Information Notice 2009-10, Transformer Failures - Recent Operating Experience
| ML090540218 | |
| Person / Time | |
|---|---|
| Issue date: | 07/07/2009 |
| From: | Dan Dorman, Mcginty T NRC/NMSS/FCSS, Division of Policy and Rulemaking |
| To: | |
| Sigmon R, NRR/DIRS/IOEB, 415-4018 | |
| References | |
| IN 2009-10 | |
| Download: ML090540218 (4) | |
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
OFFICE OF NUCLEAR MATERIAL SAFETY AND SAFEGUARDS
WASHINGTON, DC 20555-0001
July 7, 2009
NRC INFORMATION NOTICE 2009-10:
TRANSFORMER FAILURESRECENT
OPERATING EXPERIENCE
ADDRESSEES
All holders of operating licenses for nuclear power reactors under the provisions of Title 10 of
the Code of Federal Regulations (10 CFR) Part 50, Domestic Licensing of Production and
Utilization Facilities, except those who have ceased operations and have certified that fuel has
been permanently removed from the reactor vessel. All holders of licenses or certificates of fuel
cycle facilities. All holders of and applicants for nuclear power plant construction permits under
the provisions of 10 CFR Part 50. All holders of licenses or certificates for fuel cycle facilities.
PURPOSE
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice (IN) to inform
addressees of recent operating experience involving failures of large transformers. The NRC
expects that recipients will review the information for applicability to their facilities and consider
actions, as appropriate, to avoid similar problems. However, suggestions contained in this IN
are not NRC requirements; therefore, no specific action or written response is required.
DESCRIPTION OF CIRCUMSTANCES
For several years, available industry operating experience has indicated an increasing trend in
transformer failures, and has provided recommendations to reduce the chances of failure.
Improved preventive maintenance and monitoring practices have helped to identify some
problems before they developed to the point of failure, but the number of large transformers
events has not decreased and in fact continues to rise. The following are relatively recent
examples involving main power transformers:
Indian Point, Unit 3On April 6, 2007, while operating at 92-percent power, a fault
occurred on the No. 31 main transformer resulting in an automatic reactor trip and
transformer fire. Licensee Event Report (LER) 50-286/2007-002, which can be found on
the NRCs public Web site using Agencywide Documents Access and Management
System (ADAMS) Accession No. ML071620122, provides additional information.
River Bend StationOn May 4, 2007, an unplanned manual reactor scram was initiated
following the loss of cooling on the No. 2 main transformer (see LER 50-458/2007-002, ADAMS Accession No. ML071840161, for more information).
Grand Gulf Nuclear StationOn January 12, 2008, a manual reactor scram was initiated
following a loss of cooling to the main transformers (see LER 50-416/2008-001, ADAMS
Accession No. ML080700702, for more information).
Limerick Generating Station, Unit 2On February 1, 2008, a low voltage bushing
connection failed on the 2A main transformer resulting in a turbine trip and reactor
Diablo Canyon, Unit 2On August 16, 2008, an automatic reactor trip occurred resulting
from the failure of the main electrical transformer C phase. Plant operators
subsequently declared a Notification of Unusual Event due to an observed fire at the
C phase transformer (see LER 50-323/2008-001, ADAMS Accession No. ML082970221, for more information).
North Anna, Unit 2On October 29, 2008, while attempting to place the unit on line, the
turbine tripped on a generator lockout relay actuation. The C main transformer was
discovered to be spraying oil.
Oyster CreekOn November 28, 2008, an electrical fault internal to the M1A main
transformer led to an automatic reactor scram due to load reject. The transformer was
replaced with the spare, and on February 1, 2009, this transformer failed due to a
bushing failure, resulting in a reactor scram, fire, and declaration of a Notification of
Unusual Event (see LER 50-219/2008-001, ADAMS Accession No. ML090260082, and
LER 50-219/2009-001, ADAMS Accession No. ML090970735 for more information).
A review of licensees root cause evaluations for the large transformer failures shows that the
events are often the result of ineffective implementation of the transformer maintenance
program.
DISCUSSION
The events described above illustrate instances in which the loss or tripping of large
transformers resulted in plant transients, reactor trips, unnecessary starting of the emergency
diesel generators (EDGs), and declaration of plant events. Transformer failures have resulted
in eight declared plant events from January, 2007, to February, 2009, making them the second
leading reason for such declarations. While the large transformers discussed in this IN are
generally non-safety related, they are within the scope of the Maintenance Rule (Title 10 of the
Code of Federal Regulations, Section 50.65, Requirements for Monitoring the Effectiveness of
Maintenance at Nuclear Power Plants).
A relatively high incidence of transformer failures has occurred in the last few years, the majority
of which could have been avoided had the licensee fully evaluated and effectively implemented
corrective actions and recommendations identified in industry operating experience. These
corrective actions included a more effective maintenance program and a more proactive
approach to addressing abnormal indications. In particular, some utilities have installed online
automated oil analysis and monitoring system to support decisions regarding preventive and
corrective maintenance to improve transformer reliability. The Institute of Electrical and
Electronics Engineers (IEEE) provides industry guidance on this matter in Standard
C57.140-2006, IEEE Guide for the Evaluation and Reconditioning of Liquid Immersed Power
Transformers. However, it should be noted that the NRC has not endorsed this document, and
the recommendations it contains do not constitute NRC requirements.
CONTACT
This IN requires no specific action or written response. Please direct any questions about this
matter to the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
/RA/
/RA/
Timothy J. McGinty, Director
Daniel H. Dorman, Director
Division of Policy and Rulemaking
Division of Fuel Cycle Safety
Office of Nuclear Reactor Regulation
and Safeguards
Office of Nuclear Materials Safety
and Safeguards
Technical Contacts: Rebecca Sigmon, NRR/DIRS
Prem Sahay, NRR/DE
(301) 415-4018
(301) 415-8439
E-mail: Rebecca.Sigmon@nrc.gov
E-mail: Prem.Sahay@nrc.gov
NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov.
To access this information, select Electronic Reading Room and then Document Collections.
CONTACT
This IN requires no specific action or written response. Please direct any questions about this
matter to the technical contacts listed below or the appropriate Office of Nuclear Reactor
Regulation (NRR) project manager.
/RA/
/RA/
Timothy J. McGinty, Director
Daniel H. Dorman, Director
Division of Policy and Rulemaking
Division of Fuel Cycle Safety
Office of Nuclear Reactor Regulation
and Safeguards
Office of Nuclear Materials Safety
and Safeguards
Technical Contacts: Rebecca Sigmon, NRR/DIRS
Prem Sahay, NRR/DE
(301) 415-4018
(301) 415-8439
E-mail: Rebecca.Sigmon@nrc.gov
E-mail: Prem.Sahay@nrc.gov
NRC generic communications may be found on the NRC public Web site, http://www.nrc.gov.
To access this information, select Electronic Reading Room and then Document Collections.
Distribution: IN Reading File
Hard Copy to Elizabeth Doolittle (Mail Stop EBB 6003 1-D 2-M)
ADAMS Accession Number: ML090540218 TAC NO. ME0392 OFFICE
IOEB/DIRS
AC/DIRS/IOEB
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PSahay
GWilson
DATE
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DATE
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