ML18153B084
| ML18153B084 | |
| Person / Time | |
|---|---|
| Site: | Surry, North Anna  |
| Issue date: | 09/26/1994 |
| From: | Ohanlon J VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| REF-PT21-94 94-521A, NUDOCS 9410040095 | |
| Download: ML18153B084 (11) | |
Text
e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 September 26, 1994 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNIT 2 Serial No.
NL&P/MAE:
Docket Nos.
License Nos.
94-521A RO 50-280/281 50-338/339 DPR-32/37 NPF-4/7 WRITTEN NOTIFICATION OF DEFECT IN ACCORDANCE WITH 10 CFR 21 In accordance with 1 O CFR 21.21, Virginia Electric and Power Company provided initial notification of a defect with the governor valves used with turbine-driven pumps manufactured by Dresser-Rand in our letter dated September 2, 1994 (Serial No.94-521 ). Although the initial notification letter satisfied the information requirements for thirty day reporting, we are providing this letter with the initial notification letter attached to formally address the written thirty day report requirement of 1 O CFR 21.21 (c)(3)(ii).
As stated in the initial notification, a Root Cause Evaluation is still ongoing.
Preliminary findings from this evaluation have identified differences between the original and replacement valve stem and carbon spacers that may be contributing to the observed increase in corrosion and mineral deposits that are accumulating on the replacement governor valve stems. If our evaluation definitively identifies a root cause or provides findings that are significantly different from the preliminary information provided, that information will be promptly forwarded to you.
Corrective actions, as stated in the initial notification, are continuing.
Additional corrective actions, if necessary, will be based on the completion of the Root Cause Evaluation.
Should you have any questions or require additional information, please contact us.
Very truly yours,
~?CW~
James P. O' Hanlon Senior Vice President - Nuclear Attachment
e cc:
Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. R. D. McWhorter NRC Senior Resident Inspector North Anna Power Station Mr. R. M. Loughin Manager Navy Nuclear Product Engineering Dresser-Rand Steam Turbines, Motors and Generator Division 37 Coats Street Wellsville, N. Y. 14895
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VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 September 2, 1994 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Gentlemen:
VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNIT 2 Serial No.
NL&P/MAE:
Docket Nos.
License Nos.94-521 RO 50-280 50-281 50-338 50-339 DPR-32 DPR-37 NPF-4 NPF-7 INITIAL NOTIFICATION OF DEFECT IN ACCORDANCE WITH 10 CFR 21 Virginia Electric and Power Company has identified a trend in the number of steam driven auxiliary feedwater pump overspeed trips during periodic tests. In accordance with 1 O CFR 21.21, the following information is provided as initial notification of an existing defect. A written report will be provided by September 30, 1994.
- 1. Name and address of the individual or individuals informing the Commission.
Mr. A. F. Saunders Vice President - Nuclear Operations Virginia Electric and Power Company 5000 Dominion Boulevard Glen Allen, Virginia 23260
- 2. Identification of the facility, the activity, or the basic component supplied for such facility or such activity within the United States which fails to comply or contains a defect.
Surry Power Station Units 1 and 2 North Anna Power Station Unit 2 Steam Driven Auxiliary Feedwater Pump Governor Valve
- 3. Identification of the firm constructing the facility or supplying the basic component which fails to comply or contains a defect.
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- Dresser-Rand Steam Turbines, Motors and Generator Division 37 Coats Street Wellsville, N.Y. 14895 Attn: Mr. R. M. Loughin Manager Navy Nuclear Product Engineering (716) 596-3343
- 4. Nature of the defect or failurE;l to comply and the safety hazard which is created or could be created by such defect or failure to comply.
Virginia Electric and Power Company (Virginia Power) has implemented vendor recommended practices provided in the technical manual and the Dresser Industries general information letter dated March 24, 1993 (attached).
This general information letter addressed corrosion related valve stem binding.
Although we have implemented the vendor recommended practices, Virginia Power has identified a trend in the number of steam driven auxiliary feedwater pump overspeed trips during periodic tests. Since the trend was identified, the governor valve stems and carbon spacers have been replaced due to indications of corrosion related valve stem binding. Surry Unit 1 replacements occurred in December 1993 and May 1994.
