ML17229A527
| ML17229A527 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 11/06/1997 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML17229A526 | List: |
| References | |
| 50-335-97-15, 50-389-97-15, NUDOCS 9711190294 | |
| Download: ML17229A527 (14) | |
See also: IR 05000335/1997015
Text
U.S.
NUCLEAR REGULATORY COMMISSION
REGION II
Docket Nos: 50-335,
50-389
License
Nos:
Report
Nos: 50-335/97-15,
50-389/97-15
Licensee:
Florida Power
8 Light Co.
Facility:
St. Lucie Nuclear Plant.
Units
1
8 2
Location:
6351 South
Ocean Drive
Jensen
Beach,
FL
34957
Dates:
October
8 - October
30.
1997
Inspector:
J.
Munday, Acting Senior Resident
Inspector
Approved by:
K. Landis, Chief, Reactor Projects
Branch
3
Division of Reactor
Projects
Enclosure
97iii90294 97ii06
ADQCK 05000335
8
EXECUTIVE SUMMARY
St. Lucie Nuclear Plant.
Units
1
8 2
NRC Inspection
Report 50-335/97-15,
50-389/97-15
This special
inspection resulted
from the identification of deficiencies with
the St. Lucie Unit 2 containment cooling system.
During the performance of a
technical specification surveillance
on October 8.
1997, the licensee
discovered that containment cooler
fan 2-HVS-1D, was running in the reverse
direction in slow speed.
The licensee's
investigation concluded that the fan
motor was replaced
on May 9,
1997,
and post maintenance testing failed to
identify the reverse rotation while operating in the slow speed.
Additionally, subsequent
performance of the safeguards
test.
conducted
on May
19. failed to identify the problem.
Conclusions
included the following:
~
An apparent violation of Technical Specification 3.6.2. 1 was identified
for having less than two trains of containment cooling operable,
when
required.
~
An apparent violation of 10 CFR 50 Appendix B, Criterion V, was
identified for failure to perform a proper post maintenance test of
containment cooler fan 2-HVS-1D.
~
An apparent violation of 10 CFR 50 Appendix B, Criterion XI, was
identified for failure to adequately test the containment cooler fans
required by Technical Specification 4.6.2. 1. 1.a. 1.
~
The insepctors
observed that the work history revealed three separate
missed opportunities to identify that the containment
fan cooler motor
had been reversed:
1) the
PMT on 05/16/97,
2) the safeguards
test
on 05/19/97,
and the
PMT on 05/21/97.
The questioning attitude
on the part of the Assistant
Nuclear Plant
Supervisor,
who identified that the containment cooler fans were not
being tested in its emergency configuration,
was highly noteworthy.
The root cause analysis
and corrective actions taken by the licensee,
upon identification of the issue,
were comprehensive
and timely.
N8
M8.1
R~ttl t
11
Miscellaneous
Maintenance
Issues
Unit 2 Containment Cooler Fan Ino erabi lit
37551
62707
71707
and
~93702
Ins ection Sco
e
On October
8, the licensee
discovered that containment cooling fan,
2HVS-1D, rotated in the reverse direction when operated in slow speed.
The inspector monitored the licensee's
activities regarding the
identification and subsequent
investigation of the inoperable
containment
cooler fan.
The inspector monitored the Event Response
Team
activities, the management
meetings
surrounding this event,
and reviewed
CRs 97-1860,
97-1868.
and 97-1880.
In addition,
work documents
applicable to the event were also reviewed.
Observations
and Findin s
R~tt
The containment cooling system consists of two trains of containment
spray
pumps,
two trains of containment
fan coolers
(each train
consisting of two fans),
and two trains of shutdown cooling.
The
containment cooling fans are powered
by two speed
motors,
which allow
fast and slow speed operation.
Post-accident
containment
heat
removal
is satisfied
by one containment
spray
pump and two containment coolers
operating in slow speed.
