Press Information

MHI Completes Delivery of 2 Replacement Steam Generators,
To California's Largest Electric Utility
-- One of World's Largest SGs: 7-meter Diameter, 580-metric ton Weight --


Tokyo, February 24, 2009 - Mitsubishi Heavy Industries, Ltd. (MHI) has completed the delivery of two replacement steam generators (RSGs) for the San Onofre Nuclear Generating Station (SONGS) Unit 2 of Southern California Edison (SCE), California's largest electric utility. The RSGs delivered are among the world's largest, each measuring approximately seven meters in external diameter, weighing 580 metric tons and housing approximately 10,000 heat transfer tubes. The RSGs arrived at the SONGS site on February 14 and are slated to replace existing steam generators (SGs) at SONGS Unit 2 during its next refueling and maintenance outage scheduled in autumn 2009. Later this year MHI will ship two additional RSGs to SCE for installation in SONGS Unit 3 during the fall of 2010.

 [ Replacement steam generator for San Onofre Nuclear Generating Station ]
SONGS, which is located in northern San Diego County, consists of two approximately 1,100 MWe (megawatts of electricity) pressurized water reactor (PWR) units that went into operation in 1983 and 1984. The plant is Southern California's largest source of baseload power and has a capacity rating of 97 percent between refueling and maintenance outages.

MHI received the RSGs order from SCE in September 2004 after winning an international bidding competition. The RSGs were manufactured at the company's Kobe Shipyard & Machinery Works.

SGs are crucial components of PWR nuclear power plants (NPP) that transfer the thermal energy generated in the reactor vessel to the turbine generator by producing steam to drive the turbine. SGs require especially high design and manufacturing capabilities in addition to safety and reliability. MHI has manufactured components for PWRs since the dawn of nuclear power generation in Japan and is the nation's only SG manufacturer. Compared with a typical SG for a domestic PWR NPP, the RSGs for SONGS are about 1.5 times larger in size and heavier in weight, and contain almost triple in the number of heat transfer tubes.

MHI's RSGs have been highly acclaimed internationally for their technology, quality and robust track record. The company has processed overseas orders of 28 units, mainly from North America and Europe. The total reaches 122 units if SGs and RSGs for the domestic market are included. By providing RSGs and other replacement components, MHI has helped extend the operational life and boost the safety and economic efficiency of the existing PWR NPPs both in Japan and abroad.

Going forward, as a world-leading supplier comprehensively satisfying all NPP-related needs from basic planning of the PWR plants to design, manufacturing, inspections, installation, test operation and services after their operation commenced, MHI will leverage its technological expertise and excellent track record and conduct overseas marketing of its NPP components aggressively.


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Mitsubishi Heavy Industries (MHI) Group is one of the world’s leading industrial groups, spanning energy, smart infrastructure, industrial machinery, aerospace and defense. MHI Group combines cutting-edge technology with deep experience to deliver innovative, integrated solutions that help to realize a carbon neutral world, improve the quality of life and ensure a safer world. For more information, please visit or follow our insights and stories on