After more than four decades in operation, the Vermont Yankee nuclear power plant in Vermont is permanently offline.

The plant spent Monday powering down and disconnecting from the regional power grid it fed for 42 years.

"VY is off line at 12:12 pm. We have finished strong!" @VYSAFSTOR, a message posted by the Vermont Yankee Decomissioning Twitter account read. The account said that the reactor was shut down for the last time at 1:04 p.m. 

In a statement posted on Facebook, Vermont Yankee's corporate owner, Entergy, thanked the people of Vermont. Entergy CEO Leo Denault wrote, "It has been a privilege to serve you."

The facility, which employed hundreds from the Southern Vermont region and neighboring New Hampshire and Massachusetts, has been at the center of debate in Vermont for years, with state legislators once even voting to shutter it. The Nuclear Regulatory Commission later said that was not the statehouse's job to dictate.

Ultimately, Entergy cited economic reasons for the long-planned shutdown. The company insisted Yankee had been a safe source of clean, affordable power and a good neighbor for many years.

"Vermont Yankee employees have volunteered countless hours and, over the past few years alone, contributed more than a million dollars to the communities where they live and work," the statement from Denault said. "Working side by side with so many of you, Entergy is proud of our efforts to improve the lives and livelihoods of our friends and neighbors."

However, those who had expressed concerns over an aging nuclear plant operating within Vermont were glad to see this day come. "I think it's a great day for Vermont," said nuclear safety advocate Arnie Gundersen of Fairewinds Energy Education.

Gundersen told New England Cable News that to him, an orderly shutdown to the plant comes as a relief, compared to catastrophic problems he could imagine in regards to potential issues at the plant.

"The economics of nuclear power are just no longer viable," Gundersen said. "We'll see more and more plants shutting down over the next decade."

Yankee employed more than 550 people as of November 2014, according to the Vermont Labor Department. Due to Vermont Yankee's location in Vermont's southeast corner, its workers live in Vermont, New Hampshire, and Massachusetts.

"We'll put people back to work," said Vermont Commissioner of Labor Annie Noonan, who noted the labor departments in Massachusetts, New Hampshire, and Vermont have been cooperating on planning for the plant shutdown for a long time now.

Noonan told NECN she expects about 165 of the plant's staff to be laid off in the coming weeks. About 40 people will retire, she said. Nearly 80 others will take jobs at other Entergy sites, she said. Noonan added that more than 300 employees will stay on until early 2016 to help with decommissioning the plant.

"For the economy down in Windham County, this is certainly a big event, but they have a lot of state support and federal supports, financially, that will go to rebuilding other jobs in that area," Noonan said.

Kristin Carlson of Green Mountain Power said that particular utility has not bought electricity from Yankee since March of 2012. Carlson said GMP's customers should not feel a spike in their home power bills because of the plant going offline.

"We have a portfolio that is 47 percent renewable, and our goal is to increase that, at the same time we decrease costs," Carlson said.

Noonan said she expects another large round of layoffs in 2016. The Associated Press reported the plant will sit for decades while its radioactive components cool and its decommissioning fund grows. It's expected to cost nearly $1.25 billion to dismantle the plant, which likely won't occur until the 2040s or later, the AP said.

Vermont Gov. Peter Shumlin, a Democrat, said the closing "marks the end of years of controversy over operation of a nuclear plant in our state."

"I have long advocated for the closing of this plant at the end of its original license, and I believe the ceasing of operations today after nearly 43 years represents a positive step for our state and our energy future," he said in a statement. "Today, thanks to investments in renewable energy such as solar, Vermont's energy future is on a different, more sustainable path that is creating jobs, reducing energy costs for Vermonters and slowing climate change." 

In December 2013, the governor, Attorney General Bill Sorrell, and Bill Mohl, president of Entergy Wholesale Commodities, announced a settlement agreement between the state and Entergy Nuclear Vermont Yankee that resolves all ongoing litigation between the State and Entergy VY and provided a path to resolve proceedings at the Public Service Board.

Under the terms of that agreement, Entergy VY will provide $10 million in economic development for Windham County over five years and $5.2 million in clean energy development support for Windham County and elsewhere, as well as a transitional $5 million payment to the State for calendar year 2015. Entergy VY also agreed to set aside a new $25 million fund to ensure the site is restored after decommissioning.