The Nuclear Regulatory Commission has not publicly addressed the risks of terrorist attacks that would be created by the expansion of a nuclear power plant in Mississippi, environmental groups said Thursday in a filing with the federal agency.

The Sierra Club has teamed with Nuclear Information and Resource Service and Public Citizen, both Washington-based environmental groups, in urging the commission to hold public hearings on the matter.

The plan for a second reactor at the Grand Gulf Nuclear Station near Port Gibson about 25 miles south of Vicksburg is in the permitting phase.

Rose Johnson, co-chairwoman of the Mississippi chapter of the Sierra Club, said Thursday in a news release that a nuclear plant is an obvious target for terrorists, but those concerns have not been addressed.

“You don’t have to be a CIA agent to know that nuclear power plants are natural targets,” she said. “People have a right to know the potential dangers they face in their own neighborhoods.”

The expansion project is being pushed by NuStart Energy, a consortium of nearly a dozen energy companies.

An after-hours call to the Nuclear Regulatory Commission went unanswered.

Entergy officials have said it could take the consortium five years to secure the proper permits to move forward with the project and another five years for construction. No decisions have been made.

The reactor already at the site has been producing electricity since 1985, and is one of 10 reactors run by Entergy.

The environmental groups said the Ninth Circuit Court of Appeals ruled in June in a case involving a facility in California that the Nuclear Regulatory Commission must consider the risks posed by terrorists.

The environmental groups contend that the “Nuclear Regulatory Commission has the same responsibility to consider terrorist risks in evaluating the safety of a new Grand Gulf reactor.”

Entergy spokeswoman Diane Park said the company will move forward with its plans while the court case the Sierra Club cited is resolved.

“That decision is being appealed to the U.S. Supreme Court by Pacific Gas and Electric Co.,” Park said. “At this time, we are not aware that the Nuclear Regulatory Commission is changing any of its requirements for our early site permit application for Grand Gulf.”