In the garage of his house, Frank Sanns spends nights tinkering with one of his prized possessions: a working nuclear-fusion reactor. Mr. Sanns, 51 years old, is part of a small subculture of gearheads, amateur physicists and science-fiction fans who are trying to build fusion reactors in their basements, backyards and home laboratories. Mr. Sanns ... believes he's on track to make fusion a viable power source. I'm a dreamer," he says. Many of these hobbyists call themselves "fusioneers," and have formed a loosely knit community that numbers more than 100 world-wide. Getting into their elite "Neutron Club" requires building a tabletop reactor that successfully fuses hydrogen isotopes and glows like a miniature star. Only 42 have qualified; some have T-shirts that read "Fusion -- been there...done that." Called fusors and based on a 1960s design first developed by Philo T. Farnsworth, an inventor of television, the reactors are typically small steel spheres with wires and tubes sticking out and a glass window for looking inside. But they won't be powering homes anytime soon -- for now, fusors use far more energy than they produce. But the allure is strong. A fusion power plant would likely be fueled by deuterium and tritium, both isotopes of hydrogen that are in plentiful supply. Fusion advocates say reactors would be relatively clean, generating virtually no air pollution and little long-lived radioactive waste. Today's nuclear power plants, in contrast, are fission-based, meaning they split atoms and create a highly radioactive waste that can take millennia to decompose.