ML16342D780
| ML16342D780 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 09/08/1997 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML16342D779 | List: |
| References | |
| 50-275-97-14, 50-323-97-14, NUDOCS 9709110077 | |
| Download: ML16342D780 (36) | |
See also: IR 05000275/1997014
Text
ENCLOSURE
U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
Docket Nos.:
License Nos.:
Report No.:
Licensee:
Facility:
Location:
Dates:
Inspector:
Approved By:
50-275
50-323
DPR-82
50-275/97-1 4
50-323/97-1 4
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
August 4-22, 1997
M. D. Tschiltz, Senior Resident Inspector
H. J. Wong, Chief, Reactor Projects Branch
E
Attachment:
Supplemental
Information
gg 0~ I) 0%
9709ii0077 970908
ADOCK 05000275
6
EXECUTIVE SUMMARY
Diablo Canyon Nuclear Power Plant, Units
1 and 2
NRC Inspection Report 50-275/97-14; 50-323/97-14
~Oeretiene
~
Shift foreman failed to adequately
evaluate the consequences
of performing
maintenance
on the auxiliary saltwater (ASW) pump vault drain check valves on
ASW pump operability.
As a result, on numerous occasions
the applicable
Technical Specification (TS) Limiting Condition for Operation (LCO) was not entered
during maintenance
which rendered the check valves inoperable (Section 08.1).
Maintenance
An apparent violation of plant procedures
was identified when action requests
(ARs)
were not written or were written but failed to document the as-found condition of
the ASW pump vault drain check valve during inspections.
The inspections
revealed that the valves were not capable of performing their design basis function
(Section M1.1) ~
An apparent violation was identified due to the licensee's
failure to monitor the
performance or condition of the floor drain check valves associated
with the ASW
pump vaults or demonstrate
effective controls through preventive maintenance
to
assure fulfillment of function in accordance
with the Maintenance
Rule.
Specifically, as of July 10,-1996, the licensee was not monitoring Units
1 and 2
ASW systems
and the associated
floor drain check valves against licensee-
established
goals and had not demonstrated
that the performance
or condition of
the ASW pump vault drain check valves were effectively controlled through the
performance of appropriate preventive maintenance.
In 11 instances
inspections from August 2, 1994, to July 3, 1997, showed the check valves were
blocked in the open position (Section M1.1).
Numerous discrepancies
were found with the ASW pump vault floor drains.
Missing and corroded parts were noted during pump'ault inspections,
whic".'. were
indicative of inadequate
maintenance.
The poor condition of the floor drain covers
and the missing components
contributed to the accumulation of debris in the drain
lines (Section M1.1) ~
The licensee's
Quality Services organization
had not evaluated the adequacy of
corrective actions from previously documented
problems (Section M1.1).
~En ineerin
Following concerns regarding the operability of the check valves being raised by the
inspector, the licensee's
basis for continued operability was not well founded and
was nonconservative.
Subsequent
valve inspections
revealed that two of the three
valves that remained to be inspected were clogged with debris and inoperable.
This
condition was reported to the NRC by the licensee
as being outside of the plant's
design basi: (Section E4.1).
0
-2-
Review of maintenance
records for inspections of diesel fuel oil transfer (DFOT)
pump vault drain check valves revealed that a failed inspection, although
documented
on an AR, had not been properly classified as being a maintenance
preventable
functional failure (MPFF) (Section E4.1).
Re ort Details
Ins ection Sco
e
On August 4-22, 1997, the NRC inspector conducted
a special inspection, of the licensee's
maintenance
program for the ASW pump vault drain check valves.
The inspector's review
included:
past inspection results for the floor drain check valves; maintenance
applied to
the valves; how operations
addressed
TS LCO entry during past maintenance
activities on
the check valves; procedures
and training for the condition of a loss of the ASW system;
and the licensee's corrective actions related to the check valve problem.
These issues are
discussed
as follows.
The Operations section of this report addresses
how operators
had in the past failed to
enter the applicable TS LCO during maintenance
which rendered the ASW drain check
valves inoperable.
