ML16342A383
| ML16342A383 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 01/12/1994 |
| From: | Vandenburgh C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | |
| Shared Package | |
| ML16342A382 | List: |
| References | |
| 50-275-93-36, 50-323-93-36, GL-89-13, NUDOCS 9402020070 | |
| Download: ML16342A383 (28) | |
See also: IR 05000275/1993036
Text
U.S.
NUCLEAR REGULATORY COMMISSION
REGION
V
Report Nos:
Docket Nos:
License
Nos:
Licensee:
Facility Name:
Inspection at:
50-275/93-36
and 50-323/93-36
50-275
and 50-323
and
Pacific Gas
and Electric Company
Nuclear
Power Generation,
B14A
77 Beale Street,
Room
1451
P. 0.
Box 770000
San Francisco,
California 94177
Diablo Canyon Units
1
and
2
Diablo Canyon Site,
San Luis Obispo County, California
Inspection
Conducted:
December
13 through
17,
1993
Inspectors:
Approved by:
~Summar:
P.P.
Narbut,
Region
1
Team Leader
C. A.
an
en urg
ate
Soigne
Acting Deputy Dir tor
Division of Reactor Safety
& Projects
Ins ection from December
13 throu
h
17
1993
Re ort Nos.
50-275 93-36
and 50-
~323 93-36
Areas Ins ected:
Routine,
announced,
regional inspection of PGS.E's activities
performed in response
"Service Water System
Problems
Affecting Safety-Related
Equipment,"
issued
on July 18,
1989.
Temporary
Instruction (TI) 2515/118
and Inspection
Procedure
40500 were
used
as guidance
during this inspection.
Safet
Issues
Mana ement
S stem
SIMS
Items:
None
Results:
General
Conclusions
on Stren ths
and Weaknesses:
Strengths:
~
The gA organization
performed
a surveillance to determine if the
licensee's
program
and commitments for Generic Letter 89-13 were being
properly implemented.
The
gA effort was performed in technical
depth
and
had significant findings which paralleled
the inspection findings.
(Paragraph
3)
'7402020070
'324Dii2
ADOCK 05000275
8
r
k
Weaknesses:
~
The engineering organization's
technical
response
to the service water
issues
raised
was not performed in sufficient
technical
depth to identify significant operability issues
which were
subsequently
raised
by the
gA organization
and this inspection.
(Paragraph
2.b.3)
~
The engineering organization's
response
to the service water issues
raised
by the
gA surveillance of Hay 1993
was not timely.
The issues
had
not been resolved at the time of inspection in December
1993
(Para-
graph 3.a)
~
The licensee's
response
to Generic Letter 89-13 regarding
heat
exchanger
testing results
and the existence of a routine
ASW piping system
inspection
program apparently
contained
incomplete information
(Paragraphs
2.b.2
and 2.c. 1).
Si nificant Safet
Matters:
The operability of the
CCW heat
exchangers
was
not clearly established
by the licensee's
1991 heat exchanger
performance
testing,
nor by the licensee's
program for heat exchanger
preventative
maintenance,
trending,
inspection,
and flow testing.
The licensee
performed
an operability evaluation
which stated that it considered
the heat
exchangers
at least temporarily operable
due to the low winter ocean temperatures.
The
licensee further determined that the heat
exchangers
may not have
been
in the past.
Summar
of Violations and Deviations:
None.
DETAILS
Persons
Contacted
Paci fi c Gas
and
El ectri c
Com
an
- J
D
- D. H.
R.
P.
- G. H.
- W. G.
S.
R.
J.
R.
- K. A.
H.
E.
- C. H.
- J. R.
- D
- H. L.
"D. A.
- S.
C.
- D. B.
- G.
W.
- V. R.
K. S.
F. L.
J.
E.
