ML20217N462
| ML20217N462 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/31/1997 |
| From: | Salas P TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9803090028 | |
| Download: ML20217N462 (15) | |
Text
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Tennessee Valley Authority, Post Office Box 2000, Soddy-Daisy, Temessee 37379-2000
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February 27, 1998 i
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk i Washington, D.C. 20555 I Gentlemen:
l In the Matter of ) Docket Nos. 50-327 l Tennessee Valley Authority ) 50-328 I e
SEQUOYAH NUCLEAR PLANT (SON) - 1997 ANNUAL REPOPTS Enclosed are the 1997 Annual Reports for SON. These reports contain a summary of the following items: occupational exposure data, reactor coolant system specific activity analysis, and diesel generator reliability data.
These reports are being submitted to satisfy the requirements j of Technical Specifications 6.9.1.4, 6.9.1.5, and 6.9.2.2.
Please direct questions concerning this submittal to me at (423) 843-7170 or J. D. Smith at (423) 843-6672.
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C Pe alas l Licensing and Industry Affairs Manager !
Enclosure cc: See page 2 I
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9803090028 971231 PDR ADOCK 05000327 R PDR
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U.S. Nuclear Regulatory Commission
. Page 2 February 27, 1998 cc (Enclosure):
Mr. R. W. Hernan, Project Manager Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident Inspector Sequoyah_ Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center 61 Forsyth St., SW, - ite 23T85 Atlanta, Georgia 30303-3415
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TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 l l
ANNUAL REPORTS TO THE NUCLEAR REGULATORY COMMISSION JANUARY 1 - DECEMBER 31, 1997 DOCKET NUMBERS 50-327 AND 50-328 LICENSE NUMBERS DPR-77 AND DPR-79 i
I
s 8 SEQUOYAH NUCLEAR PLANT 1997 ANNUAL REPORTS TABLE OF CONTENTS Page Preface ..................................... 1 Occupational Exposure Data .................. 2 Diesel Generator Reliability Data ........... 5 Reactor Coolant System Specific Activity Analysis ........................... 11
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SEQUOYAH NUCI. EAR PLANT (SQN)
UNITS 1 AND 2 1997 ANNUAL REPORTS PREFACE The following are descriptions of the items contained in this report. ;
i Occupational Exposure Data Enclosed is the exposure data for personnel at SON that received greater than 100 millirem between January 1 and December 31, 1997.
Exposure data for special maintenance is based on the following activities:
- Hanger Modifications
- Repair Air Operated Solenoid Valve 2-FCV-62-69
- Installation of In-Mast Fuel Sipping Equipinent
- Installation of Articulated Arms for Reactor Coolant Pump (RCP)
Seal Work
- RCP Platform Modifications
- Pressurizer Tailpipe Modifications
- Seal Water Flcw Transmitter Change Outs !
- Flexible Conduit Replacement )
- Replace Feedwater Nozzle Transition Pieces
- Control Rod Drive Mechanism Duct / Shroud Modification
- Ice Condenser Floor Modificatior.s
- Inspect Canopy Seal Welds for Leakage
- Reactor Vessel Stud Repair
- Electrical Penetration Replacements
- Pressurizer Manway Modification Diesel Generator (DG) Reliability Data The reliability data for the SON 6900-volt emergency DGs is enclosed l in accordance with Technical Specification (TS) 6.9.2.2.
Reactor Coolant System (RCS) Specific Activity Analysis (Specific Iodine Isotopic Activity Concentration and/or DEI-131 Determination)
During 1997, there were no specific iodine activity results of Unit 1 or Unit 2 RCSs exceeding the limits of TS 3.4.8.a (1.0 mci /gm) during either power operation or reactor shutdown and/or start-up.
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e SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 l DIESEL GENERATOR RELIABILITY DATA REPORT )
J This report is submitted to comply with TS Requirement 6.9.2.2 ,
for an annual data report for DG reliability.
The 6.9-kV DGs at SON serve as the onsite Class 1E power source.
