The False Hope Behind Nuclear Fusion

For many of those – now a clear majority – who believe climate change is a serious long-term threat, and who therefore believe we must stop emitting carbon dioxide into the atmosphere by burning fossil fuels, the recently announced breakthrough by the Lawrence Livermore National Laboratory’s National Ignition Facility in California that nuclear fusion has at last produced net energy is an extremely hopeful sign.

They need to think again.

Fusion versus fission

Nuclear fusion has, of course, produced net energy before – in a thermonuclear bomb. Much more powerful than a fission bomb of the type that was dropped in 1945 on Hiroshima and Nagasaki, the fusion bomb – a thermonuclear bomb, also called a hydrogen bomb – has thankfully never been used in war. It has been tested, though, and one test explosion destroyed the island of Eniwetok in the Marshall Island chain in 1952.

To understand the relationship between fission and fusion, the best way is to read John McPhee’s short 1974 book, The Curve of Binding Energy, about Theodore Taylor, a Manhattan Project scientist.

Nuclear fission produces enormous quantities of heat when a heavy atom such as uranium-235 breaks apart when hit by a neutron. In addition to the heat, the collision results in two smaller radioactive atoms and additional neutrons that continue the chain reaction by hitting other nearby uranium atoms.

Nuclear fusion, by contrast, doesn’t “fission” atoms (“a splitting or breaking up into parts”); it “fuses” them. Specifically, it fuses two hydrogen atoms into a helium atom, just like the Sun does. Under extreme pressures and temperatures, two hydrogen atoms will fuse to become a helium atom, with heat energy as a byproduct. It is this process that powers the Sun’s heat and energy-bearing rays.