ML18152A442
| ML18152A442 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 09/14/1992 |
| From: | Buckley B Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9209240231 | |
| Download: ML18152A442 (33) | |
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UNITED STATES
- NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20556 September 14, 1992 Docket Nos. 50-280 and 50-281 LICENSEE: -
Virginia Electric and Power Company FACILITIES:
Surry Power Station, Units 1 and 2
SUBJECT:
Meeting Summary of August 5, 1992 A meeting was held with representatives of Virginia Electric and Power Company (VEPCO) in Rockville, Maryland on August 5, 1992.
The purpose of the meeting was to discuss actions taken by VEPCO regarding the accumulation of gas in certain safety-related piping at the Surry Power Station. The list of attendees and meeting handout are enclosed.
VEPCO personnel had observed pressure spikes in the low-head safety injection (LHSI} piping during the quarterly testing of these pumps.
Additional test*
instrumentation was installed in March 1992 and several tests were conducted in an attempt to identify the cause of the pressure spikes.
However, the test results were inconclusive, yielding inconsistent pressure spikes at different*
times following the starting of the LHSI pumps.
Venting of the LHSI piping indicated the absence of gas.
In July 1992, Surry, Unit 2 was brought to a cold shutdown to refurbish the pressurizer safety valves. Testing of the LSHI pumps during this shutdown again identified pressure spikes. Again, various.
pipes were vented and approximately 43 cubic feet (STP) were found in the LHSI pump discharge piping just upstream of the closed crossover valve to the high-head safety injection (HHSI} pumps.
VEPCO personnel indicated that the section of pipe where the 43 cubic feet of gas had accumulated had not previously been expected to be a gas collection point, i.e., the anticipated piping runs where ~as accumulation was thought tci most likely occur were*
downstream of the closed crossover valve to HHSI pumps.
Having*identified this new gas collection point, VEPCO vented the same piping_
runs on Surry, Unit 1, which was operating at 100 percent power, and initially found no gas present, but found approximately 2 cubic feet at a later venting.
Check valve back-leakage (0.1-0.2 gpm) to the refueling water storage tank is judged by VEPCO to be the principal contributor to gas accumulation in the above cited sections of pipe.
VEPCO contracted with Westinghouse Corporation to perform analyses to determine HHSI pump operability using the as found conditions in Surry, Unit 2.
The Westinghouse analyses indicated that 43 cubic feet of gas would result in a 3.93% void fraction of fluid reaching the suction of HHSI pumps.
The conclusions reached in the pump analyses that since the void fraction was less than 5% the HHSI pump(s) would have continued to operate with no significant reductions in performance during the time period the void is passed through the pumps.
f9209240231 9209'i4~/1 i
PDR. ADOCK 05000280 i
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- September 14, 1992 Compensatory measures being taken by VEPCO includes venting each shift at both Surry units, increasing the number of locations being vented, analyzing gas samples to identify gas source, taking precautions to prevent introduction of air into the various systems following valve maintenance/testing, monitoring the refueling water storage tank level, and using ultrasonic equipment to locate and measure the volume of gas that may accumulate.
Additional information is delineated in the enclosed meeting handout.
Enclosures:
- 1.
List of Attendees
- 2.
Meeting Handout cc w/enclosures:
See next page Distribution w/enclosures See next page OFC NAME DATE
't//(/92 OFFICIAL RECORD COPY FILENAME: C:\\WP\\WPDOCS\\SRMTS (Original Signed By)
Bart C. Buckley, Project Manager Project Directorate II-2 Division of Reactor Projects - I/II Office of Nuclear Reactor Regulation
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- 1,,
Virginia Electric and Power Company cc:
Michael W. Maupin, Esq.
Hunton and Williams Post Office Box 1535 Richmond, Virginia 23212 Mr. Michael R. Kansler, Manager Surry Power Station Post Office Box 315 Surry, Virginia 23883 Senior Resident Inspector Surry Power Station U.S. Nuclear Regulatory Commission Post Office Box 166, Route 1 Surry, Virginia 23883 Mr. Sherlock Holmes, Chairman Board of Supervisors of Surry County Surry County.Courthouse Surry, Virginia 23683 Dr. W. T. Lough Virginia State Corporation Commission Division of Energy Regulation Post Office Box 1197 Richmond, Virginia 23209 Regional Administrator, Region II U.S. Nuclear Regulatory Commission 101 Marietta Street N.W., Suite 2900
. Atlanta, Georgia 30323
- s C.M.G. Buttery, M.D., M.P.H.
