ML20086F644

AO 50-261/75-8:on 750429,RHR Pump Suction Valve RHR-862A Failed.Caused by Torque Switch on SMB-O Motor Operator Being Out of Adjustment.Torque Switch Adjusted.On 750430,complete Insp of Operator Found Excess Grease.Grease Removed

ML20086F644
Person / Time
Site:	Robinson
Issue date:	05/09/1975
From:	Utley E CAROLINA POWER & LIGHT CO.
To:	Moseley N NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20086F643	List: ML20086F644 ML20086F647 NG-75-1089, Revised AO 50-261/75-8:on 750429,RHR Suction Valve RHR-862A Failed.Caused by Torque Switch on Motor Operator Being Out of Adjustment,Causing Valve to Be Wedged Onto Seat & Preventing Motor from Opening Valve
References
AO-50-261-75-8, NG-75-678, NUDOCS 8401030449
Download: ML20086F644 (3)

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U CP&L Carolina Power & Light Company May 9, 1975 3

Files NG-3513 (R) Serial: NG-75-678 Mr. Norman C. Moseley, Director S k

U. S. Nuclear Regulatory Commichton 3 gN Region II, Suite 818 4 II

'h 230 Peachtree Street, N. W. b- -

Atlanta, Georgia 30303 p g g 1975 con ~

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Dear Mr. Moseley:

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H. B. ROBINSON UNIT NO. p LICENSE NO. DPR-23 FAILURE OF RHR VALVE 862A TO OPERATB 7 In accordance with 6.6.2.a of the Technical Specifications for H. B. Robinson Unit No. 2, the attached Abnormal Occurrence Report is submitted for your information. This report fulfills the requirement for a written report within ten days of our Abnoimal Occurrence and is in accordance with the format set forth in Regulatory Guideline 1.16, Revision 1.

Yours ver truly, E. E. Utley Vice-President t)

Bulk Power Supply DBW:me Attachment cc: Messrs. N. B. Bessac P. W. Howe R. E. Jones l

Donald Knuth J. B. McGirt

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D. B. Waters 40 7

f 8401030449 750711 1

PDR ADOCK 05000261 S PDR gg'/

336 Fayetteville Street . P. O. Box 1551. Raleigh N. C. 27602 e ;,i ar , ' v.. W ', ' s P.M n iOf L ~ * **U # L */iN.l'.3 COPY SENT REGION w .

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gnormal Occurrence Report

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1. Report No. 50-261/75-8 2a. Report Date May 7, 1975 2b. Occurrence Date April 29, 1975

3. Facility H. B. Robinson Unit No. 2 Hartsville, South Carolina 29550

4. Identification of Occurrence Failure of RHR pump suction valve RHR-862' A , which constitutes an Abnormal Occurrance as defined in Section 1.8.d. of the Technical Specification.

5. Conditions Prior to Occurrence Aplantheatupwasinprogressafterascheduledtwoweekmafntenance shutdown. The Reactor Coolant System was at 950 psi and 419 F, and the RHR System was being aligned for power operation.

6. Description of Occurrence At 1123 hours0.013 days <br />0.312 hours <br />0.00186 weeks <br />4.273015e-4 months <br /> while aligning the RHR System for normal power operation, valve RHR-862A failed to open when operated from the RTGB. At 1138 hours0.0132 days <br />0.316 hours <br />0.00188 weeks <br />4.33009e-4 months <br /> a reactor cooldown was commenced. At 1155 hours0.0134 days <br />0.321 hours <br />0.00191 weeks <br />4.394775e-4 months <br /> the valve was started open using the manual operator. At 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br /> the valve was completely open and capable of performing its intended function, and the reactor heatup was recommenced. An investigation revealed that the SMB-0 operator torque switch was out of e.djustment causing the valve to be jacmed on the seat. The torque switch was adjusted and the valve returned to service at 1338 hours0.0155 days <br />0.372 hours <br />0.00221 weeks <br />5.09109e-4 months <br />. The valve was cycled at this time with satis-factory results. Later, at 1757 hours0.0203 days <br />0.488 hours <br />0.00291 weeks <br />6.685385e-4 months <br />, the valve was test operated on two successive cycles, and operation was satisfactory.

7. Designation of Apparent Cause of Occurrence As previously stated the torque switch on the SMB-0 motor operator was

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out of adjustment. This caused the valve to b'e wedged onto the seat.

When the valve was moved off its seat with the manual operator, movement of the valve was free.

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8. Analysis of Occurrence Upon determination that valve RHR-862A would not meet its design function, a plant cooldown was commenced. Plant safety was not jeopardized and no personnel injuries, undue exposures, releases of radioactive materials, or threat to the public health and safety resulted from this occurrence.

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9. Corrective Action The torque switch was adjusted to prevent the valve from being forced on the seat. Also, at 1011 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.846855e-4 months <br />, April 30, 1975, a complete inspection of the operator was performed, and excessive grease was found in the Belleville spring chamber at the end of the worm gear shaf t. This could potentially create a hydraulic lock effect around the spring and not permit it to function properly. The excess grease was removed as a precaution, and the operator was returned to service at 1418 hours0.0164 days <br />0.394 hours <br />0.00234 weeks <br />5.39549e-4 months <br />. The valve operation was tested at this time with satisfactory results.

10. Failure Data None.

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