New Britain — State officials voted unanimously without discussion Thursday to allow the Millstone nuclear plant to significantly expand its nuclear waste storage capacity over the next 30 years.

Without a national site to take spent nuclear fuel, Millstone Power Station’s owner, Dominion Resources Inc., turned to the state for permission to increase storage at the Waterford site.

The nine-member council vote means Millstone may the build concrete pads necessary for an expansion of its waste storage. The plant is seeking to expand storage from 19 cask storage units now to 135 by 2045. However, Millstone’s application does not include a request to install the 135 casks, the Siting Council said.

Melanie Bachman, staff attorney for the council, said Millstone has the authorization to install 49 casks but must seek permission for the remaining 86.

Millstone’s spokesman Ken Holt said the state’s permission to build the pads gives Dominion flexibility in planning long-term storage requirements.

The key problem facing nuclear plant operators and public officials is Washington’s seeming inability to decide what to do with radioactive waste produced by nuclear power plants. Congress designated Yucca Mountain in Nevada for a nuclear waste dump, but the plan has been opposed by the state’s elected officials, including Senate Majority Leader Harry Reid, D-Nev.

In the meantime, spent nuclear fuel is stored on site at the nation’s 104 nuclear reactors in pools or in dry casks.

Local storage is Millstone’s only option, Holt said.

“It’s not our first choice,” he said. “But unfortunately, the federal government has not lived up to its obligation to take the fuel like they were supposed to.”

The state Department of Energy and Environmental Protection criticized federal inaction.

“Nuclear waste is a federal problem and needs an immediate federal solution,” the agency said in comments to the Siting Council.

Waterford First Selectman Dan Steward said he, too, has no choice but to accept local storage of nuclear waste. “It would be nice to tell the federal government we can’t do this,” he said.

The Black Point Beach Club Association, a homeowners group in Niantic across Niantic Bay from Millstone, asked the Siting Council to reject the plant’s request. State officials are not accounting for possible problems at Millstone if sea level rises as projected because of climate change, the association said. It also urged the state to wait for guidance from the Nuclear Regulatory Commission.

“All of the association’s members and all residents of Black Point are subject to potential mandatory evacuation orders and martial law and personal harm in the event of a serious accident at Millstone, including the proposed storage facility,” the group told the Siting Council.

Dominion is spending $11 million for preparation and other work, Holt said. The plant will move fuel from pools and move them into dry casks, which will be welded shut and moved to a concrete bunker. Fuel will be moved within two years, Holt said.

The Siting Council said state agencies may not regulate the dry storage activities authorized by the NRC concerning radiological health and safety. Nor may they impose siting standards that would “frustrate or undermine” NRC decisions, the Siting Council said in its preliminary approval last month of Millstone’s request.

Expanding the storage would not affect wetlands, vegetation or habitats, the Siting Council said.

In dry cask storage, spent fuel cooled for at least a year is surrounded by inert gas in casks, which are typically steel cylinders that are welded or bolted closed.