ML16342D971
| ML16342D971 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/26/1998 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML16342D972 | List: |
| References | |
| 50-275-97-23, 50-323-97-23, NUDOCS 9802050357 | |
| Download: ML16342D971 (38) | |
See also: IR 05000275/1997023
Text
ENCLOSURE
U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
Docket Nos.:
50-275
50-323
License Nos.:
DPR-82
Report No.:
Licensee:
Facility:
Location:
50-275/97023
50-323/97023
Pacific Gas and Electric Company
Diablo Canyon Nuclear Power Plant, Units
1 and 2
7 1/2 miles NW of Avila Beach
Avila Beach, California
.
Dates:
Inspectors:
Approved By:
November 23, 'l997 through January 3, 1998
David L, Proulx, Senior Resident Inspector
Donald B; Allen, Resident Inspector
Brad J. Olson, Project Inspector,
Region IV
Howard J. Wong, Chief, Reactor Projects Branch E
ATTACHMENTS:
Attachment 1:
Supplemental
Information
'7802050357
980126
ADQCK 05000275
8
0
-2-
EXECUTIVE SUMMARY
Diablo Canyon Nuclear Power Plant,:Unit's
1 and 2
NRC Inspection Report 50-275/97023; 50-323/97023
This inspection included aspects of licensee operations,
maintenance,
engineering,
and
plant support.
The report covers
a 6-week period of resident inspection.
~Qerarione
Work planning for control room painting warranted improvement because
the
configuration of the control room ventilation, the location of the compressor,
and
the effects of the painting on the control room charcoal filters were not formally
preplanned
or analyzed.
Operators took prudent and conservative
action to
minimize distractions and mitigate the effects of fumes in the control room during
the painting (Section 02.1).
inadve
Maintenance
A noncited violation was identified for failure to maintain the design basis of an
auxiliary feed pump.
A ventilation flow path for the auxiliary feed pump rooms was
rtently blocked (Section 08.3).
Auxiliary Salt Water (ASW) vault check valve maintenance
did not include a post
maintenance
test to demonstrate that the valve was installed properly.
However,
the task was performed properly in accordance
with the work order. (Section
M1.2).
Surveillance tests observed were performed well (Rection M1.3).
Plant material condition was generally good and continued to improve during this
inspection period.
Minor leaks and concerns were noted such as leaking centrifugal
charging pumps, leaking electro-hydraulic control fluid on Unit 1, and degraded
Unit 2 turbine end seals (Section M2.1).
~
A noncited violation was identified with three examples of failure to implement
surveillance requirements
(Section M8).
~ncnineering
Engineering personnel provided
a timely and technically sound response
to concerns
with the design basis of the plant's response to a spurious safety injection signal
(Section E1.1).
0
-3-
The operability evaluation associated
with containment fan cooler unit motor
cracked welds was technically sound and had good engineering
basis
(Section E2.1).
Routine personnel radiation practices were performed well (Section R1.1).
Routine security practices were performed well (Section S1.1).
0
-4-
Re ort Details
Summer
of Plant Status
Unit 1 began this inspection period at 100 percent power.
Unit
1 continued to operate at
essentially 100 percent power until the end of this inspection period.
Unit 2 began this inspection period at 100 percent power.
Unit 2 continued to operate at
essentially 100 percent power until the end of this inspection period.
I. ~Qerations
Q1
Conduct of Operations
0'l.l
General Comments
71707
The inspectors visited the control room and toured the plant on a frequent basis
when on site, including periodic backshift inspections.
In general, the performance
of plant operators was professional
and reflected a focus on safety.
Operators
continued to perform well in utilizing three-way communications,
and operator
responses
to alarms were observed to be prompt and appropriate to the
circumstances.
Limiting conditions for operation were properly entered,
as required.
02
Operational Status of Facilities and Equipment
02.1
Paintin
Control Room Panels
a.
Ins ection Sco
e 71707
The inspectors evaluated the licensee's
planning and execution of painting of the
control room electrical panels to ensure that this evolution did not adversely impact
safe operation of the facility.
b.
Observations
and Findin s
On December 31, 1997, the inspectors
noted that the licensee was preparing to
paint the lower skirts of the control room main control board panels.
