Operators at Entergy’s Vermont Yankee Nuclear Power Station (VY) took the plant offline permanently on Dec. 29 at 12:12 p.m. EST, ending a 42-year operational history.

The shutdown is the first step in what is expected to be a decades-long decommissioning process for the plant. VY follows several other nuclear plants that have begun the retirement process in recent years, including Kewaunee in Wisconsin, Crystal River in Florida, and the San Onofre plant in California.

During 2015, all of the fuel in VY’s reactor will be transferred to the plant’s spent fuel pool for initial cooling. The fuel in the pool will eventually be moved to dry casks that will be housed on two storage pads at the site.

Dry casks are comprised of sealed steel inner containers that fully enclose the spent fuel, and a steel and concrete outer shell that provides strength and radiation shielding. Residual heat in the loaded casks—weighing almost 200 tons—is dissipated by natural air circulation without the need for fans or pumps. The company expects to complete the transfer to dry casks by 2021.

The SAFESTOR decommissioning process includes an extended period of minimal activity at the site, while irradiated equipment is prepared for storage and eventual decontamination. Ultimately, the site will be decontaminated and restored in accordance with standards established by the Nuclear Regulatory Commission and the state of Vermont. According to Entergy, more than 30 U.S. reactors are in the process, or have completed, the decommissioning process.

“In the coming decades, the safe secure decommissioning of the plant will be our number one priority,” said Leo Denault, chairman and CEO of Entergy Corp. in a video thanking the people of Vermont for their support.

Aaron Larson, associate editor (@AaronL_Power, @POWERmagazine)