ML18005A440

Part 21 Rept Re Dc Motor Failure on Auxiliary Feedwater Limitorque Operated Valves.Plant Mod Will Be Implemented to Install Surge Protection for Shunt Coil Circuitry of Subject Dc Motors

ML18005A440
Person / Time
Site:	Harris
Issue date:	05/18/1988
From:	Watson R CAROLINA POWER & LIGHT CO.
To:	Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
CON-NRC-625, REF-PT21-88, REF-PT21-88-064-000 HO-880112-(O), PT21-88-064-000, PT21-88-64, NUDOCS 8806030324
Download: ML18005A440 (9)

Text

AC CELE RATED DlGBUTION . DEMONSTZION SYSTEM ow REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8806030324 DOC.DATE: 88/05/18 NOTARIZED: NO DOCKET FACIL:50-400 Shearon Harris Nuclear Power Plant, Unit 1, Carolina 05000400 AUTH. NAME AUTHOR Carolina Power AFFILIATION'ATSON,R.A.

& Light Co.

RECIP.NAME RECIPIENT AFFILIATION GRACE,J.N. Region 2, Ofc of the Director

SUBJECT:

Part 21 rept re DC motor failure on auxiliary feedwater-limitorque operated valves.

DISTRIBUTION CODE: IE19D COPIES RECEIVED:LTR i ENCL I SIZE: 6 TITLE: Part 21 Rept (50 DKT)

NOTES:Application for permit renewal filed. 05000400>

RECIPIENT COPIES RECIPIENT ~ COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-1 LA 1 0 PD2-1 PD 1 1 BUCKLEY,B 1 1 A INTERNAL: AEOD/DOA 1 1 AEOD/DS P/TPAB 1 -

1 ARM TECH ADV 1 1 NRR CRUTCHFIELD 1 1 NRR VARGA,S 1 1 NRR/DEST/ADE 8H ' 1 NRR/DEST/ADS 7E 1 1 NRR/DLPQ/QAB 10 1 1 NRR/DOEA/EAB 11- 1 1 NRR/DOEA/GCB 11 1 '

IS VIB 9D 1 1 NUDOCS-ABSTRACT 1 1 RE~I 01 1 1 RES/DE/EIB 1 1 E RP~EPY 1 1 RGN1 1 1 RGN2 1 1 RGN3 1 1 RGN4 1. 1 RGN5 1 1 EXTERNAL: INPO RECORD CTR 1 1 LPDR 1 1 NRC PDR 1 1. NSIC SILVERiE ~ 1 1 R

D"'OTAL NUMBER OF COPIES REQUIRED: LTTR 27 ENCL 26

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0 CMtt Carolina Power & Light Company op ~~ >

) Pg AI'I 97 HARRIS NUCLEAR PROJECT P. 0. Box 165 New Hill, North Carolina 27562 MAY 18 1988 File Number. SHF/10-13510 NRC-625 Letter Number: HO-880112 (0)

Dr. J. Nelson Grace United States Nuclear Regulatory Commission Region II 101 Marietta Street, Northwest (Suite 2900)

Atlanta, Georgia 30323 SHEARON HARRIS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 10CFR PART 21 NOTIFICATION DC MOTOR FAILURE

Dear Dr. Grace:

Attached is our report on the subject item which was deemed reportable per the provisions of 10CFR21, on May 13, 1988. Carolina Power & Light Company considers that the actions taken/planned are adequate for resolution of this item.

If you should have any questions regarding this matter, please contact Mr. Dean Tibbitts at (919) 362-2718.

Very truly yours, R. A. Watson Vice President Harris Nuclear Project MGW:dj Enclosure cc: Messrs. B. C. Buckley (NRR)

G. F. Maxwell (NRC-SHNPP)

NRC Document Control Desk 8806030324 8805i8 PDR ADOCK 05000400 S DCD MEM/HO-8801120/Page 1/OS1

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CAROLINA POWER & LIGHT COMPANY SHEARON HARRIS NUCLEAR POWER PLANT INITIAL WRITTEN REPORT DC MOTOR FAILURE ON AUXILIARY FEEDWATER LIMITORQUE OPERATED VALVES MAY 13, 1988 REPORTABLE UNDER 10CFR21 MEM/H0-8801120/Page 1/OS1

SUBJECT:

Shearon Harris Nuclear Power Plant, 10CFR21 reportable deficiency in the control and power circuits for DC motor operated valves associated with the operation of the turbine-driven auxiliary feedwater (AFW) pump. The motor actuators were supplied by Limitorque.

