In the wake of radioactive releases from Japan's Fukushima Daiichi nuclear plant, critics are saying a California nuclear plant's susceptibility to earthquakes and tsunamis could affect its chances of renewing its operating license.

While the federal licenses for Pacific Gas & Electric's Diablo Canyon plant, near San Luis Obispo, and Southern California Edison's San Onofre plant are valid for at least another decade, both utilities have begun the renewal process ahead of time. The Nuclear Regulatory Commission has never denied a relicensing application. But especially in PG&E's case, opponents had been citing seismic and tsunami-related concerns even before last week's 9.0-magnitude earthquake off the coast of northern Japan.