State Health Commissioner Office of the Commissioner Virgini*a Dep~rtment af Health P. 0. Bo*x 2448 * -* *.. * ** * * * * * *..
Richmond, Virginia 23218 Surry Power Station Attorney General Supreme Court Building 101 North 8th Street Richmond, Virginia 23219 Mr. M. L. Bowling, Manager Nuclear Licensing & Programs Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Blvd.
Glen Allen, Virginia 23060 Mr. W. L. Stewart Senior Vice President - Nuclear Virginia Electric and Power Company Innsbrook Technical Center 5000 Dominion Blvd.
Glen Allen, Virginia 23060
Bart Buckley Mil ton Shyml ock Gus Lainas Mark Caruso Herb Berkow Bruce Shriver David L. Benson Alan Price M. L. Bowling*
Eric W. May T. J. Gerl owski L. L. Gundrum Frank Grubelich Vern Hodge Michael Markley Narvaez Stinson Jack Ramsey Kaz Campe David Sommers August 5. 1992 List of Attendees NRC/NRR NRC/RII NRC/NRR NRC/NRR NRC/NRR ENCLOSURE I Virginia Power/Nuclear Safety Virginia Power/Engineering Virginia Power/Surry Virginia Power/Nuclear Licensing and Program Virginia Power/Engineering H/Fluid Systems Design NRC/AEOD NRC/EMEB NRC/Generic Communications NRC/LPEB NRC/NRR NRC/NRR NRC/NRR Virginia Power/Corporate Licensing
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DISTRIBUTION LIST FOR MEETING
SUMMARY
OF AUGUST 5, 1992 Docket File NRC & Local PDRs PDII-2 Reading T. Murley/F. Miraglia J. Partlow S. Varga G. Lainas H. Berkow B. Buckley D. Miller OGC E. Jordan M. Shymlock, RII M. Caruso L. L. Gundrum, AEOD F. Grubelich, EMEB V. Hodge M. Markley, LPEB N. Stinson J. Ramsey, OEAB K. Campe ACRS ( 10)
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- z UJ VIRGINIA POWER NRC TECHNICAL MEETING ON GAS ACCUMULATION AUGUST 5, 1992
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VIRGINIA POWER INTRODUCTION M. *L. BOWLING MANAGER, NUCLEAR LICENSING & PROGRAMS
NRC TECHNICAL MEETING ON GAS ACCUMULATION AUGUST 5, 1992 AGENDA INTRODUCTION DISCUSSION OF GAS ACCUMULATION SYSTEM DESCRIPTION CHARACTERIZATION CURRENT STATUS OPERATING EXPERIENCE REVIEW INDUSTRY REVIEW VIRGINIA POWER ACTIONS ENGINEERING ASSESSMENT HHSI PUMP OPERABILITY OTHER CONSIDERATIONS POSSIBLE SOURCES CONCLUSION M. L. BOWLING J. A. PRICE B. L. SHRIVER D. L. BENSON/ E.W. MAY M. L. BOWLING
VIRGINIA POWER DISCUSSION OF GAS ACCUMULATION e
J. A. PRICE ASSISTANT STATION MANAGER NUCLEAR SAFETY & LICENSING
SAFETY INJECTION SYSTEM DESCRIPTION HIGH*HEAD SAFETY INJECTION (HHSI) 2 TRAINS PUMPS CROSS-TIED TO OPPOSITE UNIT RWSTs CROSS-TIED USED AS CHARGING PUMPS IN eves LOW HEAD SAFETY INJECTION {LHSI) 2 TRAINS NOT USED IN NORMAL OPERATION NOT USED IN AHR SYSTEM PASSIVE ACCUMULATORS 1 PER LOOP MAINTAINED AT 600 PSIG 975 CUBIC FEET {EACH) OF BORATED WATER 425 CUBIC FEET (EACH) OF NITROGEN GAS
RWST A
B LT-C CS-100 D
MOV-21150 TV-81-202A 454 From Conllllnmanl Sump Frum VCT Reclrculadon ToRWST
~SI Pumps To Normal
~'?J:.l.
