IR 05000327/1993022
| ML20046B787 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/21/1993 |
| From: | Julian C, Matt Thomas NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20046B786 | List: |
| References | |
| 50-327-93-22, 50-328-93-22, NUDOCS 9308060210 | |
| Download: ML20046B787 (12) | |
Text
{{#Wiki_filter:, - [esto"v,% NUCLEAR REGULATORY COMMISSION
UNITEo STATES
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~ 73 REGION 11 . -[ ' '" g 101 MARIETTA STREET, N.W., SUlTE 2900 ! &
E ATLANTA, GEoRGfA 30323-0199 t /
%,.... f Report Nos.: 50-327/93-22 and 50-328/93-22 ' Licensee: Tennessee Valley Authority 3B Lookout Place l 1101 Market Street Chattanooga, TN 37402-2801 , Docket Nos.: 50-327 and 50-328 License Nos.: DPR-77 and DPR-79 ' Facility Name: Sequoyah 1 and 2 Inspection Conducted: June 7-25, 1993 , Inspector: Nm h. M e _,dt 9-Q )- $3 ' M. Thomas O L' Date Signed . Accompanying Personnel: J. Tedrow (June 14-18, 1993) . . Approved by: [[m [d Med [ d 9-Q l-9 2 C. Julian, Acting Chief, d (> Date. Signed i Test Programs Section Engineering Branch Division of Reactor Safety SUMMARY Scope: This special, announced inspection is one of a series of inspections being $ performed to assess the licensee's balance of plant (B0P) equipment and systems, and to evaluate 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 in this area prior to restart of the units.
Results: ' , In the areas inspected, violations.or deviations were not identified. The licensee has developed a restart plan to control and assess plant readiness , for restart. The licensee's Secondary Plant Reliability Study and other- ' third-party B0P studies were comprehensive and identified a number of , deficient material conditions that need to be corrected prior to restart.
Items identified in the TVA Secondary Plant Reliability Study as restart items , were in the process of_being corrected.
System engineers were not included in 9300060210 930722 ' PDR ADOCK 05000327 ' O PDR
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2 the review process for the normal work request / work order prioritization process that will be utilized when the units are restarted.
Numerous work i requests / work orders and modifications were being implemented to address deficient BOP material conditions.
Items identified in the third-party BOP design study as restart items were evaluated by TVA and appropriate actions
were being taken. The notebooks of backlogged items for applicable systems were comprehensive.
However, the inspectors identified several material j condition deficiencies during system walkdowns which had not been identified
by plant personnel.
In addition, the inspectors noted an overall weakness in - housekeeping regarding the Control Air and Condensate Systems. The inspectors , did not consider the deficiencies to be significant enough to impact the restart of either unit.
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- t i REPORT DETAILS 1.
Persons Contacted Licensee Employees f
- J. Baumstark, Plant Operations Manager
- H. Cooper, Restart Manager
- R. Drake, Project Management / Controls Manager
- R. Driscoll, Site Quality Manager
- R. Eytchison, Vice President, Nuclear Operations
- R. Fenech, Site Vice President
- T. Flippo, Program Manager j
- J. Gates, Outage Superintendent
- D. Lundy, Technical Support Manager
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- K. Meade, Licensing Engineer
- T. Nahay, Restart Management Team
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- S. Poage, Acting Manager, Nuclear Assurance Audit & Assessment
- J. Proffitt, Compliance Licensing Engineer
' R. Rausch, Modifications Manager i J. Robertson, Independent Safety Engineering Manager H. Rogers, Program Manager, Technical Support J R. Shell, Site Licensing Manager -
- D. Stephens, Operations and Maintenance Manager, Customer Group
- R. Thompson, Compliance Licensing Manager
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- P. Trudel, Design Engineering Manager
- J. Ward, Engineering and Modifications Manager Other licensee employees contacted included engineers, control room operators, shift technical advisors, shift supervisors, craftsmen, and other plant personnel.
