Waterford — Market stresses that have led to the planned or completed closures of at least a half-dozen nuclear power plants across the country have prompted the federal government and several states to consider how to preserve existing plants, an industry expert said Tuesday.

“The federal government is looking into what can be done for at-risk nuclear plants, and states are beginning to recognize the need to act,” Michael McGarey, senior director of state and local affairs for the Nuclear Energy Institute, told about 40 people at the annual stakeholders meeting for the Millstone Power Station.

Among those attending the meeting were local officials, state legislators and neighbors of the plant.

Nuclear power plants, particularly those that are aging and in need of upgrades, are being affected by drops in revenues from energy sales due to low natural gas prices, federal and state subsidies for renewable energy that “distort markets” and transmission constraints, among other factors, McGarey said.

“We’ve already had a handful of plant closures, and just last week, there was an announcement that the Fort Calhoun plant in Nebraska would be closing,” he said.

In New England, Entergy closed Vermont Yankee in 2014 and has announced plans to close Pilgrim station in Plymouth, Mass., in 2017.

New York, Illinois and Ohio have responded to pending plant closures by making policy changes that include subsidies for remaining nuclear plants, said Kevin Hennessey, director of federal, state and local affairs for New England for Millstone owner Dominion Resources.

In Connecticut, legislation proposed in the recently concluded session of the General Assembly to protect Millstone from market instability passed the state Senate unanimously, but failed to come to a vote in the House of Representatives.

Hennessey said he expects the measure will be reintroduced next year, and that the bill’s introduction late in the session contributed to its failure.

“It would have created a pathway for 10-year contracts, which would provide greater stability for us and for ratepayers,” he said.

Unlike the measures in other states that have addressed this issue, he said, Connecticut's legislation would not have included subsidies for nuclear power.

“The conversation is ongoing, both in Connecticut and the New England region” about what actions are needed, he said.

Dominion officials have not indicated that Millstone is in danger of closing, but have stated that plant profits have declined and that the legislation proposed would have helped counteract market volatility.

Under the proposed bill, the state would have played a larger role in regulating energy markets, enabling Dominion to sell the power generated by Millstone under long-term contracts through a new market.

That market would have included contracts with renewables including big hydroelectric plants, wind, solar and trash-to-energy plants.

Dominion officials argued that nuclear energy should be allowed to join that market because it is the largest electricity producer in the state and one of the largest in New England, and generates no carbon dioxide emissions.

The legislation, Hennessey said, had “broad support” in the legislature but was introduced too late in the session.

A new version next year, he said, “needs to be introduced sooner."

A revision Dominion would support, he said, would allow for some differentiation in how contracts from renewable sources are considered compared with nuclear power.

Promoters of renewable energy had raised objections that small renewable sources could not complete against a large nuclear plant for contracts.

j.benson@theday.com