(LoopB)
MOV-2842 To
- ACS l--!fl..J.-l-l-+H-..Lt:,<2-~~~---:r-~~-r--.1-r-;.._.,...~Co~
FE-SI 200A SAFETY INJECTION SYSTEM DIAGRAM Legs To RCS
- CHARACTERIZATION & CURRENT STATUS COMPENSATORY ACTIONS IN PLACE
- PERIODIC VENTING AND SAMPLING
- FREQUENCY
- METHOD
- ACTIONS IF GAS IS DETECTED OBTAIN SAMPLE FOR ANALYSIS OBTAIN RELEASE PERMIT RELEASE VIA ROTAMETER EVALUATION CONCLUSIONS
- . CHECK VALVE BACK-LEAKAGE PRINCIPAL CONTRIBUTOR
- , ENGINEERING ASSESSMENT PERFORMED ~ NO OPERABILITY CONCERNS
VIRGINIA POWER OPERATING EXPERIENCE REVIEW 8
8.- L. SHRIVER
- DIRECTOR, CORPORATE NUCLEAR SAFETY
POTENTIAL GAS BINDING OF HHSI PUMPS NRC DOCUMENT PLANT SOURCE OF GAS IN 88-23 FARLEY.
VCT - NORMAL CHARGING IN 88-23 S1 SOUTH TEXAS RWST - SI SUCTION LINE IN 88-23 S2 TROJAN VCT - NORMAL CHARGING IN 88-23 S3 SEQUOYAH VCT - NORMAL CHARGING
VIRGINIA POWER RESPONSE TO IN 88-23 ENGINEERING REVIEW TO DETERMINE LOCATIONS FOR POTENTIAL GAS ACCUMULATION ULTRASONIC MEASUREMENTS TO DETECT GAS IN HHSI PUMP SUCTION PIPING PIPING CONTAINING GAS VENTED WHERE POSSIBLE ENGINEERING EVALUATION OF:
NEED FOR ADDITIONAL VENTS APPLICABILITY TO RESIDUAL HEAT REMOVAL, SERVICE WATER, AUXILIARY FEEDWATER AND COMPONENT COOLING WATER SYSTEMS
VIRGINIA POWER RESPONSE TO IN 88-23
{cont'd)
ADDITIONAL VENT VALVES PROVIDED ON EACH UNIT.
VALVES WERE ADDED IN THE FOLLOWING LOCATIONS AT SURRY:
SUCTION LINE FROM RWST LHSI CROSS-TIE TO HHSI LHSI PUMP DISCHARGE PROCEDURES REVISED TO VENT PIPING.
SURRY PROCEDURES REQUIRE VENTING OF:
LHSI PUMP DISCHARGE AND LHS~ TO HHSI CROSS-TIE MOV - QUARTERLY.
LHSI PUMP DISCHARGE AND DOWNSTREAM HIGH POINT VENT - FOLLOWING MAINTENANCE
VIRGINIA POWER RESPONSE TO IN 88-23
{cont'd)
ANALYSIS OF GAS ACCUMULATION MEASUREMENT OF ACCUMULATED GAS SPECIAL SI FLOW TESTS WITH GAS IN SUCTION LINES LIMITS FOR ACCUMULATED GAS VOLUME ESTABLISHED INPO NETWORK NOTIFICATION PROVIDED LERs SUBMITTED
i VIRGINIA POWER EVALUATION OF GAS ACCUMULATION e
1 D. L. BENSON / E. W. MAV MANAGER, NUCLEAR ENGINEERING SUPERVISOR, MECHANICAL ENGINEERING
EVALUATION OF GAS ACCUMULATION CH/HHSI PUMP LHSI PUMP DISCHARGE PIPING INJECTION TO THE RCS INSTRUMENTATION POSSIBLE SOURCES THERMAL STRATIFICATION
EVALUATION OF GAS ACCUMULATION
{cont'd)
CH/HHSI PIUMP
- LOCATION OF GAS ACCUMULATION IN SYSTEM 8"-Sl-292-153 - CROSSOVER FROM "A" LHSI PUMP TO CH/HHSI PUMP SUCTION HEADER HIGHEST POINT IN THIS PORTION OF THE SYSTEM APPROXIMATELY 175 FEET OF PIPING BETWEEN ACCUMULATED GAS AND CH/HHSI PUMPS NUMEROUS ELBOWS AND TEES
- 4 DOWNWARD FLOWING VERTICAL PIPING SECTIONS
- VOLUME OF ACCUMULATED GAS 43.7 CUBIC FEET (STP) MEASURED WITH A ROTAMETER WHILE VENTING