Townsend,
Vice President
and Plant Hanager,
Diablo
Canyon Operations
Behnke,
Senior Engineer,
Regulatory Compliance
Powers,
Hanager,
Nuclear guality Services
Burgess,
Director,
Systems
Engineering
Crockett,
Hanager,
Technical
and Support Services
Fridley, Director, Operations
Hinds, Director, Nuclear Safety Engineering
Hubbard,
Engineer,
Regulatory
Compliance
Leppke, Assistant
Hanager,
Technical
Services
Seward,
Sr. Engineer,
Hechanical
Haintenance
del
Hazo,
Group Supervisor,
Nuclear Engineering Services
Howland, Hechanical
Engineer,
Nuclear Engineering
Services
Da Re,
System Engineer
Taggert, Director, Site guality Assurance
Ketelsen,
Auditor, Nuclear guality Services
Hiklush, Hanager Operations
Services
Gurley,
Power Production
Engineer
Foster,
Senior
Power Production
Engineer
Smith, Hechanical
Engineer,
Nuclear
Engineering
Se'rvices
Steinert,
Senior Scientist,
Aquatic Systems
Inc.
Anastasio,
Power Production
Engineer
U. S. Nuclear
Re ulator
Commission
H.
H. Hiller, Senior Resident
Inspector
- Denotes those attending the exit interview on December
17,
1993.
The inspector interviewed other licensee
employees
including operators,
maintenance
personnel,
engineers,
and quality assurance
personnel.
Examination of PG&E's Actions for Generic Letter 89-13
S stem Problems Affectin
Safet -Related
E ui ment."
Backcaround
The
NRC issued
"Service Water System
Problems
Affecting Safety-Related
Equipment,"
on July 18,
1989.
The generic
letter described
recurring industry problems with the service water
systems
at nuclear
power plants.
Service water systems
are important to
plant safety
as the ultimate heat sink following a design basis
event.
The generic letter
recommended
certain actions to be taken
by licensees
and required that each licensee
advise the
NRC of the programs to be
implemented
in response
to the generic letter recommendations.
Letter No. DCL-90-027, dated January
26,
1990,
provided
PG&E's respon'se
to the generic letter
and committed to perform certain actions.
Letter No. DCL-91-286, dated
November 25,
1991, provided
a supplemental
response
to the generic letter and reported
the completion of the initial
program actions.
Sco
e of Ins ection
I
The inspection
reviewed the licensee's
actions described
in the two
PGSE
letters
discussed
above
and reviewed the licensee's
implementing
procedures
for those actions.
The inspector
conducted
a wal,kdown of the
system with the system engineers
from the site
and from the design
offices.
The inspector
reviewed selected
records of licensee
tests
and
inspections
including videotape of an inspection of piping internals.
The inspector also
examined
the internals of
CCW Heat Exchanger
2-1
when
it was opened for cleaning.
In addition, after independently
making
several
findings, the inspector
was apprised of,
and reviewed,
a guality
Assurance
surveillance
which contained
many of the
same findings.
Overview
'he
inspector
concluded that the licensee
had implemented
a number of
actions
in response
to the generic letter.
Some of the actions
had
resulted in improved performance.
Examples of improved performance
included continuous chlorination of the Auxiliary Salt Water
(ASW) system
which resulted
in a greatly decreased
frequency of system cleaning
due to
macrofouling.
(Nacrofouling refers to piping and heat
exchanger fouling
due to marine organisms
such
as mussels
and barnacles.
Hicrofouling
refers to the growth of algae or other micro-organisms.)
Another example
of improved performance
was the accelerated
repair program for rusting
reinforcing bar and spalling concrete
in the intake structure.
The inspector
found that the licensee's
heat exchanger test results
showed that
one heat exchanger
did not meet the acceptance
standards
for
minimum heat transfer capacity established
by the system design
requirements.
This raised
a concern
regarding the operability of the
ASW
system which the licensee
subsequently
determined to be temporarily
acceptable
due to the cold winter sea temperatures.
Additionally, the
test data
appeared
to contradict the licensee's
statements
to the
NRC in
their November 25,
1991, letter to the
NRC regarding the acceptability of
the test results.
In addition, the inspector
found that the licensee
had not assured
that
the
ASW system maintenance
and surveillance controls were sufficient to
assure
system operability.