NRC Employees
- W. Holland, Senior Resident Inspector
- A. Long, Resident Inspector S. Shaeffer, Resident Inspector
- Attended exit meeting Acronyms and initialisms used in this report are listed in the last paragraph.
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 outag _ _ !
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3.
Background During 1992, Sequoyah experienced a significant increase in the number of transients and reactor trips associated with secondary or balance of
plant (B0P) systems and equipment.
Seven of nine reactor trips and 29
of 33 power reductions greater than 5 percent were associated with BOF
systems. The average number of reactor trips for the Sequoyah units exceeded the industry average by a factor of three.
From October 1992 . to March 1993, eleven plant transients and/or trips (3 dual unit and 8 . single unit) were the result of mainly B0P problems.
Sequoyah Units 1 and 2 were shut down on March 1 and 2, 1993, following the rupture of an i extraction steam line (B0P system) in Unit 2.
The steam line rupture ! was caused by erosion-corrosion.
After the units were shut down, the licensee developed a Sequoyah Restart Plan. This plan was discussed with NRC management on May 24, 1993. The overall objectives of the Sequoyah 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.
, i The purpose of the 80P inspections at Sequoyah is to evaluate the corrective actions taken by TVA in response to the equipment problems to , 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.
BOP Reviews and Studies
e ' a.
Secondary Plant Reliability Study As a 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 mid-January 1993, a multi-organization secondary plant reliability team was assembled and placed under the direction of the site maintenance manager.
The stated objective of the team 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.
An additional objective of the team was to identify points of single component failure which could potentially result in a loss of plant availability.
The Secondary Plant Reliability Study was issued on June 9,1993.
The study identified several areas of weakness which included the i site work prioritization process, allocation of resources to the secondary plant, and control of work and configuration.
Inadequate resource management and control of work were identified as the most significant contributors to the adverse trend in ,
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' secondary plant performance.
The study also identified numerous secondary plant material condition deficiencies which could i potentially affect secondary plant reliability and availability.
Recommended corrective actions were provided for the areas of weakness and the material condition deficiencies. The recommendations included evaluating the items for restart against i the restart criteria which had been developed by the licensee.
Numerous WRs/W0s and plant modifications are being implemented prior to restart to correct the material condition deficiencies which could affect secondary plant reliability and availability, - and operation of the units.
The inspectors reviewed the Secondary Plant Reliability Study and the recommended corrective actions. This included reviewing the restart criteria and evaluating the licensee's determination of which items would be corrected before restart and which items would be corrected after restart. The inspectors determined that the items identified by the licensee as " restart" and "non-
restart" were in accordance with the restart criteria.
During further review of the Secondary Plant Reliability Study, the notebooks of backlogged items for applicable B0P systems, and discussions with licensee personnel, the inspectors noted that some of the items identified in the reliability study were not . included in the applicable system backlog notebooks. The inspectors questioned whether the items not included in the notebooks had been reviewed by the Backlog Review Committee (BRC) , and the applicable system engineers.
Licensee personnel indicated that the system backlog notebooks included items that were identified as of May 1,1993. The licensee had decided not to include the items from the reliability study in the system backlog notebooks.
Licensee personnel further indicated that, even though . some of the items from the reliability study were not included in the system backlog notebooks, the items had been evaluated by the - reliability study team against the restart criteria. The - ' inspectors reviewed selected items from the reliability study that were not in the system backlog notebooks and determined that the items identified as restart and non-restart were in accordance with the restart criteria. Subsequent to the questions raised by the inspectors, licensee personnel initiated actions to include, in the applicable system backlog notebooks, all the items identified in the reliability study. This will ensure that the system engineers review all identified items for their assigned systems prior to restart. The inspectors will continue to review the reliability study and the system backlog notebooks during subsequent inspections.
The inspectors observed during the review of selected system backlog notebooks that emergent items identified after May 1, 1993, were being evaluated for restart against the restart criteria. These items were being added to the restart list as appropriate.
