances
of cracking.
The licensee
documented
the results of their findings in Nuclear Plant Reliability Oata
System.
The licensee
inspected
Units I and
3
RCS sample valves during the respective
refueling outages,
and discovered similar cracking in the hot leg sample
valves.
In addition,
the licensee
discovered
cracking in the inside
containment pressurizer
steam
space
sample valves in both Unit I and Unit 3.
These
valves
had
been
subjected
to fewer thermal cycles,
and the cracking
was
less
pronounced.
The inspection
and replacement
of the Unit I valves
was
completed
in Hay 1995.
Since the initial finding, the licensee
has initiated studies to determine
long term corrective actions to eliminate the stresses
which cause
cracking.
The licensee
had worked with the vendor to perform postfabrication
changes
to
the valves to reduce
thermal
stresses,
such
as reducing the mass of the
valves.
Additionally, the licensee
has explored installing
a heat
exchanger
upstream of the valves to reduce
the magnitude of thermal cycling.
At the end
of this inspection,
the licensee
had not identified
a long-term solution.
Currently,
the licensee
intends to replace existing valves at
a frequency
consistent
with the rate of crack propagation.
Although the licensee's initial survey would indicate that this issue
may be
isolated to Palo Verde, it would appear that these
model valves
are
used in
similar applications
at other sites.
The licensee
informed the inspector that
they would issue
a notice to other sites
on
a industry information network.
6.3
Potential for Auxiliar
Pum
Tri
Followin
an Excess
Steam
Oemand
Event
In March 1995,
the licensee
identified, during
a modification review of the
AFW turbine driven pump, that under certain conditions following an excess
steam
demand
(ESO) event,
such
as
a steam line break,
operators
could
unintentionally cause
the
pump to trip.
In addition,
they identified the
possibility that during
some
steam line break events
an automatic actuation
could cause
the
pump to trip.
The licensee's
evaluation
was documented
in
CROR 9-5-0200.
Following an excess
steam
demand
event,
level in the faulted
could drop to the auxiliary feedwater actuation
signal
(AFAS) level for the
generator.
For
a moderate
break,
the
AFAS in the faulted generator
would
initiate
a start of the
AFW turbine driven
pump by opening
a steam
supply from
the faulted
At some point, operators
would have to transfer
the
steam supply from the faulted generator
to the intact steam generator
to
provide continued
AFW turbine operations.
The licensee
determined that it was
,
I
likely that if the transfer
was done without resetting
the
AFW turbine
governor logic, the
AFW turbine would trip on overspeed.
Prior to the transfer,
the turbine governor valve would be open wide to allow
the relatively low pressure
steam of the faulted generator
to maintain turbine
operation.
If the nonfaulted
steam
supply was
opened without resetting
the
governor valve to maintain
a lower speed,
the governor valve would not have
time to compensate
before the turbine reached
the overspeed
setpoint.
The
licensee
used
the operator training simulator to verify the possibility of
this event.
The circumstances
would not occur
on
a larger
ESD, since
a differential
pressure
lockout of an
AFAS would actuate
before the
AFAS signal.
On
a
smaller
ESD,
steam line pressure
would not degrade
to the point
a transfer
would cause
a turbine overspeed
event.
The steam
supply transfer
can
be accomplished
successfully if the faulted
steam supply valve is closed before the nonfaulted
steam supply is opened.
This sequence
causes
the governor logic to reset
and
demand
a lower speed.
The licensee
took action to cover this change
in operator training,
procedures,
and
EOP implementation.
The inspector
observed
the implementation
of this training during
EOP training
and found it to be appropriate.
The licensee identified that there
was the possibility that
a design
basis
event could cause
the failure of the
AFW turbine driven pump.
The design
basis requires that
no operator action
can
be
assumed
to take place for the
first 30 minutes.
The
ESD would have to be of a magnitude
such that the
on the faulted generator
occurred
before the differential pressure
lockout,
and
an
AFAS on the intact generator
occurred within 30 minutes.
Although
considered
to be highly unlikely, licensee
engineers
were able to cause this
to occur
on the plant simulator for a steam line break of approximately
22.5 percent of full power.
The licensee initiated
a more detailed
study of the event to determine
the
probability of the events
The inspector
noted that these
studies
were
scheduled
to be completed at the end of July 1995
and found this to be
appropriate.