Specifically, the licensee
had high
differential pressure limits on the heat
exchangers
which allowed
macrofouling to
a degree that would exceed
the manufacturer's
tube
plugging limit and significantly reduce
the heat
removal capacity.
This
concern also affected the operability of the
ASW system which the
licensee
subsequently
determined to be temporarily- acceptable
due to the
cold winter sea temperatures.
The inspector
also found that the licensee
had not fulfilled all of the
commitments
made to the
NRC.
Specifically, the licensee
had not
estab1ished
procedures
for a routine inspection for ASW piping.
In general,
the inspector
concluded that the licensee
had not developed
a
good engineering
understanding
of the effects microfouling, macrofouling,
and heat
exchanger differential pressure
and
had not implemented
operational
controls to ensure
system operability.
This was considered
a
significant failing due to the high safety significance of the system
and
the number of opportunities
the licensee
had to address
the issues.
NRC
concerns
regarding
system operability due to differential pressure
had
been previously raised in Inspection
Report 50-275/88-11.
The licensee
responded
to those
concerns with assurances
that the differential
pressures
were acceptable.
Generic Letter 89-13 again focused attention
on the issue of heat exchanger
performance.
The failed heat exchanger
capacity test in 1991 should
have initiated additional
analysis
and
understanding,
but did not.
Finally,
a gA surveillance
in Hay 1993
raised the
same
heat exchanger
performance
issues,
but did not result in
an adequate
technical
response
from the engineering organization.
These
multiple missed opportunities indicate ineffective engineering
involvement in the issues.
Ins ection Details
a ~
Biofoulin
Controls
I
recommended
an ongoing program of surveillance
and control techniques
to reduce
the incidence of flow blockage
problems
as
a result of biofouling.
In letters
DCL-90-027, dated
January
26,
1990,
and DCL-91-286, dated
November
25,
1991,
the
licensee
explained that they would visually inspect the
ASW intake
structure
once per refueling outage,
that they would install
a
continuous chlorination system,
and that they would continue their
existing program for monthly system flow testing.
Intake Ins ection
The inspector
reviewed the licensee's
actions
for the intake.
The actions
were described
in
a series
of
computerized,
recurring,
work order tasks.
The inspection
requirements for the intake structure
appeared
to be implemented
as
described to the
NRC.
Chlorination Pro ram The licensee
implemented
a continuous
chlorination program which appeared
to be very effective
and
eventually resulted
in a significant reduction in the frequency of
heat exchanger
outages for cleaning.
However, the inspector
noted
that during the initial chlorination periods during
1992 the
frequency of cleaning
was greatly increased
due to mussel kills.
For several
months the heat
exchangers
were taken out of service
every few days for cleaning.
During this period,
the licensee
temporarily allowed the heat
exchangers
to exceed their operational
differential pressure limit of 140 inches,
be declared
and left in service until
a limit of 200 inches
was reached.
S stem
Flow Testin
- The licensee
continued to perform monthly flow
tests of the
ASW system using temporary test instrumentation.
The
ASW system at Diablo Canyon does
not have installed flow
instrumentation
available to the operators.
Operators infer
adequate
flow from the differential pressure
across
the heat
exchanger
and from the
ASW pump motor currents.
The inspector
observed that the monthly test
was performed in accordance
with
procedure
STP M-26, Revision
11,
"ASW System
Flow Testing."
The
test
acceptance
values did not include
a simple value for minimum
flow, but provided
a series of curves
dependent
on the ocean
and
Component
Cooling Water temperatures.
The licensee
stated
the
acceptance
values
are from a study done in 1992 by Westinghouse.
The study is WCAP-12526,
Revision
1, "Auxiliary Salt Water
and
Component
Cooling Water Flow and Temperature
Study for Diablo Canyon
Units
1
and 2" dated
June
1992.
The study is one of three different
design
bases
described
in the licensee's
design criteria memorandum,
DCN No. S-178 Revision 2.3, "Auxiliary Saltwater
System."
The
licensee
stated that the revised design
bases
had not been
reviewed
by the
NRC technical
branches.
The acceptability of the licensee's
revised design
bases
is considered
an open item.
