ML17306A836
| ML17306A836 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/26/1992 |
| From: | Wong H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| Shared Package | |
| ML17306A835 | List: |
| References | |
| 50-528-92-23, 50-529-92-23, 50-530-92-23, NUDOCS 9207210133 | |
| Download: ML17306A836 (22) | |
See also: IR 05000528/1992023
Text
. S.
EAR REGULATORY COMMISSION
QEGIOM V
59=52 /92-
, 59-52 / -2,
d
-5
/92-
3
~N
.
5 -52,
5 -529.
d 5 -53
N
.
IIPF-41. IIPF-51,
d
NPF-14'5
I'ct'o~o.92-119
~Lice see
Arizona Public Service
Company
P.
O. Box 53999, Station
9012
Phoenix,
AZ 85072-3999
9
9
d
9
I
5
Igg<<d
Units 1, 2,
and
3
Ins ection
d
d
~es ector
June
15 through June
19,
1992
B. Olson, Project Inspector
ong,
ie
Reactor Projects
Section
2
Ins
ction Summar
Ins ection
on June
15 throu
h June
19
1992
Re ort Numbers
50-528 92-23
50-529 92-23
and 50-530 92-23
~ld:
Np
111
p
1.1
933
I
<<
5/g
51
1 containment isolation check valve found improperly assembled
on March 18;
1992.
This condition was documented
by Unit
1 Licensee
Event Report 92-005.
Inspection
Procedure
92700
was
used
as guidance during this inspection.
Results:
Genera
Conclusions
and
S ecific Findin s:
The inspector identified concerns with the level of detail of
instructions in a valve maintenance
work order
and in the test procedure
used to verify valve op'erability subsequent
to the maintenance
activities.
As
a result of using the work order
and the test procedure,
a containment isolation check valve was returned to service
even though
9207210133
920629
s
ADOCK 05000528
8
the valve internals
were installed backwards.
This condition existed
from August 1989 to March 1992.
Si n'ficant Safet
Matters:
The concerns
noted
above represent
a weakness
in the licensee's
control
of maintenance activities.
Summ r
of Violations:
One apparent violation was identified.
0
ersons
Contacted
ETAILS
The below listed technical
and supervisory
personnel
were
among those
contacted:
'na
ub
c Service
B. Blackmore,
T. Bradish,
- H. Friedlander,
- A. Johnson,
B. Lehman,
H. McEwan
- G. Over beck,
H. Radspinner,
- R. Roehler,
System Engineer
Manager,
Compliance
Manager,
Component
and Specialty Engineering
Supervisor,
Compliance
Component
Engineer
System Engineer
Director, Site Technical
Support
(STS)
Supervisor,
Mechanical/Chemical
Engineering
Senior Engineer
Comb stion
n ineerin
H. Crawford
J.
Isakson
uclear
Re ulator
Commission
D. Coe,
Senior Resident
Inspector
- F. Ringwald,
Resident
Inspector
J. Sloan,
Resident
Inspector
Denotes
personnel
in attendance
at the Exit meeting held with the
NRC
inspector
on June
19,
1992.
n
The inspector also talked with other licensee
personnel
during the course
of the inspection.
2.
Co tainment Isolation Check Valve Ino erable
Due to Incorrect Maintenance
and
Inade uate Retest - Unit
1
On March 18,
1992, the'licensee
discovered that the valve bonnet
asse'mbly
for a Unit
1 containment isolation check valve was installed backwards.
The discovery
was
made during valve maintenance
while Unit
1 was in a
refueling outage.
The licensee
subsequently
determined that the valve
had
been improperly assembled
on August 22,
1989.
As
a result of the
improper assembly,
the licensee
declared that the valve had
been
inoperabl,e
and issued Unit
1 Licensee
Event Report
(LER)92-005.
The
LER
indicated
tPat
'the inoperabl,e',val.ve
was
a condition prohibited
by the
plant's Technical.Specific'ations'(TS).
r
Valve Back round
escri t'o
2)
3)
Unit
1 valve SIE-V133 was found to have its bonnet
assembly
installed approximately
160 degrees
from normal alignment.
