Remember the children’s car song “100 bottles of beer on the wall”? With every verse, you count down until you reach zero.

That song could be sung to count down from 100 the number of commercial nuclear power plants that are operating in the United States.

Fort Calhoun, the nation’s smallest commercial reactor, started the ball rolling, when it closed in October 2016 with the owners, the Omaha Public Power District, citing a weak outlook for profits.

With that closing, the number of U.S. reactors dropped to 99. But poor profits and expensive new safety standards are eating away at benefits for nuclear power plants and almost power source has fixed costs nearly as high as the nuclear power industry.

“99 U.S. nuclear power plants in the country; 99 nuclear plants.”

The United States Energy Information Administration said Tuesday that an additional six nuclear power plants are slated to close within the next nine years with the owners citing a reduced chance of making a profit. Most unsettling – for fans of the industry, that is – is that four of the six scheduled to close will still have more than a decade of commercial operations available to them. Despite the high costs of building a large commercial nuclear reactor, maintaining it, refueling it, upgrading to produce more power and meeting new safety standards, plant owners are bowing out before their plant licenses expire.

The EIA said that four of the plants – Palisades in Michigan, Pilgrim in Massachusetts, Oyster Creek in New Jersey and Three Mile Island in Pennsylvania – will close with more than a decade left on their operating licenses.

Some retirements are more graceful than others. Exelon, the owner of Three Mile Island, has called for the state of Pennsylvania to follow in the footsteps of Illinois and New York, which have developed economic interventions that will keep the zero-carbon power plants operating in markets where profits have dried up.

It’s not the fault of the power plants that profits have vanished. Expenses are high, but the primary causes profits have wilted are beyond their control. The most significant factor by far has been the erosion of electricity prices brought on by cheap natural gas, which has overwhelmed the market due to hydrofracking, a relatively new extraction process.

The second factor that nuclear power officials point to is the political favoritism granted to the wind and solar power, which seem to be getting breaks from the government that nuclear power proponents say are unfair, given the point that nuclear power is also a carbon emissions-free source of electricity.

Strikingly in the era in which climate change has emerged as the No. 1 environmental crisis the planet faces, the EIA noted that losing close to 5,000 MW from nuclear power plant shutdowns recently has been made up by increased electricity generation from natural gas and coal – both sources of the planet- threatening greenhouse gas emissions.

The glut on the market from natural gas is not expected to end soon, so it could be assumed that the six plant closings are only those that are already known. More can be expected.

At the same time, four new reactors are expected to come online in the next decade. Two of those are a sure thing, as Southern Power over the weekend announced it had secured $3.58 billion from financially struggling Toshiba to complete two new reactors at the Plant Vogtle power plant in eastern Georgia.

Two other Westinghouse AP1000 reactor projects are underway in South Carolina at the V.C. Summer power plant. With Westinghouse’s filing for bankruptcy in late March, it is still uncertain whether or not that project will continue or be closed down or altered.