(Followup item 50-
275/93-36-01)
Heat
Exchan er
Ca acit
Test
Generic Letter 89-13 requested
that licensees
conduct
a test program
to verify the heat transfer capability of all safety-related
heat
exchangers.
The generic letter allowed for an alternative
program
such
as .frequent regular maintenance
of the heat exchanger.
In letter DCL-90-027, dated January
26,
1990, the licensee
explained
that they would perform
a one-time heat exchanger
performance test
to confirm the baseline
heat transfer capability of the heat
exchangers.
The letter further explained that the licensee
would
implement
an alternative
program to verify the system would remain
capable of maintaining design basis capability.
The letter stated
that the licensee
would implement
a monitoring program which
combined flow testing, trending,
inspection,
and frequent
preventative
maintenance.
The letter stated
these
actions
would be
completed
by the
end of the
1991 fourth refueling outage of each
unit.
In letter DCL-91-286, dated
November 25,
1991,
the licensee
reported
that they had performed the heat exchanger
capacity test
and stated
that: "...the computer
model predicted that the heat exchanger
would
remove the design basis
heat load at design conditions."
The letter
also stated that the licensee
had
implemented
the alternate
monitoring program.
The inspector reviewed the results of the one-time heat exchanger
test.
The test
methods
and results
are described
in Field Test
Report
420DC-91. 1156,
"Diablo Canyon
Power Plant
CCW Heat Exchanger
Performance
Tests Units
1
and 2," dated
November 22,
1991.
The test
was not performed
by plant personnel
but by personnel
from the
licensee's
Technical
and Ecological Services Division in San
Ramon,
The inspector
had the following observations
and
findings:
(1)
Non Conservative Testin
Due to Inade uate Initial Test
Conditions
The inspector
found that several
important initial conditions
wer e not established
for the test.
The missing initial
conditions were:
~
An assessment
of the amount of microfouling and
"
macrofouling present
in the heat exchanger.
The lack of
this information precludes
assessing
the acceptability of
the microfouling and macrofouling found in the licensee's
regular monitoring program.
The lack of this information
also resulted
in the test result projections to design
conditions not accounting for the
maximum allowed fouling.
This approach
was not conservative.
The recording of the amount of differential pressure
present
in the heat exchanger.
The operators
use the
differential pressure
as
an assessment
of the degree of
macrofouling.
The failure to record differential pressure
precluded the use of the test data
as
an assessment
of the
adequacy of the operator's differential pressure limits.
~
A measurement
of the outlet water box water level.
The
outlet water box operates
at
a negative
pressure
and does
not run full at Diablo Canyon.
This information is based
on
an informal test performed
by the system engineer in
1988.
The water level in the outlet water box apparently
varies with the tide according to operators.
This
additional variable also affects the measurement
of
differential pressure
across
the heat exchanger.
(2)
Inaccurate
and
Incom lete Information
The licensee's letter DCL-91-286, dated
November 25,
1991,
stated that: "...the computer
model predicted that the heat
exchanger
would remove the design basis
heat load at design
conditions."
The inspector's
review of Field Test Report
420DC-91. 1156
showed that the computer prediction for Unit
1
heat
exchanger
CCW 1-2 did not show that the heat
exchanger
would remove the design basis
heat load.
Rather,
the test
results
showed the heat exchanger
capacity to be at 98.7
percent of design.
The inspector also determined that the
differential pressure
across
the heat exchanger
was probably at
only 101-104 inches
based
on informal records.
Therefore,
the
heat
removal capacity would have
been less if the licensee
had
accounted for the maximum allowed differential pressure
of 140
inches.
In response
to the inspector's
finding,
and in accordance
with
their procedures,
the licensee initiated
a Prompt Operability
Assessment
(POA) for the heat exchanger test failure.
The
licensee
concluded that the heat exchanger
was operable
under
the existing conditions of cold winter ocean
temperatures.
The
licensee
also initiated
a more complete long term operability
assessment
which was to be completed in
7 days.
The apparent failure to provide complete
and accurate
information to the
NRC in regards
to the
CCW 1-2 heat
exchanger's
ability to meet the design basis
heat load is
considered
an unresolved
item pending further examination of
the circumstances
of the omission.