Additionally, this section of the report addresses
the procedures
and
operator training associated
with the backup fire water cooling system that is used to
provide cooling to the centrifugal charging pumps in the event the ASW system is
The Maintenance
section of the report provides the background of the ASW pump vault
drain check valve inspection results and the Maintenance
Rule findings.
Additionally, this
section addresses
the corrective actions taken to address the historical problems that the
licensee encountered
with the ASW pump vault drain check valves, deficiencies in the floor
drains, and an assessment
of the risks associated
with inoperable check valves.
The Engineering section of the report addresses
the initial determination of check valv'e
operability and the review of maintenance
of DFOT pump vault check valves that are
utilized to prevent potential backflooding of safety-related equipment.
ASW Pum
Vault Confi uration
Each unit has two ASW pumps which are housed
in separate
watertight vaults in the
intake structure.
Each pump vault drains via a floor drain to the intake structure sump
located in the invert area of the intake.
Each drain tine has a check valve installed':to
prevent backflow in the event of flooding of the intake structure (e.g., circulating water
pump moderate energy line break (MELB), seismic event, or tsunami).
The check valves
prevent backflooding of the vaults through the floor drain lines.
In this capacity, the
check valves perform an important safety function in the event of flooding of the intake
structure.
~
~
-2-
I. ~Qerations
08
Miscellaneous Operations Issues
08.1
ASW Pum
Vault Drain Check Valve Maintenance
Im act on ASW Pum
0 erabilit
a.
Ins ection Sco
e
92901
The inspector reviewed the licensee's
past practices for evaluating the impact of
performing ASW pump vault drain check valve inspections
and maintenance
on
ASW pump operability.
b.
Observations
and Findin s
Review of the historical information, provided by the licensee, indicated that the
operators
had not, at times, entered the action statement for the applicable TS LCO
when the ASW drain check valves were removed for maintenance.
During time
periods when maintenance
was performed on the ASW drain check valves, the
licensee failed to enter the applicable TS LCO. Typically, only one of the ASW
pump vault drain check valves had been removed for maintenance;
however, on
August 9, 1991, both Unit 1 ASW pump vault drain line check valves were
removed at the same time for a period of approximately 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
Section 1.0 (Definitions) of the Diablo Canyon TS defines a system as OPERABLE
when it is capable of performing its specified function(s) and when all necessary
attendant instrumentation,
controls, electric power, cooling or seal water,
lubrication or other auxiliary equipment'hat
are required for the system, subsystem,
train, component,
or device to perform its function(s) are also capable of performing
their related support function(s).
The Diablo Canyon FSAR Update, Revision 11A,
Section 3.4.1 specifies that "... each pump is housed
in a separate watertight
compartment"
and therefore the ASW pump vault drain check valves perform a
related support function for the ASW system which enables the ASW pumps to
remain operable during certain design basis events that result in the flooding of the
intake invert area.
Specifically, TS 3.7.4.1 requires that at least two ASW trains shall be OPERABLE
and, with only one ASW train OPERABLE, restore at least two trains 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 be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and
in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.
During that 24-hour period in
1991, operators
did not recognize that the valve maintenance
affected ASW pump
operability and, therefore, did not take the actions specified by TS 3.0.3.
In an internal memorandum
dated August 13, 1991, from the engineering project
manager to the Diablo Canyon maintenance
manager, the licensee incorrectly
evaluated the condition as being within design bases
and, therefore, the occurrence
was not reported to the NRC. The licensee recently reassessed
the determination
~
~
-3-
as a part of the review of the failed ASW check valve inspections, determined that
both pumps should have been considered
and plans to include this
information in Revision
1 to Licensee Event Report 50-275;323/97-11.
Review of the associated
recurring task work order utilized for performing
maintenance
on the check valves indicated that it had been incorrectly coded to
denote that the check valve work did not affect component operability.
This may
have contributed to the decision not to consider an ASW pump inoperable during
~
work, on the associated
The failure to enter the applicable TS LCO action statement,
when performing ASW
pump vault drain line inspections,
is an unresolved item pending review of additional
information related to equipment, which may have also been removed from service
at the same time as the maintenance
on the check valves.
This information is to be
provided by the licensee during the predecisional enforcement conference
(URI 50-275;323/9714-01).