The
valve was manufactured
by Borg-Warner
and is
a three inch swing
check,
model
77700.
The bonnet
assembly
includes the attached
valve disc,
and the bonnet
assembly is secured to the valve
body with a bonnet retainer held by studs,
nuts,
and washers.
A silver plated seal
between the bonnet
and valve body provides
leakage protection.
The valve design allows the bonnet
assembly to be rotated in the valve body when the retainer
an'd
seal
are not present.
Attachment
1 depicts the valve assembly.
d
SIE-V133 is located in the high pressure
safety injection
(HPSI) system leading to reactor coolant system loop lA.
The
valve is located inside of containment,
within five feet of the
containment wall.
Upstream of the valve,'nd outside of
containment,
the two HPSI trains join to form one line.
A
motor operated
valve
(HOV) is located outside of containment
in
each of the
HPSI trains.
Downstream of SIE-V133, the low
pressure
safety injection (LPSI) system connects to the
injection piping.
Attachment
2 depicts the location of the
check valve in the safety injection system.
The valve remains
shut for normal plant operation.
Upon
initiation of HPSI, the valve would open to provide flow from
both
HPSI trai,ns.
e ulator
Basis
The two upstream
HOVs and check valve SIE-V133 are part of the
containment isolation system for containment piping penetration
number
15.
Section 6.2.4. 1.1 a) .of the Combustion
Engineering
Standard
Safety Analysis Report
(CESSAR) indicates that two
isolation valves
are provided at each containment penetration:
one inside the containment,
and
one outside the containment.
Section 6.2.4.2
and Figure 6.2.4-1A of the
CESSAR along with
Table 6.2.4-1 of the Palo Verde Updated Final Safety Analysis
Report
(UFSAR) indicate that this penetration
design satisfies
10 CFR Part 50, Appendix A, General
Design Criterion
(GDC) 55.
GDC 55 requires,
in part, that containment penetrations
have
an
automatic isolation valve located inside
and outside of
containment.
The check valve is considered
to be
an automatic
valve for the purpose of containment isolation.
SIE-V133 is listed in TS Table 3.6-1
as
a containment isolation
valve for penetration
15.
The applicable
TS Limiting Condition
II
t
t'I
1
for Operation, 3.6.3,
in'dicates that the valve is to be
operable in Modes 1, 2, 3,
and 4.
Following valve maintenance,
TS Surveillance
Requirement 4.6.3.1 indicates that the valve
shall
be demonstrated
to be operable prior to returning it to
service.
Although SIE-V133 forms part of the containment
isolation system,
TS Table 3.6-1 exempts
the valve from the
Type
C containment leak testing requirements of 10 CFR Part 50,
Appendix J.
SI -V133 Maintenance Activities
Work Order
(WO) 00356906
was prepared
in May 1989 to rework valve
SIE-V133 to fix a body-to-bonnet leak.
The valve was disassembled
on August 22,
1989, in the following procedure'sequence:
the studs,
nuts,
washers,
and bonnet
clamp were removed;
the bonnet retainer
.
was partially unscrewed,
and the bonnet
clamp was reinstalled;,a
scribe line was marked from the center line of 'one of the studs to
the valve body; the nuts were re-tightened to break the body-to-,
bonnet seal;
and the bonnet
was free to be lifted from the body.
The purpose of the scribe line was to provide alignment indication
for the bonnet
assembly
and the valve body.
Following inspection,
the valve seal
was replaced,
and the valve was assembled
on August
22,
1989.
The inspector reviewed SIE-V133
WOs issued
subsequent
to the
1989
seal
replacement
and noted that the valve was not disassembled
again
until March 18,
1992,
using
This
WO indicated the
valve was suspected
of leaking because
pressurizer
level dropped
approximately
one percent
every two minutes
when the "A" train of
shutdown cooling was in service with one of the
MOVs upstream of
'IE-V133
open.
In addition to reworking SIE-V133 to stop the
leakage
past the valve seat,
the
WO was to repair
a body-to-bonnet
leak.
During disassembly,
the licensee
found that the bonnet
assembly
was installed about
160 degrees
from normal alignment.
