JSP-552-93, Part 21 Defect 21-93-029:on 931007,discovered Broken Motor Shaft Pinion Key in Limitorque Actuator of motor-operated HPCS Sys Injection & Outboard Containment Isolation Valve 1E22-F004.Broken Motor Pinion Key Replaced

Part 21 Defect 21-93-029:on 931007,discovered Broken Motor Shaft Pinion Key in Limitorque Actuator of motor-operated HPCS Sys Injection & Outboard Containment Isolation Valve 1E22-F004.Broken Motor Pinion Key Replaced

ML20062K141
Person / Time
Site:	Clinton
Issue date:	12/10/1993
From:	Jamila Perry ILLINOIS POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
REF-PT21-93 21-93-029, 21-93-29, JSP-552-93, U-602214, NUDOCS 9312200222
Download: ML20062K141 (5)

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lilhols Power Company

. Clinton Power Stabon

, P.O. Box 678 CMton. IL 61727 Tel 217 93s-6226

. Fax 217 93s-4c32 J. Stephen Perry Senor Vice President RLLENOIS uom4 POVJER JSP-552-93 December 10, 1993 Ll6-93010LP 4F.140 ,

December 10, 1993 Docket No. 50-461 10CFR21.21 Document Control Desk Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

10CFR21 Defect 21-93-029: Potential for Motor Pinion Key Failure in Limitorque Aculators due_1.0 Excessive Torque During Valve Bac]sicating and MOVATS Testing

Dear Sir:

i On October 7,1993, Illinois Power (IP) discovered a broken motor shaft pinion key in the actuator of motor-operated High Pressure Core Spray (HPCS) system injection and outboard containment isolation valve IE22-F004 while installing a modification to change the actuator gear ratio and replace the valve stem and disc. The failure existed undetected until the valve was disassembled to install the modification.

On November 9,1993, following a root cause investigation, IP identified the broken key issue as a condition potentially reportable under the provisions of 10CFR21.

Based on subsequent evaluation of this matter, IP has concluded that this' condition constitutes a defect and is providing the following information to the Nuclear Regulatory Commission (NRC) in accordance with the requirements of 10CFR, Part 21.21 (c) (4).

Initial notification of this matter will be provided by facsimile of this letter to the NRC Operations Center in accordance with 10CFR, Part 21.21 (c) (3) on the date this letter is signed.

(i) J. S. Perry, Senior Vice President ofIllinois Power, Clinton Power Station, Post Oflice Box 678, Clinton, Illinois 61727, is informing the NRC of a 10CFR, Part 21 -

defect by means of this report.

(ii) The basic component involved in this reportable defect is the motor actuator ofI figh Pressure Core Spray system injection and containment outboard isolation valve IE22-F004, installed at Clinton Power Station (CPS). The actuator is Limitorque model SB, size 3 with a forty foot-pound,3600 revolutions per minute motor. The -

valve is designed to automatically open in response to an HPCS initiation signal to 170030 e 93122002h$hbh61  !

PDR ADO s

PDR e M /9 tj o . .

i provide water to the reactor vessel in the event of a Loss of Coolant Accident. The valve is also designed to automatically close in response to a high rc .: tor vessel water level signal.

(iii) The motor actuator was designed and manufactured by Limitorque Corporation for i the 10" gate valve manufactured by Anchor / Darling Valve Company (A/D). The valve and actuator were supplied to CPS by General Electric Company (GE). 1 Equipment used (at the most probable time of motor pinion key failure) to test and analyze the valve's performance and procedures for using that equipment were supplied to CPS by ITI MOVATS, Incorporated. IP incorporated the MOVATS procedures into CPS maintenance procedure CPS 8451.02, "MOV Signature Analysis," which provides the instructions for operating the MOVATS test equipment.

(iv) The defect is the potential for motor pinion key failure in Limitorque actuators due to excessive torque during valve backscating and MOVATS testing. When testing 1 the motor-operated valve in accordance with the MOVATS test procedure, the actuator is opened into a stationary load cell during the spring pack calibration process. The actuator is also opened into the stationary load cell during adjustment of the open torque switch. When the valve stem is suddenly restrained from further l motion by backscating the valve or by the MOVATS test process described above, the motor and acLator gear train inertia must be absorbed within the actuator. The actuator worm dissipates the inertia by compressing the spring pack as the worm attempts to climb the stationary wormgear thus resulting in a braking action (torque ,

reversal) on the wormshan. The torque reversal is transmitted through the -

wormshan gear to the motor pinion. De Anding on the ratio of the various gears, i" the inertia of the motor and the stiffness of the spring pack, the torque reversal ,

opposing the motor inertia may result'in impact loads on the motor pinion key that j exceed the shear strength of the motor pinion key. Other combinations of actuator size and actuator motor characteristics may also be affected. An engineering -

i evaluation based on a motor deceleration time of 0.025 seconds resulted in identification of other potentially susceptible motor-operawJ valves at CPS (see section vii). The deceleration time selected was based on limited data and engineering judgment.

The test procedure supplied by MOVATS does not recognize the potential for excessive torque on the motor pinion key. IP review of Limitorque literature did not identify any specific cautions or limitations regarding backseating.

