Nuclear fusion in a nutshell Analysis/Commentary For close to 70 years, since fusion was first broached in the early '30s, physicists have dreamed of using it to heat their homes and power their hedge trimmers. They have even made some progress toward implementing it. Unlike its cousin, "fission," "fusion" requires atoms to fuse instead of split. Fusion uses light elements instead of heavy ones -- it works from the opposite side of the table of elements used by fission. And the old Einsteinian principle of Energy = Mass (E = mc squared) holds, but in fusion, no nasty radioactive pollutants. Just heat deuterium and tritium (derived from lithium) to a temperature of 100,000,000 degrees Kelvin. In fusion, the "ions" in a particle-nucleus soup known as "plasma" begin to meld and change their chemical properties. The result is harmless helium, and an energy burst hotter than the surface of the sun. The resulting helium, minus the energy loss, weighs less than its component chemicals. The principle of fusion has been widely compared to the production of solar energy. In the sun, hydrogen atoms pass through four states, aided by the trigger of gravity and by elements already present in the sun's hot core. Like earth-based fusion, solar fusion produces helium, an element that will eventually overwhelm the sun's balance of heat intake and heat expulsion -- a few billion years down the road. Fusion has theoretical advantages. Scientists use isotopes (heavy versions of common elements) found in sea water for deuterium, and lithium remains fairly abundant. The major problem seems to be controlling the plasma. Also, for plasma to heat sufficiently to be a self-sustaining energy source, scientists must overcome the electrostatic force that repels atoms from each other, the coulomb barrier. To date, although they have come close, research teams have failed to achieve a self-supporting ignition. The production of energy consumes more power than it gives. Hardly something to tell Congress. And, reportedly, $10 billion has been spent. Worse yet, earth-manufactured fusion has begun to lose its headline value. Like particle acceleration, fusion lacks the gee-whiz appeal of the latest Intel chip or the gosh-look-Ma razzle-dazzle of cellular networks and satellite feeds. Never mind that oil prices are rising, or that landfills are brimming with radioactive plutonium. "If it ain't there yet, we're not gonna invest in it," the moneyhandlers seem to be saying. Oddly, fusion isn't exactly a homegrown science. A German refugee who worked on the Manhattan Project first explained it, and the Russians first created its practical reaction vessel -- a magnetic containment reactor, the Tokamak. Although another process involving atomic compression, known as inertial confinement, has been attempted by American researchers, the Tokamak has graduated to best-of-class status. Difficulties lie in the mathematics of plasma control and container resilience. Like its namesake, the fusion bomb (H bomb), peaceful fusion poses a few dangers. Some observers worry that scientists are building a doomsday machine. On the other hand, fusion holds the promise of direct electrical current, instead of the daisy chain of energy to steam to turbine used by fission plants. And just think: one ton of deuterium in a fusion reaction might produce the equivalent energy of 29 billion tons of coal. Enough to power up that handy-dandy hedge trimmer. January 3, 2001