[ RadSafe ] Arnie Gunderson and Harvey Wasserman knew that shutdown of San Onofre nuclear station was a “seismic event” for the industry

[ROY HERREN]

I'm under the impression that it was management incompetence that lead to the closure of San Onfre.  I think the final straw had something to do with a design and/or manufacturing problem with replacement steam generators.
http://www.sandiegouniontribune.com/news/2016/jan/30/san-onofre-anniversary/