Southern California Edison Submits Response to Confirmatory Action Letter
and Unit 2 Restart Plans to Nuclear Regulatory Commission
ROSEMEAD, Calif. -- October 04, 2012
Southern California Edison (SCE) has submitted its response to the Nuclear
Regulatory Commission’s (NRC) Confirmatory Action Letter, along with its
restart plan for Unit 2 of its San Onofre Nuclear Generating Station. The
response, the restart plan and supporting analyses can be read at
www.SONGScommunity.com. The unit cannot be restarted until all plans have been
approved by the NRC.
“Safety is our top priority, and after conducting more than 170,000
inspections to understand and prevent the problem, and confirming the
corrective actions we have taken to solve the problem with the top experts
from around the world, we have concluded that Unit 2 at San Onofre can be
operated safely and within industry norms,” said Ron Litzinger, president of
SCE. “When implemented, this plan will get San Onofre Unit 2 back to providing
reliable and clean energy to Southern Californians.”
The response and restart plans are being submitted simultaneously to provide
the NRC with all the relevant information needed to evaluate the full spectrum
of repairs, corrective actions and additional safety measures proposed for
restart and safe operations at the plant. Unit 3 will remain offline while the
utility continues to study the potential solutions that are unique to that
The response to the NRC covers the causes of the tube wear, repairs and
corrective actions required for the Unit 2 steam generators, actions to
prevent the extensive tube-to-tube wear observed in Unit 3, and inspection and
safe operation protocols.
*SCE determined the tube-to-tube wear in the Unit 3 steam generators was
caused by a phenomenon called fluid elastic instability, a combination of
high-steam velocity and low-moisture conditions in specific locations of
the tube bundles and ineffective tube supports in the same locations.
*The high-steam velocity and low-moisture conditions existed in Unit 2 and
hence Unit 2 was susceptible to the same vibration-causing environment.
However, of the almost 20,000 tubes in Unit 2, all except two are known to
have been effectively supported throughout its 21-month operating period.
*SCE will operate Unit 2 at 70 percent power, which will prevent the
vibration-causing environment by decreasing steam velocity and increasing
moisture content. The 70 percent power level will result in steam
velocities and moisture content consistent with those that the industry
has successfully operated under for many years.
*SCE has chosen a conservative operating period of five months. SCE will
shut down Unit 2 after five months for inspection of the steam generator
tubes to ensure the continued structural integrity of the tubes, to
measure tube wear and to confirm that the solutions are working. The
five-month operating period affords an additional safety margin beyond the
analysis provided by the independent experts.
*SCE has plugged six tubes in Unit 2 indicating wear with greater than 35
percent through wall depth and preventively plugged more than 500 other
tubes. Steam generators are built with an allowance of extra tubes so that
tubes may be taken out of service for a variety of reasons, including
wear, and only 2.6 percent of the total tubes in Unit 2 have been plugged.
The restart plan covers the above repairs, corrective actions and operating
parameters, and also includes additional monitoring, detection and response
activities. Three independent experts in steam generators have performed
analyses that validate the safety of the restart and operations plans.
Proposed additional monitoring, detection and response activities include:
*Installation of early warning monitors that can detect extremely small
tube leaks faster;
*Enhanced sensitivity of vibration monitors;
*Additional monitoring and analysis systems; and
*Enhanced operator training to respond to extremely small tube leaks.
SCE anticipates discussing its Confirmatory Action Letter response with the
NRC in a public format.
Unit 2 was taken out of service Jan. 9, 2012, for a planned outage. Unit 3 was
safely taken offline Jan. 31, 2012, after station operators detected a small
leak in a steam generator tube. Unit 3 remains safely shut down for continued
inspections, analysis and testing.
For updates, please visit www.SONGScommunity.com, or follow us on Twitter at
www.twitter.com/SCE_SONGS and on www.facebook.com/SCE.
The San Onofre plant is jointly owned by SCE (78.21 percent), San Diego Gas &
Electric (20 percent) and the city of Riverside (1.79 percent).
About Southern California Edison
An Edison International (NYSE:EIX) company, Southern California Edison is one
of the nation’s largest electric utilities, serving a population of nearly 14
million via 4.9 million customer accounts in a 50,000-square-mile service area
within Central, Coastal and Southern California.
Southern California Edison
Media Relations, (626) 302-2255
Investor Relations Contact:
Scott Cunningham, (626) 302-2540
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