The inspector will follow the results of the analysis
in
a
future inspection.
The inspector discussed
this issue with licensee
management
and noted that they should
keep in mind the potential
generic
aspects
of this event.
6.4
Tar et Rock Valves with Weak
S rin s
During
a routine review of an industry events bulletin, the licensee
found
that Target
Rock Corporation,
a vendor of solenoid operated
valves,
had
identified that
some valve springs
had
been provided to Entergy Operations for
the River Bend site which did not meet Target Rock's spring force
specifications.
The licensee
contacted
Target
Rock and determined that the
valve springs
from the
same lot had
been delivered to Palo Verde
as
replacement
parts.
The valve springs,
which assist
solenoid valve closure,
were provided
by
a sub-supplier for I and 2-inch valves.
i
i
-25-
Target
Rock had performed testing which identified that the lower spring
forces did not affect the operation of the solenoid valves at River Bend.
However, following discussions
with Arizona Public Service,
Target
Rock
initiated site-specific testing to determine
whether the lower spring forces
would have
an impact at Palo Verde.
At the
end of the inspection period,
the
study
had not been completed;
however,
the licensee
had
a high degree of
confidence that the lower spring force would be determined
to be adequate
for
the Palo Verde applications.
In the interim, the licensee
identified ten safety-related
installed valves
which could potentially have the suspect
springs
and performed
an operability
determination,
which concluded that the installed valves
had either
been
satisfactorily tested
at design basis
pressures,
or did not have
a design
function to close.
In addition,
replacement
springs
in the warehouse
were
quarantined.
The inspector
reviewed the operability determination
and found
it to be appropriate.
The inspector will review the assessment
of the valve
springs
by the vendor
when it becomes
available.
7
FOLLOWUP OPERATIONS
(92901)
7. 1
Violation 530 9413-02
CLOSED
Circuit Breakers
Not Pro erl
Racked
Out
This violation occurred
when the inspector
observed
various circuit breakers
which were not racked out in accordance
with operating
procedures
and,
as
a
result,
may not have
been seismically restrained.
The licensee's
corrective
actions
included revising circuit breaker operating
and maintenance
procedures
to define appropriate
breaker positions
and to require that the control
room
be informed of final breaker
status after racking operations.
The licensee's
training department
also developed job performance
measures
for breaker
racking operations,
and this event
was reviewed with operators.
The inspector
reviewed the licensee's
root cause
evaluation for this violation, the
operating
and maintenance
procedure
changes,
and the job performance
measures.
The inspector
found the licensee's
corrective actions
to be adequate.
During
plant walkdowns,
the inspector
observed that breakers
were properly
positioned.
8
FOLLOWUP MAINTENANCE (92902)
8.1
Follow u
Item 529 9437-01
Closed
Multi le
Emer enc
Diesel
Generator
~Tri
s
This item involved several
nonsafety-related
trips of the Unit 2 Train
B
between
December
14
and
16,
1994.
The inspector
was concerned
that
inappropriate
maintenance
may have contributed to
some of the trips
and that
the
EDG was unavailable for over
20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br /> for repair.
This item was
opened
to
review the licensee's
root cause
evaluation
and corrective actions.
The licensee
performed
a root cause
investigation of this event
and determined
that the
EDG tripped twice during the start
sequence,
twice during the
cooldown cycle,
and failed to stop once.
The licensee
determined that one of
the trips was caused
by
a high resistance
contact
in
a continuously energized
Agastat relay,
two of the trips were caused
by leaking check valves,
and
one
of the trips was caused
by
a leaking temperature
control valve.
The failure
ft
to stop
was caused
by the installation of capillary tubing during
troubleshooting activities that subsequently
restricted air flow to the
shutdown valve.
8.1.1
Corrective Actions
The licensee
determined that the leaking check valves
were caused
by pieces of
teflon tape that were caught
on the valve seat.
The licensee
determined that
the debris
was introduced during the troubleshooting
eFforts.
The licensee
already
had corrective actions in place to replace
the check valves with a new
design that
had
an internal filter and
a stronger spring to minimize the
leakage
from the valve.
In addition,
the licensee
conducted
a training class
on
EDG troubleshooting
and emphasized
the importance
oF maintaining
system
cleanliness.
