In recent years, a rise in greenhouse gas emissions has tended to follow nuclear plant closings, since they are most often replaced by natural gas, industry executives say. This was the case in California and New England after the San Onofre and Vermont Yankee plants folded.

But the nuclear industry is facing a crisis of old age. The majority of the country’s 99 nuclear reactors are more than 30 years old and were opened before deregulation. Starting in the late 1970s, under federal rules established to help reduce the price of electricity, independent power producers gained the ability to compete in wholesale electricity markets. When prices were relatively high, nuclear plants were able to fare well because their facilities, once up and running, were inexpensive to operate.

However, the recent slowdown in the demand for electricity and the glut of natural gas from the rise in fracking has driven down wholesale prices. That lower revenue poses special challenges for nuclear plants, which operate potentially for as long as 80 years, and so require costly upgrades and repairs during their life spans.

“At these prices,” said Jay Apt, a professor and a director of the Electricity Industry Center at Carnegie Mellon University, “they can’t save up enough to have cash on hand for periodic capital investments.”

Supporters of the bailouts say the current prices undervalue nuclear power, given the method’s lack of greenhouse gas emissions and ability to operate at all hours. The low prices make it hard for the plants to compete with other clean technologies like wind and solar, which receive subsidies and are bolstered by mandates that require purchases of clean power. They argue that the environmental and efficiency value of nuclear plants mean they should be eligible for similar subsidies or be included in clean energy mandates.



“We get no recognition for the fact that we emit nothing,” said Marvin S. Fertel, chief executive of the Nuclear Energy Institute, an industry trade group.

Support for plans to save nuclear energy has come from a seemingly unlikely group — environmentalists, some who have come to believe that the climate benefits of nuclear energy far outweigh the risks.