ML17312B717
| ML17312B717 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 10/08/1997 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML17312B715 | List: |
| References | |
| 50-528-97-22, 50-529-97-22, 50-530-97-22, NUDOCS 9710150071 | |
| Download: ML17312B717 (25) | |
See also: IR 05000528/1997022
Text
ENCLOSURE 2
U.S. NUCLEAR REGULATORY COMMISSION
REGION IV
Docket Nos.:
License Nos.:
Report No.:
Licensee:
Facility:
Location:
Dates:
Inspector:
Approved By:
50-528
50-529
50-530
NPF-51
50-528/97-22
50-529/97-22
50-530/97-22
Arizona Public Service Company
Palo Verde Nuclear Generating Station, Units 1, 2, and 3
5951 S. Wintersburg Road
Tonopah, Arizona
September 8-12, 1997
C. J. Paulk, Reactor Inspector, Maintenance
Branch
Dr.'ale A. Powers, Chief, Maintenance
Branch
Division of Reactor Safety
ATTACHMENT:
Supplemental
Information
97iOi5007i 97i008
ADOCK 05000528
G
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EXECUTIVE SUMMARY
Palo Verde Nuclear Generating Station, Units 1, 2, and 3
NRC Inspection Report 50-528/97-22; 50-529/97-22; 50-530/97-22
This special inspection was conducted to review the licensee's
response
to an inadvertent
dilution of the Unit 2 spent fuel pool on August 12, 1997.
The inspection also assessed
the evaluation of the event that was performed by the licensee.
Maintenance
The licensee's
evaluation of the inadvertent dilution of the Unit 2 spent fuel pool
was thorough and of high quality (Section M8.1).
The root cause analysis conclusion and corrective actions for the inadvertent
dilution event of the Unit 2 spent fuel pool were well documented
and supported
(Section M8.1). '
lack of adequate
inter-departmental
communications
during concurrent work
activities was a large contributor to the inadvertent dilution event in the Unit 2
spent fuel pool (Section M8.1).
A work order that failed to include a requirement to prohibit fuel movement or
handling during the implementation of a modification placed additional 'challenges to
operators responding to the boron dilution event.
This inadequate
work order was
identified as a violation (Section M8.1).
jl
l
-3-
Summar
of Plant Status
Units
1 and 3 were at full power and Unit 2 was its eighth refueling outage.
II. Maintenance
M8
IVliscellaneous Maintenance Issues (92902)
M8.1
Closed
Unresolved Item 50-529 9715-04:
Inadvertent dilution of the spent fuel
pool during installation of a design modification to provide a backup air supply to
the spent fuel pool transfer canal gate.
Beckceround
On August 12, 1997, maintenance
personnel were installing a modification to add a
permanent
backup air supply to the spent fuel pool transfer canal gate seal
~
Depressurization
of both the spent fuel pool transfer canal and cask loading pit gate
seals was required to install the modification.
The spent fuel pool contained borated
water at a concentration
of approximately 4337 ppm and the adjacent cask loading
pit contained demineralized water.
Upon depressurization
of the cask loading pit
gate seal, an exchange
of water began, resulting in an inadvertent dilution of the
spent fuel pool ~
At the time of the event, two other activities were in process
in the spent fuel pool
area.
One activity was the movement of new fuel into the pool in preparation for
the outage.
The other activity was a training exercise being conducted
by radiation
protection technicians to replace the filter on a pump that had been temporarily
placed in the cask loading pit. The shift control room operating crew was aware of
the modification work and the fuel movement, but were unaware of the filter
replacement training.
Licensee personnel took immediate actions-to secure new fuel movement after an
initial boron sample taken in the area of the cask loading pit gate indicated
1767 ppm.
A spent fuel pool bulk sample was taken at the discharge of the fuel
pool cleanup pump that indicated
a boron concentration
of 3942 ppm.
Technical Specification 3.1.2.6a., which requires
a minimum boron concentration
of
4000 ppm,
was entered on declaration from the shift supervisor.
Restoration
measures
were taken and, subsequently,
the boron concentration
was returned to
4018 ppm approximately 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> after the bulk concentration was found to be
less than 4000 ppm.
Ins ection Sco
e
The purpose of this special inspection was to evaluate
the licensee's
actions taken
during the event, to review the licensee's
evaluation of this event, to review the
proposed
corrective actions, and to independently
assess
the event.