The licensee
also discussed
appropriate
precautions
when
installing test
equipment during troubleshooting activities during the
training class.
The licensee
determined that the leaking temperature
control valve was not
identified during installation
because
the procedure
did not require the valve
to be leak tested after the valve was calibrated.
The licensee
updated
the
calibration procedures
to require the valves to be leak tested.
The licensee
also
had corrective actions
in place to replace all continuously energized
Agastat relays during the Unit 2 outage
in Harch
1995.
The inspector concluded that the licensee
conducted
a thorough root cause
evaluation
and identified appropriate corrective actions to reduce
the
amount
of nonsafety-related
EDG trips.
8. I.2
Additional
EDG Trips
On June
7, the Unit 2 Train
B
EDG tripped during
a surveillance test run due
to
a faulty low turbocharger
lube oil pressure
relay.
This relay was replaced
during the last outage
in Harch
1995
as part of the corrective actions listed
above
and
was found to have
an internal fault which caused
the relay to open.
On June
8, the Train
B
EDG tripped during
a postmaintenance
test run after
installation of a new low turbocharger
lube oil pressure
relay.
The licensee
initially suspected
an intermittent problem with some of the continuously
energized
relays in the shutdown circuit
The technicians
checked
three of
the most probable relays
and did not identify any high resistance
contacts.
The inspector
observed
the troubleshooting efforts
and verified that the
relays
had
been
replaced during the last outage
in Harch
1995.
The inspector
also noted effective interaction
between
the technicians,
the maintenance
engineer,
and nuclear
assurance
evaluator during the troubleshooting
activities,
and that the procedure
specified appropriate
acceptance
criteria
for replacing the relays,
The licensee
determined
that the June 8,
EDG trip was caused
by
a broken
contact
on the base of the low turbocharger
lube oil pressure
relay.
The
licensee
determined that when the
new relay was installed it was inserted
and
removed
several
times into the relay base until good contact
was
made.
The
relay base
also
needed
to be filed to allow good contact
between
the relay
and
the base.
The licensee
believed that during these
repairs
the base of the
f
I'
I
!
1
l
0
-27-
relay was
damaged.
The licensee
subsequently
replaced
the relay base
and the
Train
B
EDG was satisfactorily tested.
The inspector
concluded that although the licensee
had reduced
the number of
nonsafety related
EDG trips, the problems with relay bases
highlighted the
need for continued attention to the maintenance
of the nonsafety related
control
system.
The licensee initiated another
CRDR to evaluate
the cause of
the relay problems.
The inspector will monitor the adequacy of the licensee's
corrective actions.
8.2
Unresolved
Item 528 9434-03
Closed
Poor Work Orders
on Tar et Rock
Valves
This item involved the adequacy of a work order used to disassemble,
reassemble,
and set the stroke of certain Target
Rock solenoid-operating
valves.
Specifically, the inspector questioned
the quality of the work order
in that mechanics
had to rely heavily on the vendor technical
manual
instructions for setting the stroke of the valve.
The inspector's
observations
were similar to earlier observations
documented
in
NRC Inspection
Report 50-530/94-26,
for which the licensee
had initiated
an action to revise
the work order.
The inspector
reviewed
Model Work Order 002002 for the disassembly,
rework,
and reassembly
of Target
Rock Model
76HH-008 solenoid-operating
valves.
The
inspector
found that the revised
work order included
more vendor technical
.
manual
information for setting the valve stroke than the previous work order.
However,
the inspector
noted that mechanics
would still need to refer to the
vendor technical
manual for the adjustment of disc-to-bonnet
Clearance
A, as
the work order did not define the clearance,
and earlier work order steps
defined
a different Dimension A.
The inspector
also
found that partial
disassembly
of the valve internals
was required .to obtain
a disc-to-body
Measurement
B, although the work order steps did not specify disassembly,
and
previous work order steps
completed
the assembly of the internals.
Finally,
the inspector
found that one work step did not list part reassembly
in a
logical sequence,
and that
some work order steps referred to valve part
numbers specified
in drawings while other steps
did not identify the part
numbers.
The inspector
concluded that the revised
work order was usable
but
could still be improved.