This design allows for the failure of a single
(EDG), which supplies
power to one complete
train.
The system is normally operated with three coolers in service with the
fans in f'ast speed.
The remaining fan is in standby.
Upon initiation
of a Safety Injection Actuation Signal
(SIAS), the three operating fans
shift to slow speed
and the idle fan starts in slow speed.
The inspector
reviewed the operating procedures
associated
with this
.system,
the applicable sections
in the
UFSAR, electrical
schematics
depicting the SIAS initiation logic, and conducted
interviews with
several
licensed operators
and engineers
to verify both normal
and
emergency
system response.
Identification of Ino erable
Containment Coolin
Fan
Technical Specification Surveillance 4.6.2. 1. 1.a requi red, in part, that
each cooling train be demonstrated
OPERABLE by starting
each cooling
train fan unit from the control
room and verifying that each unit
operated for at least
15 minutes.
(The Technical Specification
does not
discern
between fast and slow speed.)'he
licensee
performed this
surveillance weekly, in accordance
with Normal Operating
Procedure,
NOP-
2-2000020,
Revision 2,
"Containment Cooling'ystem Operation."
The idle
fan would be started in fast speed
and one of the running fans would
then be secured.
Over
a period of four weeks,
each of the fans
was
operated,
in fast speed,
for a period of time in excess of 15 minutes..
An Assistant
Nuclear Plant Supervisor
(ANPS), expressed
concern that the
containment cooler fans were not being tested in their emergency
configuration,
slow speed.
CR 97-1860
was initiated to determine if
Technical Specification Surveillance 4.6.2. 1. 1.a
was being satisfied.
The licensee
subsequently
determined that the surveillance
was
inadequate
and tested the fans in slow speed,
thei r emergency
configuration.
When the "D" fan was started,
a low air flow annunciator
was received.
CR 97-1868 was written to document the events
evaluate operability,
and
develop
a troubleshooting
plan.
The licensee
subsequently
declared the
fan inoperable
and entered the action statement of the Technical
Specification,
which required that the fan be returned to service within
seven
days.
or
be in Mode 3 within six hours
and in Mode 4 within the
following six hours.
On October 7.
as part of the troubleshooting effort, the licensee
operated all four fans in the slow speed to simulate operation following
a SIAS.
As expected,
the low air flow annunciator for the
"D" fan
alarmed
when the fan was initially started.
In addition, after the fans
had operated
approximately
10 minutes,
the "A" low air flow annunciator
alarmed.
At that point, the licensee
declared the "A" fan cooler
and entered into the action statement
which required that one
of the coolers
be restored to operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />,
or
commence the aforementioned
shutdown.
On the morning of October 8, the licensee
entered
containment to
troubleshoot
and perform inspections of the "A" and the "D" fan units.
The duct f'r the
"D" fan was opened,
and the fan was observed to be
rotating backwards while operating in the slow mode.
The fan rotated
proper ly in the fast mode.
The licensee initiated
CR 97-1880 to
document the event
and the requi rement that
a one hour
NRC notification
be made in accordance with 10 CFR 50.72(b)(ii)(B), as
a condition during
operation that resulted in the nuclear
power plant being outside the
design basis of the plant.
This decision
was based
on the design basis accident occurring
simultaneously with the single fai lure of the
EDG supplying power to the
train in which both fans were operable.
Because the
"D" fan operated
backwards in the other train, the event would result in having only one
containment cooler fan operable.
Although the containment
spray
pump
would still be available,
the loss of the
"D" cooling fan would have
resulted in the plant being in- an unanalyzed condition.
On October 9, the licensee rolled two of the fan motor leads at the
Motor Control Center to correct the reverse rotation.
Post maintenance
testing verified proper rotation.
Maintenance Histor
The licensee
reviewed the work history associated
with the
"D" fan motor
to determine
how and when the error occurred.
