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ROSEMEAD, Calif., May 28, 2013 — Letters released today by Southern California Edison (SCE) demonstrate that it exercised responsible oversight of the vendor of the San Onofre nuclear plant replacement steam generators before any designs were completed or approved.

SCE is restating its position after allegations from U.S. Sen. Barbara Boxer at a press conference this afternoon regarding correspondence from SCE to Mitsubishi Heavy Industries (MHI), the manufacturer of the replacement steam generators. SCE provided the November 2004 correspondence referenced by Sen. Boxer and a June 2005 letter from SCE to MHI to the Nuclear Regulatory Commission (NRC) in April in connection with ongoing NRC proceedings.

“In response to Sen. Boxer’s statement, we believe that the determination for restart must be made based on technical merits, through the established nuclear regulatory process,” said Pete Dietrich, SCE senior vice president and chief nuclear officer.

“SCE’s own oversight of MHI’s design review complied with industry standards and best practices.” He added. “SCE would never, and did not, install steam generators that it believed would impact public safety or impair reliability.”

The November 2004 and June 2005 letters have also been provided to parties involved in a California Public Utilities Commission investigation and are now posted online.

These letters emphasize the importance of careful attention to the design of the steam generators. Recognizing that SCE was not the designer of the steam generators and that there were limitations on the assistance SCE could provide, the letters identify a number of design issues that SCE asked MHI to focus on to ensure that design flaws were not inadvertently introduced.

SCE took numerous steps to ensure that MHI appropriately addressed these concerns, including design review meetings, executive oversight meetings, and meetings of many other groups of SCE and MHI personnel.

“We take very seriously our responsibility to ensure we protect the public’s health and safety,” Dietrich said. “These documents demonstrate the type of careful oversight that SCE exercised during the replacement steam generator project and also served to establish our expectations of MHI.”

In the November 2004 letter, SCE emphasized the care that would be needed during the design phase because of the differences between the new and old units. These differences—which were intended to improve the overall performance of the new units—were permitted under the NRC’s 50.59 process, which allows changes to a nuclear facility if certain criteria are met. Contrary to Sen. Boxer’s suggestion, Section 50.59 does NOT require that replacement equipment be “like for like” or identical to the equipment being replaced.

Instead, the very purpose of the regulation is to permit certain types of design changes. In general, a licensee may make a change to the design of a licensed facility without prior NRC approval if the change does not require a change to the plant’s NRC-approved technical specifications or if the change would not change the facility “as described in the safety analysis report.” This report is the official description of the nuclear plant that was approved by the NRC in the initial licensing, as updated throughout the life of the plant.

SCE advised the NRC that the San Onofre steam generators contained a number of different features from the previous design. In fact, safety evaluations prepared by the NRC in connection with amendments to the San Onofre license associated with the steam generator replacements described the most important of those changes in detail. At no time did SCE hide the differences from the NRC, nor did it seek to mislead the NRC concerning the applicability of Section 50.59 to the project. Any suggestion that seeks to draw from the November 2004 letter a contrary conclusion is simply incorrect and relies on the fundamental error of viewing Section 50.59 as applying to identical, or “like for like” replacements.

A leak occurred in one of the San Onofre steam generators in January 2012, and both units have remained shut down since then. The NRC has determined that the problems in the steam generators were associated with errors in MHI’s computer modeling, which led to underestimation of thermal hydraulic conditions in the generators.

The San Onofre nuclear plant is the largest source of baseload generation and voltage support in the region and is a critical asset in meeting California’s clean energy needs. Both units at the plant are currently safely shut down. 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 leak in a steam generator tube.

More information is available at and at San Onofre is jointly owned by SCE (78.21 percent), San Diego Gas & Electric (20 percent) and the city of Riverside (1.79 percent). Follow us on Twitter ( and Facebook (

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.


SCE Exercised Responsible Oversight for Replacement Steam Generators at the San Onofre Nuclear Plant