Nuclear power, though still fulfilling 20 percent of U.S. energy demand, appears to be on the way out. No surprise there. The names Three Mile Island, Chernobyl, and Fukushima are known to everyone as examples of what can go wrong with older nuclear energy plants. In addition, storage of radioactive waste appears to be an intractable issue.

These famous disasters were all associated with water-cooled plants that were designed in an earlier era. If connection to the power grid and emergency power sources are lost, as happened at Fukushima, there is no way to cool the reactor core.

So is there a new generation of nuclear power plants that is safer and that can help us combat the threat of climate change?

First, some history. In 1951, the first nuclear power plant, Experimental Breeder Reactor One, validated the breeder reactor concept. The fuel was cooled not with water but with liquid sodium and potassium. The low melting point and high boiling point of this mixture meant there was no need for the thick steel pressure vessel required for water-cooled plants.

Experimental Breeder Reactor Two was a full-scale plant. In 1986, nuclear scientists from around the world were present at Argonne National Laboratory to witness a unique experiment: The reactor power and coolant supply were purposely shut off while the reactor was running at full power. Significantly, the reactor simply shut itself down because the rising temperature triggered thermal expansion and flooding with sodium, reducing the chain reaction. This reactor ran safely for 30 years until the program was canceled.

This liquid metal cooling design was never realized commercially because the Navy was developing water-cooled reactors for warships, and adapting military research for domestic nuclear power seemed the logical approach. Also, after Three Mile Island in 1979 and Chernobyl in 1986, there was little public support for nuclear power research.

Our current climate dilemma has boosted research on power from nuclear fission. A major goal is to commercialize what are known as Generation-4 plants. These plants have different core designs and different coolants, some reminiscent of the old experimental breeders.

For example, Microsoft's Bill Gates has co-founded a company called TerraPower that is developing a sodium reactor that would not need refueling or the reprocessing of spent fuel. The reactor is designed to run on cheap and plentiful depleted uranium rather than enriched uranium. With this reactor there would be no need to store depleted nuclear fuel.

A thorium-based molten salt reactor was successfully tested at Oak Ridge National Laboratory in the 1960s. Building on this work, startup companies are now experimenting with molten salt reactors that use liquid rather than solid fuel. The Dutch recently activated the first new thorium reactor in decades. Many believe thorium reactors provide the cleanest, safest path to nuclear power.

Another company, NuScale, in Oregon, is designing small, modular reactors in which the containment and the reactor vessel sit underground and underwater. Its plant requires no pumps and no electricity.

In addition, an international research effort on nuclear fusion reactors was begun in 1985. Princeton and MIT are among the many universities currently studying nuclear fusion as a future option for power generation.

In their book, "A Bright Future," Joshua Goldstein and Staffan Qvist assert that we need to decarbonize quickly and that nuclear power is a way to fill the gap that exists as we continue to solve the energy-storage problems associated with solar and wind.

In 2018, global carbon emissions reached an all-time high, so we will need all the methods we can assemble to reduce greenhouse gases in our atmosphere. These will include solar and wind power, new methods of energy storage, carbon sequestration, and also nuclear power. There is no silver bullet as we attempt to kick the fossil-fuel habit.

To foster alternative energy use and research, please contact your senators and representatives in Congress and urge them to support the Energy Innovation and Carbon Dividend Act, H.R.763, that has been newly introduced in the U.S. House of Representatives. This legislation will help us to move forward with alternatives to fossil fuels by putting a price on carbon. The proceeds will be returned to Americans as dividends.

David Gerhart of Duluth has a doctorate in aquatic ecology from Cornell University and has published and reviewed manuscripts for scientific journals in the fields of ecology and biochemistry. This commentary was reviewed and edited by Byron Steinman, a climatologist and assistant professor at the Large Lakes Observatory at the University of Minnesota Duluth, before it was submitted to and edited by the News Tribune.