This evolution
was to be done by hand using sprayers.
The inspectors were concerned
that the
paint would introduce fumes that would affect the operators
and cause the control
room ventilation system charcoal filters to become inoperable.
In addition, the
inspectors were concerned that paint spray could cause control room instruments to
be inoperable and the noise of the sprayers could distract the operators from their
licensed duties.
-5-
The inspectors discussed
the licensee's
plans with the operations
manager.
The
operations
manager provided the inspectors with copies of the risk assessment
and
work order C0155269 associated
with the job.
The risk assessment
stated that
preparations for and painting of the control boards was considered
a high risk job.
For contingencies,
the risk assessment
required
a briefing of the workers, an
operations walkdown with the work crew, and the supervisor to check-in with the
shift foreman.
In addition, the painters employed
a water-based
rather than enamel
paint to minimize the effect of fumes on the control room envelope.
This action
was taken in response to a 1995 action request in which paint fumes became
intolerable to the point of several operators having to exit the control room for fresh
air. The inspectors considered the licensee's preparations
to be acceptable with the
following concerns.
The inspectors asked the operations manager how the licensee had analyzed the
effect of the painting on the operability of the control room emergency filtration
charcoal filters. The licensee stated that they would perform an after-the-fact
evaluation should the system inadvertently actuate.
The inspectors considered this
to be nonconservative
because
volatile organic compounds
found in most paints
were known to be detrimental to charcoal filtration.
The licensee noted that certain aspects of the task were not formally documented
in
the work plan.
The work plan did not address the location of the compressor for
the paint sprayers.
At the start of the job, the paint crew planned to locate the
compressor
such that control room doors would be propped open.
The shift
supervisor rejected this plan, and instead the compressor was relocated to the shift
supervisor's office with the lines to the sprayers running under the door.
The
inspectors noted that this configuration precluded propping open any doors and kept
the noise to a minimum.
In addition, the work order or risk assessment
did not
formally discuss methods to remove fumes.
Prior to the task, operators placed the
in mode 2 operation which provides 100 percent makeup of
outside air. This action minimized the effect of fumes on control room personnel.
The inspectors noted that the painting activities were executed well overall.
The
inspectors concluded that although operators took prudent and conservative
action
to minimize distractions in the control room, and mitigate the effects of fumes, the
work planning warranted improvement because
the configuration of the control
ventilation and the location of the compressors
occurred just prior to work initiation
and should have been considered
in the work planning process.
Conclusions
Work planning for control room painting warranted improvement because
the
configuration of the control room ventilation, the location of the compressor,
and
the effects of the painting on the control room charcoal filters were not formally
preplanned
or evaluated.
Operators took prudent and conservative
action to
minimize distractions and mitigate the effects of fumes in the control room during
the painting.
-6-
08
Miscellaneous Operations Issues (92700;.92901)
08.1
,
08.2
Closed
Violation 50-275 96019-02:
failure to report off clearance prior to
removing ground buggies.
This violation was cited for not following procedures
when removing ground buggies from 4 kV auxiliary feeder breakers.
As a result of
this occurrence,
and more significantly, an October 1995 event in which an
auxiliary transformer failed due to improper installation of ground buggies, the
licensee implemented new controls for the use ground buggies.
The licensee
revised procedures
for clearances
and tag-outs, electrical maintenance,
and
energization of electrical busses.
As documented
in NRC Inspection Reports
50-275/97-01
and 50-275/97-06, inspectors observed
actions to re-energize
electrical buses during a Unit
1 refueling outage.
The licensee's
actions were
performed using the revised process for the control of ground buggies,
The
inspectors observed that the activities were performed in a deliberate manner, with
self and peer-checking
evident.
The inspectors
also documented that the operators
were well aware of how inadequate
ground buggy control led to the failure of an
auxiliary transformer.
During this inspection period, the inspectors reviewed the
procedure changes
made for the control of ground buggies.
The inspectors
had no
additional comments regarding the licensee's corrective actions.
Closed
Violation 50-323 96-009-01'and
Licensee Event Re ort
LER 50-275 95-
006-00:
loads moved over the spent fuel pool'with the ventilation system not
capable of being powered automatically from an operable emergency power source.