Surveillance requirements (SRs) of the TSs that demonstrate operability of the DGs are accomplished by the routine performance of the following Surveillance Instructions (sis):
1 1-SI-OPS-082-007.A, " Electrical Power System - DG 1A-A" l 1-SI-OPS-082-007.B, " Electrical Power System - DG 1B-B" 2-SI-OPS-082-007.A, " Electrical Power System - DG 2A-A" 2-SI-OPS-082-007.B, " Electrical Power System - DG 2B-B" 0-SI-OPS-082-007.0, " Diesel Generator Operability Verification"
!4 1-SI-OPS-082-026.A, " Loss of Offsite Power with Safety Injection - DG 1A-A Containment Isolation Test" 1-SI-OPS-082-026.B, " Loss of Offsite Power with Safety Injection - DG 1B-B Containment Isolati ri Test" 2-SI-OPS-082-026.A, " Loss of Offsite Power with Safety Injection - DG 2A-A Containment Isolation Test" 2-SI-OPS-082-026.B, " Loss of Offsite Power with Safety i Injection - DG 2B-B Containment Isolation Test" SI-102 Series documents the performance of vendor recommended maintenance.
The information listed below is a tabulation of DG testing data taken from 0-SI-OPS-082-007.M, " Diesel Generator Surveillance Frequency." The data was taken from testing p.rformed during the l period of January 1 through December 31, 1997. " Valid Test" and '
" Invalid Test" are defined in accordance with the criteria established in Regulatory Guide 1.108, Revision 1, August 1977.
START VALID VALID INVALID INVALID DG DEMANDS TESTS FAILURES TESTS FAILURES !
/ DG STARTS 1A-A 34 / 43 16 0 27 2 1B-B 27 / 32 14 0 18 1 2A-A 33 / 46 20 2 26 0 2B-B 30 / 39 16 0 23 1 TOTALS 124 / 160 66 2 94 4 i Two valid failures and four invalid failures occurred in the calendar year of 1997. The following is a description of each event:
DG 1A-A -. Invalid Failure - 03/23/97 - Start 1307 - Test No. N/A l
- Failure of the Droop Relay (DR)
During the performance of 1-SI-OPS-082-026.A, DG 1A-A was paralleled to the grid and loaded to approximately 4840 kW and 2.4 MVAR. Following a very short time frame into the test, an odor of heated electrical insulation was detected. Visual inspection revealed smoke trailing from !
the reset coil of the DR relay. DG 1A-A was removed from service for troubleshooting / repair. The performance of 1-SI-OPS-082-026.A was continued following replacement of tue DR and the associated post maintenance test.
The DR is utilized to place the generator voltage j regulator in the unit mode (operate position of the DR) or droop mode (reset position of the DR). The emergency mode ,
for the relay is in the operate position. The DR is a Westinghouse Electric Corporation MG-6 auxiliary relay.
Referencing Westinghouse document I.L.41-753.1K, visual inspection of the installed DR revealed heavy oxidation on the edge of the latch plate and the shoulder of the latch screw resulting in the required reset force to exceed the capability of the reset coil.
The DG would have performed it's intended safety function since the operate position of the DR is the emergency mode and does not require the reset coil to achieve the operate position.
i' DG 1A-A - Invalid Failure - 05/21/97 - Start 1323 - Test No. N/A
- Failure to Control Output Voltage During performance of 1-SI-OPS-082-007.A, when the 86 LOR was reset, the generator output voltage increased to approximately 9000-volt ac. When the 86 LOR is in the tripped (emergency) state, a Voltage overshoot Reduction j Device (VORD) is connected to the generator field circuit to suppress high excitation during transient conditions by clipping the excitation voltage. Voltage regulator failure can be obscured by the action of the VORD during emergency operation. Correct voltage regulator operation during testing or emergency operation can be determined by observing control current in the range of 1.0 to 2.5 amps while the 86 LOR is in the tripped state.
Preliminary troubleshooting did not reveal any problems with the voltage regulator or 86 LOR. A decision was made f
l to replace the voltage regulator card since electronic I devices can operate intermittently providing similar
. problems. During the voltage regulator card replacement, a broken panel wire at the voltage regulator connection block (probably occurred during the voltage regulator card replacement) was identified and corrected.