Conclusions
When authorizing maintenance
on ASW pump vault drain check valves, the shift
foreman failed to appropriately consider the effect of the maintenance
on ASW
pump operability.
08.2
0 erations Procedures
and Trainin
for Establishin
Fire Water Coolin
to
Centrifu al Char in
Pum
s
a.
Ins ection Sco
e 92901
In an event in which the ASW system became inoperable, operators would connect
temporary lines to a fire water supply in order to provide cooling water to the CCPs.
The inspector reviewed the licensee's
procedure for establishing backup cooling to
the CCPs, which is included as Appendix C of Abnormal Operating
Procedure
OP AP-11, Revision 10, Malfunction of Component Cooling Water (CCW)
System.
The training materials covering the topic were also reviewed.
b.
Observations
and Findin s
In 1989 the licensee installed Design Change M-'41009 to provide the capability to
supply fire water to cool CCPs following a seismic event that resulted in the loss of
The operator actions required to align the firewater cooling to
the CCP, providing seal injection for the reactor coolant pumps, are considered
as
risk-significant operator recovery actions.
-4-
Material Condition of the Fire Water Coolin
S stem
During walkdowns of the Units
j and 2 fire water cooling systems, the inspector
noted that the material condition of the systems was good and no discrepancies
were identified that would have impacted the operability of the system.
Review of past problems with the system indicated that, following installation of the
system and initial acceptance
testing in 1989, there were no surveillances
performed to verify operability of the systems until 1994, even though the licensee
had identified the need to periodically test the system in 1991.
Additionally, in
1993, the licensee identified corroded fittings on the Unit
1 system that were
judged to be in a condition that would have prevented the installation of one of the
four jumper hoses.
Corrosion was also noted on a fitting in the Unit 2 system.
Following discovery, these deficiencies were corrected.
In 1995, the licensee noted
that one of the hoses utilized for connecting the Unit
1 fire water backup cooling
system was missing.
The hose was subsequently
replaced.
The inspector noted
that, although there had been several material condition problems in the past, those
conditions had been identified and corrected by the licensee.
Licensee Procedures
for Su
I in
Fire Water Coolin
to the CCPs
Review of the abnormal operating procedure for connecting fire water cooling to the
CCPs indicated that appropriate instructions had been written. However, the
inspector noted that the procedure
required that the firewater flow be throttled on
the inlet to the CCP coolers as opposed to throttling the cooler outlet.
Additionally,
the inspector noted that the outlet of the cooling water was directed to the floor
drain, which was at an elevation below'the coolers.
This difference in elevation,
combined with the throttling of the inlet valves to the coolers, appeared
to create
the potential to partially drain the cooler during operation.
This question was posed
to the licensee and their response
noted that the fire water cooling system had been
tested in the configuration in question ahd test results demonstrated
that the fire
water to the CCPs provided adequate
cooling.
Further review determined that the licensee had not performed calculations to
determine the flow rate needed to provide adequate
firewater cooling to a CCP
pump.
Operating Procedure
AP-11 establishes
12 gpm to the oil cooler for all of the
CCPs, with the exception of CCP 2-2, which receives an additional 8 gpm of
cooling flow to its seal cooler.
An evaluation had'previously been performed and
documented
on AR A0369365, in which the licensee concluded that the flow rate
established
by the procedure was adequate
to provide cooling to the CCPs following
a loss of CCW accident in which there would be normal as opposed to accident
heat loads on the CCP.
Additionally, it should be noted that the procedure utilized
for system operation allowed for adjustment of flow rates and that the CCPs have
temperature
alarms that annunciate
in the control room that would alert the
operators to the need for providing additional cooling flow.
-5-
0 erator Trainin
for Ali nin
the Backu
Fire Water Coolin
to CCPs
Review of operator training records revealed that licensed operators received
detailed recurring training on the firewater cooling system.
Initial training was
provided to operators within several months following the initial installation of the
design change
in 1989 and for nonlicensed
operators
in 1990.
The licensee also
had written job performance
measures
to test both senior reactor operators
and
reactor operators
on the applicable procedures.
were
also included in the training package that is provided to both licensed and
nonlicensed
operators.
Additional training was provided in 1997 following CCP
design changes
which resulted in modifications to the system and operating
procedure,
C.