Surry Unit 2 replacements occurred in January 1992, February 1994 and August 1994. North Anna Unit 2 replacements occurred in November 1993 and August 1994. North Anna Unit 1 has not recently replaced the governor valve stem and carbon spacers. Note that all of the Units with the exception of North Anna Unit 1 have experienced overspeed trips related to governor valve stem binding.
A Root Cause Evaluation is ongoing. Preliminary findings have identified the following:
- a. Corrosion and mineral deposits are accumulating faster than expected 011 the replacement governor valve stems. This accumulation may not allow the governor to move in the closed direction after the start of the turbine.
The turbine would then overspeed and trip rendering the auxiliary feedwater pump inoperable.
Based on metallurgical analysis the corrosion products are formed due to galvanic corrosion, crevice corrosion, and pitting corrosion. It has been identified that the graphite (carbon) spacers received from the Dresser-Rand Steam Turbines, Motors and Generator Division have approximately 1.29% sulfur as a contaminant. It has not been determined what form the sulfur is in or if it has accelerated the corrosion process.
- b. Three differences have been identified between the original and replacement valve stem and carbon spacers:
Nitride thicknesses (original 12-14 mills, replacement 4-5 mills)
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Percent of contaminates in carbon spacers (original essentially pure carbon, replacement approximately 1.29%)
Flatness of the end of the stem that slides in the plug (original flat on bottom, replacement has a manufactured recess).
- 5. The date on which the information of such defect or failure to comply was obtained.
July 29, 1994
- 6. In the case of a basic component which contains a defect or fails to comply, the number and location of all such components in use at, supplied for, or being supplied for one or more facilities or activities subject to the regulation in this part.
There are three steam driven auxiliary feedwater pumps which are affected by this notification. At Surry, there is one in each of the Unit 1 and 2 Main Steam Valve Houses and at North Anna there is one located in the Unit 2 Steam Driven Auxiliary Feedwater Pump House.
- 7. The corrective action which has been, is being, or will be taken; the name of the individual or organization responsible for the action; and the length of time that has been or will be taken to complete the action.
The corrective actions to ensure operability are based on the type of corrosion, observed corrosion rate and design of the steam supply piping. At North Anna and Surry Power Station pitting corrosion has been observed in the stem packing area. Surry is also experiencing corrosion build up near the gland seal leakoff area of the stem. In addition, the governor valve at Surry is the low point of the system, and the steam supply valves are approximately 4 feet from the governor valve. At North Anna the steam supply valve is greater than 100 feet from the governor valve. With the steam supply valve close to the governor valve, the ambient temperature of the governor valve is significantly warmer, which affects the corrosion rate.
Based on these factors, the corrective actions to ensure operability at each station are as follows:
Surry
- a. A maintenance procedure to stroke the.governor valve stem is performed weekly.
- b. Monitoring of the corrosion build up in the gland seal leakoff area is performed weekly.
- c. Monitoring of the amount of overshoot (RPM) during the monthly periodic test is performed.
North Anna
- a. The periodic maintenance procedure to stroke the governor valve stem is performed monthly for North Anna Unit 2. This is followed by running the steam driven turbine.
Additional corrective actions, if necessary, will be based on the completion of the Root Cause Evaluation.. This information will be transmitted to you in the required written report.
- 8. Any advice related to the defect or failure to comply about the facility, activity or basic component that has been, is being, or will be given to purchasers or licensees.
Virginia Power advises other licensees not to replace original equipment (stems, carbon rings, bushings and washers) until this issue is corrected. If these components have been replaced, the licensees should consider* 1) increased monitoring of initial turbine startup parameters and 2) replacement of the 41 O nitrided stainless steel valve stem with a chrome plated valve stem as discussed in the general information letter from Dresser Industries dated March 24, 1993 (attached).
. Should you have any questions or require additional information, please contact Mr.
M. L. Bowling, Manager Nuclear Licensing and Programs (804) 273-2699.
Very truly yours, rfZJJ~
R. F. Saunders Vice President - Nuclear Operations Attachment
cc:
Regional Administrator U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, N.W.
Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch NRC Senior Resident Inspector Surry Power Station Mr. R. D. McWhorter NRC Senior Resident Inspector North Anna Power Station Mr. R. M. Loughin Manager Navy Nuclear Product Engineering Dresser-Rand Steam Turbines, Motors and Generator Division 37 Coats Street Wellsville, N. Y. 14895
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- --DISPLAY OF RECORD 0489 Record Last Revised: 05/12/93 GENERAL INFORMATION INITIAL REPORT DATE: 03/24/93. IATEST REPORT DATE: 03/24/93 NRC ISSUE NUMBER:
0 REPORTING COMPANY: DRESSER INDUSTRIES ACTIVITY:
PRIMARY COMPONENT:
VALVE
- SUB COMPONENTS:
VALVE STEM PRIMARY MANUF.:
DRESSER INDUSTIUES SECONDARY MANUF.:
REFERENCES AFFECTED MODEL NUMBERS ZS GS NEQ904-5051-006 AFFECTED PLANTS/Ul1LI11ES UTILITIES:
ENTERGY OPERATIONS DUQUESNE LIGHT CO.
TENNESSEE VAllEY AlITHORI1Y CAROLINA POWER & LIGHT CO.
UNION ELECTRIC CO.
BALTIMORE GAS & ELECTRIC CO.
DUKE POWER CO.
IWNOIS POWER CO.
TEXAS trnLITIES ELECTRIC CO.
NEBRASKA PUBUC POWER DISTRICT FLORIDA POWER CORPORATION TOLEDO EDISON CO.
PACIFIC GAS & ELECTRIC CO.
AMERICAN ELECTRIC POWER SERVICE IOWA ELECTRIC UGHT & POWER CO.
GEORGIA POWER CO..
DETROIT EDISON CO.
CONNECTICtIT Y ANKE:E ATOMIC POWER CO.
PUBLIC SERVICE ELECTRIC & GAS CO.
CONSOLIDATED EDISON OF NEW YORK NEW YORK POWER AtrrHOR11Y ALABAMA POWER COMPANY WISCONSIN PUBUC SERVICE CORP.
COMMONWEAI.ni EDISON COMPANY PHILADELPHIA ELECTRIC.CO.
MAINE YANKEE ATOMIC POWER CO.
NORTiiEAST UI1IJ11ES NIAGARA MOHAWK POWER CORP.
VIRGINIA POWER ARIZONA PUBUC SERVICE CO.
CLEVELAND ELECTRIC IU.U.MINATING CO.. BOSTON EDISON CO.
-=--~~ -
=--~:;NSIN ELE~OWER CO.
NORTIIERN,ATES POWER CO.
SACRAMENTO MUNICIPAL unu1Y DISTRICT GULF STATES UI1UTIES
- *. SOUTHERN CALIFORNIA EDISON CO.
NEW HAMPSHIRE YANKEE LONG* ISLAND LIGHTING CO.
HOUSTON LIGHTING & POWER COMPANY FLORIDA POWER & UGHT CO.
PENNSYLVANIA POWER & LIGHT CO.
PORTI.AND GENERAL ELECTRIC CO.
VERMONT YANKEE NUCLEAR POWER CORP.
sourn CAROLINA ELECTRIC & GAS PLANTS:
ARKANSAS NUCLEAR ONE BRUNSWICK 1 BEA VER VAllEY BROWNS FERRY CAllA WAY CALVERT CUFFS CATAWBA 1 COOPER DlABLO CANYON HATCH HADDA.i\\1 NECK FITZPATRICK LASALLE MCGUIRE NINE MILE POINT PEACH BOTIOM POI!\\'T BEACH RANCHO SECO SAN ONOFRE HARRIS ST. LUCIE TROJAN SUMMER WATTS BAR CUNTON COMANCHE PEAK CRYSTAL RIVER DA VIS-BESSE COOK ARNOID FERMI 2 GRAND GOU:
. HOPE CREEK INDIAN POINT 2 FARLEY KEWAUNEE LIMERICK MAINE YANKEE MIUSTONE MONTICELLO NORTH ANNA PALO VERDE 1 PERRY PILGRIM PRAIRIE ISLAND QUAD CITIES RIVER BEND SALEM SEABROOK SEQUOYAH SHOREHAM SOUIH TEXAS PROJECT SURRY SUSQUEHANNA TIJRKEY POINT VERMONT YANKEE VOGTI.E WATERFORD WNP ZION REPORT TEXT DATED MARCH 24, 1993:
REFERENCE:
TERRY 1YPE GS AND ~
. AUXIUARY FEED PUMP DRIVERS/RCIC GOVERNOR VALVE STEM GENTI.EMEN:
WE ATTACHED HERETO A COPY OF A LETI'ER DATED MARCH 18, 1993 WHICH WAS SENT TO TiiE PI.ANlS IJSTED.
