The Nevada Test Site, home to nuclear weapons testing for more than 40 years, may have a brighter future. Clear skies and high insolation - the amount of solar radiation available at ground level - make the test site one of the best places in North America for capturing solar energy, according to a feasibility study by the Energy Department. The study concluded that solar collectors covering less than 7 percent of the 1,350-square-mile test site could produce up to 10,000 megawatts of electricity, as much as 10 large coal or nuclear plants. The Energy Department has named a task force of government and solar industry representatives to develop plans for a "solar enterprise zone" at the former atomic proving ground. No nuclear weapons have been exploded there since the fall of 1992, when Congress passed a moratorium on testing. This spring, President Clinton extended the moratorium until September 1995. The southern Nevada test site is also being studied as a permanent repository for spent radioactive fuel from commercial nuclear reactors and as a storehouse for the plutonium cores from dismantled atomic bombs.