ML18038B737

LER 96-004-00:on 960717,ECCS Division I Instrumentation Rendered ECCS Equipment Inoperable.Caused by Loss of Inverter Output.Cleared Fuse,Shorted SCR & Failed Inverter Control Board Was Replaced in ECCS Division I Atu Inverter

ML18038B737
Person / Time
Site:	Browns Ferry
Issue date:	08/16/1996
From:	Jay Wallace TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML18038B736	List: ML18038B735 ML18038B737
References
LER-96-004-03, LER-96-4-3, NUDOCS 9608220104
Download: ML18038B737 (12)

Text

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 31504104 (4-95) EXPIRES 04/30/98 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS MANDATORY INFORMATION COLLECTlON REQUEST:

60.0 HRS. REPORTED LESSONS LEARNED ARE LICENSEE EVENT REPORT (LER) INCORPORATED INTO THE UCENSING PROCESS AND FED BACK TO INDUSTRY. FORWARD COMMENTS REGARDING (See reverse for required number of FACILITY NAIIE II) digits/characters for each block) 8URDEN ESTIMATE TO THE INFORMATIONAND RECORDS MANAGEMENT BRANCH (TA F33). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC DOCKET NUllSER (I) 2~

FACE P) 1, Browns Ferry Nuclear Plant (BFN) Unit 3 05000296 1 OF6 TITLE ie)

Loss of the Emergency Core Cooling Systems (ECCS) Division I Instrumentation Renders ECCS Equipment Inoperable.

EVENT DATE 5 LER NUMBER 6 REPORT DATE OTHER FACIUTIES INVOLVED 8 FACIUTY SEQUENTIAL REVISION DAY YEAR DAY YEAR NUM8ER NUMBER N/A FACIUTY NAM 07 17 96 96 004 00 08 16 96 N/A OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR: (Check one or moro) (11)

MODE (9) N 20.2201(b) 20.2203(a)(2)(v) 50.73(a)(2)(i)(B) 50.73(a)(2)(viii) 20.2203(a)(1) 20.2203(a)(3)(i) 50.73(a)(2)(ii) 50.73(a)(2)(x)

POWER 100 LEVEL (10) 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20,2203(a)(4) 50.73(a)(2)(iv) OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50.73(a)(2)(v) Speci/y In Abstract below or in NRC Form 366A 20.2203(a)(2)(iv) 50.36(c)(2) X 50.73(a)(2)(vii)

UCENSEE CONTACT FOR THIS LER (12)

NAMF TELEPHONE NUMBER 0oervde Atee Code)

James E. Wallace, Compliance Licensing Engineer (205) 729-7874 COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 13 CAUSE SYSTEM COMPONENT MANUFACTURER

','AUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS X AD SCR H177 X AD FU B569 AD INVT H177 SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR YES SUBMISSION NO DATE (15) 10 30 96 (If yes, complete EXPECTED SUBMISSION DATE).

ABSTRACT (Limit to 1400 spaces, l.e., approximately 15 single-spaced typewritten lines) (16)

On July 17, 1996, with Units 2 and 3 at approximately 100 percent power and Unit 1 shutdown and defueled, Unit 3 operators declared ECCS Division I instrumentation inoperable, in accordance with TS 3.2.B. This event was presumed to be caused by a failed control board in the ECCS Division I Analog Trip Unit Invefter, which resulted in the loss of the inverter output. Unit 3 entered several limiting condition for operations (LCO) and prepared to shut the unit down.

Operators initiated troubleshooting that found a cleared fuse, a shorted silicon control rectifier, and the failed ATU Inverter control board. The failed components were replaced, the ECCS instrumentation was declared operable, and the LCOs were exited. On August 6, 1998, a second similar event occurred. When TVA has determined the root causes and corrective actions for these events, TVA will provide a supplemental report.

This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(vii) as any event where a single cause or condition caused at least one independent train or channel to become inoperable in multiple systems.

Previous LERs on similar events were: 260/94001, 260/94006, and 260/94010.

9608220104 960816 PDR ADDCK 05000296 S PDR

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NRC FORM ~MBA U.S. NUCLEAR REGULATORY COMMISSION (4-95)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FAG ILITX NAME DOCKET PAGE NUMBER NUMBER Browns Ferry Unit 3 05000296 6 of 6 96 -- 004 -- 00 TEXT more space rs requrr, use rrrooa copes orm (17) failure. However, the root cause of the event was determined to be a failure of the ECCS ATU Inverter control board. Since this event occurred on a different unit, the corrective actions taken in LER 260/94001 would not have precluded this event (296/96004).

LER 260/94006 described the failure of an ECCS Division I ATU Inverter, 250v DC reactor motor operator valve (RMOV) breaker trip.

This ECCS RMOV breaker tripped as a result of 'a shorted SCR.

Therefore, corrective actions taken for LER 260/94006 would not have precluded this event (296/96004).

LER 260/94010 addressed the failure of Cl capacitor in the Division II ATU Inverter capacitor bank. This failed capacitor was a result of a manufacturing defect. Therefore, corrective actions for LER 260/94010 would not have precluded this event '(296/96004).

TVA has had previous similar events. At this time, TVA believes that corrective actions taken to resolve those events would not have precluded this event. However, due to the aggzegate of these events, TVA is conducting a broader evaluation of inverter problems. Consequently, TVA's current presumption that past

'inverter problems were separate and isolated may change. This evaluation result will be addressed in the supplemental report.

VZZ. CQbRCZQKENTS TVA expects to submit a supplemental report by October 30, 1996.

Energy Industry Identification System (EIIS) system and component, codes are identified in the text with brackets (e.g., [XX)).

NRC FORM 366A (4-95)

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