But under a new emergency plan that Edison has before the federal Nuclear Regulatory Commission, the sirens, which the utility says could also be used by local governments in the event of a non-nuclear emergency, will go silent. Edison says that the fact the reactors are no longer active reduces the necessary scope of future emergency planning, effectively rendering the siren system obsolete.

Still, "Protecting the health and safety of workers and the public remains our most important responsibility," said Edison vice president and chief nuclear officer Tom Palmisano in a release.

Despite the utility's statements to the contrary, nuclear watchdog groups say there's still a cause for concern over the state of highly radioactive nuclear waste that's been piling up at San Onofre since the plant opened in 1968.

"The federal government required an emergency zone, and the utilities and industry fought hard to limit coverage" when the plant first went online, notes Alliance for Nuclear Responsibility executive director Rochelle Becker. "There is no longer a profit to be made from waste storage, but there is nowhere for that waste to go. California should not stand idly by while the federal government abandons radioactive dumps," she cautions.

Becker goes on to warn that spent nuclear fuel rods are stored in overcrowded waste pools, where they must remain for a number of years before it's safe to transition them to dry-cask storage (another temporary measure at best).

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