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' The inspectors noted that the system engineers are currently involved in the process of evaluating backlogged and emergent WRs , and W0s for restart for their assigned systems. The inspectors ' noted during review of the norcal WR/WO prioritization process, which will be utilized after restart,'that the system engineers do not appear to be included in the review process. The inspectors expressed concern that the syste. engineers are not included in the review process for WR/WO prioritization,-given that the site work prioritization process was one of the areas identified as a weakness in the reliability study. This item was discussed with licensee personnel who indicated that, although operations personnel currently perform the WR/WO prioritization, the process was under review for inclusion of the system engineers. The inspectors will continue to follow this item during subsequent i inspections.
t The inspectors concluded that the licensee's Secondary Plant Reliability Study was comprehensive and thorough in identifying i the areas of weakness and material condition deficiencies which have contributed to the adverse trend in secondary plant performance.
Implementation of the recommendations should improve the availability of the secondary plant and provide for more reliable plant operation.
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B0P Design Review In addition to performing the in-house reliability study, the licensee contracted an architect engineering organization to i 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 review, which = was performed from March 24, 1993 to April 9,1993, involved an evaluation of flow and piping drawings, plant walkdowns, a review of TVA design standards and descriptions of systems, discussions with TVA personnel, and a general review of calculations.
' The results of the design review concluded that, although the Sequoyah B0P design contains a number of overall design features that were not commonly observed in the industry, none of the overall design features, in specific or in combination, should preclude safe and reliable unit operation. A number of recommendations were made to improve the reliability and operation of the units.
The inspectors reviewed the results of the B0P design review and the recommendations. There were 12 recommendations identified.
Two of the twelve recommendations were considered to be restart items. The inspectors verified through the review of applicable documentation that the licensee had evaluated the items considered to be restart and appropriate actions were being taken to address ' the items prior to restart. The inspectors also noted that the licensee was completing another one of the recommendations prior . _ .
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to restart. The other nine recommendations were being incorporated into the licensee's Site Improvement Plan for implementation.
The inspectors concluded that the licensee had taken adequate > actions to address the items identified in the B0P design review.
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B0P System Backlog Review The inspectors reviewed the backlogs for the B0P systems discussed below. The review included checking the system backlog notebooks and performing preliminary system walkdowns to observe material conditions.
Additional systems were reviewed and are discussed in NRC inspection reports 50-327, 328/93-26 and 50-327, 328/93-27.
a.
Control Air System The inspectors reviewed the Control Air System (SCSA) description provided in the FSAR, section 9.3.1.
The licensee's Plant Reliability Study (dated June 9,1993) was reviewed as well as third-party evaluations of secondary plant equipment performance / reliability to determine the scope and depth of these efforts to identify necessary SCSA items for repair prior to the restart of the units.
In addition, the licensee's Independent Safety Engineering evaluations of air system events were reviewed to determine if recommendations were included in work to be accomplished before unit restart.
The inspectors reviewed the backlog of open work requests and work orders for the SCSA to identify items which had been excluded from the current list of items to be completed prior to Unit I and Unit 2 restart. Maintenance prioritization codes were utilized to perform this determination. Also a review of design change notices was performed to identify similar items. The backlog review committee disposition of these items was then reviewed.
The inspector found that appropriate recommendations had been made by this committee for items to be worked prior to Unit I and Unit 2 restart. Once identified by the BRC, MRRC approval was necessary to delete an identified restart item. The inspectors considered this administrative control to be adequate.
The non-safety-related SCSA system consists of four reciprocating compressors which provide a common air header to both units. The station service air system is usually cross-tied with the control air system.
In addition, two safety-related standby Auxiliary Control Air System (ACA) compressors are provided. Air is processed from the SCSA compressors through regenerative desiccant-type dryers and filters to non-essential plant components. The SCSA also normally supplies air to the essential loads of the ACA system through the ACA system dryers and filters.