In order to
accomplish these goals, the inspector reviewed the licensee's
evaluation,
interviewed licensee personnel,
reviewed the design change package
and associated
documents
(listed in the Attachment), reviewed the event time line documented
in
the Attachment, and reviewed licensee procedures
and Technical Specifications.
b.
Observations
and Findin s
The inspector noted that the licensee's
evaluation team considered
the filter
replacement training as a planned activity; however, the activity was not on the
work schedule,
and control room operations
personriel were not aware of the
activity. The inspector also noted, as did the evaluation team, that, while each
activity was being supervised,
no one considered
the synergistic effects of three
activities being performed simultaneously.
The inspector found that the lack of
inter-departmental
communication was a major contributor to this event.
This
finding was similar to findings in other NRC inspection reports that documented
other recent events (e.g., 50-528;-529;-530/97-09
and 97-15).
The inspector observed that the work order used to perform the filter replacement
training (Work Order 00803435) was initially written as an "activity tracking only"
work order.
Also, the work order stated that the purpose was to perform a pre-
outage test on a pump in the "cast [sic] wash down pit," and that this area was to
be partially filled with water.
This work was performed the week of July 24, 1997;
however, the pump was inadvertently placed in the cask loading pit contrary to the
location specified in the work order.
The inspector noted that, since the activity
was performed under
a tracking only work order,
a hard copy of the work order was
not required.
Therefore, the radiation protection technicians performing the test did
not have hardcopy information to indicate that the pump was in a location that was
different from that prescribed
on the work order.
As dicussed later in this section,
the placement of the pump in the cask loading pit was a contributor to the dilution
event.
While the pre-outage
testing of the pump was completed
in July, the work order
remained open.
The inspector noted that this was to allow the tracking of time
spent by the radiation protection technicians for training on the pump.
The
inspector found this to be a weakness
in the licensee's work control process since
the radiation protection technicians were allowed, by procedure,
to perform
activities that were not specified on the tracking only'ork order.
After the inspector identified the wrong location for the pump testing described
in
the tracking only work order, the work order was revised to indicate that the pump
was in the cask loading pit. However, the work order remained cpen.
-5-
Technical Specification 6.8.1 requires,
in part, that written procedures
shall be
established,
implemented,
and maintained covering the applicable procedures
recommended
in Appendix A of Regulatory Guide 1.33, Revision 2, February 1978.
Regulatory Guide 1.33, Appendix A, Revision 2, Section 9, requires that
maintenance
that can affect the performance of safety-related
equipment should be
performed in accordance
with written procedures,
documented
instructions, or
drawings appropriate to the circumstances.
The inspector noted that the work
order (WO 00793132) for the implementation of the modification of the backup air
supply system did not contain a requirement that no fuel movement or handling was
allowed during the installation of the modification.
This requirement was contained
in the design change package
(DMWO 00793132, Part II, "Other Design Input
Considerations,"
Section 1, "Dismantling and Rearranging of Existing Items" ). The
inspector found that, while this omission did not contribute to the event, it created
additional challenges to the operators'esponse
to the event because
a fuel bundle
was in the process of being moved at the time the operators were informed of the
low boron concentration.
This bundle had to be placed in a safe configuration and
required. the attention of control room operators until the bundle was safely stored.
The inspector found that the failure to translate the requirement that no fuel
movement or handling was allowed during the installation of the modification to be
a violation of Technical Specification 6.8.1 (50-528;-529;-530/9722-01).
The inspector noted that, while not a contributing factor to the event, the engineer
performing the safety evaluation for the design change package
assumed
that there
would be "no credible significant driving mechanism to cause the boron dilution to
exceed this assumed
rate [35 gpm (132.5 Lpm)J." This statement was based
on
the fact that both the fuel transfer canal and the cask loading pit would be at
approximately the same level when the cask loading pit gate seal was
depressurized.
The inspector verified through review of operator logs that the two levels were
within 2 inches (5 cm) of each other at a level of approximately 137 feet 10 inches
(42 m). Because the levels were approximately equal, the only other driving force
that was expected was that resulting from the differences in densities of the two
water volumes.
The inspector reviewed a licensee calculation that was performed
after the event and determined that the driving force due to the difference in water
densities
and temperatures
was insignificant.
