ML20083D403

From kanterella
Jump to navigation Jump to search
Problem Investigation Rept 1-C91-0157:on 910414,discovered That Actuators for Two of Four Steam Generator Blowdown Sys Containment Isolation Bypass Valves May Not Close Valves. Improved Lubrication Method Developed
ML20083D403
Person / Time
Site: Catawba Duke Energy icon.png
Issue date: 09/11/1991
From: Hampton J
DUKE POWER CO.
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
1-C91-0157, 1-C91-157, IIR-C91-024-1, IIR-C91-24-1, NUDOCS 9109300262
Download: ML20083D403 (6)


Text

{{#Wiki_filter:11 I , % vi, u tx,, n,, u.-n I i' ii a : s (; r jf%; DUKCPOWER September 11, 1991 Document Control Desh U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Subject:

Catawba Nuclear Station Docket No. 50-413 IIR C91-024-1; PIR 1-C91-0157 Gentlemen: Attached is our Problem Investigation Report 1-C91-0157, submitted concerning IMPROPER VALVE STEM LUBRICATIONS DUE TO DEFECTIVE PROCEDURES. This incident has been determined to be non-reportable but has been investigated and is being documented as a Special Report to ensure industry awareness of this event. The health and safety of the public were not affected by this incident. Very truly yours, f / W. Hampton Station Manager ken: REPORT.SP xc. Mr. S. D. Ebneter M & M Nuclear Consultants Regional Administrator. Region 11 1221 Avenuen of the Americas U. S. Nuclear Regulatory Commission New York, NY 10020 101 Marietta Street, NW, Suite 2900 Atlanta, GA 30323 R. E. Partin INPO Records Center U. S. Uuclear Regulatory Commission Suite 1500 office of Nuclear Reactor Regulation 1100 Circle 75 Parkway Washington, D. C. 20555 Atlanta, GA 30339 Mr. W. T. Orders 7 NRC Residet.t Inspector Catawba Nuclear St M in" / i h O( C93 3 ( s

-______-._m.

m. _.

'At' =-' 1 i DUKE POWER COMPANY CATAWHA NUCLF.AR STATION I PROBLEM INVESTIGATION REPORT NO. 1-C91-0157 IMPROPER VALVE STEM LUBRICATIONS DUE TO DEFECTIVE PROCEDURES i ABSTRACT on April 14, 1991, with Unit 1 in No Mode, Defueled, and Unit 2 in Mode 1, Power Operation, it was discovered by instrumentation and Electrical personnel during valve testing that the actuators for two of the four Unit 1 Steam Generator Blowdown (BB) System Containment Isolation Bypaas valves may not close the valves based on calculated thrust requirements provided by Design Engineering. On April'15, at 1600 hours, Maintenance Engineering Services' perconnel determined that the two valve actuators would not produce the xpected thrust due to_the Rotork actuator stem nut not being lubricated. The .tandard stem lubrication-method was found to be inadequate for these particular valves. An improved lubrication method-was-developed, and all- .cight of the affected BB valves were properly lubricated by April-18. This incident;is attributed to a defective procedure, because the yoke spacer. design and short stroke of these-valves were not taken into account. Corrective actions included proper lubrications of the BB valves affected, and will include revision of the procedures used for valve stem lubrication, r b 'These valves are required to be operable as containment isolation valves per Technical Specifications. Although initial thrust values were not as expected for the two valves, all of the affected BB valves were operable prior to the . improved stem lubrication. This report is being submitted as a Special

