ML20046B148

LER 93-012-00:on 930702,reactor Core Isolation Cooling Sys Declared Inoperable Due to Associated Bus Voltage Dropping Below TS Limits.Sent Operator to Cycle Timer Which Caused Affected Contact to reclose.W/930730 Ltr

ML20046B148
Person / Time
Site:	LaSalle
Issue date:	07/30/1993
From:	Schmeltz J, Sharko D COMMONWEALTH EDISON CO.
To:	Office of Nuclear Reactor Regulation
References
LER-93-012-02, LER-93-12-2, NUDOCS 9308030176
Download: ML20046B148 (4)

Text

i i

j Commonw:alth Edison  !

. LaSalle County Nuclear Station  !

'2601 N. 21st. Rd.

Marseilles, Illinois 61341 Telephone 815/357-6761 July 30, 1993 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Mail Station Pl-137 Hashington, D.C. 20555

Dear Sir:

Licensee Event Report #93-012-00, Docket #050-373 is being submitted to your office in accordance with 10CFR50.73(a)(2)(v).  !

.c., e J. V. Schmeltz Station Manager LaSalle County Station JVS/DS/gry i Enclosure xt: Nuclear Licensing Administrator NRC Resident Inspector NRC Region III Administrator INPO - Records Center IDNS Resident Inspector 1

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9309030176 930730 2" PDR ADOCK 05000373 h / /

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LICENSEE EVENT REPORT (LER) ,

Facility Name (1) Docket Number (2) Pace (3)

LaSalle Cbunty Statien Unit 0 15 10 10 10 1 31 71 3 1l of! 0 l 3 Title (4) Reator Core Isolation Cooling System Declared Inoperable Due to Associated Bus Voltage Dropping Below Technical Specification Limits Event Date (5) LER Number (6) Report Date (7) Other Facilities Involved (B)

Month Day Year Year /// Sequential //jj

/ Revision Month Day Year Facility Names Docket Number (s) f j/j/j/ Number /// Number 0 15 10 10 10 I I I 01 7 01 2 91 3 91 3

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011 l2

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010 017I310 91 3 0 15 10 10 10 l I l THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10CFR OP W M

• PODE (9) 1 20.402(b) _ 20.405(c) _ 50.73(a)(2)(iv) _ 73.71(b)

POWER _ 20.405(a)(1)(i) __ 50.36(c)(1) ,. X__ 50.73(a)(2)(v) _ 73.71(c)

LEVEL 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) Other (Specify l9 l9 (10) 0 _ 20.405(a)(1)(iii) _._ 50.73(a)(2)(i) __ 50.73(a)(2)(viii)(A) in Abstract

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j ///// j// f _ 20.405(a)(1)(iv) _ 50.73(a)(2)(ii) _ 50.73(a)(2)(viii)(B) below and in f3333333333333333f33333333 20.405(ani nv> _ 50.73on2nno _50.73(an2n ) Too  ;

LICENSEE CONTACT FOR THIS LER (12) l Name TELEPHONE NUMBER AREA CODE Deb Sharko. System Enaineer Ext. 2247 81115 3 15 17 I -16 17 16 I COMPLETE ONE LINE FOR EACH COMPON N FAILURE DESCRIBE 0 IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE TUPER TO NPRDS TURER TO NPRDS i X BlN IT IM IR P 13 11 19 Y l l l l l 1 l t i l 1 I I I i i l i I I I SUPPLEMENTAL REPORT EXPECTED (14) Expected Month I Day I Year Submission lyes (!f ves comolete EXPECTED SUBMISSION DATE) X l NO l l1 ll ABSTRACT (Limit to 1400 spaces, i.e, approximately fif teen single-space typewritten lines) (16) 0 On July 2,1993, Unit 1 was in Operational Mode 1 (Run) at 99.7% power. At 1329 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.056845e-4 months <br />, a 250 VDC bus (121Y) undervoltage alarm was received. Locally, the 250 VDC battery charger (1DC03E) output was observed to have f ailed to zero (0) amps.

For the Reactor Core Isolation Cooling (RCIC, RI) System to be operable, Technical Specification 4.7.3.d.1.a requires the bus 121Y voltage to be greater than or equal to 250V and that the battery charger be operable.

Since neither of these conditions were satisfied, the RCIC System was declared inoperable and a 14 day timeclock was started (per Technical Specification 3.7.3).

Locally, the 250 VDC battery charger timer was cycled. The charger output then returned to normal.

The cause of this event was loss of continuity of a timer contact on the 250 VDC battery charger.

System Engineering will investigate the feasibility of permanently bypassing the battery charger timer.

The safety consequences of this event were minimal, since the High Pressure Core Spray (HPCS) System was fully operational.

LICENSEE EVENT REPORV (LER) VEXV CONTINUATION Form Ree 2.0 FACILITY NAME ,(1) DOCKET NUMBER (2) LER NUMBER (6) Paae (3)

Year ,j/j/ Sequential

/ //

/j/j f

Revision

/// Number // Number LaSalle County St a ti on 0 1 5 1 0 1 0 1 0 1 31 71 3 9I3 -

0I1l2 - 0 10 01 2 0F 01 3 TEXT Energy Industry Identification System (EIIS) codes are identified in the text as [XX)

PLANT AND SYSTEM IDENTIFICATION:

General Electric - Boiling Water Reactor Energy Industry Identification System (.IIS) codes are identified in the text as [XX).