Conclusions
Operators
had received appropriate training for establishing
fire water cooling
to the CCPs.
The material condition of the system was good and previous material
problems identified by the licensee had been corrected.
There was a procedural weakness
in that the procedure for aligning the
firewater created the potential to partially drain the CCP cooler when aligned
to the fire water system.
Although system testing had been performed utilizing fire water cooling to
the CCPs,
no calculations had t}een performed to determine the bounding
conditions for providing adequate
fire water cooling to the CCPs.
II. Maintenance
M.1
Conduct of Maintenance
M1.1
Nlaintenance of ASW Pum
Vault Drains
a
N
Ins ection Sco
e 62707
92902
The inspectors reviewed the maintenance
history of the ASW pump drain check
valves as a part of the review conducted for the closeout of IFI 50-275/9506-02
(See Section EG.1).
During the inspection, the following procedures
and documents
were reviewed:
~
Component Work Order Closure Remarks for Valves SW-1-987, SW-1-988,
SW-2-987, and SW-2-988 periodic inspections
-6-
ARs written following ASW pump vault check valve inspections (A0347014,
A0408657, A0408656, A0438707, A0438834, A0349968, A0406271,
A0438794)
Nonconformance
Report (NCR) DC1-91-MM-N067, Revision 0, ASW Pump
Vault Drain Check Valves and AR A0238503
Quality Evaluation 00009386, ASW Pump 1-2 Vault Floor Drain Clogged
Diablo Canyon Maintenance
Rule Technical Basis Document, Revision
1
NRC Information Notice (IN) 83-44, Supplement
1: Potential Damage to
Redundant
Safety Equipment as a Result of Backflow though the Equipment
and Floor Drain System
NRC Standard
Review Plan (NUREG 0800), Section 9.3.3, Equipment and
Floor Drainage System
AR A0135577, Create Routine Task Work Orders for ASW Vault Drain
Inter-Departmental Administrative Procedure
OM7-ID1, "Problem
Identification and Resolution - AR," Revision 7
b.
Observations
and Findin s
ASW Pum
Vault Drain Check Valve Maintenance
Histor
Review of the check valve maintenance
history revealed that the valves had
routinely failed the periodic inspections.
Inspection results documented that the
valves had been partially stuck open during 9 ofthe 11 most recent inspections
performed between August 2, 1994, and June 26, 1997.
The "as found" stuck
open condition of the valves was, in most cases,
due to the accumulation of sludge
and debris in the valves which rendered them inoperable and unable to perform their
design function of preventing backflooding of the ASW pump vault.
Review of the maintenance
history indicated that, based upon the failed inspections,
the licensee had changed the periodicity from every 36 months to 24 months in
November 1994, and from every 24 months to every 12 months in July 1996.
Although sludge and debris accumulation had been identified as the cause for the
check valves sticking in NCR DC1-91-MM-N067, Revision 0, there was no
indication that the drain lines had been flushed with the check valves removed.
In
addition, the corrective actions taken failed to prevent debris from accumulating in
the line.
-7-
Historical Problems With ASW Pum
Vault Drain Check Valves
The inspector noted that prior to 1991 there had been numerous problems with the
NCR DCO-91-MM-N067 and AR A0238710 documented
repeated
instances
where check valves had been found stuck open prior to 1991.
Quality
Evaluation Q0009386 had also been written on prior problems with the check
valves.
One of the identified corrective actions was to develop adequate
housekeeping
for the drain lines to ensure that debris does not collect in the valves
such that they cannot close.
The recommended
action was to perform routine
flushing of the lines.
Although the action had been indicated as being completed,
the routine tasks for the valve maintenance
had not been revised to specify flushing
of the lines.
Discussions with licensee personnel indicated that the
postmaintenance
flow verification that had been added could be considered
a flush
of the line; however, flushing the drain lines after performing the maintenance
created the potential to flush debris in the lines into the valves after they had been
cleaned.
NRC IN 83-44
Su
fement
1
Potential Dama
e to Redundant
Safet
E ui ment as
a Result of Backflow Throu
h E ui ment and Floor Drain S stem
Supplement
1 to NRC IN 83-44, issued on August 30, 1990, expanded
the
concerns
raised in the initial,lN to include the potential for flooding safety-related
compartments
as a result of backflow through equipment and floor drainage
systems.