(Unresolved
item 50-275/93-
36-02).
Inade uate Preventative
Maintenance
Limits
The inspector
observed that the heat exchangers
were taken out
of service for cleaning of macrofouling accumulations
when the
differential pressure
across
the heat exchanger
approached
140
inches of water.
The alarm setpoint for the differential
pressure
alarm was set at )40 inches
and this was
used
by the
operators
as the limit for system operability.
The inspector
examined the basis
document for the alarm setpoint to determine
the technical
basis for the
140 inch limit.
The setpoint basis
document stated that the setpoint
was
based
on engineering
judgement,
but did not provide
a technical
basis for this
judgement.
In order to make
an independent
engineering
judgement,
the
inspector
examined
CCW Heat Exchanger
2-1 which had
been taken
out of service at
a differential pressure
of about
125 inches
per the shift foreman.
The heat exchanger
had
been
taken out
of service in November for cleaning,
was getting
a high
differential pressure
much sooner
than the other heat
exchangers
and
was expected to have less macrofouling than the
other
CCW heat
exchanger's
would at the
same differential
pressure.
Heat exchanger
CCW 2-1 was more sensitive
than the
other heat exchangers
due to
a known buildup of calcification
on the outlet end.
The key point was that the other heat
exchangers
would show more macrofouling than
CCW 2-1 at
a given
differential pressure.
In
CCW 2-1, the inspector
noted that
10 tubes
were permanently
plugged
due to tube wear problems.
Fifteen tubes
were plugged
with mussels
and barnacles.
Three crabs
were in the head which
would have represented
at least another
3 tubes
being blocked
in service.
Therefore,
the inspector estimated
a total of 28
blocked tubes.
Since heat exchanger
CCW 2-1 was taken out of
service with only 125 inches of differential pressure,
the
inspector estimated that the amount of macrofouling
and the
number of plugged tubes at 140 inches would have
been
much
higher.
Also, because
CCW 2-1 was running at
a higher initial
differential pressure
after cleaning
due to its greater
calcification, the amount of macrofouling
and plugged tubes in
the other heat exchangers
and
CCW 2-2) would
be even more severe
than the macrofouling in
CCW 2-1 for any
given differential pressure.
Therefore,
the inspector
concluded that any of the heat exchangers
would have
significantly more than
28 tubes
plugged with a differential
pressure
of 140 inches.
The licensee
stated that their tube plugging limit was
2
percent of the total tubes or 24 plugable tubes total.
This
limit was provided to the licensee
on March 30,
1993,
by
a
facsimile memorandum
from Yuba Heat Transfer Division.
The
memorandum stated that:
"There is
an inherent factor of safety
in the heat transfer formulas such that the heat
exchangers
should achieve the design heat transfer rate with as
many
as
2
percent of the tubes
plugged."
Based
on the above information, the inspector's
technical
judgement
was that the differential pressure limit of 140
inches
was excessive
and that the heat
exchangers
may have
been
inoperable during conditions of warmer ocean
temperatures.
In response
to the inspector's
finding, and in accordance
with
their procedures,
the licensee
included this issue in the
Pro'mpt Operability Assessment
(POA) written for the heat
exchanger test failure.
The licensee
concluded that the heat
exchanger
was operable
under the existing conditions of cold
winter ocean temperatures.
The licensee
also initiated
a more
complete long-term operability assessment
which was to be
completed
in 7 days.
This operability evaluation
was completed
on December
30,
1993,
as discussed
in Section 3.d. of this
inspection report.
This issue is
a significant item due to the high safety
significance of the system
and the number of opportunities
the
licensee
had to address
the issue.
System operability concerns
due to differential pressure
had
been raised in Inspection
Report 50-275/88-11
and the licensee
responded
to those
concerns with assurances
that the differential pressures
were
acceptable.
Generic Letter 89-13 again focused attention
on
the issue of heat exchanger
performance
and maintenance
practices.
The failed heat
exchanger
capacity test in 1991
should
have triggered investigative actions
but did not.