Automatic isolation of the SCSA system from the ACA system occurs on lowering header pressure and the ACA compressors automatically
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start to ensure an adequate air supply to control essential plant components.
Even though the SCSA system is not safety-related, the system supplies non-essential air to several safety-related air-operated containment isolation valves. These valves fail to a safe position on the loss of non-essential air.
However, as discussed in the following paragraphs on Operational History, the failure of this system can significantly challenge safety systems.
(1) Operational History The inspector reviewed the history of system operation and reviewed the licensee's corrective action for operational problems encountered. The licensee's corrective action was checked to verify it was completed or included in the restart list.
The licensee has experienced a considerable history of problems with the SCSA system: Fourteen work tickets had been initiated since 1989 to
remove / repair obstructions in the SCSA water traps and drain lines.
In 1990, in response to NRC Generic Letter 88-14,
" Instrument Air Supply System Problems Affecting Safety-Related Equipment," the licensee implemented routine air quality testing of the SCSA (quarterly) and ACA (semiannually) systems, moisture element set-point verification, and evaluations of the need for local filters for components served by the systems.
On July 15, 1991, the "A" SCSA compressor tripped on
high outlet air temperature which was caused by a cooling water leak in the aftercooler. When rebuilding the compressor, sediments of corrosion products were found in the air side of the compressor aftercooler and intercooler.
In October 1992, water intrusion in the SCSA system
contributed to a Unit I turbine / reactor trip and a Unit 2 automatic turbine runback. This event was reported in LER 50-327/92018. The cause for the water intrusion was determined to be sediment accumulation ) in the bottom of the air receiver which blocked the drain line for moisture removal. Corrective actions for this event were extensive and included an evaluation of single failure modes for plant systems i that could potentially challenge safety systems, blowdown of the system with nitrogen, increased weekly testing of SCSA air quality, monthly blowdowns of air w -- - - -
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headers, modifications to system piping, and the addition of local air filters to several components i supplied by the system.
In December 1992, a loss of non-essential control air
resulted when the SCSA air compressor sequence selector switch failed. An automatic turbine runback i occurred on both Unit I and Unit 2.
This event was i reported in LER 50-327/92025.
, As evidenced by the recurring problems with the SCSA system,
the licensee's corrective actions were not comprehensive and
timely to prevent thc occurrence of further problems. The monthly blowdown of the SCSA system and installation of air filters in the remaining components supplied by the system have improved system reliability. The weekly air quality samples and inspection of the local filters indicate that the air quality has remained good with little debris / rust / particulate material being found. The licensee has therefore extended the sampling / blowdown frequency to quarterly. liowever, the moisture problem in the SCSA system could have a long-term detrimental effect as a result of the ) production of corrosion particles. The inspector considered ' the air quality sampling effort to be important and should be continued in accordance with the licensee's commitment to ! GL 88-14.
(2) System Walkdown ,
A walkdown of the SCSA and ACA systems was performed to , verify appropriate material condition prior to plant restart i and to verify that significant problems had been identified / evaluated by plant personnel for inclusion in the j restart list. Major components inspected included the air-j compressors, aftercoolers, receivers, filters, dryers and
several air operated valve end users. At the time of the inspection, the "C" SCSA compressor was secured and the "D" SCSA compressor was out of service for maintenance. The following minor deficiencies were identified: "A" SCSA compressor shaft seal leakage.
- Two pipe hangers for the system piping between the "A"
SCSA aftercooler and receiver were bent.
Minor oil leaks on the "B" SCSA air compressor around
the oil filter and under the shaft coupling.
! Through wall cooling water leaks on ERCW drain lines
for the "A" and "C" aftercoolers upstream of the <
aftercooler drain valve I i I . l
Even though these deficiencies had not been identified by plant personnel, the inspectors did not consider the findings to be significant enough to jeopardize unit i restart. After notification of these deficiencies, licensee personnel initiated work requests for repair.