The IN also related information to licensees
concerning the potential for
flap type check valves to stick open as a result of debris and corrosion buildup.
The licensee completed their review of'the IN on February 12, 1993, and concluded
that the ASW pump vaults were susceptible to backflooding of the drainage system;
however, the preventive maintenance
performed on the ASW pump vault drain
check valves was adequate
to ensure the valves were operable.
The inspector
questioned
whether the maintenance
history of the valves had been consider" J
'uring
the review.
The licensee indicated that, since an NCR had been issued on
past problems with the valves sticking open, the corrective actions from the NCR
were thought to encompass
the issue,
Therefore, the licensee closed the review of
IN 83-44, Supplement
1, based upon the corrective actions for the NCR written on
the recurring problems with the ASW pump vault drain check valves prior to 1992.
Review of the maintenance
history after the NCR corrective actions had been
initiated, and prior to closeout of the IN, revealed that one check valve inspection
had been performed in October 1992 where a check valve was found to be stuck
open.
This appeared to have been
a missed opportunity by the Quality organization
to identify ineffective corrective actions.
-8-
Maintenance
Rule Re uirements A
licable to ASW Pum
Vault Drain Check Valves
Review of the licensee's program for implementation of the Maintenance
Rule
confirmed that the ASW pump vault drain check valves had been included within
the scope of the rule. Specifically, the licensee had included the valves since they
were relied upon to prevent the loss of an ASW pump during a tsunami or following
a main circulating water pump discharge
line break.
If flooding of the intake were
to have occurred, the inability of a check valve to close could have resulted in the
associated
ASW pump becoming inoperable.
Since the ASW pump vault drain check valves are included in the Maintenance
Rule
program, the problems noted during inspections of the valves are required to be
evaluated to determine whether they constitute MPFFs.
Engineering reviews of the
maintenance
performed within the 36 months prior to implementation of the
Maintenance
Rute did not identify any of the failed ASW pump vault check valve
inspections
as MPFFs.
For the period from 36 months prior to implementation of the Maintenance
Rule
until June 26, 1997, there had been nine separate
instances
where the check
valves had failed inspections.
Of these failures, there had been ARs written for,four
of the inspections which documented
that the valves were found stuck open.
Of
those, the licensee had evaluated three as not being MPFFs and the fourth, which
documented
the results of a June 25, 1997, inspection, had yet to be reviewed.
For the remaining five instances,
no evaluation had been performed since the
as-found stuck open condition of the valves had not been documented
in an AR.
The licensee was evaluating the cause of the three mischaracterized
Licensee Procedural
Re uirements for Documentin
E ui ment Problems
Inter-Departmental Administrative Procedure
OM7-1D1, "Problem Identification and
Resolution - ARs," a..quality-relate'd
procedure,
requires that problems be
documented
on an AR. Attachment 7.2 to the procedure defines problem criteria,
in part, as conditions which render an item or activity unacceptable
or indeterminate
or could negatively impact the structure, system or component, if left uncorrected.
The failure to document the as-found inspection results, which indicated that the
associated
ASW pump vault check valve was inoperable, for inspections performed
on August 2 and 8, September
8, and November 16, 1994, and August 27, 1996,
as required by Inter-Departmental Administrative Procedure
OM7-ID1, is an apparent
violation of 10 CFR Part 50, Appendix 8, Criterion V, "Instructions, Procedures,
and
Drawings" (EEI 50-275;323/9714-02).
Reevaluation of Past ASW Pum
Vault Drain Check Valves Ins ections
After the historical inspection problems were brought to the attention of the
licensee by the inspector, the licensee reevaluated
the past failures of the valves to
-9-
determine whether the failures should be considered
as MPFFs.
The licensee
determined that all eight of the previous failed inspections within the 36 months
prior to the implementation of the Maintenance
Rule were MPFFs.
None of the
failed inspections
had previously been considered
as MPFFs.
Following the most
recent failed inspection of the check valves, the licensee determined that, in
addition to the eight prior MPFFs, the three check valve inspections performed on
June 26 and July 2-3, 1997, were also MPFFs.