The details of that
investigation are
as follows:
1
04/14/97
Containment cooler fans A, B,
C,
and
D removed from service.
(The unit was in a refueling outage.)
05/01/97
1&C Maintenance
removed containment cooling fan D, air flow
switch, to support
removal of 'the fan motor by Mechanical
Maintenance.
05/04/97
Mechanical
Maintenance
removed fan assembly
and motor
as
part of normal preventive maintenance.
in accordance with
Work Order
(WO) 96023113
and Haintenance
Procedure
2-
0950173,
Revision 9,
"The Overhaul
Of Containment
Fan Cooler
Motors 2HVS-1A. 1B,
1C,
1D (EQ Motors)."
05/09/97
Mechanical
Maintenance installed refurbished
fan assembly
and motor.
05/10/97
05/16/97
05/19/97
I&C Maintenance reinstalled
containment cooling fan D, air
flow switch.
Electrical Maintenance
performed
motor rotation verification
in accordance
with HP-2-0950173.
section 9.9.
Safeguards
test is performed,
which satisfied,
among other
things, Technical Specification 4.6.2. 1. 1.b.
It requi red
that,
each containment cooling train be demonstrated
OPERABLE .at least
once per
18 months,
during shutdown,
by
verifying that each containment cooling train start
automatically
on an SIAS test signal.
05/21/97
Operations
reported trouble with containment cooling fan D,
air flow switch.
was initiated which stated.
"Alarm coming in for no reason."
05/21/97
I&C Maintenance identified air flow switch mounted upside
down with the flow element facing in the reverse direction.
The switch was
removed
and oriented properly.
A post
maintenance test,
consisting of a channel
check
and
functional test.
was completed satisfactorily.
(The
functional test operated the fan in fast speed.)
05/22/97
Unit 2 enters
Operational
Mode 3.
The insepctors
observed that the above work history revealed three
separate
missed opportunities to identify that the containment
fan
cooler motor leads
had been reversed:
1) the
PMT on 05/16/97,
2) the
safeguards
test
on 05/19/97,
and the
PMT on 05/21/97.
The licensee
concluded that the motor leads
had been reversed
when the
new motor was installed in accordance
with WO 96023113.
The post-
maintenance test following replacement of the motor required the fan to
be operated
in both the slow and fast speeds
with verification of proper
fan rotation.
However, the licensee collected historical data
from the
sequence
of event's
recorder which indicated that,
although the fan was
started twice, it was started in the fast
mode both times.
The licensee
attributed this failure to poor communication
between the personnel
observing the fan during testing
and the Operator
who started the fan
for the test.
Vendor Evaluation of Si nificance
The licensee
requested
ABB Combustion Engineering
Nuclear Operations
(ABB CENO) to perform an evaluation
on the safety significance of'he
containment
fan cooler.
The assessment
focused
on the
containment
response to the Loss Of Coolant Accident
(LOCA) coincident
'ith
the loss of an Emergency Diesel Generator.
The assessment
focused in two areas;
1) containment
peak pressure
and 2)
equipment qualification temperature
envelope.
The most limiting case
with regard to containment
peak pressure
was
a double-ended
suction leg
slot break with minimum safety injection flow.
This case
produced
a
peak pressure of 36.2 psig.
This pressure
was within both the
Integrated
Leak Rate Test (ILRT) pressure of'1.8 psig and the
containment
design pressure of 44 psig.
The most limiting case with
regard to equipment qualification was
a double-ended
discharge
leg slot
break with minimum safety injection flow.
Each of these
cases
assumed
only one containment
spray
pump and two containment cooler fans were
operational.
I
The assessment
concluded that the loss of an additional
containment
cooler fan would result in a containment
peak pressure
increase of 0.5
psig for the
same scenario..
For the case
concerning
equipment
qualification, the assessment
concluded that the loss of one containment
cooler fan would cause
a slight increase in the long term temperature
profile.