The violation was issued after multiple instances
where the licensee did not
maintain the fuel handling building ventilation system operable when required by
Technical Specifications.
Included in these instances was an event described
in
LER 50-275/95-006-00.
The licensee determined &at the root causes of the events
were somewhat different, but all were attributed to personnel
errors.
As corrective
actions for the violation and the LER, the licensee counseled
personnel,
provided
lessons
learned,
and changed procedures to ensure that emergency power was
available to the ventilation systems.
The inspectors noted that the licensee had not
experienced
a recurrence of this problem during recent refueling outages.
The
inspectors reviewed the licensee's corrective actions and found them acceptable.
(
08.3
Closed
LER 50-275 96-009-00:
auxiliary feedwater pump inoperable due to
inadvertent blockage of a ventilation flow path.
This LER was submitted after the
licensee discovered
a steel plate blocking the ventilation path from the turbine drive
auxiliary feedwater pump room.
The licensee removed the steel plate and
determined that the condition could have caused the environment in the room to
exceed conditions assumed
in the steam line break analysis.
The licensee reviewed
other ventilation flow paths to identify hatches
or grates which could be readily
blocked and affect air flow required to meet plant or system operation.
The licensee
installed signs to warn personnel not to'block the identified hatches
or grates.
The
inspectors reviewed the licensee's corrective actions and verified the installation of
signs.
The inspectors found the licensee's corrective actions to be acceptable.
-7-
Failure to maintain the design basis of the auxiliary feed pump is a violation of
10 CFR Part 50 Appendix B, Criterion III. However, this licensee-identified
and
corrected violation is being treated as a noncited violation, consistent with
Section VII.B.1 of the NRC Enforcement Policy (50-275/97023-01).
II. Maintenance
M1
Conduct of Maintenance
M1.1
Preventative Maintenance
on Solenoid Tri
Box Unit 2
a.
Ins ection Sco
e 62707
The inspectors observed
portions of work orders AT MM AR0443341, C0155045,
and C0152077, "Remove Turbine Trip Solenoid Box" and
"Inspect and Lubricate
Trip and Throttle Valve for Auxiliary Feed Water Pump 2-1."
b.
Observations
and Findin s
Maintenance
personnel were knowledgeable
of the equipment, procedures,
and
tasks to be performed.
The work documents
and applicable procedures
were at the
work site, and were used and signed as the work progressed.
The system engineer
was present and assisted
in the removal of the turbine trip solenoid box, which had
been abandoned
in place.
Clearance tags were hung to protect the equipment and
personnel.
C.
Conclusions
'0
The maintenance
activities were performed in accordance
with the procedural
requirements.
The personnel performing the activity were knowledgeable
of the
equipment, procedures,
tools and methods used.
The results of the maintenance
appeared to be effective in ensuring the components
willfunction as designed.
M1.2
ASW Vault Check Valve Preventive Maintenance
Unit 1
a.
Ins ection Sco
e 62707
The inspectors observed performance of work order RO177189, "ASW Vault Check
Valve SW-2-9881nspection
and Preventative Maintenance."
b.
Observations
and Findin s
NRC Inspection Report 50-275;323/97014
discussed
issues associated
with
improper maintenance
of the ASW vault check valves.
The inspectors noted in that
report that the preventative maintenance
task of cleaning and inspecting these
valves revealed the valves to be frequently stuck open.
Because these valves were
0
-8-
part of the design basis to mitigate flooding in the intake structure, the valves were
considered
important to safety.
Part of the corrective actions for this previous
concern included more frequent valve inspections
and improvements to the work
procedure.
On December 31, 1997, the inspectors
noted that the work order required a flush
of the ASW vault drain piping while the valve was removed from the system for
cleaning and inspecting.
The inspectors noted that this was an improvement
because
the flushes had previously been performed following reinstallation of the
Performing the flushes following reinstallation may have resulted in
debris being lodged in the valve internals and rendering the check valves inoperable.
During the valve inspection, the inspectors noted only sedimentation
in the valve
internals, which was documented
in the work package by the system engineer.
This minor sedimentation
did not appear to render the valve inoperable.
Following
valve inspection and cleaning, the mechanics
installed the valve and tightened the
flange nuts properly.