ITEM: Deficiency in turbine-driven AFW System operation.

SUPPLIED BY: Ebasco Services Incorporated, New York, New York.

NATURE OF DEFICIENCY: Due to the lack of surge protection for DC motors on Limitorque operated valves, a common mode failure mechanism is created. Upon opening the starter contacts "following a DC valve operation, a high voltage transient is experienced in the shunt coil due to the collapsing field. This voltage transient in the shunt coil may have a magnitude of several thousand volts and typically exceeds the rating of the insulation on the coil windings. Consequently this voltage transient can result in insulation damage and subsequent shorting of the shunt coil and/or an open shunt in the shunt coil. The loss of the shunt coil field results in a loss of speed control and may result in an inoperable valve. The fact that no surge protection is provided for the discharge of the shunt field is considered a design and application defect.

DATE PROBLEM WAS CONFIRMED TO EXIST: On March 1, 1988 a DC motor operated AFW isolation valve (2AF-V117SA-1) failed a routine maintenance periodic test due to an open shunt coil. Because of a similar failure of a DC motor operated valve at CP&Ls Brunswick Nuclear Plant, the motor was removed and sent to CP&Ls HE&EC laboratory to determine the cause of failure. Subsequent review and evaluation by CP&Ls Nuclear .Engineering Department and the Harris Plant Nuclear Safety Committee determinec this item to be reportable per 10CFR21 on May 13, 1988.

PROBLEM REPORTED: D. L. Tibbitts notified the NRC (Mr. R. E. Carroll, Jr.)

that this item was reportable under 10CFR21 on May 13, 1988.

MEM/HO-8801120/Page 2/OS1

SCOPE OF PROBLEM: The deficiency involves the operability of the turbine-driven AFW pump and the capability to isolate AFW flow to a faulted steam generator during a postulated main steam line break.

SAFETY IMPLICATIONS: DC motors without surge protection are utilized on six Limitorque operated valves in the AFW System. All are associated with the operation of the turbine-driven AFW pump. These valves are 2AF-V118SA-.,1, 2AF-V117SA-1 (the failed valve), 2AF-V118SA-1, 2MS-VBSA-1, 2MS-V9SB-1, and 1MS-T (see Figure 1).

j v The first three valves listed are normally open and operate to isolate feedwater flow to a faulted steam generator. These valves are powered from the Train A battery. Failure of any of these three isolation valves is compensated for by an electrohydraulic AC powered flow control valve in series with the isolation valve. These flow control valves are supplied by the Train B battery via the uninterruptible power supply system. These valves are not subject to the same voltage problem. The next two valves are normally closed and are opened to provide steam to the auxiliary feedwater pump turbine.

These valves are redundant with one fed from the Train A battery and one fed from the Train B battery. Failure of both of these valves to operate would result in the inability to automatically or manually from the main control board provide steam to the turbine-driven auxiliary feedwater pump turbine. The last valve (1MS-T) is a turbine trip and throttle valve. This valve is normally open and provides protection from a turbine overspeed. Failure of this valves DC motor to,operate would result in the inability to remotely open the valve following a AFW turbine trip, resulting in the inability to provide steam, to the turbine-driven AFW pump turbine.

REASON PROBLEM IS REPORTABLE: DC motor failures in this system in conjunction with a loss of AC power could result in the loss of both the (AC) motor-driven AFW pumps and the (DC) turbine-driven AFW pump thereby creating a major reduction in the degree of protection provided. In addition, the three isolation valves are required to isolate AFW to a faulted steam generator in the event of a postulated main steam line break accident.

MEM/HO-8801120/Page 3/OSl

CORRECTIVE ACTION: Resistance measurements have been taken on each of the subject DC motors to verify the integrity of the shunt field. Until surge protection is installed, controls have been, established to require resistance measurements be taken after each valve operation. Since the voltage spike which may cause failure occurs at the end of the valve stroke, upon opening the contactors, a verification after operation will provide reasonable assurance that the valve will operate the next time it is required to do so ~

To correct this deficiency a plant modification will be implemented to install surge protection for the shunt coil circuitry of the subject DC motors. The projected completion date for installation of the modification is October 1, 1988.

MEM/HO-8801120/Page 4/OSl

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