ML20057C322
| ML20057C322 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 09/14/1993 |
| From: | Casto C, Matt Thomas NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20057C319 | List: |
| References | |
| 50-327-93-36, 50-328-93-36, NUDOCS 9309280214 | |
| Download: ML20057C322 (9) | |
See also: IR 05000327/1993036
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UNITED STATES
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Report Nos.: 50-327/93-36 and 50-328/93-36
Licensee: Tennessee Valley Authority
6N 38A Lookout Place
1101 Market Street
Chattanooga, TN 37402-2801
Docket Nos.:
50-327 and 50-328
License Nos.: DPR-77 and DPR-79
Facility Name: Sequoyah I and 2
Inspection Conducted: , August 9-20, 1993
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Inspector:
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C.'Casto, Chief
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Test Programs Section
Engineering Branch
Division of Reactor Safety
SUMMARY
Scope:
This special, announced inspection was conducted in the areas of balance of
plant (B0P) activities to assess the licensee's corrective actions being taken
in response to B0P equipment that has been unreliable and has contributed to
unplanned challenges to reactor safety systems.
Findings identified during
this inspection will be followed up during subsequent inspections that will be
performed prior to restart of the units.
Results:
In the areas inspected, violations or deviations were not identified. An
inspector followup item (IFI) was identified to review the licensee's
evaluation and resolution of the essential raw cooling water (ERCW) system
containment isolation motor operated valve (MOV) issue.
In general, the
prioritization and scheduling of corrective actions for BOP restart work items
was performed appropriately. However weaknesses were identified by the NRC in
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the backlog review process as described in paragraph 4.
The corrective
actions already completed, plus those planned, adequately address the
significant material problems that were identified as having contributed to
the adverse trends in the reliability and availability of BOP components and
sy:tems. The corrective actions should improve the material condition of the
BOP.
Except for the issue with PVC jacketed cables (discussed in NRC report
9309280214 930916
ADOCK 05000327
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50-327,328/93-35), the material condition of the BOP should be satisfactory
for restart and operation after all planned corrective actions are completed.
The cable issue was still in the early stages of resolution and the potential
impact on restart and operation of the units had not been determined at the
conclusion of inspection 50-327, 328/93-35. The Site Quality department has
been active in assessing B0P activities for restart and aggressive in
identifying areas of weakness to plant management.
The efforts by the Site
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Quality Department were considered to be a strength.
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REPORT DETAILS
1.
Persons Contacted
Licensee Employees
- M. Anderson, Design Control Manager, Site Engineering
- J. Bajraszewski, Licensing Engineer
- J. Baumstark, Operations Manager
- C. Brimer, Project Engineering and Support Manager
- L. Bryant, Maintenance Manager
- M. Burzynski, Site Engineering Manager
- M. Cooper, Maintenance Program Manager
- R. Drake, Project Management / Controls Manager
- R. Driscoll, Site Quality Manager
- R. Fenech, Sequoyah Site Vice President
- T. Flippo, Site Support Manager
D. Keuter, Nuclear Readiness Vice President
- D. Lundy, Technical Support Manager
- J. Maciejewski, Operations and Maintenance (0&M) Manager
K. Meade, Licensing Engineer
- M. Needham, Customer Group 0&M Manager
- S. Poage, Quality Audit and Assessment Manager
- K. Powers, Plant Manager
- J. Proffitt, Licensing Engineer
H. Rogers, Technical Support Program Manager
- R. Shell, Site Licensing Manager
- M. Skarzinski, Technical Programs and Performance Manager
- R. Thompson, Compliance Licensing Manager
P. Trudel, Design Engineering Manager
- J. Ward, Engineering and Modifications Manager
Other licensee employees contacted included engineers, operators, shift
supervisors, QA/QC personnel, craftsmen, and other plant personnel.
NRC Employees
- C. Casto, Section Chief, Region II
- W. Holland, Senior Resident Inspector
- P. Kellogg, Section Chief, Region II
- A. Long, Resident Inspector
- S. Shaeffer, Resident Inspector
- Attended exit meeting
Acronyms and initialisms used throughout this report are listed in the
last paragraph.