The
licensee
also observed
damage to the valve internals
as
a result of
installation in the reverse orientation.
The licensee initiated Condition Report/Disposition
Request
(CRDR)
1-2-0177 to investigate
the root cause of SIE-V133 being improperly
assembled.
The licensee
speculated,
but could not confirm, that the
improper assembly
was
due to incorrect scribe lines (possible
multiple scribe lines existed),
removal
and replacement
of a marked
stud in a different sequence,
or personnel difficulty associated
with working in a respirator during valve reassembly.
This event
was treated
as
an isolated occurrence.
The inspector
reviewed the
WOs associated
with the disassembly
of
SIE-V133 and noted that there were
no specific instructions for
marking the line from a valve stud to the body.
The inspector noted
that this action
was critical as mismarking could allow the valve to
be reassembled
in the wrong orientation.
The licensee
indicated
that this action
had
been considered
to be. within the skill of the
H
~
t
craft.
The inspector also noted that the sequence
of WO steps
was.
. different than -specified
by the vendor manual.
The first step for
disassembly
in the Borg-Warner manual
was to mark the-body-to-bonnet
orientation.
The licensee,'s
WOs marked the valve orientation after
removal of the studs
and nuts, partially unscrewing the bonnet
retainer,
and reinstalling the studs
and nuts.
The inspector
questioned if some misalignment might occur while unscrewing the
bonnet retainer
and inadvertently rotating the bonnet
assembly prior
to match marking.
The licensee
indicated that while misalignment
was possible, it would be unlikely due to the force needed to break
the seal
between the bonnet
assembly
and the valve body.
The
licensee
added that the seal
in SIE-V133 did not show any markings
.
to indicate that it had rotated.
The inspector also noted that the
Borg-Marner manual
specified
measurement
of a seating
dimension for
the bonnet retainer,
and the
WOs did not specify making the
measurement.
ost Maintenance
ests
The licensee
conducted
a surveillance test for SIE-V133 following
the
1989 maintenance.
The test procedure,
73SR-IXI29, consisted of
operating the
pumps
and measuring, the flow through the check
valve.
Since the test
was satisfactory,
even though the valve
internals
were reversed,
the valve was returned to service.
The
inspector reviewed the results
from tests
performed
on August 29,
1989,
and
on November 2,
1989,
and did not observe
any unusual
results
which may have indicated that SIE-V133 was improperly
assembled.
One stated objective of the licensee's
test procedure
was to satisfy
the requirements
of TS 4.0.5.
TS 4.0;5 indicates that inservice
testing of ASME Code Class
2 valves shall
be performed in accordance
with Section
XI of the
ASME Boiler and Pressure
Vessel
Code.
The
test procedure referred to Section XI, Subarticle
IWV-3520 of the
ASME Boiler and Pressure
Vessel
Code,
1980 Edition, Winter 1981
Addenda.
Subarticle
IWV-3520 indicated that check valves shall
be
exercised
'to the position required to fulfilltheir function,
and
the subarticle described test requirements
for normally, open
and
normally shut check valves.
The inspector
noted that the test
procedure
did not refer to Subarticle
IWV-3200 of ASME Section XI
which indicated that
a valve shall
be tested to demonstrate
that the
performance
parameters
which could
be affected
by maintenance
are
within acceptable limits.
Another stated objective of the test procedure
was to demonstrate
valve operability.
Testing to ensure
valve operability was required
by TS 4.6.3.1,
which indicated that containment isolation valves
shall
be demonstrated
operable prior to returning
a valve to service
after maintenance,
repair, or replacement
work is performed
on the
valve.
I
The inspector
noted that while the surveillance
procedure
would test
that valve SIE-V133 would pass flow, it would not test that the
valve, provided isolation capability.
The inspector discussed
the
function of SIE-V133 with various licensee
personnel
including
a
component engineer,
system engineers 'and
an engineer responsible for
the test procedure.
Licensee
personnel
indicated that the function'.
of the valve was to open after safety injection initiated.
These
personnel
did not indicate that the valve had
a design feature to
shut for the purpose. of containment isolation.