The original voltage regulator card was returned to Bassler Electric Corporation for testing. No problem was identified with any component on the card. The 86 LOR had been replaced because of a latching spring problem approximately one month before the occurrence. The 86 LOR is HEA design with self-wiping contacts. Since minimal trip / reset operations of the new 86 LOR had been performed, it was deduced that high resistance existed on the 86 LOR contact associated with the voltage regulator Motor Operated Potentiometer (MOP) circuitry since no other problems were identified. The contact high resistance would have been unknowingly corrected during troubleshooting activities because of multiple operations of the 86 LOR.
During monthly surveillance testing, the voltage regulator control current is observed by the system engineer to be in the range of 1.0 to 2.5 amps while the 86 LOR is in the tripped (emergency) state confirming the voltage regulator is operating properly with the VORD enabled. The monthly surveillance procedures are being revised for the voltage regulator control current to be observed by the Operations staff while the 86 LOR is in the tripped state.
Based on the vendor evaluation of the voltage regulator ,
card and adequate output voltage while the 86 LOR was tripped, the DG would have performed the intended safety function.
DG 1B-B - Invalid Failure - 04/02/97 - Start 1251 - Test No. N/A
- Imbalance Relay Operation !
l During the monthly performance of 1-SI-OPS-082-007.B, the DG tripped on a phase imbalance relay operation while increasing load from 1,000 kW to 2,000 kW. The setting of the phase imbalance relay was verified with no problem identified. DG 1B-B was paralleled to 6.9-kV Shutdown Board 1B-B while the output voltage and load was i monitored. DG 1B-B was tripped again by a phase imbalance '
relay operation at approximately 1.5 mW. Troubleshooting checked the integrity of the emergency feeder breaker to 6.9-kV Shutdown Board 1B-B, DG control functions,
'4 generator stator windings, and generator excitation system with.no problems identified. DG 1B-B was paralleled to 6.9-kV Shutdown Board 1B-B and the load applied in small incremental values. The load was increased to approximately 4200 kW without tripping on a phase imbalance. Based on the successful operation of DG 1B-B with the incremental. loading technique, DG 1B-B was again paralleled to 6.9-kV Shutdown Board 1B-B and_the load increased using similar ramp rates as utilized in 1-SI-OPS-082-007.B with no problems identified. On April 05, 1997, DG 1B-B was declared operable based on the proven loading capability and successful performance of 1-SI-OPS-082-007.B with no problems identified with any aspect of the DG- .
On April 06, 1997, a voltage balance problem was identified on several of the plant auxiliary ac boards.
The problem was determined to be a single phase condition on 6.9-kV Start Bus Breaker 1614, which is the alternate supply for 6.9-kV Start Bus 1A. 6.9-kV Start Bus 1A was transferred to breaker 1514 and the voltage balance problem was corrected. Visual inspection of the main and auxiliary contacts on breaker 1614 revealed indications of excessive overheating on two of the three poles.
The DG would have performed the intended safety function since the defective breaker is not included in the emergency power supply system.
DG 2A-A - Valid Failure - 02/13/97 - Start 1437 - Test No. 354 -
Governor / Actuator failure During approximately the last thirty minutes of the post maintenance test of a 4840-kW, two-hour load run, the Governor Actaator Difference Alarm initiated repeatedly.
The governor actuator on engine No. 2 appeared sluggish.
Troubleshooting confirmed sluggish response of the actuator on engine No. 2 as it approached normal operating temperature. Equipment failure analysis of the governor actuator by Power Control Systems identified a blister on the inside surface of the pilot valve's positioning coil.
The reduced clearance resulted in high frictional forces, and thus the sluggish actuator response. Power Control Systems theorized the root cause of the blister to be exposure of the coil circuit to a high voltage spike.