After completion of the work, the inspectors noted that the work package
did not
contain a post maintenance test.
The inspectors discussed
this concern with the
system engineer and the supervisor.
The licensee considered that no additional
information could be gained by a post maintenance test because
of the redundant
verification of proper valve installation.
In addition, the licensee stated that if the
check valves were installed backwards, operators would have ample time to
respond to any potential flooding that could affect the ASW pumps.
The inspectors
noted that draining water through the ASW vault drain lines as a post maintenance
test would demonstrate
that the valves were installed properly to provide additional
assurance
that the valves were operable.
I icensee management
agreed with the
inspectors'oncerns
and indicated that the procedure would be changed to include
a post maintenance
test,
c.
Conclusions
Auxiliary Salt Water (ASW) vault check valve maintenance
did not include a post
maintenance
test to demonstrate
that the valve was installed properly.
However,
the task was performed properly in accordance
with the work order.
M1.3
Surveillance Observations
a.
Ins ection Sco
e 61726
(
Selected surveillance tests required to be performed by the Technical Specifications
were reviewed on a sampling basis to verify that:
(1) the surveillance tests were
correctly included on the facility schedule;
(2) a technically adequate
procedure
existed for the performance of the surveillance tests; (3) the surveillance tests had
0
-9-
been performed at a frequency specified in the Technical Specifications;
and (4) test
results satisfied acceptance
criteria or were properly dispositioned,
The inspectors
observed
all or portions of the following surveillances:
~
STP M-9I
Diesel Generator Testing Frequency Determination, Revision 12
~
STP M-9A
Data Sheet - Routine Surveillance Test of Unit 1 Diesel
Generators,
dated 10/1/97
STP'V-3R5
Exercising Steam Supply to Auxiliary Feedwater
Pump Turbine
Stop Valve, FCV-95, Revision 10
STP M-16N1 Slave Relay Test for Operation of Interposing Relays for FCV-
95 (K632AX and K632BX), Revision
1
b.
Observations
and Findin s
Prior to the performance of Procedure
STP M-9A, operations performed a briefing in
the control room,
The briefing was thorough, covering the purpose of the test,
expected results, interface and communications with personnel at the diesel
generator,
precautions
and limitations, as well as the significant procedural steps.
The operators performed well in coordinating their timing of the diesel start
parameters to determine minimum operating parameters
of speed, frequency, and
voltage.
The steam supply to the auxiliary feedwater pump turbine Valve FCV-95 was
exercised
as directed by the surveillance Procedure
STP V-3R5. The operator
performing the test was knowledgeable
of the equipment operation and procedural
requirements.
The operators properly documented
the test results, which
demonstrated
that the valve stroke time met the test requirement.
c.
Conclusions
The inspectors found that the surveillances
observed were being scheduled
and
performed at the required frequency.
The procedures
governing the surveillance
tests were technically adequate
and personnel performing the surveillance
demonstrated
an adequate
level of knowledge.
The inspectors noted that test
results appeared
to have been appropriately dispositioned.
0
-10-
M2
Maintenance and Material Condition of Facilities and Equipment
M2.1
Plant Material Condition
a.
lns ection Sco
e 62707
During this inspection period, the inspectors conducted routine plant tours to
evaluate plant material condition.
b.
Observations
and Findin s
Centrifugal Charging Pumps;
The inspectors noted that each of the
centrifugal charging pumps on both units had noticeable oil leaks.
These oil
leaks were documented
and tracked by the licensee for correction.
None of
these leaks posed operability concerns.
Electro-hydraulic Control System:
The inspectors noted minor fluid leakage
near the front standard of the Unit 1 main turbine.
The licensee had
previously identified and documented
these leaks, and was periodically
adding electro-hydraulic control fluid to keep up with the leak.
These leaks
were scheduled to be repaired during outage
1R9.
Turbine End Seals:
The Unit 2 turbine end seal was degraded
and the
licensee was frequently monitoring its condition.
This item was scheduled to
be worked during outage 2R8.
Further degradation of this system could lead
to an unscheduled
shutdown of Unit 2.
'0
Although the inspectors observed
some material condition issues,
as described
above, the inspectors noted that licensee management
continued to properly focus
on improving the overall material condition of the facility and on reducing the
maintenance
backlog.
