MONTPELIER, Vt. — Vermont’s only nuclear plant stopped sending power to the New England grid Monday after more than 42 years of producing electricity.

The shutdown came just after noon as the Vermont Yankee plant completed its 30th operating cycle when workers inserted control rods into the reactor core and stopped the nuclear reaction process, the plant’s owner said.

In its decades of operation, the plant in the southeastern Vermont town of Vernon produced more than 171 billion kilowatt-hours of electricity. During that same period the plant provided 71.8 percent of all electricity generated within Vermont, or 35 percent of the electricity consumed in the state, the company said, citing information from the U.S. Energy Information Agency.

Bill Mohl, president of Entergy Wholesale Commodities, said economic factors, especially related to the natural gas market in the Northeast, were the primary reasons for the shutdown. The decision to close the plant was announced weeks after the company won a protracted legal battle with the state, which had been pushing for the plant’s closure.

“The Northeast has undergone a shift in supply because of shale gas, resulting in sustained low natural gas prices and low wholesale energy prices,” Mohl said in a statement.

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.

Vermont Gov. Peter Shumlin, who had pushed for the closing of the plant, said the shutdown is a positive step for the state.

“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,” Shumlin said.

When Entergy announced in August 2013 that it would close Vermont Yankee, the plant employed more than 600 people. The workforce will be cut in half after a round of layoffs and retirements Jan. 19.

Vermont Public Service Commissioner Chris Recchia said Monday that the state hasn’t received power from the plant in almost three years. “We are moving full speed ahead with local, sustainable, no-carbon renewables in Vermont,” Recchia said.

Marcia Blomberg, a spokeswoman for ISO New England, which manages the regional electric grid, said the loss of power from Vermont Yankee wouldn’t pose a problem, but the region faces long-term challenges from the loss of a number of older power plants.

“We’ve studied the power system in that area and we’ve determined that the regional power grid can be operated reliably without that resource,” Blomberg said of Vermont Yankee. “However, the bigger picture is that the region is seeing more and more retirements of non-natural-gas-fired generation, and that’s a concern.”