Additional nuclear powerplant shutdowns will make it harder for the United States to meet its climate goals, a new policy brief from the nonprofit Center for Climate and Energy Solutions concludes.

Further, more retirements could lead to more widespread blackouts, similar to those seen in the Northeast during 2014's polar vortex, said Bill Mohl, president of Entergy Wholesale Commodities, a division of Entergy Corp., on April 28.

Since October 2012, four power companies have said they will retire five nuclear reactors earlier than expected. As a result of these and nuclear-plant closures in Germany and Japan, some Wall Street analysts have speculated that more retirements could be in the works.

Officials from the Dept. of Energy and industry and policy groups said at an April 28 briefing that nuclear power is an important part of the nation's energy mix and will be essential to meet President Obama's goal of a 17% reduction in greenhouse-gas emissions by 2020.

Nuclear powerplants provide more than 60% of the nation's zero-emission electricity. Although renewable energy sources are also an important part of the mix, they cannot provide reliable base-load power, said Eileen Claussen, president of the Center for Climate and Energy Solutions.

Carol Browner, a former EPA administrator, noted Chancellor Angela Merkel's 2011 decision, following the Fukushima disaster that March, to shut down all 17 of Germany's nuclear powerplants by 2022, thus shifting to a greater use of coal and fossil fuels to meet the country's base-load needs.

Peter Lyons, assistant secretary for nuclear energy at the DOE, said the federal government is moving forward with plans to strengthen the nuclear market in the U.S. In February, the DOE finalized $6.5 billion in loan guarantees to enable Southern Co. to proceed with the construction of two new reactors at the company's Vogtle plant in Waynesboro, Ga.

Moreover, the DOE has supported the development of small modular reactors (SMRs), Lyons said. While the much anticipated "renaissance" in the U.S. has yet to materialize, "there sure seems to be a global renaissance," with 77 nuclear plants under construction around the world, Lyons noted.