C.
Conclusions
Plant material condition was generally good and continued to improve during this
inspection period.
Minor leaks and concerns were noted such as leaking centrifugal
charging pumps, electro-hydraulic control fluid, and degraded
Unit 2 turbine end
seals, which were entered
and tracked in the licensee's work management
system.
M8
Miscellaneous Maintenance issues f92700, 92902)
lII
M8.'l
Closed
LER 50-275 96-002-00:
Technical Specification 3.6.1.1 not met due to
personnel
error.
This LER was based on the failure to complete
a routine monthly
check of containment isolation valves due in part to the failure to adequately
communicate
the incomplete status of parts of a surveillance test.
The licensee
0
-1 1-
attributed the cause of the missed surveillance to personnel
error in that an operator
failed to verify proper completion of a procedure.
The licensee counseled
the
individuals involved in this issue and issued an incident summary to all operating
crews.
The inspectors reviewed the licensee's corrective actions and found them
acceptable.
The inspectors considered this item to be an isolated occurrence
and
not programmatic in nature.
This licensee-identified
and corrected violation is being
treated as a noncited violation, consistent with Section VII.B.1 of the NRC
Enforcement Policy (NCV 50-275/970230-02,
Example 1),
M8.2
Closed
LER 50-275 96-004-00:
Technical Specification 3.3.3.5 not met due to
personnel
error.
This LER was based on the failure to complete
a routine
verification of the capability of each control circuit and transfer switch for the hot
shutdown panel.
The licensee attributed the cause of the missed surveillance to
personnel error in that a shift technical advisor thought the surveillance had been
completed and incorrectly marked procedure steps as not applicable.
The licensee
counseled the individuals involved in this issue and generated
recurring task work
orders to ensure verification of future surveillances.
The inspectors reviewed the
licensee's corrective actions and found them acceptable.
The inspectors considered
this item to be an isolated occurrence
and not programmatic in nature.
This
licensee-identified
and corrected violation is being treated as a noncited violation,
consistent with Section VII.B.1 of the NRC Enforcement Policy (NCV 50-
275/97023-02,
Example 2).
M8.3
Closed
LER 50-275 85-043-00:
Technical Specification 3.3.2 was not met due to
an inadequate
procedure.
This LER was submitted after the licensee determined
that containment purge valves had been opened numerous times without a current
valid slave relay test.
The licensee made their determination after reviewing a
surveillance test procedure
and finding that engineering
personnel
had failed to
include the requirement for the slave relay test.
The licensee also determined that,
although the slave relay test had not been performed, the valves were operable
and
would have closed to provide containment isolation, if required.
As corrective
action, the licensee revised surveillance procedures
to test the containment isolation
function prior to entering refueling outages
and to perform timing tests of isolation
valves on a quarterly basis.
The inspectors reviewed the licensee's corrective
actions and found them to be acceptable.
The inspectors considered this item to be
an isolated occurrence
and not programmatic
in nature.
This licensee-identified
and
corrected violation is being treated'as
a noncited violation, consistent with Section
VII.B.1 of the NRC Enforcement Policy (NCV 50-275/97023-02,
Example 3).
-1 2-
III. ~En ineerin
E1
Conduct of Engineering
E1.1
Inadvertent Safet
In ection Desi n Basis
an
Ins ection Sco
e
37551
The inspectors evaluated the licensee's
actions with respect to action request
0449600 which addressed
the design basis of the plant's response to an
inadvertent safety injection.
b.
Observations
and Findin s
Chapter 15.2.15 of the Updated Final Safety Analysis Report described the plant's
response
to an inadvertent safety injection event.
The sequence
of events assumed
that the positive displacement
pump (one per unit) was initially in operation.
Upon
initiation of the safety injection signal, both centrifugal charging pumps would
initiate and immediately inject into the core.
Operators would take approximately
16 minutes to diagnose the event and take action to secure the operating charging
pumps and restore normal letdown.
The pressurizer safety valves would lift and
temporarily pass water, but would seat properly without damage
in the assumed
Chapter 15 safety analysis.
However, the vendor identified that a scaling factor used in the design basis
calculations was nonconservative.
