ML19290E989

LER 80-001/01T-0:on 800221,during Full Power Operation, Momentary Loss of Red Instrument Bus Occurred,Resulting in Power Range Channel N41 Failing Low.Caused by Faulty Capacitor in 2DY01 Power Supply.Capacitor Replaced

ML19290E989
Person / Time
Site:	Point Beach
Issue date:	02/28/1980
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19290E981	List: ML19290E980 ML19290E989
References
LER-80-001-01T-01, LER-80-1-1T-1, TAC-42249, TAC-42250, NUDOCS 8003170421
Download: ML19290E989 (2)

Text

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EVENT OESCRIPTION AND PROBABLE CONSEQUENCES h ITiTTl l During normal full power operation at 1831 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.966955e-4 months <br /> on 2-21-80, a momen- l o 3 l tary loss of the red instrument bus was experienced. This momentary 1014 l [ negative spike caused power range Channel N41 to fail low, resulting in o s I a turbine runback. Failure of Channel N41 resulted in a loss of redun j IO is i dancy until the bistable was placed in the tripped mode at 1842 on l 0 7 l 2-21-80 in accordance with ICP 10.2. This event is reportable in ac- l 0 a i cordanca with Technical Specification 15. 6. 9. 2. A. 2. LER 78-018/0lT-0 l 7 8 9 Unit 1 is similar. 80 SYSTEM CAUSE CAUSE COMP. VA LV E CODE CODE SUSCODE COMPONENT CODE SU8 CODE SUSCODE 7

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33 34 JS 3/ 40 el 42 43 44 CAUSE OESCRIPTION AND CORRECTIVE ACTIONS h i O l The negative cower spike which blew the Channel N41 fuses, was caused l li li l I by a faulty capacitor in the 2DY01 cower supply. The Channel N41 fusest iii2i l were replaced, the red instrument bus shif ted to the alternate power I i 3 l supply and all bistables returned to normal at 1858 on 2-21-80. The l Li_14_] I capacitor was replaced and the normal power supply restored at 1043 on l 7 8 9 2-22-80.8o

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ATTACH!iENT TO LICENSEE EVENT REPORT 80-001/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant Unit 2 Docke t No. 50- 301 During normal full power operation at 1831 hours0.0212 days <br />0.509 hours <br />0.00303 weeks <br />6.966955e-4 months <br /> on February 21, 1980, a momentary loss of the red instrument bus was experienced. This momentary negative spike caused power range Channel N41 to fail low and resulted in a turbine runback of 20% . Failure of power range Channel N41 low reduced the degree of redundancy for reactor trip instrumen-tation to less than that required by the Technical Specifi-cation (one versus two degrees o f redundancy) . The operator immediately initiated ICP 10.2 and restored the required redundancy by 1842 hours0.0213 days <br />0.512 hours <br />0.00305 weeks <br />7.00881e-4 months <br /> on February 21, 1980, by placing Channel N41 in the tripped mode.

Normal operation is with four channels operable , with two channel indications required for a reactor trip, yielding a redundancy of two channels. With Channel N41 in the tripped mode, an indication from any one of the three remaining operable channels would cause a reactor trip, thus , a redun-ddncy of two is again provided. The Technical Specification allows operation with a minimum of three channels operable and a minimum degree of redundancy of two'.

Following implementation of ICP 10.2 to regain full redundancy, a return to full power was commenced. The Channel N41 instrument fuses were replaced during this re turn to full power and the red instrument bus was shif ted nanually to the alternate power supply. By 185 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> on February 21, 1980, all bistable trip switches were returned to normal.

The following day at 1043 hours0.0121 days <br />0.29 hours <br />0.00172 weeks <br />3.968615e-4 months <br />, the red instrument bus was returned to the original power supply after a faulty capacitor was found and replaced in the 2DY01 power supply.

No further corrective action is required.

This event is reportable in accordance with Technical Specification 15.6.9.2.A.2.