The inspector discussed
the work order
comments with a valve services
engineer,
who acknowledged
the
comments
and indicated that valve services
was
working with mechanics
to review and revise the model work order.
9
FOLLOWUP ENGINEERING/TECHNICAL SUPPORT
(92903)
9,1
Unresolved
Item 530 9503-01
CLOSED:
0 erabil it
Evaluation of
Essential
Coolin
Water
Inspection
Report 50-530/95-03 identified that the licensee
had not completed
an evaluation of the operability of the
ECW system during
a period
between
1992
and April 1994 for the impact of a seismic qualiFication deficiency.
i
-28-
The
ECW system
was initially designed
to rely on the seismically qualified
condensate
transfer
(CT) system to provide makeup
from the condensate
storage
tank.
The
ECW process
radiation monitors
and associated
instrumentation
were
not seismically qualified.
Initial design calculations
demonstrated
that the
CT system would provide sufficient makeup to the
ECW system following a
seismic
event which ruptured the instrument lines.
In 1992, for a number of reasons
discussed
in
NRC Inspection
Report 50-530/95-03,
the licensee
disabled
the
CT system
makeup to the
ECW
system.
However, until April 1994,
the licensee left the
ECW radiation
monitors in service.
Therefore,
during this period, if the nonseismically
qualified instrument tubing had failed following a seismic event,
the
ECW
surge
tanks for both trains could have drained
and the
ECW pumps could have
lost net positive suction
head.
The licensee
recognized
in April 1994 that the condition was potentially
reportable
under
10
CFR 50.73.
However,
at the time of IR 50-530/95-03,
the
licensee's
evaluation
had not been completed.
The evaluation
was dependent
on
an assessment
of the ability of the nonseismically qualified radiation monitor
instrument tubing to withstand
a seismic event.
The licensee
made
a 4-hour nonemergency
report to the
NRC in accordance
with
10
CFR 50.72
on June
22, concluding that the system
was not seismically
qualified.
However, this conclusion
was
made
based
on field walkdowns that
indicated that the installed configuration of the radiation monitor
instrumentation
did not meet installation specification.
The licensee
subsequently
performed
computer modeling of the as-found configuration of the
instrumentation,
which demonstrated
that actual
stresses
would have
been
significantly lower than
code allowable stresses.
The
10
CFR 50.72 report was
retracted
on June
29, after computer modeling
was completed.
The inspector
reviewed the bases
of the licensee's
evaluation
and found them to be
appropriate.
9.2
Unresolved
Item 528 9437-02
Closed
Main Steam Safet
Valve
Information Notice
This item involved the licensee's
response
to information notice (IN) 94-61,
"Potential Overpressurization
of Main Steam System",
issued
on August 22,
1994.
Unit
1 was operating
at
98 percent
power with two MSSVs inoperable,
as
allowed by TS 3.7.2,
when the licensee
received
The licensee
did an
initial review of the
IN as part of a
TS submittal to allow Unit
1 to return
to
100 percent
power with the two inoperable
The licensee
concluded
that the concerns
identified in the
IN did not affect the
amendment
request,
and
on December
14, the
TS amendment
was approved
and Unit
1 returned to 100
percent
power.
The inspector
reviewed the licensee's
evaluation
and
had additional
discussions
with nuclear fuels engineering
personnel.
8ased
on these
discussions,
the inspector
had the following observations:
~
The licensee
reviewed the specific concern
discussed
in the
IN and
found
that Combustion
Engineering,
Inc.
(CE)
made the
same
assumption of a
-29-
linear reduction in power with inoperable
HSSVs.
The licensee
subsequently
used
the existing
CE simulation
and modeled the specific
core conditions in Unit
1 with one
HSSV inoperable
per
SG and found the
peak secondary
pressures
were acceptable.
~
The
IN stated
that the potential for problems
was greater at lower power
levels,
since there
was
more time to add heat to the secondary
before
a
reactor trip occurred.
The licensee
reasoned
that since Unit
1 was
returning to
100 percent
power, the concerns
in the
IN were not
applicable to the
TS amendment.
The inspector
subsequently
concluded that the licensee
adequately
addressed
the concerns
in the
IN prior to the Unit
1
TS submittal for raising
power to
100 percent.
