An Energy Department advisory panel is refusing to approve the department's plans for restarting one of its reactors at Savannah River, S.C., next summer. The panel of 12 engineers and scientists appointed by Energy Secretary John S. Herrington said at a public meeting Tuesday that more complete inspections and analyses of newly discovered cracks at another reactor at the site are needed to determine whether the reactor can withstand an earthquake. "This will be read, and read correctly, as our declining to endorse the restart strategy," said one panel member Harold Lewis, a physics professor at the University of California at Santa Barbara. The panel's chairman, John Ahearne, a former chairman of the Nuclear Regulatory Commission, said the panel "found a lot of weaknesses with the plan. There was a lack of a clear approach. The goals have to be more clearly identified."