The San Onofre Nuclear Generating Station, shut down since 2012 and now being decommissioned. Photo courtesy Southern California Edison

Times of San Diego: San Onofre Shutdown Due to ‘Redlined’ Steam Generators

By Hoa Quach  | View the original article

Times of San Diego, July 19, 2016

The cause of a leak in 2012 that led to the permanent shutdown of the San Onofre Nuclear Generating Station was steam generators being deliberately run too hot, too hard and too fast, according to a report released Tuesday by an independent watchdog organization.

But Southern California Edison countered that the source of the report was misinformed.

The analysis asserts that operators of the plant in northern San Diego County intentionally red-lined the system beyond its breaking point until it was overloaded and began to shake itself to pieces, according to the Public Watchdogs organization.

The study was conducted by Vinod Arora, a former fire protection engineer at SCE, co-owner of the power plant with San Diego Gas & Electric, according to a statement released by Public Watchdog.

The group said the conclusion was based on confidential documents that were released by the Nuclear Regulatory Commission under the Freedom of Information Act.

“Edison knew they were pushing San Onofre’s steam generators past the original design limit, but did it anyway for the sake of short-term profits and to correct other design deficiencies as a result of SCE’s unverified analytical assumptions,” Arora alleged.

“SCE was forced to make those assumptions because of time pressures to deploy the generators quickly,” Arora said. “As a result, SCE failed to perform the necessary research or ask the critical questions required to understand the impact of their design changes between the original and replacement steam generators.”

Shaking steam tubes, or what SCE called “critical in-plane vibrations” from tubes filled with superheated pressurized radioactive water, caused the tubes to bang together violently as a result of dry steam, according to Arora.

He said the impact of the abrasion and metal fatigue from the tube collisions ultimately created dangerous leaks.

Previous investigations have faulted the design of the steam generators, manufactured by the Japanese firm Mitsubishi Heavy Industries. Edison, which has retired San Onofre’s two reactors, is seeking financial compensation from the company.

Rosemead-based SCE released a statement saying the release issued today by Public Watchdog “relies on comments by a former SONGS employee that is simply misinformed.”

“As far back as September of 2013, the Nuclear Regulatory Commission identified flaws in how Mitsubishi Heavy Industries used its computer codes to design the failed steam generators at SONGS. The NRC further issued a ‘Notice of Non-Conformance’ against MHI for its flawed computer modeling in the failed design,” the statement said.

“In particular, the NRC reports indicated that MHI’s use of its computer codes in the design of the steam generators inaccurately predicted thermal hydraulic conditions in the steam generators, leading to tube vibration and wear, and a steam generator tube leak,” the statement continued. “The NRC inspection findings reinforced an NRC Augmented Inspection Team report in 2012 that identified MHI’s computer modeling errors.”

–City News Service

This article is published under the fair use provision of U.S. copyright law. Not a word has been changed. View the original article here.

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