The inspector found that the
assumption
of no credible significant driving force to be valid, provided the
prerequisites
and requirements from the design change package were satisfied.
While licensee personnel
had not reached
a definite conclusion, they suspected
that
the force of the water being discharged
from the pump being tested in the cask
loading pit at the time the gate seal was depressurized
was enough to move the
gate and cause the flow between the two water volumes.
The inspector discussed
this theory with a licensee engineer and found the basis to be reasonable.
The
S
I
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inspector found that the testing of the pump was not included in the safety
evaluation and was not accounted
for in the prerequisites.
The inspector found the licensee's evaluation of the dilution event (Root Cause
Investigation for CRDR 2-7-0259, dated August 29, 1997) thorough and of high
quality.
The conclusions
reached,
the root cause(s)
identified, and the corrective
actions proposed
were well documented
and supported.
The corrective actions
included:
the revision of the safety evaluation to address
fuel movement during the
Units
1 and 3 installation of the modification; the determination of whether or not
the cask loading pit should be filled with borated water during the installation of the
modification, or should the pit be filled indefinitely with borated water; the revision
of a calculation for determining the volume in the different areas of the spent fuel
pool; the development
of a strategy to increase
a questioning attitude about
activities in adjacent work areas;
and, the enhancement
of job briefings, in general,
and sensitive issues briefings when one or more activities are to be performed in the
spent fuel pool areas, including new fuel movement.
The recurring theme from the evaluation of poor inter-departmental
communications
was a concern.
Licensee management
stated that the communications
at the plant
did not meet their expectations.
While management's
heightened
attention to the
problem with communications was apparent
(as noted through interviews), the
actions taken to correct. the issue have not had time to be effective.
Conclusions
The licensee's
evaluation of the boron dilution event was thorough and of high
quality.
The root cause analysis conclusions
and corrective actions were well
documented
and supported.
A lack of adequate
inter-departmental
communications
during concurrent work activities was a significant contributor to the event.
An
inadequate
work order that failed to include a requirement to prohibit fuel movement
or handling during the implementation of a modification placed additional challenges
to operators
responding to the event and was identified as a violation of Technical Specification 6.8.1.
8.2
Closed
Ins ection Followu
Item 50-528 -529 -530 9601-01:
Design
requirements
for the nonessential
auxiliary feedwater system not consistently
translated.
The licensee was requested
to respond to the subject inspection report to document
a verbal commitment to clarify the licensing basis for the nonessential
auxiliary
feedwater train.
The inspector reviewed the licensee's
June 1996 letter from
Mr. W. L. Stewart to Mr. L. J. Callan.
The inspector found the letter to have adequately
addressed
the concerns that
minimum acceptable
requirements
for the auxiliary feedwate.
pumps were
substantially less than the original design capability.
The inspector noted that the
-7-
manner in which the probabilistic risk assessment
took credit for the nonsafety-
related nonessential
auxiliary feedwater system to reduce core damage frequency,
and the description of the auxiliary feedwater system in the Updated Final Safety
Analysis Report, caused confusion.
In the June 1996 letter, the licensee provided
Licensing Document Change
Request 3654 that modified the wording in the
Updated Final Safety Analysis Report to clarify the basis of the nonessential
auxiliary feedwater system.
The inspector found the licensee's
response
to have adequately
addressed
the
concerns identified in the subject report.
8.3
Closed
Ins ection Followu
Item 50-528 -529 -530 9619-0'I:
Use of ultrasonic
test block of different material than tested.
This item was reviewed in NRC Inspection Report 50-528;- 529;- 530/97-11
and
left open pending identification of the scope of the required corrective action and
the planned implementation of the corrective actions.
The inspector reviewed the
licensee's corrective actions and the schedule for implementing the actions.
The
inspector found that the scope was limited to the steam generator
nozzles which
were scheduled
to be reinspected
using an ultrasonic probe calibrated on the same
type material as being examined.
The reinspections
were appropriately scheduled
for the next refueling outage on each unit.
8.4
Closed
Violation 50-528 -529 -530 9709-01:
Procedural requirements
not met
(four examples).
The inspector verified the corrective actions described
in the licensee's
response
letter, dated June 2, 1997, to be reasonable
and complete.