The failure of the motor pinion key in the actuator for valve IE22-F004 did not I make the valve incapable of performing its safety functionsc Mechanical binding between the sheared _ key and the motor shan, in conjunction with the reseating of the pinion gear's setscrew in its shan indentation, created a mechanical coupling . l capable of driving the actuator in all operations following the key failure. Powever,

• mechanical binding may not always occur in a mowr pinion key failure; therefore, ,

. this deviation could have resulted in valve 1E22-F004 being incapable of performing.

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its safety functions of opening to allow HPCS system water injection to the reactor pressure vessel and closing to isolate the containment from the outside environs.

(v) The broken motor shaft pinion key was discovered on October 7.,1993, by maintenance personnel who were installing a plant modification to change the actuator gear ratio and replace the valve's stem and dise. On November 9,1993, following an investigation to determine the root cause for the broken key, Illinois Power identified that the broken key was potentially reportable under the provisions of10CFR21.

(vi) Illinois Power has identified Limitorque motor actuators for thirteen additional-Anchor / Darling safety-related valves at CPS which may be susceptible to motor pinion key failure as a result of backseating or MOVATS calibration.

Valve Identificatipa Valve Function Actuator / Motor Size Number 1B21-F065 A Feedwater Line ShutofrValve SMB-3-150/1 LOO 1B21-F065B Feedwater Line Shutoff Valve SMB-3-150/1800 -

1B21-F098A Main Steam Line ShutofrValve SMB-3-150/1800

. I B21-F0988 Main Steam Line Shutoff Valve SMB-3-150/1800 '

IB21-F098C Main Steam Line ShuteTValve SMB-3-15P'1800 1B21-F098D Main Steam Line ShutofrVe ce SMB-3-150/1800 1E22-F023 High Pressure Core Spray SMB-3-150/1800 (HPCS) Return to Suppressiun Pool Flow Control Valve 1EL HPCS to Reactor Core Isolation SMB-4-200/1800 Cooling Storage Tank Bypass Valve IE22-F011 HPCS Test to RCIC Storage SMB-4-200/1800 Tank Valve 1E22-F015 HPCS Suction from Suppression SB-1-40/3600 Pool Valve IE12-F008 RHR Pump Suction Shutdown SMB 0-40/1800 Cooling Outboard Isolation Valve IE12-F009 R.HR Pump Suction Shutdown SMB-0-40/1800 ,

Cooling Inboard Isolation Valve 1E22-F012 HPCS Minimum Flow to SB-0-25/3600 Suppression Pool Valve IP does not have any infonnation about potentially deficient valves supplied to other purchtL.crs.-

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(vii) IP replaced the broken moter pinion key made from AISI 1018 materialin 1E22-- '

F004 with a key fabricated from~AISI 4140 material. (AISI 4140 materialis the-replacement key material provided by Limitorque). The actuator motor for valve .

IE22-F004 was replaced to provide assurance of proper fit between the motor pinion gear and the motor shaft ,

l Illinois Power will replace existing supplies of Limitorque motor pinion keys '

fabricated from AISI 1018 material with AISI 4140 material keys (AISI 4140 material is the replacement key material provided by Limitorque).  !

IP will revise Clinton Power Station procedures that apply to specific actuator size and motor combinations. These combinations include: .Limitorque Model SMB/SB-0 actuators with 25 foot-pounds start torques,3600 Revolutions Per ,

Minute (RPM) motors or 40 foot-pounds start torque 1800 or 3600 RPM motors; SMB/SB-1 actuators with 40 or 60 foot-pounds start torque,3600 RPM motors;  !

and any actuator SMB/SB-3 or larger. Maintenance procedure CPS 8451.02 d "MOV Signature Analysis," will be ravised to add a limitation preventing the use of ,

calibration and open torque switch setting s;eps that require opening into 'a a stationary load cell. Maintenance procedure CPS 8_451.09, " Electrical Backscating of MOVs, Generic Procedure for," will be revised to add a precaution identifying the potential failure of motor pinion keys Maintenance procedure CPS 8451.50, ,

"MOV Testing with VOTES," will be revised to add a precaution to indicate 'j potential failure of motor pinion kep in de event cf unintentional backseating.

Illinois Power previously replaced AISI 1018 motor pinion keys in the ac*.uators of:

the fo'nowing CPS valve, with keys made of AISI 4140 material in response to NRC 3 Information Notice 81 08, " Repetitive Failures of Limitorque Operator SMB Motor-to-Shaft Kes ." No key deficiencies were noted at the time orkey replacement.

1B21-F065A 1B21-F098D 1B21-F065B 1E22-F023 ,

IB21-F098A lE22-F010 1B21-F0988 - IE22-F0l l 1B21-F098C lilinois Power determined that the AISI 1018 motor pinion keys in the actuators of the following valves are acceptable based on further engineering evaluation.

1E12-F008 1E22-F015 1El2-F009 1E22-F012 4

(

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(viii) IP has no additional advice or information to provide to other purchaseis or licensees regarding this defect. The IP contact for this defect is J. D. Funston, Mechanical Design and Analysis, (217) 935-8881, extension 3919.

Documentation related to this defect is available for your review at our offices.  !

Sincerely yours, O

J. S. Perry Senior Vice President i

RSF/nis ,

cc: NRC Resident Oflice, V-690 -

NRC Clinton Licensing Project Manager '

Regional Administrator, Region III, USNRC Director, Office of Nuclear Reactor Regulation t

. INPO Records Center -

Illinois Department of Nuclear Safety ,

ITI MOVATS, Inc. .i

, Limitorque Corporation t

.I

?

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