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2.
Plant Status
Unit I was in the refueling condition (Mode 6) to support a refueling
outage and Unit 2 was in the cold shutdown condition (Mode 5) for a
forced outage.
3.
Background
During 1992 and early 1993, Sequoyah experienced a significant increase
in the number of transients and reactor trips associated with secondary
or B0P systems and equipment. Sequoyah Units 1 and 2 were shut down on
March 1 and 2,1993, following the rupture of an extraction steam line
(B0P system) in Unit 2.
After the units were shut down, the licensee
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developed a Sequoyah Restart Plan. The overall objectives of the
Restart Plan are to ensure the comprehensiveness of the restart efforts,
to provide an integrated framework for consistent and effective
implementation of those efforts, and to assist in the management and
communication of those efforts.
The purpose of the B0P inspections at Sequoyah is to evaluate the
corrective actions taken by TVA in response to the equipment problems to
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determine if the corrective actions are adequate to ensure that the
material condition of B0P equipment and systems is acceptable prior to
unit restart.
4.
B0P Assessments and Studies
As i result of the adverse trend in the performance of the secondary
plant and the impact on reliability and availability at Sequoyah, site
senior management initiated a Secondary Plant Reliability Study in
January 1993. The objective of the reliability study was to understand
the root cause of the increased contribution of the secondary plant to
unit transients and reactor trips at Sequoyah and, based on this
understanding, provide specific recommendations to site management to
reduce the occurrence of secondary plant induced events. The licensee
also contracted Stone and Webster Engineering Corporation (SWEC) to
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perform an independent design review of selected B0P systems in order to
identify additional problems or vulnerabilities in the B0P which could
jeopardize plant reliability.
The reliability study identified several areas of weakness, with
inadequate resource management and control of work being the most
significant contributors to the adverse trend in secondary plant
performance. The study also identified numerous secondary plant
material condition deficiencies which could potentially affect secondary
plant reliability and availability.
Recommended corrective actions were
provided for the areas of weakness and the material condition
deficiencies.
NRC inspectors have performed several inspections in the 80P area during
the period June-August 1993. The inspectors reviewed the results and
the recommended corrective actions from the backlog review process, the
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TVA reliability study, and the SWEC independent design review. The NRC
inspection efforts are documented in inspection reports (IR) 50-327,
328/93-22, 93-26, 93-27, 93-31, 93-32, 93-35, and 93-36.
B0P Material Condition
The licensee identified the backlogged work that existed as of
May 1, 1993 for the focus systems identified in the Restart Plan.
The backlogged work was prioritized for completion before or after
restart, based on the restart criteria specified in the Restart
Plan.
Improvements were made that were identified in the TVA
reliability study and the SWEC design study. The licensee
performed material condition walkdowns to determine if all
hardware problems had been identified. The walkdowns resulted in
a significant number of work requests (WR) being written (over
3000) for material condition deficiencies. The inspectors noted
from earlier discussions with licensee personnel that the
walkdowns were initially planned to be performed after corrective
actions had been implemented in order to verify the readiness of
the applicable systems.
It was only after NRC inspectors
identified material condition deficiencies during their walkdowns
(IR 50-327,328/93-22 and 93-26) that the licensee decided to
perform material condition walkdowns of the focus systems.
Modification and maintenance work activities are currently on-
going to correct material deficiencies.
NRC inspectors selected 13 of the focus systems and reviewed the
applicable system notebooks of backlegged work, performed material
condition walkdowns, and reviewed the licensee's prioritization
and scheduling of backlogged items for work off. The inspectors
also reviewed the TVA reliability study and the SWEC BOP design
study. System walkdowns performed by NRC identified material
condition deficiencies that TVA had not identified. After the NRC
walkdowns, TVA's threshold and criteria for material condition
walkdowns were changed to identify more deficient conditions. As
stated above, the TVA walkdowns have resulted in over 3000 WRs
(B0P and safety related) being written for deficient material
conditions.