Finally,
a gA surveillance
in Hay 1993 (discussed
in Section
3
of this report) raised the specific issue of the
adequacy of
the differential pressure
setpoint,
but did not elicit a
studied
response
from the engineering
organization.
These
multiple missed opportunities
indicate that engineering
was
ineffective.
The apparent failure to establish
adequate differential
pressure limits to ensure
CCW heat exchanger operability is
an
unresolved
item pending the licensee's
assessment
of
operability and the inspector's
review of that assessment.
(Unresolved
item 50-275/93-36-03)
Ins ection
and Maintenance of the
ASW S stem
Pi in
recommended
that
a routine inspection
and
maintenance
program for the service water system piping and
components
be established
so that corrosion,
erosion,
coating
failure, silting,
and biofouling would not degrade
the performance
of the system.
In letter DCL-90-027, dated January
26,
1990, the
licensee
stated that they would develop
a program
and that
procedures
to establish
a routine inspection
and maintenance
program
for the
ASW system would be established
by the
1991 fourth refueling
outages
of Units
1 and 2.
In letter DCL-91-286, dated
November 25,
1991,
the licensee
stated that they had established
a routine
inspection
and maintenance
program.
(1)
Lack of a Pi in
Ins ection
Pro ram
The inspector
examined
a sample of the licensee's
program
and
procedures for the inspection
and maintenance
of the
ASW
system.
The inspector
found that the licensee
had not
established
a routine inspection
program or procedures
to
inspect the
ASW piping.
During the Unit
1 fourth refueling outage
in March of 1991,
the
licensee
inspected
1790 feet (about
50 percent) of the Unit
1
piping using
a temporary procedure
which utilized
a television
camera.
Unit 2 was inspected
in a similar manner in October
1991.
Both inspections
did not reveal significant problems,
although two small
areas of damaged
coating
and localized
corrosion
were observed.
The two areas
required weld repair to
restore
minimum wall.
However,
subsequent
to the initial
inspection the licensee
did not establish
a program defining
the
amount or period of any additional
inspections
to be
conducted.
No additional
inspections
were done in the fifth
refueling outages of Units
1 or 2.
Responsible
engineers
stated that there were no plans for an inspection during the
sixth refueling outages
in 1994.
The licensee
had
an
open
action request
(AR) No. A0221696,
dated
March 6,
1991,
which
requested
that the temporary inspection
procedure
be made
a
permanent
plant procedure
and that
a regular period
be
established.
However,
those actions
had not been completed.
The apparent failure to develop
a routine inspection
program
for the
ASW system piping by the end of the
1991 fourth
refueling outages of Units
1
and 2,
as committed to in letter
DCL-90-027 dated January
26,
1990,
and the apparent failure to
provide accurate
implementation status of the piping inspection
program in letter DCL-91-286, dated
November 25,
1991,
are
considered
unresolved
pending further inspection of the
circumstances
involved.
(Unresolved
item 50-275/93-36-04)
d.
Confirmation of the Licensin
Basis of the
ASW S stem
Generic Letter 89-13 requested
that licensees
confirm that the
service water system
can perform its intended function in accordance
with the licensing basis for the plant.
In letters
DCL-90-027 dated
January
26,
1990,
and DCL-91-286, dated
November 25,
1991,
the
licensee
explained that they had completed
the development -of Design
Criteria Memorandums
(DCMs) in 1990
and that
no signiFicant design
deficiencies
were identified confirming that the ASW'ystem would
perform its intended function in accordance
with the licensing
basis.
Although the inspector did not examine the licensee's
actions for
confirming that the
ASW system would perform its intended
design
function, the inspection results
discussed
in Section 2.b. of this
report regarding
a lack of engineering
understanding
of the validity
of the operational
controls for microfouling, macrofouling,
and heat
exchanger differential pressure
suggest that the licensee's
actions
were not sufficient.
Likewise, there were significant technical
findings in the licensee's
gA surveillance of the licensee's
commitments for Generic Letter 89-13 discussed
in Section
3 of this
report.
The gA findings suggest
that engineering
controls
on
operational
configurations
were not sufficient to preclude
pump
runout conditions in certain situations.