In December
1994,
the licensee
conducted
a preliminary analysis of the
concerns
in 94-60
and determined that operating with one or more
HSSVs
may cause
overpressurization
of the secondary
system.
The licensee
also determined that CE's analysis of the loss of condenser
vacuum accident,
used to allow operation
at
100 percent
power with one inoperable
MSSV, did not
explicitly analyze
the secondary
side pressure
with the most conservat'ive
parameters
of the TS.
The licensee
subsequently
performed
a detailed evaluation of the secondary
pressure
overpressurization
event using the actual
core conditions in Unit
1
at
100 percent
power with one inoperable
HSSV in both
SGs.
The licensee
determined that the actual
conditions in Unit
1 did not result in exceeding
110 percent of the design
maximum secondary
pressure.
The inspector
concluded
that the licensee
had performed
an adequate
evaluation to determine
the
potential
problem with the
CE simulation.
The inspector
noted that the licensee
conducted
additional calculations of all
the possible
combinations of inoperable
HSSVs
and the actual
and projected
core conditions of all three units
and found that the peak secondary
pressures
were acceptable.
However,
the licensee
determined that
a modification to the
TS for inoperable
HSSVs
was required to ensure that the actual
core moderator
temperature coefficient was negative.
The inspector
concluded that the
licensee's
corrective actions
were appropriate.
9.3
Deviation
528 9431-07
CLOSED
Boric Acid Pro
ram Commitments
Not
Followed
This deviation occurred
when the licensee's
boric acid prevention
program did
not incorporate
Generic Letter 88-05 commitments to list potential
leak
locations
in procedures.
The inspector
reviewed Revision
8 to
Procedure
73TI-9ZZ13, "Visual Examination for Leakage,"
and found that the
licensee
added
Appendix
B to the procedure
to provide
a boric acid walkdown
checklist with walkdown attributes
and specific locations
where leakage
could
cause
degradation
of the reactor coolant
system pressure
boundary.
Subsequently,
the licensee
issued
Procedure
70TI-9ZC01, "Boric Acid Corrosion
Prevention
Program,"
which further defined
program requirements
and the list
f
-30-
of potential
leak locations.
The inspector
concluded that the licensee's
corrective actions
were appropriate.
10
ONSITE REVIEW OF LICENSEE
EVENT REPORTS
(LERs)
(92700)
10.1
0 en
LER 528
529
530 93-011
Revision
1:
Potential
Safet -Related
E ui ment Problems
Due to De raded
Grid Volta e and
0 en
LER 528 95-
01
Revision 0:
Entr
Into TS 3.0.3
Due to
De raded Volta e
10.1.1
Licensee's
Reports
LER 93-011,
Revision
1',
was issued
February
6,
1995,
and noted that
a
previously unanalyzed
condition could occur due to low grid voltage.
The
unanalyzed
condition involved double sequencing
of safety-related
pumps during
an accident.
Following an emergency
safety features
actuation,
the licensee
noted that the potential existed to not only start
sequencing
safety-related
equipment
onto preferred offsite power,
but also to initiate load shedding
due
to the Class
1E 4. 16kV undervoltage
relays dropping out and not resetting,
and
then resequencing
the equipment
onto the emergency
diesel
generator.
The licensee
stated
in LER'93-011,
Revision
1, that if grid voltage
was kept
above 99.5 percent,
its calculations
indicated that the double
sequencing
would not occur.
The licensee
also discussed
long term corrective actions
and
stated that pending completion of these
actions the grid would be kept above
100 percent.
However,
on February
15,
1995,
the licensee
entered
due to grid voltage falling below 100 percent during planned
evolutions.
The licensee
and Energy Control Center
(ECC) personnel
restored
the voltage
by increasing
the reactive voltampere
(VAR) output of the main
generators
at the site.
The licensee
issued
LER 95-001,
Revision 0,
on
March 15,
1995, to report the February
15,
1995, occurrence.
10. 1.2
Licensee's
Actions
The licensee
determined that its corrective actions for LER 93-011,
Revision
1,
had not been effective to maintain grid voltage
above
100 percent.
The licensee
provided further instructions
and guidance to its control
room
operators
and to personnel
in the
ECC in Phoenix,
who control the Palo Verde
grid.