- . 21.3 CUBIC FEET ACTUAL VOLUME MEASURED WITH UT
. EQUIPMENT UNDER HEAD OF RWST OF 19.8 PSIG (- 50 CUBIC FEET AT STP)- USED FOR ASSESSMENT
e
EVALUATION OF GAS ACCUMULATION
{cont'd)
CH/HHSI PUMP (cont'd)
- ASSUMPTIONS OF ASSESSMENT LOWEST PRESSURE IN LHSI PUMP DISCHARGE (MAXIMIZE VOLUME OF ACCUMULATED GAS)
SINGLE LHSI PUMP OPERATING LHSI PUMP SUCTION FROM CONTAINMENT AT MINIMUM PRESSURE HIGHEST FLOW RATE (INCREASE TENDENCY TO SWEEP GAS)
SINGLE CROSSOVER LINE USED (MOV-28638 FAILS CLOSED)
TWO CH/HHSI PUMPS OPERATING GAS ACCUMULATION IN 8!'-Sl-292-153 ONLY A CONCERN DURING SI RECIRCULATION PHASE
EVALUATION OF GAS ACCUMULATION (cont'd)
CH/HHSI PUMP (cont'd)
METHODOLOGY
.VOLUME OF.ACCUMULATED GAS AT MINIMUM LHSI PUMP DISCHARGE PRESSURE CALCULATED: 8.1 CUBIC FEET TURBULENCE AT ELBOW TO FIRST DOWNCOMER BREAKS UP MOST OF BUBBLE SMALL BUBBLES CARRIED DOWN VERTICAL LEG (< 1/4" DIA)
LARGE BUBBLES RISE AGAINST FLOW (> 1" DIA)
SWEEPING OF GAS OCCURS OVER APPROXIMATELY 2 MINUTES FLOW IN HORIZONTAL PIPING IS SUFFICIENT TO SWEEP SMALL BUBBLES ADDITIONAL VERTICAL DOWN FLOWING SECTIONSA ELBOWS AND TEES.BREAK UP GAS BUBBLES THAT MIGHT vOALESCE IN HORIZONTAL SECTIONS VO!D FRACTION AT PUMP SUCTION CALCULATED: - 3.9°/o VO~D FRACTIONS< 5°/o ACCEPTABLE FOR LONG TERM PUMP OPERATION I
EVALUATION OF GAS ACCUMULATION
{cont'd)
CH/HHSI PUMP (cont'd)
- ADDITIONAL CONSIDERATIONS CH/HHSI SUCTION BOOSTED BY LHSI PUMP - MINOR PERFORMANCE DEGRADATION IS NOT A CONCERN NO ACCUMULATION OF GAS IN PUMP SEAL REGION METHODOLOGY IS BOUNDING FOR OTHER POSSIBLE CASES SINGLE CH/HHSI PUMP OPERATION BOTH CROSSOVER LINES FLOWING BOTH LHSI PUMPS OPERATING
- CONCLUSION CH/HHSI PUMPS REMAINED OPERABLE WITH NO SIGNIFICANT PERFORMANCE DEGRADATION IN SPITE OF THE EXISTENCE OF THE IDENTIFIED GAS ACCUMULATION
EVALUATION OF GAS ACCUMULATION (cont'd)
LHSI PUMP DISCHARGE PIPING GAS ACCUMULATION SUSPECTED DUE TO SLOW PRESSURIZATION AND PRESSURE TRANSIENT DURING PUMP TESTING SEARCH LED TO DISCOVERY/VENTING OF GAS IN 8"-Sl-292-153 EVALUATION OF EFFECT OF PRESSURE TRANSIENT ON LOW PRESSURE PORTION OF THE SYSTEM FOUND TO BE ACCEPTABLE SUBSEQUENT TESTING SHOWED MODERATE PRESSURE TRANSIENT ON STARTUP OF THE PUMP NO UNUSUAL SOUND OR PIPE MOVEMENT NOTED DURING ANY TEST r
- EVALUATION OF GAS ACCUMULATION
{cont'd)
- . INJECTION TO THE RCS
- 200 CUBIC FEET OF GAS (AT STP) ANALYZED SMALL BREAK LOCA LHSI INJECTION/RECIRC MODE TRANSFER OCCURS LONG AFTER PCT IS REACHED ACCUMULATION IN THE RCS AND DISPLACEMENT OF WATER INJECTED HAVE NEGLIGIBLE EFFECT
EVALUATION OF GAS ACCUMULATION (cont'd)
INJECTION TO THE RCS (cont'd)