No similar problems
were identified.
8.5
Closed
Violation 50-528 -529 -530/9709-02:
Provisions were not established
to
assure that the safety-related function of the gate seals would not be lost.
The inspector verified the corrective actions described
in the licensee's
response
letter, dated June 2, 1997, to be reasonable
and complete.
No similar problems
were identified..
8.6
Closed
Violation 528 -529 -530/9709-03:
Gate seal inspection procedure was
inadequate.
The inspector verified the corrective actions described
in the licensee's
response
letter, dated June
2, 1997, to be reasonable
and complete.
No similar problems
were identified.
L
-8-
V. Mana ement Meetin
s
X1
Exit Meeting Summary
The inspector presented
the inspection results to members of licensee management
at the
conclusion of the inspection on September
12, 1997.
The licensee representatives
acknowledged
the findings presented.
The inspector asked the licensee representatives
whether any materials examined during
the inspection should be considered
proprietary.
No proprietary information was identified.
ATTACHMENT
SUPPLEMENTAL INFORMATION
PARTIAL LIST OF PERSONS CONTACTED
Licensee
S. Bauer, Licensing Section Leader, Nuclear Regulatory Affairs
M. Burns, Department Leader, Design Engineering
R. Buzard, Senior Consultant,
Nuclear Regulatory Affairs
K. Farley, Senior Engineer, Design Engineering
W. Ide, Vice President,
Engineering
M. Karbassian,
Section Leader, Nuclear Engineering
J. Levine, Senior Vice President,
Nuclear
D. Marks, Section Leader, Nuclear Regulatory Affairs - Compliance
H. Mortazavi, Senior Engineer, Design Engineering
G. Overbeck, Vice President,
Nuclear Production
M. Shea, Director, Radiation Protection
D. Smith, Director, Operations
NRC
N. Salgado, Acting Senior Resident Inspector
INSPECTION PROCEDURE USED
Followup - Maintenance
ITEMS OPENED AND CLOSED
O~ened
50-529/9722-01
Failure to translate requirements
from design change package
to installation work order
Closed
50-528/9601-01
IFI
Design requirements for Auxiliary Feedwater
N Train Not
Consistently Translated
50-529/9601-01,
IFI
Design requirements for Auxiliary Feedwater
N Train Not
Consistently Translated
50-530/9601-01
IFI
Design requirements for Auxiliary Feedwater
N Train Not
Consistently Translated
1
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50-528/9619-01
IFI
Use of Ultrasonic Test Calibration Block of Different Material
Than Tested
50-529/961 9-01
IFI
Use of Ultrasonic Test Calibration Block of Different Material
Than Tested
50-530/961 9-01
IFI
Use of Ultrasonic Test Calibration Block of Different Material
Than Tested
50-528/9709-01
Procedural Requirements
Not Met, Four Examples
50-529/9709-01
Procedural
Requirements
Not Met, Four Examples
50-530/9709-01
Procedural Requirements
Not Met, Four Examples
50-528/9709-02,
Provisions Were Not Established to Assure That the Safety-
Related Function of the Gate Seals Would Not Be Lost
50-529/9709-02
Provisions Were Not Established to Assure That the Safety-
Related Function of the Gate Seals Would Not Be Lost
50-530/9709-02
Provisions Were Not Established to Assure That the Safety-
Related Function of the Gate Seals Would Not Be Lost
50-528/9709-03
Gate Seal Inspection Procedure Was Inadequate
50-529/9709-03
Gate Seal Inspection Procedure
Was Inadequate
50-530/9709-03
Gate Seal Inspection Procedure
Was Inadequate
50-529/9715-04
Inadvertent Dilution of Spent Fuel Pool
LIST OF DOCUMENTS REVIEWED
PROCEDURES
PROCEDURE
REVISION
TITLE
30DP-OMR01
30DP-9MT01
20
Maintenance Instruction Writer's Guide
2
Maintenance
Rule
22
Conduct of Maintenance
5
Assessment
of Risk When Performing Maintenance
'
-3-
PROCEDURE
REVISION
PROCEDURES
TITLE
30DP-9WP02
31 MT-9IA01
31 MT-9PC02
51DP-9OM03
90DP-OIP03
8
Work Identification
21
Work Document Development and Control
Installation and Removal of Temporary Air/Nitrogen for Fuel
Transfer Canal Gate
F<<el Transfer Tube. Quick Closure Device
Conduct of Shift Operations
Site Scheduling
Fuel Transfer Machine
Condition Report Screening
and Processing
Condition Reporting
OTHER DOCUMENTS
Root Cause Investigation for CRDR 2-7-0259, August 29, 1997
DMWO 00793132, Revision 1, Design Change to:
add
a permanently connected
source of
backup air supply to the fuel transfer canal gate; add seal pressure
instrumentation;
resize
the gas supply orifices; reclassify the spent fuel pool transfer canal and cask loading pit
gate seals as nonquality-related;
and reclassify the fuel transfer canal gate valve as quality-
related
Calculation 13MC-IA-306, "SFP Gate Seal Gas LK Ec BU Bottle Usage Rate Det.,"
Revision 0
Calculation 13-MC-IA-307, "Orifice and PRV Sizing for the IA System to the SFP Gate
Seals," Revision 0
Calculation 13-MC-PC-208, Appendix C, "Spent Fuel Pool Water Temperature,"
Revision 0
1L
DRAWING NUMBER
REVISION
DRAWINGS
TITLE
01-P-IAF-503
02-P-I AF-503
02-M-IAP-003, SH.