Because of this, the Diablo Canyon Power Plant
safety analysis was reviewed, and the licensee noted that damage to the pressurizer
safety valves was not prevented
by the existing analysis.
Because of the change
in
analysis parameters,
the pressurizer safety valves would lift and pass water more
than three times, but the valves were only qualified for three water lifts.
The licensee initiated an operability evaluation that contained several interim
corrective actions.
The licensee altered their normal method of operation to operate
a centrifugal charging pump for normal charging instead of the positive
displacement
pump.
This action reduced the charging assumed
in the Chapter 15
spurious safety injection analysis.
The licensee placed an operating restriction to
allow'a maximum pressurizer level of 56 percent.
In addition, the licensee revised
the inputs to the computer code for the spurious safety injection such that each
charging pump was secured sequentially,
so that the assumed flow at various times
during the event would be less.
With the positive displacement
pump secured,
the
restrictive pressurizer
level, and the revised assumptions
in the sequence
of events,
the vendor reanalyzed the spurious safety injection event.
This new analysis
revealed that the pressurizer safety valves would not pass water several times prior
to operator action to mitigate the event, and were therefore operable.
-13-
The inspectors reviewed the licensee's operability evaluation and found it to be
technically sound.
The inspectors noted that on October 24, 1997, the licensee
experienced
a spurious safety injection event.
Timely operator action mitigated this
event and prevented
pressurizer overfill as discussed
in NRC Inspection Report
50-275; 323/97019.
Therefore, the inspectors concluded that the licensee's
reanalysis and operability evaluation to be conservative.
C.
Conclusions
Engineering personnel provided a timely and technically sound response to concerns
with the design basis of the plant's response to a spurious safety injection signal.
E1.2
Technical S ecifications Inter retations
a.
Ins ection Sco
e
37551
The inspectors reviewed the licensee's Technical Specifications interpretations to
evaluate if they were consistent with.NRC requirements.
b.
Observations
and Findin s
NRC Information Notice 97-80, "Licensee Technical Specification Interpretations,"
discussed
several issues in which licensees
had Technical Specifications
interpretations that conflicted with the specific wording of the Technical
Specifications.
In December 1996, Diablo Canyon personnel
performed a review of
their Technical Specification interpretations
and identified several concerns with
these interpretations,
After identifying these concerns,
the licensee has continued
to implement these interpretations while preparingdicense
amendments
for them.
Specifically, the inspectors
had concerns with Technical Specifications
interpretations
88-01 (applicability of 25% grace period for conditional
surveillances),
89-07 (compliance with off-site power specifications), 94-08
(allowance of centrifugal charging pump usage during low temperature/over
pressure
conditions), 96-05 (actions to be taken when both undervoltage
relays are
and 94-07 (use of positive displacement
pump during low
temperature/overpressure
conditions).
These items are pending further NRC review to determine the validity of the
licensee's
position.
This is an unresolved item (URI 50-275;323/97023-01).
-14-
E2
Engineering Support of Facilities and Equipment
E2.1
O erabilit
Evaluation of Containment
Fan Cooler Units
CFCU with Stator to Motor
Frame Weld Cracks
Ins ection Sco
e 37551
Operability Evaluation 97-07, Revision 1, was reviewed to determine the technical
adequacy of the evaluation and the operability of the CFCU motors with cracks in
the stator compression
bars to motor frame
welds.'bservations
and Findin s
The licensee discovered cracks in two stator compression
bar to frame welds during
an inspection of a spare CFCU motor removed from Unit 1 during 1R8. Two other
spare CFCU motors, offsite for repair, had similar cracked welds.
Engineering
operability evaluation Operability Evaluation 97-07 documented
the conclusion that
the ten installed CFCUs were operable.
The CFCU motors are two speed motors, with 300 and 100 horsepower ratings for
high and low speed, respectively.
The CFCUs were normally operated
in high
speed, but switch automatically to slow speed
on a safety injection signal.
The
motor stator consisted,
in part, of hundreds of thin segmented
circular laminations.
These laminations were held together by 3/4 inch thick circular end rings.
During
construction,
a compressive force was applied to the end rings to hold the
laminations in place.
