LOS ANGELES (AP) — Federal regulators Thursday concluded that the operator of the San Onofre nuclear power plant in California did not mislead the government about modifications to its troubled steam generators, where unusual damage has been found on scores of tubes that carry radioactive water. Environmental activists had accused Southern California Edison of duping the Nuclear Regulatory Commission about a series of changes to the massive machines before they began operating in 2010 and 2011, including boosting the number of tubes and redesigning internal supports that hold them in place. The seaside plant between San Diego and Los Angeles has been idle since January, after a tube break in one of the generators released traces of radiation and set in motion a series of events that led to a federal probe.