However, it was stated that this increase
would not challenge
the capability of the Class
1E equipment to perform its intended safety
functions.
Root Causes
and Corrective Actions
The licensee initiated an Event Review Team
(ERT) to review the event,
identify root causes,
and develop corrective actions.
The root cause for the fan rotating backwards
was determined to be
a
breakdown in communication
between Electrical Maintenance
personnel
inside containment
and the control
room staff.
Other weaknesses
contributing to this root cause
were:
1) the maintenance
procedure did
not identify the fan motor
as having dual windings, 2) the procedure did
not requi re signatures
for verification of rotation in both speeds,
only
the slow speed
and 3) lack of three part communication.
The root cause identified for the inadequate
surveillance
was
an
apparent error in the preparation of the surveillance
procedure.
The
Technical Specification did not explicitly state that the fans were to
5
be surveilled in the slow speed.
The fact that the emergency function
of the fans was for them to operate in the slow speed,
was overlooked.
The licensee's
corrective actions are
as follows:
1)
NOP-2-02000020,
Revision 3, "Containment Cooling System
Operation,"
was approved for use
on October
13,
1997.
2)
MP-2-0950173,
"The Overhaul of Containment
Fan cooler Motors 2HVS-
'1A,
1B,
1C,
1D (EQ Motors)," will be revised to requi re signatures
for rotational testing for both speeds,
and to add
a caution to
test both motor speeds
following maintenance.
3)
ADM-78-01, "Post Maintenance Testing," will be revised to add
a
caution about testing multiple speed
motors.
4)
5)
ADM-17-11, "50.59 Screening," will be reviewed to determine if
additional guidance is needed to ensure that the reviewer
considers
the intent of the Technical Specifications
as well as
the
UFSAR requirements
when revising procedures.
Operations will review control
room practices to determine if
additional tracking of annunciators
is needed
during safeguards
tests.
6)
Maintenance will review the method for installing the air flow
switches to determine if additional
guidance or training is
needed.
7)
Engi.neering will complete the "extent of condition" review.
8)
Maintenance will conduct training on the event
and 3-way
communication.
9)
Operations will conduct training to ensure
missed survei llances
are considered
an operability concern.
10)
Corrective Actions Group will ensure that Condition Reports
associated
with missed surveillances
are considered
an operability
concern.
c.
Conclusions
The inspector
reviewed the documents identified throughout this report
and conducted
interviews with various Operations
and Maintenance
personnel.
Although the assessment
of safety significance generated
by
ABB CENO indicated that the impact on containment
due to the faulted
containment
fan cooler was minimal, the significance of'he event
was
significantly higher because of its duration
and the prior opportunities
that were available to identify the condition.
The inspectors
observed
that the work history revealed three separate
missed opportunities to
identify that the containment
fan cooler motor leads
had been reversed.
X1
In addition, the inspector thought that the lack of rigor in identifying
all annunciators
in alarm during the safeguards
test to be
a particular
weakness
in the performance of that surveillance.
However, the inspector concluded that the questioning attitude
on the
part of the ANPS,
who initially identified the issue, to be especially
noteworthy.
Additionally. the inspector concluded that the root cause
analysis
and corrective actions taken by the licensee.
upon
identification of the issue,
were comprehensive
and timely.
The inspector concluded that containment cooling fan,
2-HVS-1D, had been
unavailable for operation in the slow speed
from April 14,
1997.
when it
was
removed
from service. until October 9,
1997,
when the motor leads
were rolled and proper rotation was verified.
Technical Specification 3.6.2. 1 states
that two containment
spray trains
and two containment
cooling trains shall
be
OPERABLE, in Operation
Modes l. 2 and 3.
However,
on May 22.
1997. the licensee
entered
Mode 3 with only one
train of'ontainment cooling operable.
