Information Notice 1986-93, IEB 85-03 Evaluation of Motor-Operators Identifies Improper Torque Switch Settings

IEB 85-03 Evaluation of Motor-Operators Identifies Improper Torque Switch Settings

ML031250142
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant, Skagit, Marble Hill
Issue date:	11/03/1986
Revision:	0
From:	Jordan E L NRC/IE
To:
References
BL-85-003 IN-86-093, NUDOCS 8610310306
Download: ML031250142 (4)

t -SSINS No.: 6835IN 86-93UNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF INSPECTION AND ENFORCEMENTWASHINGTON, DC 20555November 3, 1986IE INFORMATION NOTICE NO. 86-93: IEB 85-03 EVALUATION OF MOTOR-OPERATORSIDENTIFIES IMPROPER TORQUE SWITCH SETTINGS

Addressees

All nuclear power reactor facilities holding an operating license or a con-struction permit.

Purpose

This notice is provided to alert recipients of a potentially significant safetyproblem discovered while performing the evaluations requested by IE Bulletin85-03, "Motor-Operated Valve Common Mode Failures During Plant Transients Dueto Improper Switch Settings," (IEB 85-03). It is expected that recipients willreview the information for applicability to their facilities and consideractions, if appropriate, to preclude similar problems from occurring at. theirfacilities. However, suggestions contained in this notice do not constituteNRC requirements; therefore, no specific action or written response isrequired.

Description of Circumstances

As a result of followup on IEB 85-03, Duke Power Company (DPC) discoveredproblems with valves operated by Rotork valve actuators at McGuire NuclearStation. Specifically, the problem involved valves for which the factory-settorque switch settings had been previously changed at the plant site using ageneric correlation between actuator torque output and torque switch setting.This could cause valve actuator motors to switch off before the valves completetheir travel. Arbitrarily raising the torque switch setting to its maximum mayresult in damage to the valve and/or motor especially since thermal overloadprotection has been eliminated in many applications. Based upon thisinformation, DPC has declared safety systems inoperable and shut down McGuireUnits 1 and 2.Discussion:The vendor states that whenever the factory torque switch setting is changed inthe field, an individual calibration curve or a bench test is required toaccurately determine torque output.8610310306 IN 86-93November 3, 1986 According to information recently provided by the vendor, torque switch set-tings of 1, 2, 3, 4, and 5, do not always correspond to rated torque outputvalues between 40 and 100 percent as was used based on general informationavailable several years ago. Tests and analytical evaluations by the licenseenow confirm that the correlation used by the licensee was incorrect for someactuators. For example, evaluation of several valve actuator certificates forthe same model revealed that the actual torque output with a switch setting of"1" varied through a range of 11 to 55 percent of maximum actuator torque output.The review did not indicate a variation in maximum output at the number 5setting.Analysis of two valves installed in the normal charging path, which would berequired to close during safety injection, indicated that they may not be ableto do so under differential pressure conditions which could exist following aloss-of-coolant accident. Although the as-found switch setting agreed with thedesign setting determined by DPC the application of output torque values beinglinear between 40 and 100 percent was not correct for all actuators.Preliminary data indicates that up to 41 nuclear units may have some Rotorkvalve actuators. It is not known whether or not these are used in safetyrelated applications.The above example specifically deals with improper setting of the torqueswitches and illustrates the need for exercising extreme care in the setting ofmotor-operator switches because all types of switches must be set properly toensure that the valves will function properly when needed. In fact, thespecific event that prompted the issuance of IEB 85-03 was caused by improperlyset torque bypass switches. Improperly set thermal overload switchesrecently (October 22, 1986) rendered the high-pressure coolant injection systeminoperable at the Hope Creek Nuclear Station Unit 1. Both of these instancesinvolved actuators manufactured by a company other than Rotork.In addition, care must be taken to insure that all of the ramifications ofchanges to any of the motor-operator switches are fully understood. Forinstance, IE Information Notice 86-29, "Effects of Changing ValveMotor-Operator Switch Settings," describes how the changing of the limitswitches on certain motor-operated valves resulted in a control room indicationthat the valves were closed when, in fact, they were partially open. This ledto an excessive cooldown rate in the reactor coolant system at San OnofreNuclear Generating Station Unit 3.The information herein is being provided as an early notification of a possiblysignificant matter that is still under consideration by the NRC staff. Recipi-ents should review the information for possible applicability to their facili-ties. If NRC evaluation so indicates, further licensee actions may berequeste IN 86-93November 3, 1986 No specific action or written response is required by this information notice.If you have any questions about this matter, please contact the RegionalAdministrator of the appropriate regional office or this office.4 dw J DirectorDivis of Emergency Preparednessand Engineering ResponseOffice of Inspection and EnforcementTechnical Contacts: George Schnebli, RII(404) 331-5582Richard J. Kiessel, IE(301) 492-8119

Attachment:

List of Recently Issued IE Information Notices

... .. --- ---- -..-- ---.-T. -.-Attachment 1IN 86-93November 3, 1986LIST OF RECENTLY ISSUEDIE INFORltATION NOTICESDate ofInfTormationNotice No.86-82Rev. 186-9286-9186-9086-8986-05Sup. I86-25Sup. 186-8886-8786-86Sub 1ectFailures Of Scram DischargeVolume Vent And Orain ValvesPressurizer Safety ValveReliabilityLimiting AccessAuthorizationsIssue11/4/8611/4/8611/3/86Requests To Dispose Of Very 11/3/86Low-Level Radioactive WastePursuant to 10 CFR 20.302Uncontrolled Rod Withdrawal 10/16/86Because Of A Single FailureMain Steam Safety Valve Test 10/16/86Failures And Ring SettingAdjustmentsTraceability And Material 10/15/86Control of Material AndEquipment, ParticularlyFastenersCompensatory Measures For 10/15/86Prolonged Periods Of SecuritySystem FailuresLoss Of Offsite Power Upon An 10ilO/86Automatic 3us TransferClarification Of Requirements 10/10/86For Fabrication And Export OfCertain Previously ApprovedType 8 PackagesIssued toAll power reactorfacilities holdingan OL or CPAll PWR facilitiesholding an OL or CPAll power reactorfacilities holdingan OL or CP; fuelfabrication andprocessing facilitiesAll power reactorfacilities holdingan OL or CPAll BWR facilitiesholding an OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CPAll power reactorfacilities holdingan OL or CP; fuelfabrication andprocessing facilitiesAll power reactorfacilities holdingan OL or CPAll registered usersof NRC certifiedpackagesUNITED STATESNUCLEAR REGULATORY COMMISSIONWASHINGTON. D.C. 2E55OL z Operating LicenseCP = Construction PermitFIRST-CLASS MAILPOSTAGE & FEES PAlOUS. RACWASH 0 CPERMIT No G4LOfICIAL BUSINESSPENALTY FOR PRIVATE USE. $3