The licensee
also
issued
a
new procedure for operator actions
in
response
to
a degraded grid and
added
degraded grid voltage to the Unit
1
Plant Honitoring System displays.
The licensee
stated that the following long
term corrective actions
would make all three units operable
above
98 percent
grid voltage.
Removal of loads
from Unit 1, the most heavily loaded unit
Addition of an accurate grid voltmeter in Unit 1,
so licensed
operators
will have ability to routinely monitor grid voltage
Transformer
upgrades
and sequencer
changes
Automatic block of fast
bus transfer
i
f
I
4P
-31-
10.1.3
Inspector's
Actions During the Present
Inspection
The inspector
reviewed both
LERs, the licensee's
procedure for response
to
degraded grid voltage,
the licensee's
review of the potential for further
occurrences
for degraded grid voltage,
the licensee's
long term corrective
actions,
and the requirements
the licensee
provided to the
ECC.
In addition,
the inspector
toured the
ECC,
reviewed the grid information available at the
ECC and discussed
the Palo Verde site voltage requirements
with
ECC personnel.
The inspector also reviewed
use of site
VARs to restore grid voltage,
in that
during
a future event,
none of the site main generators
may be operating.
The inspector
noted that the Palo Verde site did not have accurate
on-line
capability to monitor grid voltage.
Unit
1 has
a meter,
but it was not
accurate
enough to detect
small
changes
in grid voltage..
The inspector
had
taken part in discussions
between
the licensee
and regional
and Office of
Nuclear Reactor Regulation
(NRR) staff personnel
subsequent
to the
February
15,
1995,
TS 3.0.3 entry.
NRR personnel
reported
they were reviewing
a licensee
request
to change
the
TS degraded grid voltage relay setpoint
and
range.
The inspector reviewed
Procedure
"Degraded
Grid Voltage,"
Revision 4.
This procedure
provided operator
guidance for all three units for
response
to degraded grid voltage in various plant modes.
The basic action
was to restore
one emergency
bus in each unit by blocking the fast
bus
transfer of nonsafety-related
loads to the startup transformers
which supplied
the safety-related
loads.
The inspector
reviewed the affect of blocking the
fast
bus transfer
and determined that licensee calculations
indicated this
block would allow safety-related
voltage to. remain
above the degraded
voltage
relay setpoint.
The inspector determined that grid voltage, current,
and
VAR information were
readily available in the
ECC.
The inspector discussed
the February
15,
1995,
event with
ECC personnel.
ECC personnel
indicated that operators
were
aware
that their actions
could lower grid voltage
and they were prepared
to raise
the voltage
as necessary.
Based
on discussions
with the licensee,
personnel
stated that in the future they would raise grid voltage first before
taking actions similar to those of February
15.
The inspector
reviewed
licensee letter File 95-005-419.8,
"PVNGS Expectations
Regarding
Evaluations
Potentially Affecting Grid Voltage
Range Limits," dated
February
23,
1995,
and
ECC internal instructions,
and noted that operational
expectations
were
clearly stated.
In addition,
the inspector
noted that the
ECC had in place
an
audible
alarm for when grid voltage at the site
approached
100 percent.
The inspector
noted that the licensee
had
used the site main generators
to
raise grid voltage during the February
15, event
and questioned
the licensee
as to whether
ECC personnel
could have raised this voltage external
to the
site
on February
15, or during future occurrences
when there
was
no site
generation.
The licensee
provided the inspector
a grid study titled,
525kY Voltage Regulation
Study Report."
This report concluded that the grid
could reliably be maintained
above
98 percent,
without site generation
support.
i
1
l
-32-
Based
on the discussion
above,
the inspector
concluded that the licensee
had
taken reasonable
corrective actions to identify when
a low voltage condition
existed
on the grid,
and what actions to take to ensure that Palo Verde units
remained
and complied with TS shutdown criteria.
The inspector also
noted that most of the calculations
associated
with these
LERs were
based
upon
a
new
TS setpoint
and range of operation of the degraded grid relays which
were currently under review by the
NRC staff.
These
LERs will remain open,
pending
NRC staff approval of the degraded grid
relay
TS change,
inspector review of associated
calcu'lations,
and review of
completed
or committed long term corrective actions.
