ML20028F244

Final Deficiency Rept Re Undetectable Failure in Solid State Protection Sys.Initially Reported on 820804.Test Procedures Modified to Provide Adequate Assurances That Sys Can Be Functionally Tested W/O Creating Undetected Failure

ML20028F244
Person / Time
Site:	South Texas
Issue date:	01/24/1983
From:	Oprea G HOUSTON LIGHTING & POWER CO.
To:	Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-930, NUDOCS 8301310301
Download: ML20028F244 (4)

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, The Light co m P u y ><e'e 'ia'i8 8 & re er no. nex i7oo iie ste".T 77ooi <7is> 22s.e2ii l

January 24, 1983 ST-HL-AE-930 File Number: G12.129 SFN: V-0530 Mr. John T. Collins Regional Administrator, Region IV o I[ II' I , [j3 Nuclear Regulatory Commission l d

[a 611 Ryan Plaza Dr. , Suite 1000 j JAN25l983  :

Arlington, Texas 76012 L _l pl

Dear Mr. Collins:

South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Final Report Concerning Ilndetectable Failure in the SSPS On August 4, 1982, pursuant to 10CFR50.55(e) Houston Lighting & Power Company (HL&P) notified your office of a potentially reportable deficiency discovered by Westinghouse concerning an undetectable failure which could exist in on-line testing circuits for relays in the Solid State Protection System (SSPS). An interim report on this deficiency was transmitted to you on September 3, 1982. Attached is the Final Report which describes HL&P's proposed corrective action.

If you should have any questions concerning this matter, please contact l Mr. Michael E. Powell at (713)877-3281.

Very truly yours, 1 f?

. 'p a r I

Exe' tive ice President 1

MAM/mg Attachment l

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1 31 8301310301 830124 DR ADOCK 05000

inomien 1.ighting & Power Onnpany January 24, 1983 cc: G. W. Oprea, Jr. ST-HL-AE-930 J. H. Goldberg File Number: G12.129 J. G. Dewease Page 2 J. D. Parsons D. G. Barker M. R. Wisenburg R. A. Frazar J. W. Williams R. J. Maroni J. E. Geiger H. A. Walker S. M. Dew J. T. Collins (NRC)

H. E. Schierling (NRC)

W. M. Hill, Jr. (NRC)

M. D. Schwarz (Baker & Botts)

R. Gordon Gooch (Baker & Botts)

J. R. Newman (Lowenstein, Newman, Reis, & Axelrad)

STP RMS Director, Office of Inspection & Enforcement Nuclear Regulatory Commission Washington, D. C. 20555 G. W. Muench/R. L. Range Charles Bechhoefer, Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board P. O. Box 2121 U. S. Nuclear Regulatory Commission Corpus Christi, Texas 78403 Washington, D. C. 20555 H. L. Peterson/G. Pokorny Dr. James C. Lamb, III City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514 Austin, Texas 78767 J. B. Poston/A. vonRosenberg Mr. Ernest E. Hill City Public Service Board Lawrence Livermore Laboratory P.' O. Box 1771 University of California San Antonio, Texas 78296 P. O. Box 808, L-46 Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan, III Assistant Attorney General Harmon & Weiss for the State of Texas 1725 I Street, N. W.

P. O. Box 12548 Suite 506 Capitol Station Washington, D. C. 20006 Austin, Texas 78711 Lanny Sinkin Citizens for Equitable Utilities, Inc.

Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn 5106 Casa Oro Route 1, Box 1684 San Antonio, Texas 78233 Brazoria, Texas 77422 Jay Gutierrez, Esquire Hearing Attorney '

Office of the Executive Legal Director U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Revision Date 12-20-(7:

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c Final Report Concerning Attachment Undetectable Failure in the SSPS

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I. Summary A pushbutton test switch is'used in the Solid State Protection System (SSPS) to remove the shunt from 0 proving lamp. Failure of this pushbutton test switch to reinstate the shunt'following the test could result in an undetectable failure whereby associated safeguards devices would not actuate.

II. Description of the Incident On August 4, 1982, Houston Lighting & Power Company (HL&P) notified NRC-01E Region IV pursuant to 10CFR50.55(e) of a potentially reportable deficiency discovered by Westinghouse concerning an undetectable failure which could exist in on-line testing circuits for relays in the SSPS.

Westinghouse submitted a letter to NRC-0IE Headquarters (E.P. Rahe 'to R. DeYoung, NS-EPR-2638) dated August 6, 1982 describing this problem.

On September 3,1982, HL&P provided a First Interim Report regarding this deficiency.

Periodic testing of the SSPS includes actuu: ion of master relays which actuate safeguards systems. When a preselected a ster relay is energized, a proving lamp in series with the output (slave) relay coil confirms electrical continuity through the output relay coil. Operation of the output relay is prevented by reducing the output relay coil circuit voltage from 120VAC to 15VDC during the test. The master relay is operated by means of a pushbutton test switch, which also removes the shunt from the SSPS proving lamp and allows the 15VDC to energize the lampsto confirm the continuity of the output relay coil. Upon completion of the master relay and output relay coil continuity tests,120VAC circuit voltage is restored. However, if the switch p

contacts which shunt the proving lamp should fail to reclose as expected, 120VAC would be applied to the lamp when the system was called upon to~

operate. Depending on the output relay. coil impedance and the number of output relays being operated by the caster ralay contacts, the current #

through the lamp could cause,it to burn 'cpan before the output relay (s) energized. In such an instance assoc'iated safeguards devices in the affected train would not actuate.

III. Corrective Action ,

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Westinghouse and Bechtel have evaluated the subject deficiency and determined that modifications to the test procedure will provide adequate assurance that the SSPS can be functior; ally tested without creating a -

potential for the described undettcted iailure. This test procedure, which will basically follow the guidance provided by Westinghouse in the above referenced letter to R. DeYoung (NS-EPR-2638), will ensure that the shurt is reinstated after completion of the test.' Tlie South Texas Project test procedures and training will incorporate this test procedure.

IV. Recurrence Control This deficiency occurred due to a unique circumstance resulting from the design of the SSPS. Therefore, a formal recurrence control is not applicable in this instance. -

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!. Page 2 V. Safety Evaluation No dett iled safety evaluation was perfonned. It was assumed that l

failure of the SSPS to properly actuate safeguards devices is considered to

be a safety hazard. The appropriate corrective action as described above j will be implemented.

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