This was
an apparent violation
of technical specifications that existed
from May 22 unti 1 the problem
was corrected
on October 9,
and is identified as
EEI 50-389/97-15-01,
"Failure to Maintain Two Trains of Containment
Coolers
as
Required
By Technical Specifications."
In addition, the inspector
concluded that on May 16,
1997, the licensee
failed to properly implement Maintenance
Procedure
2-0950173,
Revision
9,
"The Overhaul
Of Containment
Fan Cooler Motors 2HVS-1A, 18,
1C,
1D
(EQ Motors)," in that the required post maintenance test for the 2-HVS-
1D was not perf'ormed
upon completion of WO 96023113.
This was
an
apparent violation of 10 CFR 50, Appendix 8, Criterion V, and is
identified as 50-389/97-15-02,
"Inadequate
Post Maintenance
Test
Following Replacement
of Containment, Cooler Fan Motor."
The inspector also concluded that NOP-2-2000020,
Revision 2.
"Containment Cooling System Operation," did not adequately verify
compliance with Technical Specification 4.6.2. l.l.a. 1, in that it did
not test the 2-HVS-1D, in its emergency
alignment.
This is an apparent
violation of 10 CFR 50 Appendix 8, Criterion XI, and is identified as
50-389/97-15-03,
" Inadequate
Surveillance Test of Containment
Cooler
Fans."
V. Mana ement Meetin s and Other Areas
.Exit Meeting Summary
The inspectors
presented
the inspection results to members of licensee
management
at the conclusion of the inspection
on October 29,
1997.
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.
Licensee
.7
PARTIAL LIST OF
PERSONS
CONTACTED
C. Bible, Site Engineering
Manager
W. Bladow, Site Quality Manage
D. Fadden,
Services
Manager
H. Johnson,
Operations
Manager
J.
Marchese,
Maintenance
Manager
C. Marple, Operations
Supervisor
J. Scarola,
St. Lucie Plant General
Manager
A. Stall, St. Lucie Plant Vice President
E. Weinkam, Licensing Manager
Other licensee
employees
contacted
included operations,
engineering,
and
maintenance
personnel.
INSPECTION
PROCEDURES
USED
IP 37551:
Onsite Engineering
IP 62707:
Maintenance
Observations
IP 71707:
Plant Operations
IP 93702:
Prompt Onsite Response to Events at Operating
Power Reactors
ITEMS OPENED,
CLOSED,
AND DISCUSSED
~0ened
50-335,389/97-15-01
50-335,389/97-15-02
50-335,389/97-15-03
Closed
None
Discussed
None
"Failure to Maintain Two Trains of Containment
Coolers Operable
as Required
By Technical
Specifications"
(Section
H8. 1c)
"Inadequate
Post Maintenance
Test Following
Replacement
of Containment
Cooler
Fan Motor"
(Section H8.1c)
"Inadequate Surveillance Test of Containment
Cooler Fans"
(Section H8.1c)
ADM
ANPS
ATTN
CENO
CFR
CR
ERT
HVS
NPF
pslg
TS
LIST OF ACRONYMS USED
ASEA Brown Boveri
(company)
Administrative Procedure
Assistant
Nuclear Plant Supervisor
Attention
Combustion Engineering
Nuclear
Operations
Code of Federal
Regulations
Condition Report
Demonstration
Power Reactor
(A type of operating license)
Enforcement Action
Emergency Diesel
Generator
Escalated
Enforcement
Item
Equipment Oualification
Event Review Team
Heating
and Ventilating Supply (fan, system, etc.)
Integrated
Leak Rate Test(ing)
Loss of Coolant Accident
Maintenance
Procedure
Normal Operating
Procedure
Nuclear
Production Facility (a type of operating license)
Nuclear Regulatory
(NRC Headquarters
Pub1ication)
NRC Public Document
Room
Pounds
per square
inch (gauge)
Safety Injection Actuation System
Technical Specification(s)
Updated Final Safety Analysis Report
United States
Nuclear Regulatory
Commission
Work Order