1 1
IN-OFFICE REVIEW OF LERs
(90712)
The following LERs were reviewed in-office and determined
to be acceptable:
LER 528/95-05:
EOG inoperable
due to debris in cooling water heat
exchanger.
This issue
was reviewed in detail in NRC Inspection
Report 50-528/95-06;
50-529/95-06;
50-530/95-06.
LER 528/95-08:
Reactor Trip on low SG level
due to the inadvertent
closing of a feedwater isolation valve (Section
2>>1).
')f
I
(
0
ATTACHMENT 1
1
Persons
Contacted
1. 1
Arizona Public Service
Com an
- T. Cannon,
Acting for Director,
System Engineering
- B. Grabo,
Section
Leader,
Nuclear Regulatory Affairs
- J. Hesser,
Director, Design
8 Projects
Engineering
- W. Ide, Director, Operations
- A. Krainik, Department
Leader,
Nuclear Regulatory Affairs
J.
Levine, Vice-President,
Nuclear Production
R. Lucero,
Department
Leader,
Electrical Maintenance
- D. Mauldin, Director, Maintenance
J. Minnicks, Department
Leader,
Maintenance
Valve Services
- W. Montefour, Senior Representative,
Strategic
Communications
M. Muhs, Section
Leader,
System Engineering
- G. Overbeck,
Vice-President,
Nuclear Support
M. Radspinner,
Section
Leader,
Design Engineering
F. Riedel,
Department
Leader,
Operations
Unit 2
M. Salazar,
Section
Leader,
Maintenance
Valve Services
- C. Seaman,
Director, Nuclear Assurance
D. Smith,
Department
Leader,
Operations
Unit
1
W. Stewart,
Executive Vice-President,
Nuclear
- R. Stroud,
Regulatory Consultant,
Nuclear Regulatory Affairs
J. Taylor, Department
Leader,
Operations
Unit 3
P. Wiley, Department
Leader,
Operations
1.2
NRC Personnel
- K. Johnston,
Senior Resident
Inspector
- D. Garcia,
Resident
Inspector
- A. MacDougall,
Resident
Inspector
1.3
Others
- J. Draper, Site Representative,
Southern California Edison
- F. Gowers, Site Representative,
El
Paso Electric
- R. Henry,
Site Representative,
Salt River Project
- Denotes those
present
at the exit interview meeting held on June
29,
1995.
The inspector also held discussions
with and observed
the actions of other
members of the licensee's
staff during the course of the inspection.
2
EXIT MEETING
An exit meeting
was conducted
on June
29,
1995.
During this meeting,
the
inspectors
summarized
the scope
and findings of the report.
The licensee
acknowledged
the inspection findings documented
in this report.
The licensee
did not identify as proprietary
any information provided to, or reviewed by,
the inspectors.
'i
t
'
ATTACHNENT 2
LIST OF ACRONYNS
AOY
CROR
/ CT
(
- EQ
ESO
ECW
'pm
'-'ELB
.HR
J IIrc
-,y IN
.r KV
'.:LER
"LOCV
.MOV
-;,NSSV
VASSS
'-"'NPRDS
g~PRC
"='NRR.
'OR
9
public document
room
preventive maintenance
Palo Verde Nuclear Generating
Station
refueling and maintenance
services
+f'VNGS
~MNS
~RCA
-.:RCS
-:kG
aSOV
'.SS
--SSN
>~ST
.TS
m VAR
rrQ~
- ~ WO
e
radiological controlled area
solenoid operated
valve
shift supervisor
site shift manager
surveillance test
Technical Specification '
reactive voltampere
vendor
teehnr'eah~nual
work order
atmospheric
dump valve
auxiliary feedwater actuation
signal
auxiliary operator
Arizona Public Service
Combustion Engineering,
Inc.
condition report/disposition
request
control
room supervisor
condensate
transfer
energy control center
emergency diesel
generators
emergency operating
procedure
equipment qualification
excess
steam
demand
essential
cooling water
gallons per minute
high pressure
safety injection
recombiner
instrumentation
and controls
NRC Information Notice
kilovolt
licensee
event report
loss of condenser
vacuum
motor operated
valve
.
main steam support structure
Nuclear Plant Reliability Data System
Nuclear Regulatory
Commission
Office of Nuclear Reactor
Re ulation
%% ~
a
~
aa
t
1
1