The inspectors concluded that, in general, the prioritization and
scheduling of work items for restart was performed appropriately
and conservatively. However, there were weaknesses identified in
the backlog review process and during the implementation of one
design change notice (DCN). These weaknesses included:
1) some
backlogged items were either not reviewed for restart or were
inadequately reviewed by the Backlog Review Committee (BRC);
2)
some restart items were deleted from the outage schedule without
the knowledge of the applicable system engineer or the BRC (this
weakness was identified by the licensee); 3) the licensee's
scheduling of material condition walkdowns were not timely;
and
4) field installation of a DCN was not in accordance with the DCN
requirements.
Except for the issue concerning PVC jacketed cables
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(discussed in IR 50-327,328/93-35), the material condition of the
B0P should be satisfactory for operation after all planned
corrective actions are completed.
B0P Reliability
As discussed previously in this report, TVA performed a Secondary
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Plant Reliability Study which identified a number of BOP high
priority modifications and maintenance activities that needed to
be corrected before restart to improve the reliability of the B0P.
The SWEC B0P design study also recommended items that should be
addressed prior to restart. TVA took actions to address the
findings and recommendations from the reliability study and the
SWEC study.
The inspectors reviewed the TVA reliability study and the SWEC
design study, the prioritization and scheduling of the items from
the studies, the licensee's justification for items determined to
be non-restart, and performed field inspections to verify that
corrective actions were being adequately implemented.
The studies were determined to be thorough and comprehensive.
Appropriate corrective actions were planned and scheduled.
Adequate justifications were provided for the items that were
considered to be non-restart. The studies provided TVA management
with a better understanding of the condition of the B0P. The
corrective actions performed to date and those scheduled for
completion prior to restart should improve the reliability and
availability of the 80P.
Emeroent Issues
Subsequent to the licensee establishing the backlog of existing
work as of May 1,1993, numerous material deficiencies were
identified through the licensee's material condition walkdowns and
during other on-going work activities. The items were documented
in the licensee's corrective action program. The licensee was
evaluating all of the emergent issues to determine which items
needed to be corrected before restart. There were several
significant issues identified. These included the ERCW
containment isolation MOVs, PVC jacketed cable, turbine trip
circuitry, and fuses, etc. The ERCW H0Vs are discussed in this
report below. The PVC jacketed cables, turbine trip circuitry,
and fuses are discussed in IR 50-327,328/93-35. Corrective
actions were being performed to address the emergent issues
identified as restart items.
During this inspection, 24 (12 per unit) ERCW containment
isolation MOVs were identified that were wired to close on torque
switch trip rather than limit switch.
Problem evaluation report
SQPER 930302 addressed this issue and, after review, the licensee
determined the condition to not be a restart item.
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The inspectors reviewed the restart evaluation of SQPER 930302
which the licensee had prepared regarding the condition. The
actuators for these MOVs torque against the mechanical stop in the
90 degree gear box located between the Limitorque actuator and the
valve at valve closure. The vendor recommended limit switch
closure and advised the licensee that the gear box was not
intended to be torque closed. However, the gear boxes had been
subjected to testing in which the gear box was tested to 30 ft-lbs
of torque for 14,000 cycles and then to 67 ft-lbs. The evaluation
contained diagnostic test data that determined the torque values
to range from 22 to 49 ft-lbs for the Sequoyah MOVs.
The inspectors requested that the licensee perform a visual
inspection of a gear box. This request was an effort to determine
if any damage had occurred as a result of using the mechanical
stops to trip the torque switch and stop the valve motion rather
than the vendor recommended limit switch method.
The licensee submitted the results of an inspection and evaluation
of the gear box for 2-FCV-067-131-B, which had been subjected to a
torque condition of approximately 140 ft-lbs. This condition had
occurred due to the failure of a motor contactor to open properly
which caused the actuator motor to develop stall torque against
the gear box mechanical stop. The licensee determined this
approximate torque value using the Limitorque equation for stall
torque. The evaluation report indicated that there was no
degradation of the gears, grease, or gaskets for the gear box.