Other Occurrences
The licensee
had three other occurrences
where the bonnet
assembly
of similarly designed
valves
was misaligned.
Through discussions
with licensee
personnel
and review of documents,
the inspector learned of two previous
instances
where bonnet
assemblies
had
been improperly installed.
In 1986, during Unit 3
pre-operational
testing,
valves
SIE-V134 and SIE-V144 were found.to
have their bonnet
assemblies
installed approximately
30 degrees
from
normal.
Corrective action for these
two valves included repair of
minor defects
observed
during valve inspection.
The inspector did
not find any documentation
to indicate that corrective actions
were
taken to prevent future occurrences.
On April 30,
1992, Unit
1 valve SIA-V404, the HPSI "A" pump
discharge
was disassembled
and the bonnet
assembly
was
found to be
180 degrees
out of normal alignment.
The licensee
had
been alerted to
a problem with the check valve when
a 300 to 1,000
psi pressure
drop across
the valve was observed
during flow testing
of the pumps's
discharge
HOV.
Additionally, the licensee
observed-
reduced safety injection flows during the testing.
SIA-V404 had
been previously disassembled
during the refueling outage,
and the
valve internals
had
been reversed
only during
a time period when the
HPSI train was inoperable.
Corrective Actions
Unit
1
LER 92-005 indicated that mechanical
maintenance
personnel
would be briefed
on the misassmbly of SIE-V133.
The
LER also
indicated that since starting
a check valve inspection
program in
February
1990,
no other check valve alignment problems
had
been
identified,
and SIE-V133 was
an isolated occurrence.
The
LER stated
that before SIE-V133, there
had
been
no previous similar events
reported
pursuant to 10 CFR Part 50.73.
Following the discovery of SIA-V404 misassembly,
the licensee
initiated
CRDR 1-2-0310 to identify the root cause
and evaluate
additional corrective actions
since the valve was the second
one
found to be misassembled
during the Unit
1 refueling outage.
The
licensee
took the additional action of assessing
the need
for'urther
testing of check valves at all units.
This assessment
resulted in the identification of 208 bonnet
hung swing check valves
for all three units.
Most of these
valves were judged not to be
suspect
due to being reverse flow tested or due to the bonnet
, bolting directly to the valve body (versus the silver seal
valve
design which allows bonnet rotation after positioning the
internals'nside
the valve body).
The licensee
determined that
10 valves per
.unit required verification.
The licensee
chose to use
an ultrasonic
(UT) technique to identify the orientation of a groove cut into the
underside of the bonnet.
The location of the groove verified the
orientation of the hanging disc.
The
10 valves in each unit were
inspected
and were found to be satisfactory.
In addition to the
CRDRs issued for the two Unit
1 valves found
misassembled,
the licensee initiated Engineering Evaluation
Request
(EER) 91-SI-032 to evaluate
the safety function and determine if
reverse
flow testing is required for HPSI
pump discharge
check
valves
and the LPSI and
HPSI containment isolation check valves that
are not required to be leak tested.
Safet
S
n f ca
ce
During the period when Unit
1 operated
at power with SIE-V133
improperly assembled,
three reactor trips occurred
and two shutdowns
were performed.
The licensee did not report
any abnormal
operation
of the safety injection system during these
events.
At the time of
completion of this inspection,
the licensee
indicated that
an
assessment
of the effects of design
bases
accidents
coupled with
valve misassembly
would be performed.
The safety significance of the misassembly of SIE-V133 is based
primarily on the generic implication of not. performing acceptable
post maintenance
tests
on safety related
check valves prior to their
return to service.
Many of these
check valves are
opened
and
inspected
in accordance
with the licensee's
check valve preventive
maintenance
program,
and therefore,
continue to be vulnerable to
misassembly
and inadequate
testing.
As discussed
above,
two
instances
arose in which safety related
check valves in the
same
system
were similarly misassembled.
One,
SIA-V404, was identified
prior to returning the valve to service,
and the other,
SIE-V133,
was not.
As a result of SIE-V133 misassembly,
GDC requirements
for
containment isolation were not met for an entire fuel cycle.
Adherence to,the General
Design Criteria is still required to
maintain the "defense
in depth" posture
inherent in the
10
CFR
requirements.