A. CONDITTCW PRIOR TO EVENT Untt(s): 1 Event Date: 07/02/93 Event Time: 1329 Hours Reactor Mode (s): 1 Mode (s) Name: Run Power Level (s): 2Ll%

B. DESCRIPTION OF EVENT On July 2,1993 with Unit 1 in Operational Mode 1 (Run) at 99.7% power. At 1329 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.056845e-4 months <br />, a 250 VDC bus (121Y) undervoltage slann was received. There were no evolutions in progress which would have caused l this alarm. Bus 121Y voltage was noted to be less than 250V. Locally, the 250 VDC battery charger l (1DC03E) output was observed to have f ailed to zero (0) amps.

For the Reactor Core Isolation Cooling (RCIC, RI)[BN) System to be operable, Technical Specification 4.7.3.d.1.a requires the bus 121Y voltage to be greater than or equal to 250V and that the battery charger be operable. Since neither of these conditions were satisfied, the RCIC System was declared inoperable and a 14 day timeclock was started (per Technical Specification 3.7.3).

The Battery Charger Timer was cycled to a setting of several hours and then back to zero. After performing this action, the battery charger output returned to normal.

AN ENS Notification was made at 1549 hours0.0179 days <br />0.43 hours <br />0.00256 weeks <br />5.893945e-4 months <br />, on July 2,1993, due to a loss of a safe shutdown capability as a result of RCIC being declared inoperable.

This event is reported to the Nuclear Regulatory Comission as a Licensee Event Report in accordance with 10CFR50.73(a)(2)(v) due to a loss of a safe shutdown capability.

C. APPARENT CAUSE OF EVENT The root cause of this event was the loss of continuity of a timer contact on the 250 VDC Battery Charger due to either physical displacement or glazing over of the contact.

The 250 VDC Battery Charger Timer is in series with the float / equalize circuit. During nonnal operation, the charger is on float and the timer is positioned at 0 (2ero) hours, causing the associated contact to be closed. This contact completes the circuit, providing charger output to the battery and buses 121X and 121Y. When contact continuity was lost, the circuit was opened and charger output dropped to zero. When the timer was cycled, the contact reclosed and the circuit was completed. At this time, the charger output returned to normal.

, Mn j@w LICENSEE EVENT REPORT (LQLJEkT CONTIE8.Tlfit Form Rev 2.0

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FACILITY NAME (1) DOCKET NUM8ER (2) LER PfR b 6) Pace (3)

Year // /// Revision Fe/.l

'e Sequential Numeer F/3 Number taSalle Cosnty Station 01510l0l0131713 913 - Ol112 - 0 IO 01 3 0F 01 3 TEXT Energy Industry Identification System (EIIS) codes are identified in the text as (XX]

D. SAFETY AMALYSIS OF EVENT The safety consequences of this event were minimal. The Unit 1 High Pressure Core Spray (HPCS, HP)(BG)

System was fully operational during this event. Also, although RCIC was declared inoperable, there were no other RCIC component f ailures that would inhibit operation of the system. The Unit 1 250 VDC battery would have provided the designed loads, if required.

E. CORRECTIVE ACTIONS The innediate corrective action was to send an operator to cycle the timer which caused the affected contact to reclose. The battery charger output then returned to nonnal, and was verified operable per LaSalle Operating Surveillance LOS-0C-Wl, " Weekly Surveillance for the Safety related 250 VDC,125 VDC and Diesel Fire Pump Batteries." The timer contacts could not be cleaned because they are internal to the timer.

As a long term solution LaSalle Operating Procedure LOP-DC-07 " Battery Equalizing Charges" will be revised to eliminate use of the timer when performing a battery equalize charge. The procedure revision will apply to all battery chargers (safety and non-safety related) which have a timer and a float /equalire switch. Currently, battery charge durations are controlled by procedure, making use of the Charger Timer unnecessary. Additionally, Systems Engineering will investigate the feasibility of permanently bypassing the Charger Timer. Action Item Record ( AIR)373-1BO-93-0052401 will track this i nves ti ga ti on.

F. PREVIOUS EVENTS None.

G. COMPONENT FAILLRE DATA I

P%NUFACTURER NOMENCLATURE MODEL NUMBER MFG PART NUMBER Power Conversion Timer Q55-13 0000958433 Products, Inc. 0-120 hours

pnA m-les 95 1 00 514 PZF R 3 VENT StKMARY sus" ' l AND o?_P_ _=!_"

CAL"S3 COD 38 Reactor trip , NRC violation, levei___

p Lost generation

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Cost > $25,000 EST actuation GSEP event, class ____.!

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Hazard or spill

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NRC reportable Tech Spec LCO  !

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~._ Personnel injury A LER313[geg Potential or future los:'

Com pone nt SALP functional ares __

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