LARGEBREAKLOCA ACCUMULATORS INJECT IMMEDIATELY FOLLOWED BY LHSI 200 CUBIC FEET OF GAS INSIGNIFICANT COMPARED TO 47,000
- CUBIC FEET (STP) OF NITROGEN INJECTED FROM ACCUMULATORS ANALYSIS METHODOLOGY ASSUMES ACCUMULATOR NITROGEN IS SWEPT THROUGH RCS INTO CONTAINMENT ACCUMULATED GAS WOULD BEHAVE SIMILARLY AND HAVE r
NEGLIGIBLE IMPACT ON CONTAINMENT ANALYSIS e
AMOUNT OF WATER DISPLACED BY GAS IS ALSO SMALL THE ACCUMULATION OF GAS FOUND DID NOT APPROACH 200 CUIBIC FEET
EVALUATION OF GAS ACCUMULATION
{cont'd)
INSTRUMENTATION SAFETY INJECTION FLOW INSTRUMENTS IN CONTAINMENT ARE DESIGNED TO BE SELF-VENTING WHERE AIR HAS CAUSED ERRONEOUS INDICATION OF FLOW, THE CONDITION HAS RETURNED TO NORMAL OVER A SHORT PERIOD OF TIME, INDICATING THAT SELF-VENTING IS EFFECTIVE UNDER ACTUAL FLOW CONDITIONS, NO IMPACT IS EXPECTED ON INSTRUMENTATION DUE TO GAS* ACC'-lMULATION
EVALUATION OF GAS ACCUMULATION
{cont'd)
POSSIBLE SOURCES TESTING CHECK VALVE TESTING SEQUENCE CAN LEAVE MODERATE AMOUNTS OF GAS IN LHSI AND HHSI SYSTEM LOW HEAD SAFETY INJECTION PUMP TESTING CAN RELOCATE ACCUMULATED GAS WITHIN THE SYSTEM
EVALUATION OF GAS ACCUMULATION (cont'd)
POSSIBLE SOURCES {cont'd)
INLEAKAGE INLEAKAGE TO SAFETY INJECTION SYSTEM FROM REACTOR COOLANT AND CHARGING SYSTEMS WILL RESULT IN GAS ACCUMULATION GAS SAMPLES INDICATE THAT CURRENT INLEAKAGE TO RWST IS FIROM THE RCS OR FROM THE CHARGING/HIGH HIGH SAFETY INJECTION SYSTEM TOTAL IN LEAKAGE TO RWST IS APPROXIMATELY 0.18 GPM BACK LEAKAGE HAS BEEN CONFIRMED THROUGH SI CHECK VALVES AT "C" LOOP*
A VENTING AND SAMPLING PROGRAM CONTINUES TO IDENTIFY POSSIBLE SOURCE{S) OF GAS
EVALUATION OF GAS ACCUMULATION
{cont'd)
THERMAL STRATIFICATION A CONCERN IF SOURCE OF GAS IS BACKLEAKAGE FROM RCS THROUGH LHSI SYSTEM INTERFACE CHECK VALVES
- HOT RCS WATER LEAKING INTO DEPRESSURIZED COOL SYSTEM
- VERSUS COLD WATER LEAKING INTO RCS
- - LEAKAGE ACROSS VALVE CAUSES SOME FLASHING AND TURBULENCE PIPING ARRANGED WITH SHORT VERTICAL AND HORIZONTAL PIPE RUNS NEAR RCS TIE-IN, THEN LONG VERTICAL LEG MIN~MIZES PIPING WHICH COULD BE EXPOSED TO
. STRATIFICATION
VIRGINIA POWER CONCLUSIONS M. -L. BOWLING MANAGER, NUCLEAR LICENSING & PROGRAMS
CONCLUSIONS ON GAS ACCUMULATION DOES NOT RENDER SI SYSTEM INOPERABLE POSES NO SIGNIFICANT SAFETY CONCERN FOUND IN A LOCATION NOT EXPECTED BY PREVIOUS OPERATIONAL EVENT REVIEWS VIRGIN!A POWER REVIEWS AND ACTIONS HAVE BEEN EXTENSIVE TO FULLY ADDRESS KNOWN ISSUES DO NOT EXPECT FUTURE SIGNIFICANT GAS ACCUMULATION PERIODIC VENTING AND SAMPLING WILL BE CONTINUED SPECIAL ATTENTION, TO INCLUDE PROCEDURE ENHANCEMENT, WILL BE GIVEN TO MAINTENANCE EVOLUTIONS AND DURING STARTUPS