The fission of uranium-235 ceased Sept. 20 at Three Mile Island in Pennsylvania and a year before, nearly to the day, at Oyster Creek Nuclear Generating Station in New Jersey.

As the steam generated by the heat of the atoms nuclei splitting dwindled to a wisp and the turbine generators fell silent, the regional power grid lost more than 1,400 megawatts of carbon-free electricity generation -- enough to power more than 1.1 million homes.

More nuclear power plant retirements may be on the horizon: PJM, the Pennsylvania-based coordinator of wholesale electricity in 13 states plus the District of Columbia, has already begun planning for the planned retirements of the dual-reactor, 1,813-megawatt Beaver Valley Power Station in Pennsylvania and the DavisBesse and Perry nuclear power plants that together generate 2,143 megawatts in Ohio.

PJMs grid, which covers Pennsylvania and New Jersey, had 183,454 megawatts of installed generating capacity available as of May 2019. The company puts the total capacity of the recently retired nuclear plants and the three planned for retirement at 5,387 megawatts, or about 3% of overall capacity. (PJM says its all-time highest power use was 165,563 megawatts in the summer of 2006.)

Had PJM identified reliability concerns with either Three Mile Island or Oyster Creek, it could have paid their operators to remain open, through what is called a "reliability must run," PJM spokesman Jeff Shields said. Or it could have outlined new power-transmission projects needed to offset the loss.

Neither step was necessary.

"And we also have a pretty healthy queue of replacement generation that's coming in, especially in Pennsylvania and Ohio with the shale gas," he said.

The grid counts 11,415 megawatts of new natural gas-fired electricity generation coming online in 2018 and 2019 and an additional 10,514 megawatts from gas expected to go in-service in 2020 through 2023. Operators of those future plants have signed what are called interconnection service agreements with PJM.

"That's sort of a stage at which the projects are likely to get built," Shields said of the agreements.

All told, new gas, wind and solar plants are projected to add 29,097 megawatts to the grid, as 19,037 megawatts of capacity are lost from retired coal, gas and nuclear plants, PJM says. That's a net increase of more than 10,000 megawatts.

The loss of more than 5,000 megawatts of carbon-free electricity from nuclear plants comes at a time when local and state leaders are looking to stem greenhouse gas emissions.

Pennsylvania Gov. Tom Wolf on Thursday took a step toward capping greenhouse gas emissions from power plants, as part of an effort to fight climate change in a heavily populated and fossil fuel-rich state that has long been one of the nation's biggest polluters and power producers, The Associated Press reports.

The Democrat ordered his administration to start working on regulations to bring Pennsylvania into a nine-state consortium of Northeastern and mid-Atlantic states that sets a price and limits on greenhouse gas emissions from power plants, according to the AP; joining the Regional Greenhouse Gas Initiative, however, could face pushback from the Republican-controlled Legislature, which is historically protective of Pennsylvanias influential coal and natural gas industries.

The good news is that new power plants, fueled by natural gas from the Marcellus Shale underlying Pennsylvania and neighboring states, are more efficient than the old fossil fuel plants they are replacing, PJM says.

"The gas generation, those generators are increasingly more efficient," Shields said. "They still do have carbon emissions. To that extent, that argument will continue.

"Basically we've seen emissions go way down in our footprint, and that's mostly explained by the replacement of coal for gas and renewables, although renewables are still making headway."

Kurt Bresswein | For lehighvalleylive.com

Materials are amassed Friday, Oct. 4, 2019, for construction of the new Pohatcong Solar Farm at Carpentersville Road and High Street in Pohatcong Township. The township land use board in July 2019 approved the project, which WFMZ-TV 69 reports will generate 10 megawatts for the regional power grid.

PJM projections show that if all three nuclear plants planned for retirement in Pennsylvania and Ohio go offline, carbon dioxide emissions would rise by about 3.7% above 2019 levels. Other emissions, sulfur dioxide and nitrogen oxide, would drop, thanks to older fossil fuel plants shutting down. If those nuclear plants remain online and all or even half of the new gas plants open, all three pollutants would drop across PJMs territory.

Three Mile Island, the site of the United States worst commercial nuclear accident in 1979, was closed by operator Exelon Corp. because it was no longer profitable, according to the Pennsylvania Public Utility Commission. Left with a single reactor, like Oyster Creek, TMI lost more than $100 million between 2012 and 2016, the commission says. It also lost out on valuable revenue from PJM in what are known base residual auctions.

Across all of PJM, 10,643 megawatts of nuclear capacity did not clear in this years auction for 2021-22, compared with 3,243 megawatts that failed to clear last year, according to Exelon.

This represents the largest volume of nuclear capacity ever not selected in the auction. Thats partly to blame on cheaper natural gas, as Pennsylvanias become the nations second-largest gas producer after Texas, state and federal analysts say.

Statewide, natural gas has replaced nuclear as the top source of electricity in Pennsylvania, the U.S. Energy Information Administration says.

From a cost perspective, PJM projects the closure of costly nuclear power plants to drive down the price of electricity as that trend toward natural gas continues.

As for the future of the nuclear plants recently shut down in Pennsylvania and New Jersey, Exelons Oyster Creek is set to become an interconnection station between the companys proposed 1,100-megawatt offshore Ocean Wind project and PJMs grid, nj.com reported last month.

At Three Mile Island, the federal Nuclear Regulatory Commission on Sept. 26 certified cessation of power operations and the permanent removal of fuel from the Unit 1 reactor vessel that remained online after the 1979 partial meltdown that ended Unit 2s run. Decommissioning of both reactors is now underway, the commission says.

Editors note: This article contains charts that can be viewed on your web browser if they are not displaying properly.

Kurt Bresswein may be reached at kbresswein@lehighvalleylive.com. Follow him on Twitter @KurtBresswein and Facebook. Find lehighvalleylive.com on Facebook.

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