WE TRUST 1liAT TIIE ENCLOSED IS SELF EXPLANATORY; HOWEVER, If WE CAN BE Of FURTiiER ASSISTANCE, PLEASE DO NOT HESITATE TO CONTACT US.
BEST REGARDS, CARLTON M. SLATER SERVICE ENGINEER
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GENTI.EMEN:
- i.
ON All TERRY MODEL ZS AND GS 1URBINES USING nIE 2 1/2" VEEPORT AND 3"
- VENTIJRl GOVERNOR VALVES, TIIE VALVE STEMS ARE MADE OF NITRIDED 410 STAINLESS STEEL WI11i CARBON RINGS FOR PACKING.
TiiERE HAS BEEN A FEW NUCLEAR PI.ANTS EXHIBmNG CORROSION REI.A TED VAL VE STEM BINDING. IT IS AGREED TiiAT VALVE STEMS OF THIS CONSTRUCTION ARE SUSCEPTIBLE TO CORROSIVE ATIACK DURING PROLONGED EXPOSURE TO AN ENVIRONMENT OF STAGNANT OXYGENATED WATER.
TiiE DESIGN SELEcnON IS MADE WITH EXPECTATION (BACKED UP BY VERY EXTENSIVE EXPERIENCE) TIM T TiiE RESIDUAL CORROSION RESISTANCE OF NITRIDED 410 IS ADEQUATE IN A 1YPICAL STEAM TIJRBINE VALVE STEM ENVIRONMENT. TiiE FACT THERE ARE TIIOUSANDS OF STEAM TURBINES W111i NITRIDED 410 VALVE STEMS AROUND TI-IE WORLD, INCLUDING MANY OF TIIEM IN STANDBY SERVICE PROVIDES A STRONG TESTIMONY TO TiiE EXPECTATION. AfSO, TiiERE ARE ONLY EIGHT OUT OF 140
- NUCLEAR Pl.ANTS ON OUR INSTAllATION UST WHICH HAVE REPORTED PROBLEMS WITii CORROSION RELATED VALVE STEM BINDINGS. 1HEREFORE, nus SUGGESTS S"raONGLY TiiA TA REASONABLY NON-CORROSIVE VALVE STEM ENVIRONMENT IS BEING MAINTAINED BY TiiE OTIIER PLANTS. THERE IS A SIMILARI1Y TO TiiESE TIJRBINES IN NUCLEAR PLANTS. THIS SIMILARITI' IS, TiiEY ALL HA VE EXTENDED PERIODS OF IDLE STANDBY STATIJS.
TiiE PLANTS TiiAT ARE. HAVING THIS CORROSION ENVIRONMENT PROBLEM ARE NOT ADEQUATELY DRAINING 1HE UNIT AND/OR HAVE CORROSIVE WATER CHEMISTRY IN THE STEAM. IBIS WATER IS STAGNATING IN TiiE VALVE STEM PACIONG GLAND (L-GLAND). THE REAL SOLtmON IS TO HA VE ADEQUATE DRAINAGE AND EUMINATE 1HE CORROSIVE ENVIRONMENT. HOWEVER, SOME OF 1HESE PLANTS HA VE CONCLUDED THAT IBEY ARE UNABLE TO ASSURE A DRY AND NON-CORROSIVE CONTROL VALVE ENVIRONMENT.