In addition
to the above material deficiencies, the inspectors noted an l overall weakness in housekeeping regarding the Control Air ' System at the facility.
(3) Assessment From the review of outstanding work / design items and the system walkdown results, the inspector considered that
appropriate work items had been completed or were scheduled to be completed prior to unit restart. However, due to the
significant impact that this system has had on safety systems in the past, the inspector considered the continuing air quality sampling and periodic system blowdowns to be important to continued reliable system operation.
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Condensate System The inspectors reviewed the condensate system description provided in the FSAR, section 10.4.7.
The licensee's Plant Reliability Study was reviewed as well as third-party evaluations of secondary plant equipment performance / reliability to determine the scope and depth of these efforts to identify necessary condensate system items for repair prior to the restart of the units.
The inspectors reviewed the backlog of open work requests and work ' orders for the condensate system to identify items which.had been excluded from the current list of items to be worked prior to Unit 1 and Unit 2 restart. As with the SCSA system, maintenance prioritization codes were utilized to perform this determination.
Also, a review of the design change notices was performed to identify similar items. The Backlog Review Committee disposition of these iterrs was then reviewed.
The inspector found that appropriate recommendations had been made by this committee for items to be worked prior to Unit I and Unit 2 restart.
' The inspector reviewed the history of system operation and found only infrequent minor power reductions to perform maintenance on system components.
i The non-safety-related condensate systems were identical for the two units and consisted of three hotwell pumps, three condensate booster pumps, an in-line gland sealing steam condenser, two in-line main feedwater pump turbine condensers, two common unit i condensate storage tanks, and seven stages of feedwater heaters.
Although the plant's FSAR and system training lesson plans stated _ that a unit needed only two hotwell pumps and two condensate l booster pumps for 100 percent power operation, discussion with . - - -
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system engineers revealed that a plant trip would most likely , occur from the loss of a hotwell pump when operating from 100 percent power. As identified in the Plant Reliability Study, the > multiple-component condensate system is susceptible to failures ' that could result in challenges to safety systems.
(1) System Walkdown i , A walkdown of the condensate systems for Unit I and Unit 2
was performed to verify acceptable material condition prior to plant restart and to verify that significant problems had been identified / evaluated by plant personnel for inclusion in the restart list. Major components inspected included the hotwell pumps, condensate booster pumps, gland sealing steam condenser, main feedwater pump turbine condensers, condensate storage tanks, and feedwater heaters. At the time of the inspection, the condensate systems were secured . ' and drained of water.
The following minor deficiencies were identified: Condensate storage tank drain valves 0-2-500 and 0-2-
501 were exposed to the outside environment and in need of lubrication.
. A bolt was missing from the mounting plate for Unit 2 . "A" main feedwater pump turbine condenser.
' i Equipment labels on suction flanges on several hotwell + pumps indicated strainers installed even though these devices had been removed after preoperational testing.
These deficiencies were communicated to licensee personnel . who initiated work requests for repair. -In addition to the above material deficiencies, the inspectors noted an overall weakness in housekeeping regarding the condensate system at , the facility.
(2) Assessment The drained system condition inhibited a meaningful assessment of system readiness.
6.
Exit Interview The inspection scope and results were summarized on June 18 and 25, 1993, with those individuals identified by an asterisk in paragraph 1 above. The inspectors described the areas inspected and discussed in detail the inspection findings.
Proprietary information is not i contained in this report. Dissenting comments were not received from the licensee.
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7.
Acronyms and Initialisms f ACA Auxiliary Control Air BOP Balance of Plant BRC Backlog Review Committee
ERCW Essential Raw Cooling Water FSAR Final Safety Analysis Report l LER Licensee Event Report MRRC Management Restart Review Committee NRC Nuclear Regulatory Commission SCSA Station Control and Service Air TVA Tennessee Valley Authority l WO Work Order j WR Work Request i I < l P W
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