The Palo Verde
UFSAR did not appear to credit SIE-V133 with an
isolation function since it was always
assumed
to be open for safety
injection flow throughout
any analyzed
accident.
Even if one train
of HPSI sustained total failure (single failure criteria),
system
design
would continue to provide opposite train flow through the
The inspector
noted that the
CESSAR stated that check
valve failures were not considered
credible
and therefore,
analysis
did not consider
such
a failure.
Other containment isolation check
valves are credited with design functions related to different
system failure modes.
For example,
CESSAR 6.3.2.5.4,
"Capacity to
Maintain Cooling Following a Single Failure,"
and Table 6.3.2.-2,
"Safety Injection System Failure Nodes
and Effects Analysis," (Item
No. 6) credits the
containment isolation check
valves with preventing recirculation
mode backflow from HPSI
pumps
if the
NOV containment isolation valve for LPSI fails open.
The
inspector thus noted,'t
was fortunate that
a more significant valve
did not suffer degradation.
g.
Conclusions
Based
on the discussion
above,
the inspector
concluded
the
following:
1)
The licensee initially limited the scope of corrective actions
because
SIE-V133 was considered
to be
an isolated event.
The
licensee
did not take into account
two previous
instances
where
similarly designed
valves were found to be misassembled.
Additional corrective actions
were initiated as
a result .of
finding SIA-V404 misassembled.
Unit
1
LER 92-005 did not
address
the previous occurrences.
2)
The maintenance
procedure
did not provide sufficient detail for
marking the orientation of the valve during disassembly.
The
procedure relied
on the skill of the craft to ensure that this
action
was successfully
accomplished.
In addition, the
maintenance activities did not accomplish the intended
goal of
proper valve reassembly.
3)
The function of the valve to provide containment isolation was
not fully considered
when developing the post maintenance test
procedure to demonstrate
operability.
Isolation capability was
not tested.
4)
As
a result of the improper maintenance
and the lack of testing
to demonstrate
isolation capability, the valve was
inappropriately placed into service.
The unit was operated
in
Nodes
1, 2, 3,
and
4 with the valve inoperable,
and the
TS 3.6.3 action requirements
were not met.
This is an apparent
violation of NRC requirements
(Violation 528/92-23-01).
5)
The actual safety significance of plant operation with SIE-V133
appeared
to be low in that the check valve was not
called
upon to perform a containment isolation function during
the period of improper assembly.
In addition, it appeared
that
the Palo Verde
UFSAR accident
analyses
did not credit the
ability of the valve to close (safety function is to open for a
safety injection).
h.
Licensee
Commitments
The conclusions of the inspector
were presented
to licensee
management
at the exit meeting.
Licensee
management
made the
following commitments:
1)
To evaluate
the need for a supplement to LER 92-05 or a new LER
'o assess
the
TS surveillance
and
ASME Section XI requirements
and
any needed corrective action (clarifying the position that
there were
no requirements
to test
SIE-V133 for reverse flow),
and to modify the statement that SIE-V133 was
an isolated
occurrence.
2)
To review the guidance
promulgated in Generic Letter 89-04 for
adequacy.
This generic letter addressed
reverse
flow testing
of check valves.
3)
To review guality Assurance
(gA) program involvement
and the
need for program modifications, if necessary.
4)
To review the mechanical
technician valve maintenance
training
program for needed modifications.
5)
To develop
a Model Work Order for disassembly
of silver seal
bonnet valves.
6)
To evaluate
the safety significance of SIE-V133 being
misassembled
when coupled with design basis accidents.
7)
To perform an inspection or test to confirm isolation
capabilities of the
pump discharge
and the
and LPSI'containment isolation check valves that are not
, tested for leakage.
The'inspection
or test would be performed
after any maintenance activity that is completed prior to the
licensee
completing their evaluation of the need for reverse
flow testing of the valves.
One apparent violation of NRC requirements
was identified.
3.
Exit Meetin
30702
An exit meeting
was held
on June
19,
1992, with licensee
management
and
the inspector during which the observations
and conclusions
in this
report were generally discussed.
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