The licensee had established
a criteria of a maximum of two MPFFs for placing the
ASW system in goal setting.
The licensee commenced
monitoring of the ASW
system as prescribed
in Section (a)(1) of 550.65 on April 17; 1997, based on two
instances
in which an ASW pump was declared inoperable due to excessive
packing
leakage and evaluated
as MPFFs.
The licensee began monitoring the ASW system
in accordance
with Section (a)(1) on July 31, 1997, based
on the clogged floor
drain check valves.
From July 10, 1996, the date of implementation of the Maintenance
Rule, the
licensee elected to not monitor the performance
or condition the ASW system
against established
goals under the requirements of Section (a)(1)..However, the
licensee had not demonstrated
that the performance
or condition of the QSW
system (specifically the floor drain check valves) had been effectively controlled
through the performance of.appropriate preventive maintenance
in accordance
with
Section (a)(2).
Eleven failures of these check valves had occurred from
August 2, 1994, to July 3, 1997.
Eight failures had occurred prior to the time that
the NRC inspector began to question the licensee about the historical performance
of the check valves.
The failure to evaluate the appropriateness
of the performance
of preventive maintenance for these chhck valves when placing and maintaining the
ASW system in Section (a)(2) is an apparent violation of 10 CFR 50.65(a)(2)
(EEI 50-275;323/9714-03).
Material Condition of ASW Pum
Floor Drains
Following the July 3, 1997, check valve inspection, licensee inspections of the
ASW pump vault rooms revealed numerous discrepancies
related to the floor drains,
which compromised the ability of the drains to keep debris out of the lines.
The
drains are constructed with a slotted cover plate and a strainer basket.
The
discrepancies
noted with the drains, are detailed below.
ASW Pump 1-1: the drain cover was missing and the drain basket was corroded
and was a source of debris to clog the drain lines.
ASW Pump 1-2: the drain basket was missing.
ASW Pump 2-1: the drain basket was corroded and needed to be replaced.
-10-
ASW Pump 2-2: the drain cover was intact but corroded and the drain basket was
missing.
Based upon the results of this inspection, the licensee developed
additional actions
to vacuum near the floor drains, remove and reinspect the check valves, replace
missing or corroded drain baskets
and covers, remove and clean the remaining drain
covers and baskets,
flush the drain lines with the check valves removed, and
install
a design change to put a screen
in the drain lines.
These actions appeared
to limit
the potential for debris entering the drain line.
Assessment
of Risk Associated With lno erable ASW Pum
Vault Drain Check
Valves
The ASW system
is a risk significant system and the loss of ASW is a risk
significant event.
In order for the failed check valves to result in a total loss of
ASW, flooding of the intake structure is required.
The sources of such floods would
be:
(1) severe wave conditions (e.g., tsunami), (2) circulating water system
ruptures in the intake invert area, or (3) flooding in an ASW pump vault which
eventually results in the backflooding.
The licensee estimated that the total increase
in the loss of ASW initiating event
frequency 6.6E-4/year as a result of the failed check valves resulted in an increase
in core damage frequency of 1.2E-5/year.
This, using the criteria of the EPRI PSA
Applications Guide, represents
a small to moderate increase in risk.
lf both ASW pumps were lost due to flooding,'he licensee contends that the plant
could be maintained in Mode 3 using auxiliary feedwater and natural circulation.
The CCPs could be cooled from the fire water system so that seal injection flow to
the reactor coolant pumps could be maintained.
During the time frame that the
plant is maintained in this configuration, there would be no cooling to other CCW
cooled components,
including ventilation systems,
so there are operational concerns
regarding the length of time that the licensee could stay in this alignment.
Conclusions
Maintenance activities performed failed to assure the reliable operation of the
ASW pump vault drain check valves.
Maintenance
personnel failed to appropriately document ASW pump vault
drain check valve inspection results in five instances
in which the valves
were found stuck open.
ASW pump vault drain check valve inspections
revealed numerous instances
in which the valves were stuck open and unable to prevent backflow into the
-11-
ASW pump vaults.
None of these were correctly evaluated by engineering
as being MPFFs, which is indicative of a weakness
in the implementation of
the Maintenance
Rule.