The licensee's
DCN for the
ASW system,
DCH No.S-17B,
addresses
some
of these
issues
but only in a general
manner
such
as "...useful
heat
transfer
area is dependent
upon heat exchanger
maintenance.
Assuming the
CCW heat
exchanger is maintained
per standard
practices
the selection of a conservative
fouling factor can
be made."
and
"This heat exchanger
high differential alarm is provided
as
a
diagnostic tool which operations/maintenance
personnel
use to
determine
when cleaning is required to assure that significant
fouling and/or blockage of the heat exchanger
does not occur."
As
stated
in Section 2.b, the only basis for the alarm setpoint in the
licensee's
setpoint basis
document is described
as judgement.
In addition, the issue of the adequacy of the
140 inch differential
pressure limit was specifically questioned
in NRC Inspection
Report
50-275/88-11.
The licensee
responded
to the issue in letter
DCL-88-
215, dated
September
13,
1988.
This response
was also general
in
nature
and stated, "...a heat
exchanger
high differential alarm was
provided
as
a diagnostic tool which operations/maintenance
personnel
use to determine
when cleaning is required to assure
that
significant fouling and/or blockage of the heat
exchanger
does
not
occur."
The inspector
concluded that the licensee's
review of their design
basis to verify that the
ASW system would perform its intended
design function did not identify several
important design basis
issues.
An assessment
of the need to reperform
an assessment
of the
adequacy of their design basis for the
ASW system is
a followup
item.
(Followup item 50-275/93-36-05)
Licensee
0 erabilit
Evaluations
On December
30,
1993, the licensee
made
a
10 CFR 50.72 report to the
NRC which concluded that
on August 23,
1990,
and perhaps
dates prior
to and subsequent
to that date,
the
CCW heat
exchangers
for both
units may have
had sufficient fouling to have precluded
the systems
from meeting their design
bases.
Also on December
30,
1993,
the
licensee
performed,
and the Plant Safety Review Committee
(PSRC)
approved,
an operability evaluation
and concluded that the
ASW
system
was operable
since the initiation of the continuous
chlorination program in October
1992.
-10-
3.
Review of
A Involvement
The inspector
reviewed the licensee's
gA surveillance report S(A-93-0031,
dated July 28,
1993.
The licensee
conducted
the audit from March
5 to
Nay 7,
1993.
The report raised
many of the
same
issues
as were raised
by
the inspector
and other issues
not identified by the inspector.
The
inspector
noted that the surveillance
was
an in depth examination of not
only the commitments
made to the
NRC, but also the underlying technical
bases
involved with the commitments.
The inspector further noted that
the
gA personnel
had not only raised the issues
but also critically
reviewed the responses
of engineering
and rejected the answers
when
appropriate.
Although the issues
were formally identified to engineering
in Hay of 1993 by action requests,
the issues
had not been resolved at
the time of the inspection.
Examples of issues identified by the inspector
and
gA report included:
~
The failure of CCW Heat Exchanger
1-2 to pass its performance test.
The
gA report requested
engineering
to provide
a written evaluation
of'he results in Action Request
{AR) A0306715.
The engineering
response
to the
AR was not accepted
by gA and
a reevaluation
was
requested
on August 12,
1993,
Engineering
had not responded
to the
request for a revaluation at the time of the inspection.
~
The concern with the
140 inch differential pressure
setpoint for the
CCW heat
exchangers.
Likewise, the issue
had not been resolved at
the time of the inspection.
Additional excellent technical
issues
were identified by the
gA report.
Examples of these
issues
included:
~
A concern
regarding
the fact that test results
showed that the
ASW
system flow was reduced
by much more than
was concluded
by licensee
calculations for the condition where system flow was aligned through
the
pump cross-tie.
This problem was identified in AR A0309356 dated
June ll, 1993.
~
A concern regarding the lack of operational limits for protecting
the system from high flow rates
under
1
pump
and
2 heat
exchanger
configurations.
The inspector considered
the number,
importance,
and technical
depth of
the
gA surveillance findings to be
a licensee
strength.
