The Atomic Safety and Licensing Board on Thursday dismissed four contentions filed by San Luis Obispo Mothers for Peace.
That group is critical of the nuclear power industry. It argued that plant owner Pacific Gas and Electric Co. understated earthquake risks and ignored renewable energy sources that could replace power from the reactors.
PG&E says the plant between Los Angeles and San Francisco is safe.
The Nuclear Regulatory Commission is evaluating whether to grant 20-year extensions to the plant's twin-reactor operating licenses, which expire in 2024 and 2025.
PG&E hasn't decided whether to move forward with related state requirements.