ASW pump vault drains had not been maintained
in accordance
with design
requirements,
since inspections
revealed corroded parts and drain cover
plates and strainer baskets that were missing.
Corrective actions for past failure of ASW pump vault drain check valves
were incomplete and ineffective.
In addition, there had been no evaluation
of the adequacy of corrective actions by the licensee's
Quality Services
organization.
III. ~En ineerin
E4 Engineering Staff Knowledge and Performance
E4.1
En ineerin
Resolution of Ino erable ASW Pum
Vault Drain Check Valves
Licensee Corrective Actions Followin
Identification of Concern for ASW Pum
Vault Drain Check Valve 0 erabilit
I
After the inspector raised the concern to licensee management
of the condition of
the floor drain check valves with the history of being clogged in the open position,
the ASW pump vault drain lines were flushed and then three of the four ASW pump
vault drain check valves were disassembled
and inspected.
The fourth valve had
been disassembled
and inspected the previous week and was found stuck open and
then cleaned, reassembled,
and returned to service.
Prior to the licensee disassembling
the valves, the inspector questioned
the basis for
considering the three valves that had not been inspected
The licensee
indicated that the flush of the line had most likely removed anything in the valves
that would cause them to stick open.
The inspector questioned
the licensee's
basis
for operability since, given the configuration of the piping, the design of the valve
and the material that had been previously found in the valves it appeared that
flushing of the valve could be ineffective.
Subsequent
inspection of the three
remaining check valves showed that two of the three valves were stuck open.
After the licensee completed the inspection of both Unit 2 valves and found one
valve stuck open, the ASW pump associated
with the Unit 1 valve that remained to
be inspected was declared inoperable.
Inspection of the remaining valve revealed
that it also was stuck open.
On July 3, 1997, the licensee made
a 1-hour
nonemergency
report to the NRC in accordance
with 550.72(b)(1)(ii)(B), after
having determined that Units
1 and 2 ASW systems
had been inoperable due to the
ASW pump vault drain check valves not being functional.
-1 2-
The licensee's
evaluation of past ASW check valve inspection results is described
in
Section M1.1 of this inspection report.
Review of Plant Floor Drains for Other Safet -Related
E ui ment
The inspector reviewed the maintenance
history for the check valves installed in the
floor drains of the DFOT pump vaults.
The check valves are included within the
mechanical structure, system, or component that are included within the scope of
the Maintenance
Rule for the emergency
diesel generator fuel transfer system.
The
DFOT pump vaults drain to the turbine building sump.
The maximum water level
before overflow of the turbine building sump is approximately at elevation 68 feet
6 inches.
The sump overflow weir flows into an 18-inch diameter drain pipe.
Therefore, backflow into the pump vault is unlikely from the turbine building.
Other
sources for backflow are other drain lines headered
with the DFOT pump vault
drains.
The Final Safety Analysis Report, Section 9.5.4.3(3), states that the vaults
are drained to the turbine building sump and are protected with backwater valves.
Maintenance
Histor
of DFOT Pum
Vault Drain Check Valves
Review of the maintenance
history showed that the DFOT pump vault backwater
check valves had historically passed
periodic inspections performed since October
1989.
However, the inspector noted that the backwater check valve for DFOT
Pump 0-2 (Valve DEG-0-1033) had failed an inspection performed on
September
15, 1994.
During the inspection, the valve was noted to have debris on
its disc that prevented the valve from stopping backflow.
Review of the associated
AR indicated that this had not been considered
as an MPFF. After questioning by
the inspector, the licensee determined that the failed inspection should have been
considered
an MPFF. At the time the valve failed the inspection, the licensee had
already planned
a design change for the floor drain to reduce the possibility of
debris entering the lines.
The inspector noted that the corrective actions planned,
and subsequently
completed by the licensee, reduced the susceptibility of the valve to becoming
clogged with the debris.
The inspector considered
the missed MPFF determination
a weakness
in the licensee's review process but that subsequent
corrective actions
were adequate
to prevent recurrence of a similar problem.
Conclusions
After questions
regarding the operability of the ASW pump vault drain check
valves arose, the licensee's
basis for the continued operability of the valves
that remained to be inspected was nonconservative
and not founded upon
good engineering judgement.
