Who could have predicted the unique reactor tube vibrations that caused radioactive steam leaks and crippled the San Onofre Nuclear Generating Station 15 months ago?
That is not a rhetorical question. Researchers posted two articles in the Journal of Pressure Vessel Technology in 2005 and 2006 which, according to U-T San Diego, should have set off alarm bells at manufacturer Mitsubishi Heavy Industries and plant operator Southern California Edison.
Laypersons could, perhaps, be excused for passing up a chance to read “Fluidelastic Instability and Work-Rate Measurements of Steam-Generator U-Tubes in Air–Water Cross-Flow,” the original article in the February 2005 issue, which said it wasn’t enough to study the side-to-side motions of reactor tubes. It’s the front-to-back vibration that poses a real problem.
Apparently that was missed or ignored.
“What’s the purpose of doing the research if not to come up with information so that it doesn’t happen in the field?” Daniel Hirsch, a lecturer on nuclear policy at the University of California, Santa Cruz asked the U-T. “Do you want to go to a doctor who doesn’t read the journals and says, ‘I wait until someone keels over?’ ”
The scientific papers warned of “fluidelastic instability” from the front-back motion, the problem said to plague the San Onofre reactors. Scientific conventional wisdom, until then, assumed that addressing side-to-side vibration would take care of motion in the other direction. One scientist consulted by the U-T, M.K. physicist Au-Yang, said that calculations in the past had indicated the problematic front-back vibration, but it had never shown up in the real world and was generally ignored.
Edison said problems at the plant were unknowable and unpredictable when generators were upgraded in 2010 and 2011. Investigations after the plant closed in 2012 found that hundreds of eroded steam tubes, used to help cool the reactor, had been damaged by vibration.
Edison, which has proposed restarting at least one of the two operative reactors at 70% power by July 1 to see if its fixes will prevent the destructive vibrations, is awaiting word from the U.S. Nuclear Regulatory Commission (NRC). In the interim, Mitsubishi has adopted calculations for the front-back motion as standard practice, according to the U-T.
Around 8.7 million people live within 50 miles of the San Onofre plant, located between San Diego and Los Angeles.
–Ken Broder
To Learn More:
Journal Warned of San Onofre Issue (by Morgan Lee, U-T San Diego)
Fluidelastic Instability and Work-Rate Measurements of Steam-Generator U-Tubes in Air–Water Cross-Flow (by V. P. Janzen, E. G. Hagberg, M. J. Pettigrew and C. E. Taylor, Journal of Pressure Vessel Technology)
Fluidelastic Instability of an Array of Tubes Preferentially Flexible in the Flow Direction Subjected to Two-Phase Cross Flow (by R. Violette, M. J. Pettigrew and N. W. Mureithi, Journal of Pressure Vessel Technology)
NRC Paves the Way for Quick San Onofre Restart Without Hearings on its License (by Ken Broder, AllGov California)