Because System Engineering could not identify how the ,
circuit could have been exposed to high voltage, the l defective coil was sent for additional analysis to Failure Prevention International (FPI). FPI performed a root cause analysis for_TVA-SQN to determine what caused the blister on the pilot valve positioning coil. FPI
. . determined that the probable cause was a small void that formed during manufacturing. Over a period of time, oil intrusion into the void with heating / cooling cycles from equipment operation resulted in separation of the potting compound from the pilot. valve positioning' coil. and reduction of the internal diameter of the pitot valve positioning coil. The findings concluded the most probable cause for the blister on the internal diameter of the pilot valve positioning coil was defective workmanship in the application and subsequent adhesion of the potting compound to the pilot valve positioning coil. Research into FPI files and other databases did not reveal any similar occurrences that were documented.
FPI recommended the failure be considered an' isolated event.
The DG could have failed to deliver its rated electrical load due to overloading of engine _No. 1 if the actuator pilot piston had bound in a low power. position on engine No. 2. The DG was delivering 110 percent of its continuous rating without exceeding the cylinder or turbocharger exhaust temperature limits at the time of discovery.
DG 2A-A -Valid Failure - 07/02/97 - Start 1461 - Test No. 361 -
Stator Winding Failure During the performance of 2-SI-OPS-082-007.A, the generator tripped on device 50 (instantaneous overcurrent) and 87 (current differential) relay operation 24 minutes into the loaded run at 4050 kW. Troubleshooting revealed a fault had occurred between an A-phase series electrical connection and a C-phase line side terminal connection.
The fault was directly attributed to inadequate installation of support ties during the pigtail cable replacement on DG 2A-A in February 1997, and is considered a Maintenance Preventable Functional Failure (MPFF) .
The DG would have tripped and locked out on the differential relay operation had the winding failed during a postulated accident.
i DG 2B-B - Invalid Failure - 06/12/97 - Start 1150 - Test No. N/A
- Trip on Overcurrent The Emergency Feeder Breaker tripped on Instantaneous Overcurrent (IOC) relay operation at the instant when DG
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( was paralleled to 6.9-kV Shutdown Board 1B-B during performance of 1-SI-OPS-082-007.B. The IOC relay setpoint
. .is adjusted to actuate at 600 amps primary. The basis for the setpoint is to ensure the DG will be separated from 6.9-kV Shutdown Board 1B-B during perio'dic test conditions if the connection to the 6.9-kV unit board is closed and a loss of offsite power occurs. The 6.9-kV shutdown board would incur a blackout condition, and the DG would l
automatically reconnect to the 6.9-kV shutdown board in i
emergency mode of operation. The IOC relay is not active l in the control circuits when the DG is in emergency mode of operation.
The problem was determined to be inadequate instructions provided to the operator at the controls (OAC) for paralleling the DG to the 6.9-kV shutdown board. If the DG is paralleled to the 6.9-kV shutdown board at five minutes before the 12 o' clock position, the inrush current detected by IOC relay is in excess of the 600 amp setpoint. The instructions for the OAC have been revised to require the initiation of the breaker closure signal at approximately the 12 o' clock position on the synchroscope.
The DG would have performed the intended safety function since the IOC relay is not active in the control circuits when the DG is in the emergency mode and the DG runs in the asynchronous mode during an accident condition.
The data indicates a total of 124 DG start demands with two valid failures to carry load on the same DG. The 160 total starts provide an average of 40 starts per DG for the year. These facts give a strong indication that the DGs will perform when required. i I
SON recognizes the importance of reducing the number of DG starts and continues to actively work to reduce engine starts. Through procedure revisions and modifications to the DGs, the average starts per DG were reduced from 170 in 1988 to 27 in 1996. The 1997 average starts per DG have increased to 40 based on the DG two/four year maintenance being completed, an increase in DG valid / invalid failures and associated troubleshooting /PMT starts, and required increased frequency surveillance testing for i DG 2A-A. l SON will continue efforts to keep DG starts as low as possible to enhance engine life and DG reliability.
o' SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 REACTOR COOLANT SYSTEM SPECIFIC ACTIVITY ANALYSIS (Specific Iodine Isotopic Activity Concentration and/or DEI-131 Determination)
During 1997, there were no specific lodine activity results of Unit 1 or Unit 2 RCSs exceedi1M the limits of TS 3.4.8.a (1.0 mci /gm) during either power operation or reactor shutdown-and/or start-up.
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