This compression force was maintained by six 25-inch long
compression
bars (cross sectional dimensions
2 inches by 1/2 inch) spaced at 60
degrees
apart on the outside circumference of the stator.
The compression
bars
were welded at each end to the end rings.
The compression
bars extended
1-3/8
inches past the end of the stator and were welded to the end frames by fillet welds.
The dimensions of these fillet welds depended
on the amount of filler weld
necessary to properly center the stator to the end frame to ensure concentricity of
the rotor to the stator.
The compression
bar at the base of the stator was also
welded to a frame bar with two additional 1-inch welds.
Diablo Canyon Units
1 and 2 have a total of thirteen CFCU motors, five in each unit
and three spares.
One spare was in the cold machine shop when the weld cracks
were originally identified.
Prior to 1R8, the other two spare CFCU motors were sent
to a vendor for wiring modifications and overhaul.
During the overhaul, several
weld cracks were identified and repaired by the vendor.
The motors were returned
and installed, but neither motor performed acceptably during testing.
The motors
made signi;icant noise and did not reach rated speed during loaded testing.
The
motors were returned to the vendor for investigation and repair.
The licensee
believed that the weld repairs changed
the orientation of the rotor to stator,
resulting in an unbalanced
magnetic pull that prevented the motors from properly
operating under load.
-15-
The visual examination and evaluation of the cracks in the CFCU motor in the
machine shop determined the cracks to be caused
by service related fatigue.
Based
on this conclusion, the cracks would form and propagate
as a result of cyclic loads
and vibration.
The greatest cyclic loads occur during starts in slow speed.
The
motors were routinely started in slow speed before heing shifted to high speed for
normal. operations.
Engineering assessment
of the loads due to vibration during
operation determined that the loads were low when compared to loads imposed
when starting the machines.
Engineering concluded that it was improbable that
normal operating loads would propagate the weld cracks.
Therefore, crack
propagation
appeared to have occurred during repetitive motor starts.
Cracks in similar welds were identified in the 1980s at another facility. The other
licensee identified the cracks when they investigated repeated thermal overload trips
of their fan cooler motors when started in slow speed.
This other licensee
determined that a significant contributor to the failures was an unbalanced
magnetic
pull which resulted from a lack of concentricity between the rotor and the stator.
The corrective actions included frame weld repair and minor motor modifications.
The other licensee's motor problems were limited.to their ten 1969 vintage motors.
Diablo Canyon personnel performed borescope
inspections of the inservice CFCU
motors which had been manufactured
in 1969 or 1970.
The vendor provided
criteria for determining whether a motor was operable.
Without a specific analysis
of a given configuration, if each compression
bar had at least one compression
bar
to frame weld intact, it would perform its function.
Using this criterion, the utility
evaluated the two 1969 inservice motors and determined
CFCU 1-5 met the vendor
criteria and CFCU 2-3 did not.
Three 1970 vintage CFCU motors were also
inspected
and met the vendor criteria. The remaining five inservice CFCU motors
were manufactured
later.
The vendor believed the two 1978 and 1979 vintage
motors had better welds.
The three late 1980s and early 1990s vintage motors had
a different frame design and less run time.
Based on this information and no history
of failures due to cracked welds in these later models, the licensee determined these
CFCU motors to be operable.
The utility performed
a specific analysis of the CFCU 2-3 motor and concluded it
was operable
based on 1) sufficient weld cross sectional area, with conservative
margins, to meet the load requirements of a slow speed motor start concurrent with
~
a seismic event; 2) the number of starts expected
before 2RS was small and crack
growth was not expected to be significant prior to 2RS; and 3) a motor inspection
was scheduled to be performed at approximately the mid-point between the last
inspection and the start of 2RS.
Additional inspections of CFCU motors of various
vintages were tentatively planned prior to 2RS.
Conclusions
The operability evaluation considered the degraded
condition, the design and
construction of the motors, the probable cause of the cracked welds, the potential
0
-16-
failure modes, the specific safety function of the CFCUs, the inherent redundancy of
needing
o'nly two of five coolers to meet the design basis, and the history of
failures, including-those identified at another facility. The operability evaluation
provided adequate justification to support the operability determination.
Miscellaneous Engineering Issues (92903)
E8.'I
Closed
IFI 50-275'323 92016-04:
recirculation phase design basis.