-13-
Miscellaneous
Engineering
Issues (92903)
E.8.1
Closed
Ins ection Followu
Item 50-275 9506-02:
ASW vault drain calculation
for medium energy line break (M-270) did not address the limited capacity of the
intake structure sump pumps.
The inspector reviewed the licensee's
actions following NRC identification that
Calculation M-270, Revision 3, did not adequately
address the limited capacity of
the intake structure sump pumps.
The licensee subsequently
revised
Calculation M-270 to indicate that, with a MELB inside one of the ASW pump
vaults, the invert area of the intake would eventually flood to a level at which point
the ASW pump vault drain would no longer be able to pass all of the postulated
leak
rate.
Thus, the ASW pump motor in the room with the MELB would eventually be
submerged
and short and trip. The analysis assumed
no operator actions were
taken to limit the flooding.
The inspector concluded that Revision 3 to Calculation M-270 was incorrect in that
it did not adequately
consider the limited capacity of the intake structure sump
pumps.
Revision 4 to the calculation corrected this discrepancy.
In the event of a
MELB within an ASW pump vault, the intake structure sump drain system was not
relied upon by the licensee to assure the operability of the unaffected ASW pump.
The licensee relied upon the ASW pump vault drain check valves to prevent
backflooding.
As a result, the error in the calculation did not have any impact on
safety.
The licensee also revised the affected Design Criteria Memorandum to
reflect the results of Revision 4 to the calculation.
Based upon the above, this item
is closed.
V. Mana ement IVleetin s
X1
Exit IVleeting Summary
The inspectors presented
the inspection results to members of licensee management
at the
conclusion of the inspection on August 21, 1997.
In the meeting the licensee
acknowledged
the findings presented.
The inspectors asked the licensee whether any materials examined during tice inspection
should be considered
proprietary.
No proprietary information was identified.
ATTACHMENT
SUPPLEMENTAL INFORMATION
PARTIAL LIST OF PERSONS CONTACTED
Licensee
J. Anastasio,
Systc,m Engineer,
Engineering
Services
W. E. Coley, Engineer,
Regulatory Services
W. G. Crockett, Manager, Nuclear Quaiity Services
L. L. Fusco,
Maintenance
Rule Coordinator, Maintenance
Services
T. L. Grebel, Director, Regulatory Services
S. C. Ketelsen, Senior Engineer, Regulatory Services
=
R. F. Locke, PGSE Corporate Attorney
D. L. Miklush, Manager, Engineering Services
J. E. Molden, Manager, Operations Services
R. M. Nanniga, Engineer,
Engineering Services
M. N. Norem, Director, Mechanical Maintenance
J. L. Portney, Senior Engineer,
Engineering Services
R. P. Powers, Manager, Vice President
DCPP and Plant Manager
M. L. Smith, Supervisor,
Quality Services
R. L. Thierry, Director, Balance of Plant Engineering
B. J. Olson, Diablo Canyon Project Engineer
D. L. Proulx, River Bend Resident Inspector
I
INSPECTION PROCEDURES USED
IP62707:
Maintenance
IP37551:
Engineering
IP92903:
Followup - Engineering
IP92902:
Followup - Maintenance
IP92901:
Followup - Operations
ITEMS OPENED, CLOSED, AND DISCUSSED
~Oened
50-275;323/9714-01
Failure to enter TS LCO Action Statement during ASW
pump vault drain check valve maintenance
50-275;323/971 4-02
Failure to document inoperable ASW check valves on
-2-
50-275;323/9714-03
Closed
50-275/9506-02
Apparent violation of 10 CFR 50.65 a(1)
IFI
ASW vault drain calculation for medium energy line
break did not address
the limited capacity of the intake
structure sump pumps
LIST OF ACRONYMS USED
ASW
DFOT
IFI
IN
LCO
TS
action request
auxiliary saltwater
centrifugal charging pump
component cooling water
diesel fuel oil transfer
apparent violation
inspection followup item
Information Notice
limiting condition for operation
moderate energy line break
maintenance
preventable functional failure
nonconformance
report
Public Document Room
Technical Specification
unresolved
item
e
'Y