The
gA
evaluation
and rejection of poor engineering
responses
to the
gA findings
was also considered
a strength.
The failure to resolve the
gA findings
in a timely manner
was considered
a weakness.
a.
Failure to take Timel
Action
CCW Heat Exchanger
1-2 failed to meet its test
acceptance
criteria
in
a test conducted
on February
2,
1991.
The test failure was
documented
in Field Test Report
420DC-91. 1156,
"Diablo Canyon
Power
Plant
CCW Heat Exchanger
Performance
Tests Units
1 and 2," dated
November 22,
1991.
The test failure was identified again during
a
0
-11-
gA surveillance
and documented
on Action Request
No. A03066715 dated
Hay 10,
1993.
As of the end of the inspection
on December
17,
1993,
the effect of the test failure on
ASW system operability had not
been resolved.
The apparent failure to promptly resolve conditions
adverse
to
quality is considered
an unresolved
item pending further review of
the circumstances
involved.
(Unresolved
item 50-275/93-36-06)
4.
Other Observations
a ~
Use of a
Com uter
Code that
had not been Validated
When reviewing the
CCW heat
exchanger
capacity tests previously
discussed,
the inspector
noted that, the test report, Field Test
Report 420DC-91. 1156,
"Diablo Canyon
Power Plant
CCW Heat Exchanger
Performance
Tests Units I and 2," performed
by the licensee's
Technical
and Ecological Services Division, described
the use of a
computer
code to project design basis
heat transfer capacity.
The
computer
code
was described
as not having
been validated for
accuracy.
The failure to use
a validated
computer
code is
considered
an unresolved
item pending further review of the details
involved.
(Unresolved
item 50-275/93-36-07)
b.
Calcification of Heat
Exchan er Tubes
C.
The inspector learned that calcification had
been
observed
on the
inner diameter of the
CCW heat
exchanger
tubes.
The calcification
was located only at the outlet end of the heat exchanger
in the tube
sheet
area.
The system engineer
stated that the cause of the
calcification was deposits
from seawater
caused
by the impressed
voltage
system for cathodic protection of the
ASW piping.
The
system engineer further stated that the calcification was of a short
length
and would not affect the available heat transfer
area or tube
fouling factor.
The inspector
expressed
the concern that since the
buildup was not being trended for rate of buildup,
and since the
inlet of the tubes
had
a reduced
diameter,
the calcification could
cause
the tubes to plug at the outlet end which would not be
detected
by the periodic cleaning
and inspection of the inlet end.
The effect of the calcification on the heat exchanger
capacity
and
the potential effect of undetected
tube plugging is
a followup item.
(Followup item 50-275/93-36-08)
Trendin
not Performed
The inspector inquired
as to whether the system engineer
was
trending the
amount of macrofouling found in each
CCW heat
exchanger
and the consequent
amount of tube plugging.
The system engineer
stated that macrofouling was trended
by the biologists.
However,
the biologists only trended
amount
and species
but did not count
tubes
plugged.
Further discussion
with the system engineer
disclosed that system availability was
no longer trended.
System
availability had
been previously trended
and the information had
-12-
been
used to update the licensee's
(PRA).
Although there is no regulatory requirement to trend system
performance,
the inspector's
observation
was provided to licensee
management
at the exit interview for information.
d.
Lack of ASW Flow Instruments
for 0 erator Information
The inspector noted that the operators
do not have
ASW flow
information available in the control
room.
A flow instrument
installed at the intake structure
does not indicate accurately
,
according to the system engineer.
The operators
infer flow from the
differential pressure
across
the heat exchanger
and
by observing the
electrical current to the
ASW pump motors.
Although,'there is no
regulatory requirement for flow instrumentation,
this matter
was
discussed
with the licensee
at the exit interview.
5.
~Ei
M
An exit meeting
was conducted
on December
17,
1993, with the licensee
representatives
identified in Paragraph
1.
The inspector
summarized
the
scope
and findings of the inspection
as described
in this report.
The licensee
did not identify as proprietary
any of the materials
reviewed
by or discussed
with the inspectors
during this inspections