NUREG-1455, Forwards AEOD/E93-03, Engineering Evaluation Rept, Electrical Inverter Operating Experience - 1985 to 1992. Findings Show That Inverter Failures Continue to Cause ESF Actuations,Reactor Trips & Turbine Runbacks
| ML20058L539 | |
| Person / Time | |
|---|---|
| Issue date: | 12/06/1993 |
| From: | Holahan G NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Boger B, Rossi C Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20058L544 | List: |
| References | |
| RTR-NUREG-1455 NUDOCS 9312170067 | |
| Download: ML20058L539 (4) | |
Text
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- f$f MCoq$g UNITED STATES
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NUCLEAR REGULATORY COMMISSION g g'.V l
t WASHINGTON. D.C. 20555 0001
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DEC 6 1993
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MEMORAf40VM FOR:
Bruce A. Boger Director Division of Reactor Controls and Human factors Office of Nuclear Reactor Regulation Charles E. Rossi, Director 1 4 0 u,,...,-cd Division nf Reactor Inspection and Licensee Performance Office of Nuclear Reactor Regulation FROM:
Gary M. Holahan, Director Division of Safety Programs Office for Analysis and Evaluation of Operational Data
SUBJECT:
ELECTRICAL INVERTER OPERATING EXPERIENCE 1985 TO 1992 Enclosed for your information and use is a report on electrical inverter operating experience for the last 7-) years.
Common-mode loss of five inverters at Nine Mile Point Unit 2 in August 1991, and the subsequent Incident Investigation Team report documented in NUREG 1455, " Transformer failure and Common-mode Loss of Instrument Power at Nine Mile Point Unit 2 on August 13, 1991," increased awareness of inverter problems.
In addition to the Nine Mile Point Unit 2 event, an additional 11 electrical inverter failures occurred in a span of 8 months.
In 1992, the vendor inspection branch conducted inspections at inverter manufacturers. AE00 assisted in the inspection of Exide Electronics. The operating experience shows a failure decrease in the last 7-) years, however, some problems still persist.
Electrical inverters provide the alternate source of power when the primary source fails and prevents the interruption of power to the powered equipment.
Operating experience has shown that when inverters fail, the consequences can impact both nonsafety-related and safety-related equipment. AE0D performed a case study of electrical inverters in 1986, AE0D/C605, " Operational Experience Involving Losses of Electrical Inverters."
This engineering evaluation g
updates the operating experience since that report was published.
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g The major findings of this engineering evaluation are:
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Inverter failures continue to cause engineered safety feature b,
actuations, reactor trips, and turbine runbacks.
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Electrolytic component failures continue to be the number one root-cause l
g of the failures, followed by human error.
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Capacitors are the most frequent failed component followed by transformers, silicon control rectifiers, and transfer switches.
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A root-cause is not identified in 15 percent of the failures.
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The frequency of electrical inverter problems has decreased in the past j
7-1 years.
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Following vendor' recommendations for minor and major maintenance would t
reduce the number of failures.
I The decrease in electrical inverter failures,.as identified by licensee event reports, was largely due to better cooling of the inverters, more preventive maintenance, and replacement of older units.. If the licensees followed vendor maintenance recommendations more rigorously, the number of failures could be further reduced through replacement of degraded components prior to failure.
An information notice to,the licensees on the operating experience of q
electrical inverters is suggested and a draft is enclosed.
i If you have any comments or need additional information, please contact Jore Ibarra of my staff. Mr. Ibarra can be reached on extension 492-4441.
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Originals!gned by j
J. E. Rosenthal for:
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Gary M. Holahan, Director
- l Division of Safety Programs j
Office for Analysis and Evaluation i
of Operational Data
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Enclosure:
As stated j
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- See previous concurrence:
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Multiple addressees 5.
The frequency of electrical inverter problems has decreased in the ast 7-1 years.
6.
Following vendor recommendations for minor and major maintenan would reduce the number of failures.
i The decrease in electrical inverter failures, as identified by 1 censee. event i
reports, was due in part to better cooling of the units, more eventive maintenance, and replacement of older units.
If the vendor m intenance recommendations were followed rigorously by more of the lic sees, the number of failures would be reduced by replacement of degraded to onents prior to failure. An information notice to the licensees on the o erating experience of electrical inverters is suggested; and a draft infor tion notice is enclosed.
i If you have any comments or need additional informa on, please contact Jose Ibarra of my staff. Mr. Ibarra can be reached on xtension 492-4441, i
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a Gary M. Iloljt an, Director Division f Safety Programs Office f Analysis and Evaluation l
of Op. rational Data
Enclosure:
As stated Distribution w/ enclosure:
PDR Dross KRaglin, TTC Central File EJor an MTaylor, EDO ROAB R/F LSp ssard RSavio, ACRS DSP R/F KlJ ockman Plewis, INPO Jibarra Rubin DQueener, NOAC Glanik PBaranowsky VChexal, EPRI JRosenthal AChaffee, NRR VBenaroya GMarcus, NRR l
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- S-previous concurrence:
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barra:mmk Glanik JRosenthal VBenaroya GHolahan
/01/93*
6/02/93*
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4 Multiple addressees '
5.
The frequency of electrical inverter problems has decreased in the past 7-) years.
6.
Vendor recommendations for minor and major maintenance would reduce the number of failures.
j The decrease in electrical inverter failures, as identified by licensee event reports, was due to better cooling of the units, better maintenance, and more periodic component replacement.
If the vendor maintenance recommendations were followed rigorously, the number of failures would be reduced by
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replacement of degraded components prior to failure. An information notice to the licensees on the operating experience of electrical inverters is suggested; and a draft information notice is enclosed.
If you have any comments or need additional information, please contact Jose Ibarra of my staff. Mr. Ibarra can be reached on extension 492-4441.
i l
l Gary M. Holahan, Director Division of Safety Programs Office for Analysis and Evaluation l
of Operational Data
Enclosure:
As stated l
Distribution w/ enclosure:
i PDR Dross KRaglin, TTC Central File EJordan MTaylor, EDO ROAB R/F LSpessard RSavio, ACRS DSP R/F KBrockman Plewis, INP0 JIbarra SRubin DQueener, NOAC Glanik PBaranowsky VChexal, EPRI JRosenthal AChaffee, NRR VBenaroya GMarcus, NRR I
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