TVA had planned to replace all the gear boxes during the next unit
refueling outages and modify the electrical circuits to provide
for limit switch closure control of these valves as recommended by
the vendor.
Based on the findings of their inspection, the
recommendation was that TVA not replace the gear boxes but modify
the electrical circuits as planned.
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It should be noted that the safety function of these valves is to
close for containment isolation and they are only stroked an
estimated 10 times per year during leak rate testing. Therefore,
based on the results of the evaluation reviewed by the regional
inspectors, the NRC agrees that the replacement of the gear boxes
is not required. Modification of the closing circuits for these
valves should be performed during the next refueling outages for
each unit. The modification of the closing circuits for these
MOVs will be reviewed during the Phase II MOV inspection and is
identified as Inspector Followup Item 50-327,328/93-36-01, Review
the Electrical Modifications for ERCW MOVs.
The emergent issues for the 13 selected B0P systems and the
corrective actions being developed to address the more significant
items before restart were reviewed by NRC inspectors during the
inspections referenced above. The items that were determined to
be non-restart were reviewed also.
It was determined that the
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emergent issues were being evaluated for restart.
In general, the
items identified for correction before restart were considered to
be appropriate.
Based on the results of the inspections conducted in the B0P area during
the period June-August 1993, it was concluded that the corrective
actions already taken or planned to improve the material condition of
the B0P adequately addressed the more significant problems that have
contributed to the adverse trends in the reliability and availability of
B0P components and systems, as identified in the various studies.
However, there is still quite a bit of work remaining to be completed
before restart.
This includes backlogged work and emergent work
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activity.
Violations or deviations were not identified in the areas inspected.
5.
Quality Assurance (QA) Assessment and Oversight
The inspector held discussions with Site Quality personnel and reviewed
QA audits, assessments, and performance evaluations of B0P and safety
related activities conducted by the Site Quality organization. The
assessments and performance evaluations were part of the overall Nuclear
Assurance plan for oversight of restart activities at Sequoyah. The
objective of the Nuclear Assurance plan was to independently verify
completion and effective implementation of the Sequoyah Restart Plan by
assessing, overseeing, and trending station performance in relation to
the six " focus areas" identified in the Restart Plan. The inspector
reviewed results of the following Site Quality activities that were
either completed or in progress:
NA-SQ-93-033, Assessment of Design Change Process
NA-SQ-93-035, Maintenance Performance Evaluation Follow-up
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NA-SQ-93-047, Assessment of Surveillance Program Performance
SQA93308, Maintenance Audit
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In addition to reviewing results of the above activities, the inspector
reviewed several Weekly Nuclear Assurance Assessment of Restart Plan
reports and assessment results which provided inputs for the Weekly
Nuclear Assurance Assessment of Restart Plan.
The inspector found that the Site Quality organization has been heavily
involved in assessing restart activities.
This included observation of
numerous work activities in the field. Site Quality has been aggressive
in identifying work performance problems and other areas of weakness.
These efforts have identified areas to site senior management where
improvement is needed prior to restart. The inspector considered the QA
assessment and oversight activities to be a strength in the licensee's
restart efforts.
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Violations or deviations were not identified in the areas inspected.
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6.
Exit Interview
The inspection scope and results were summarized on August 20, 1993,
with those persons indicated in paragraph 1.
The inspectors described
the areas inspected and discussed in detail the 2nspection findings
listed below.
Proprietary information is not contained in this report.
Dissenting comments were not received fiom the licensee. The following
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finding was discussed:
IFI 50-327, 328/93-36-01, Review Electrical Modifications to ERCW
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H0Vs (paragraph 4).
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Acronyms and Initialisms
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B0P
Balance of Plant
Backlog Review Committee
DCN
Design Change Notice
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Essential Raw Cooling Water
Flow Control Valve
IFI
Inspector Followup Item
IR
Inspection Report
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Motor Operated Valve
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Polyvinyl Chloride
Quality Assurance
Quality Control
SQPER
Sequoyah Problem Evaluation Report
Stone and Webster Engineering Corporation
Tennessee Valley Authority
Work Request
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