This item
was opened
in 1992 when an inspector believed that the licensee may have had an
insufficient understanding
of design basis requirements for the recirculation phase of
emergency core cooling system operation,
This item involved five individual items,
three of which were subsequently
closed.
Due to an administrative error, this
followup item was closed before actions for the two remaining items were
reviewed.
The inspector reviewed licensee documents
and confirmed that the
licensee evaluated
and completed actions for the two remaining items.
Since 1992,
the inspectors note that the licensee has updated their design criteria memorandum
for the operation of the emergency
core cooling system.
The inspectors also note
that emergency core cooling system operation was reviewed and documented
in
NRC Inspection Reports 50-275;323/96023
and 50-275;323/97003.
Accordingly,
no additional action is required for this followup item.
R1
Radiological Protection and Chemistry Controls
R1.1
General Comments
During this inspection period, the inspectors observed radiation protection controls.
The inspectors noted that licensee personnel followed basic radiation practices such
as proper wearing of dosimetry and protective clothing.
doors were locked as required, and radiation protection postings were properly
maintained.
S1
Conduct of Security and Safeguards Activities
S1.1
General Comments
71750
During routine tours, the inspectors noted that the security officers were alert at
their posts, security boundaries
were being maintained properly, and screening
processes
at the Primary Access Point were performed well. During backshift
inspections,
the inspectors noted that the protected area was properly illuminated,
especially in areas where temporary equipment was brought in.
0
-1 7-
V. Mana ement Meetin s
X1
Exit Meeting Summary
The inspectors presented
the inspection results to members of licensee management
at the
conclusion of the inspection on January
16, 1998.
The licensee acknowledged
the
findings presented.
The inspectors
asked the licensee whether any materials examined during the inspection
should be considered
proprietary.
No proprietary information was identified.
ATTACHIVlENT
SUPPLEMENTAL INFORMATION
PARTIAL LIST OF PERSONS CONTACTED
Licensee
J. L. Becker, Assistant Manager, Maintenance
M, A. Crockett, Manager, Nuclear Quality Services,
R. D. Gray, Director, Radiation Protection
T. L. Grebel, Director, Regulatory Services
D. T. Miklush, Manager, Engineering Services
J. P. Molden, Manager, Operations Services
D. R. Oatley, Manager, Maintenance
Services
R. P. Powers, Vice President and Plant Manager
L, L. WomnaC, Vice President,
Nuclear Technical Services
INSPECTION PROCEDURES
(IP) USED
IP 61726
IP 71707
IP 92700
IP 92902
Onsite Engineering
Surveillance Observations
Maintenance
Observation
Plant Operations
Plant Support Activities
Onsite Followup of Written Reports of Nonroutine Events at Power Reactor
Facilities
Followup - Operations
Followup - Maintenance
Followup - Engineering
0
0
0
-2-
ITEMS OPENED AND CLOSED
~O'ened
50-275;323/
97023-01
Questionable
Technical Specification 'Interpretations
(Section E1,.2)
Closed
50-275/
95-006-00
LER
Loads moved over spent fuel pool with inoperable ventilation systems
(Section 08.2)
50-275/
96-009-00
LER
Auxiliary feedwater pumps inoperable due to inadvertent blockage of
a ventilation flow path (Section 08.3)
50-275/
96-002-00
LER
50-275/
96-004-00
LER
50-275/
85-043-00
LER
50-323/
96009-01
50-275/
9601 9-02
50-275;323/
9201 6-04
IFI
Technical Specification 3.6.1.1 not met due to personnel
error
(Section M8.1)
Technical Specification 3.3.3.5 not met due to personnel error
(Section M8.2)
Technical Specification 3.3.2 was not met due to an inadequate
procedure
(Section M8.3)
O.
Loads moved over spent fuel pool with inoperable ventilation systems
(Section 08.2)
Failure to report off clearance
prior to removing ground buggies
(Section 08.1)
Recirculation phase design basis (Section E8.1)
0 ened and Closed
50-275/
97023-01
50-275/
97023-02
Inoperable auxiliary feed pumps due to blocked ventilation flow path
(Section 08.3)
Three examples of missed surveillance tests (Section M8)