'I
02-M-IAP-003, SH. 2
02-M-IAP-003, SH.
1
02-M-IAP-003, SH. 2
02-M-PCP-001
02-M-PCP-001
03-P-IAF-503
1 3-C1 74-14
1 3-C1 74-1 5
0.00
0.00
34
34
35
35
13
0.00
10
Fuel Bldg. Unit
1 Isometric Instrument Air System
Cask Loading Pit & Fuel Transfer Canal Seal Gates
Fuel Bldg. Unit 2 Isometric Instrument Air System
Cask Loading Pit & Fuel Transfer Canal Seal Gates
P & I Diagram Instrument and Service Air System,
Sheet
1 of 2
P & I Diagram Instrument and Service Air System,
Sheet 2 of 2
P & I Diagram Instrument and Service Air System,
Sheet
1 of 2
P & I Diagram Instrument and Service Air System,
Sheet 2 of 2
P & I Diagram Fuel Pool Cooling & Cleanup System
P & I Diagram Fuel Pool Cooling & Cleanup System
Fuel Bldg. Unit 3 Isometric Instrument Air System
Cask Loading Pit & Fuel Transfer Canal Seal Gates
Spent Fuel Pool Gates Fuel Transfer Canal Gates
Spent Fuel Pool Gates Fuel Transfer Canal Gates
EVENT TIME LINE
July 24, 1997
Authorization given to perform pre-outage test on a pump in the Unit 2 cask wash down
pit in accordance
with Work Order 00803435
August 9, 1997
Cask loading pit filled to approximately 137 ft 10 in (42 m)
August 12, 1997 (all times MST)
0830
Sensitive issues briefing conducted;
boron concentration
4337 ppm
{
1
-5-
0930
1025
Late morning to 1630
1 330-1430
1520
1525
1544
1555
1600
1716
Modification work began on cask pit gate seal
Air supply to seal isolated
Filter replacement
training in cask loading pit
Existing tubing was disconnected
from seal, and the seal
depressurized;
eddy currents observed
and reported to control
room
New fuel movement commenced
Boron sample taken in vicinity of the cask loading pit gate;
concentration was 1767 ppm
Control room notified of the results of the boron sample; shift
supervisor ordered fuel handlers to stop all fuel movement and
directed chemistry to obtain a bulk sample
Fuel movement stopped (after remaining fuel assembly was
placed in a safe configuration)
Bulk sample results indicated
a boron concentration of
3942 ppm; shift supervisor entered the action statement for
Technical Specification 3.1.2.6a.
Using the time as 1544
Cask loading pit gate seal repressurized
August 13, 1997
0916
0925
1245
Fuel handling activities resumed; boron concentration
equalized
at approximately 3870 ppm (greater than the 2150 ppm
Technical Specification 3.9.13 requirement for fuel movement)
Last new fuel assembly was stored
Addition of boron initiated
August 14, 1997
1725
Boron concentration
at 4018 ppm, within Technical
Specification allowable; exited Technical Specification 3.1.2.6a. action statement