ACCORDINGLY, 1HEY HA VE IDENTIFIED A NEED FOR A VALVE STEM WITH HIGHER CORROSION RESISTANCE - SPECIFICAllY A STEM WITH CHROME PLATING APPUEO OVER A 1A YER OF ELECTROLESS NICKEL A 1TACHED IS A UST OF 1HESE PLANTS AND TiiEIR EXPERIENCES. AFTER READING 11i1S USf ONE CAN SEE TIIAT THERE IS NO SELEcnON OF VALVE STEM MATERIALS WHICH, CAN BY ITSELF, PRELUDE TiiE P0SSIBIU1Y OF SURFACE DETERIORATION OR ASSURE INDEFINITE FREEDOM FROM BINDING.
BECAUSE DRESSER-RAND HAS A HIGH REGARD FOR CUSTOMER SATISFACTION, TiiERE IS A WIWNGNESS TO SUPPLY NUCLEAR GRADE CHROME PLATED VALVE STEMS TO TiiE PLANTS Tii.AT CAN NOT ASSURE A DRY AND CORROSIVE PRE£ ENVIRONMENT AND ARE..
EXPERIENCING A CORI\\OSIVE RELATED BINDING PROBLEM.. TiiAT MEANS NOT All PLANTS FIT nus NEED ANI? FOR THEM, NO CHANGE IS REQUIRED.
GOVERNOR VALVE STEMS DO NOT HAVE A INFINITE UFE SPAN. BASED ON DATA ON 11-IE NUMBER Of-1liE 410 NITRATED VALVE. STEMS USED, 1HE AVERAGE SERVICE UFE
- * * **
- 1s s PLUS YEARS. duGGESIS TI:IAT lHESE VALVE £s ARE REPLACED ON A
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PREVENTATIVE BASIS AT NORMAL INSPEcnON INTERVALS, NOT BECAUSE OF BINDING.
,. /~
ONLY VIGILANT A TIENTION TO GOOD OPERA TING AND MAINTENANCE PRAcnCES CAN ASSURE A FREE AND OPERATION READY CONTROL VALVE. THESE PRACI1CES SHOUID
(
INCLUDE Btrr NOT BE UMITED TO:
- 1)
CRITICAL ATI"ENTION TO TiiE CONTROL VALVE ENVIRONMENT. TiiIS INCLUDES STEAM CHEMISTRY AND ANY OTiiER POTENTIAL SOURCES OF CORROSIVES AS WEll AS SYSTEM ARRANGEMENTS AND PRACI1CES TiiAT PROMOTE A WEU.
DRAINED CONTROL VALVE, I.E., DRY ENVIRONMENT FOR STEM AND PACKING ASSEMBLY, WHILE IN STANDBY STATIJS.
- 2)
PERIODIC INSPECilON OF TiiE VALVE STEM TO DETECT ANY SURFACE DETERIORATION TiiAT COUID LEAD TO BINDING AND/OR PERIODIC MONITORING OF TIIE FORCE REQUIRED TO MOVE 11iE VALVE 1HROUGHOUT ITS STROKE RANGE.
TI-IE S1cM SHOUID BE REPlACED IF EmiER SURFACE *DETERIORATION OR INCREASE IN REQUIRED STROIONG FORCE ARE FOUND TO BE SIGNIFICANT.
- 3)
CRITICAL ATI"ENTION TO ANY BINDING TENDENCIES TiiAT MAY BE EXHIBITED BY TIIE CONTROL VALVE DURING REGULAR SURVEILLANCE TESTING.
HOWEVER, IF YOUR PLANT IS ONE TiiAT CAN NOT ASSURE A DRY AND CORROSION FREE ENVIRONMENT, YOU CAN PURCHASE A NUCLEAR GRADE CHROME PLATED VALVE STEM (SPECIFICALLY 410 STAINWS STEEL BASE MATERIAL Wllli CHROME PLATING APPLIED OVER A LAYER OF ELECTROLESS NICKEL) TO ACCOMMODATE TiiE ADDITIONAL CORROSION RESISTANCE REQUIRED.
IF YOU HA VE ANY QUESTIONS REGARDING TiiE ABOVE OR WISH TO PURCHASE TiiE CHROME PLATED STEM, PLEASE CONTACT US. FOR QUESTIONS CAll ED GRANDUSKY:
716-596-3631, TO PURCHASE PARTS CAll MIKE LAUZZE: 716-596-3436.
BEST REGARDS, CARLTON SLATER SERVICE ENGINEER