ML20087L635

Ro:On 730303 & 0426,test of Undervoltage Relays of 1A01 & 1A02 Nonsafeguards Bus Undervoltage Relays Disclosed Three Out of Four Malfunctional.Caused by Setting of Shaft in Guide Bearing.Relays Removed & Returned to Vendor for Exam

ML20087L635
Person / Time
Site:	Point Beach
Issue date:	05/14/1973
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8403270317
Download: ML20087L635 (2)

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231 WEST MICHIGAN, MILWAUKEE, WISCONSIN 53201, op. 73

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t' O , 's May 14, 1973 b y bs Mr. John F. O' Leary, Director y Directorate of Licensing  %

U. S. Atomic Energy Commission Washington, D. C. 20645

Dear Mr. O' Leary:

DOCKET NO. 50-266 FAILURE DURING TEST OI:

NON-SAFEGUARDS BUS UNDERVOLTAGE .tELAY POINT BEACH NUCLEAR PLANT In accordance with Section 15.6.6.A.3.b of the Technical Specifications for Point Beach Nuclear Plant, Units 1 and 2, Facility Operating License Nos. DPR-24 and DPR-27, this report is submitted with respect to the failure of a non-safeguards bus undervoltage relay to operate when tested.'

Following a five months' refueling and maintenance shut-down and immediately prior to taking Unit.,1 critical at Point Beach on March 3, 1973, a test of the undervoltage relays of the 1A01 and 1A02 non-safeguards bus undervoltage relays disclosed that, at the first test, three out of the four undervoltage relays 3

failed to perform their function of opening the reactor trip -

breaker. All operated satisfactorily on the second and numerous .'

subsequent tests. A careful examination of the relays indi.cated no damage and it was concluded that the long period of idleness during the refueling shutdown had permitted the relays to develop a " set" which was corrected after some periodic test operation of the relays. .

A routine periodic test of the relays was repeated on April 10, 1973, and all four relays operated satisfa'ctorily.

On April 26, 1973, a further periodic test was conducted on the relays. This time the 1-274-A02 relay failed to operate the first time it was tested. It did operate on subsequent tests. '

It should be noted that this was the first failure of this parti cular relay; the relay having successfully operated on all previous ~~~ '

tests.

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s Mr. John F. O' Leary, Director May 14, 1973

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These relays are Westinghouse Type SV, Style 1876099 and consist of a plug in the center of a wound coil. Energizing of

., the coal " floats" the plug. Loss or reduction of voltage in the coil permits the plug to drop and this motion is transmitted via a light shaft through a Teflon guide bearing at the top of the coil to contacts, which, upon closing, initiate the reactor trip.

" Setting" of the shaft in the guide bearing appears to ,

, be the possible cause of the relay's malfunction at this date.

The function of the relays in question is to initiate a' Unit 1 reactor trip should an undervoltage condition occur on the 4160 V LA01 and 1A02 non-safeguards buses. A one out of two signals off each bus is required to initiate the trip. There-fore, the failure of one relay to operate would not prevent under-voltage on these buses tripping the reactor. Additional redun-dancy is provided in that under-frequency on these buses also leads to tripping of the reactor coolant pumps, main steam gen-erator feed pumps and main condenser circulating pumps, each of which via additional channels of redundancy lead to reactor trip-ping. It is concluded therefore that the failure of one of the 4160 V non-safeguards bus undervoltage relays to operate would

] not create a condition seriously affecting nuclear unit safety.

Following the periodic test of April 26, 1973, the four relays were removed and were returned to the vendor for examina-tion and analysis. Four new relays of the same manufacture and type have been installed and will be tested biweekly until fur-ther analysis of the relays' behavior is made by the vendor.

Very truly yours,

^ / 0 Sol Burstein Senio Vice President cc: Mr. Boyce H. Grier, Regional Director Directorate,of Regulatory Operations, Region III U.S. Atomic Energy Commission 799 Roosevelt Road

Glen Ellyn, Illinois 60137 4

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