Report, E

I 9 I ______r,_

~~~~ DUKE POWER COMPANY / CATAWBA NUCLEAR STATION

  • plR l-C91-0157 /Special Report Pago 2

) System is designed to maint ain BACAGHOUND The Steam Generator Blowdown IE11S:WI) (BBshell side chemintry by removingconsist (S/G) The BB System proper Steam Generator [EIIS,HXIundesired solids resulting f r orronion. exchangers, two a blowdown tank, two 100% capacity pumpu(Ells: is extracted demireralizers and domineralizer profilters Blowdown flow 1211S: PSP), valves [E11S:V], and instrumentation.from l tion valves and control d valves to the blowdown tank, where t e wa inolat ion signal, both the h on a Phase A cont ainment inment inolation bypace valvec in the blowdown lines are separated, t containment isolation valves and the con a Pressure (BB147B, DB140B, BB1498, BB150B) would close. d between the outside containment Water harmier could oct.ur 11 the would drop and a void would be create sudden surge of isolation valves and the blowdown tank. isolation valves were to reopen, d linen are provided to id. The bypaanUned for this purpoce, containment pressurized water into a low pressure volimited periods of time while lishing flow. initiating repressurize the lines prior to reestab these valves would only be open f or S/G blowdown. k and Limitorque Valve operators at The Valve Operation Test t The procedure used at Catawba to test Ro or i ith VOTES. Catawba in Ip/0/A/3820/04A, MOV Test ng wor on the valve yoke to measure o The general mechanical and Evaluation System (VOTES) usen a nons senting and unseating forces within the va ve.f motor IElls:MO) operat ed valven l Valve actuators are designed to condition and electrical control setup o (MOVs) can be assessed using this system.to ensure proper valve operation i Engineering. provide an output torque and thrustThe required values are supplied by Des gn design basis events. the containment isolation valves Technical Specification (T/S) 3.6.3 requires be operable in Mode 1, Power If (CIVs) listed on Tabmes 3.6-2a and 3.6-2b todby, and Mode 4, Hot Shutdown. ithin four hours Operation, Mode 2, S ;artup, Mode 3, Hot Stan ]t must be restored to operable status w lve (or isolated by a deenergized automatic voin at least Mode 3 w a CIV is inoparable, or the penetration must be t be Units 1 manual valve or flange), or the Unit mus i hin the following 30 houru. required to be opera next nix hours and in Cold Shutdown w t and BBibOB are and 2 BB1478, BB148B, BB149B, " Safety Related EVENT DESCRIPTION 1989, the NRC issued Generic Letter (GL) 89-10,GL 89-10 requented (MOV) Testing and Surveillance".perabilit y of all salety-relate On June 28, Motor-Operated Valve Bulletin 85-03 had required licensees t oh t s h a program be established to ensure t e o under design basis conditions. develop and implement a The bulletin recommende l that ditions. were operable under design basis con torque bypass, position limit,

torque,
DUKE, POWER COMPANY / CATAWBA NUCLEAR STATION

^ PIR l-C91-0157/Special Report ' page 3 selected, set, and maintained so that the MOVs would operato under design basis conditions for the life of the plant. GL 89-10 extended thu scope of Bulletin 85-03 to include all safety related MOVs. As a result of Bulletin 85-03 and GI. 89-10, an extensive program for MOV 4 testing and improved maintenance is being imolemented. A detailed evaluation of lubricant types, application methods, lut rication interval, etc. is presently in progress for the industry-spontnred MOV Users Group. The Catawba MOV program has established a lubrication interval of at least every Refueling Outage for program valves, and will follow the jndustry effort to ensure -lubrication type, application, and interval are adequate. Rotork actuated valve stem-lubrication can be done under IP/0/A/3820/02B, Rotork Actuator Preventive Maintenance, IP/0/A/3820/07, Troubleshooting and Maintenance of ~ Rotork Actuators, or IP/0/A/3820/09, Removal, Replacement, and Field Set-up of Rotork-Actuators. The Catawba program has recognized the need for periodic stem lubrication; however, no specific guidance.on how to apply the lubricant was included. 'No industry. experience or manufacturer supplied information was available to' indicate the need for specific techniques of applying stem lubrication. ' Design Engineering calculated the thrust required to close the BB containment isolation bypass valves under worst caso conditionn. The worst caso design basis condition:was a line break downstream of the valveu (between the bypass valves and the blowdown tank) such that the valves would be exposed to S/G pressure on'one side, and atmospheric pressure on the.other side. A worst case differential pressure of 1210 psid was used. The thrust calculated to be required _to close the bypass valves was 7162 lbs. Work Requests 3867-3870 NSM were originated to test-the Unit 1 BB containment isolation bypass valves, with a required thrust value of 7162 lbs. This value was based on conservative-thrust calculations. -On-April 14, 1991, with Unit 1 in -tk> Mode, Defueled, and Unit 2 in Mode 1, - Power Operation, it was discovered by Instrumentation and Electrical (IAE) personnel