The Vermont Yankee nuclear power plant's operator said Thursday it will apply for state approval to build a second concrete pad to store spent nuclear fuel on site in dry casks.

The company will ask state regulators June 30 for permission to build a security-protected pad adjacent to an existing one currently holding 13 dry casks, Entergy officials said. Each cask holds about 68 spent fuel assemblies

Entergy, a Louisiana-based company that operates the plant in Vernon, announced last year it will close the plant by the end of the year. The proposed project would allow the company to transfer spent nuclear fuel from a storage pool into steel- and concrete-reinforced dry casks. The radioactive material would remain in the casks indefinitely.

There is currently no location to bring or recycle spent nuclear fuel in the United States. As a result, utilities store nuclear waste on site in cooling pools and dry casks. The U.S. Department of Energy pays utilities to move their spent fuel into dry casks and assumes ownership of the radioactive waste.

Vermont Yankee currently stores 2,627 fuel rod assemblies - which measure up to 12 feet tall and a few square inches around - in a spent fuel pool, according to a company representative. The company says it can store up to 3,353 in the pool.

The new pad would be completed by 2017, the company said in a statement.

The company will use air-cooled dry casks, which circulate air to cool the fuel without any mechanical process.