during valve-testing that the actuators for valves 1BB147B and 1BB150B would not produce the calculated thrust which would be needed to close the valves under worst' case differential pressure conditions. On-April 15, 1991 at 1600 hours,-Maintenance Engineering Services (KES) personnel ~ ' determined that the two BB containment isolation bypass valve actuators would -not produce the needed thrust due to the stem nut not being lubricated. The standard stem lubrication method had been to lubricate the stem and then cycle the valve, to enable the lubricant to reach the stem nut. However, in this = case,Ean-unusual' yoke / spacer design and short valve stroke prevented the lubricant.from reaching the stem nut. -The portion of the stem engaging the stem nut was hidden from view, and the short valve stroke did not enable the lubricated portion of the stem to reach the stem nut. An improved lubrication method was developed, in which the Rotork actuator handwheel would be removed, luoriaant applied from the top, and the valve y 7- - -. -.-., .-,w -.-v-.-,-.


.--y,..n v-

.c 4,- v

t

DUKE POWER COMPANY / CATAWBA NUCLEAR STATIOli
  • PIR l-C91-0157/Special-Report

--Page 4 cycled. On April 16, 1991 at 1400 hours, the corresponding Unit 2 BB valves were' declared inoperable per T/S 3.6.3 until the sten,s could be properly lubricated per work requests 4327MES, 4328MES, 4329MES, and 4330MES. Valves 2BB147B, 2BB148B, 2BB149B, and 2BB150B were tagged closed and deenergized along with their corresponding-Train A '.nside containment Isolation Valves, in compliance with the actions required by T/S 3.6.3. By April 18, all eight affected valves were properly lubricated, and the four Unit I valves were ~ successfully VOTES tested. On April 18, at 1650 hours, the four Unit 2 valves were declared operable. Other valves having this type of yoke / spacer design have been identified at Catawba. All additional safety-related valves of this type are larger than the BB valves and have a longer stroke. Testing of some larger size valves has been performed without any special lubrication methods and the measured' thrust valves were.as expected. The lubrication problem is specific to short stroke valves, as approximately 300 motor operated valves have been successfully tested at Catawba without any similar problems of improper lubrication. ^ CONCLUSION This. incident is attributed to a defective procedure, because the lubrication method in IP/0/A/3820/02B, IP/0/A/3820/07, and IP/0/A/3820/09 did not take the yoke / spacer design or the short valve stroke of these' valves into account. 1These prededures will be revised to reflect the improved method, which ensures that the stem nut;is lubricated. A lubrication interval of at least every refueling outage was established for all applicable valves in conjunction with the GL 89-10 program,- 7 Lubrication w111 be-performed under IP/0/A/3820/02B_at each MOV: test interval or under an appropriate Standing Work Request (SWR). Although the initial thrust values for 1BB147B and 1BB150B were-not as -expected, all of the-affected BB valves were subsequently determined to have beenLeperable prior to the improved stem lubrication, based on the thrust values of 1BB147B and -1BBIE0B, and en the _ torque switch _ settings of the other valves. This report is being submitted as a Special Report.' A raview of the Operating Experience Program database has shown no other ' incidents resulting from improper valve stem lubrication..Therefore, this is not determined to be a recurring problem. . CORRECTIVE ACTION: ' SUBSEQUENT 1). _ Valves 1BB147B, IBB148B, 1BB149B, and 1BB150B were lubricated using ~ the improved method per work requests 3867NSM, 3868NSM, 3869NSM, and 3870NSM. -l i )

DUKE POWER COMPANY / CATAWBA NUCLEAR STATION PIR 'l-C91-0157/Special Report ~ . Page 5 2) Valves 2BB147B, 2BB14BB, 2BB149B, and 2BB150B were lubricated using the improved method per work requests 4327, 4328, 4329, and 4330MES. PLANNED 1) MOV maintenance procedures will be revised to incorporate the improved lubrication method. SAFETY ANAL'lS1S The BB Containment Isolation Bypass Valves (1,2BB147B, 14BB, 149B, and 150B) are normally closed during plant operation except curing testing or when establishing blowdown. They are opened when placing the BB System in service to equalize pressure before establishing full flow through the Contairunent Isolation Valves. If one or more of these valves were open and an incident occurred requiring containment isolation, both the inside (Trein A) and outside (Train B) BB Containment Isolation Valves would have closed. The Train A valves would have isolated the penetrations. Design Engineering provided a Past Operability Evaluation, in which it was stated that the Unit 1 and Unit 2 valves were operable based on the thrust values of IBB147B and 1BB150B, and on the torque switch settings of the other valves. The expected (set-up) thrust values were based on a conservative valve factor. The actual thrust values, while less than the set-up valaes, did not render the valves inoperable. Therefore, the health and safety of the public were not affected by this incident. =}}