Forgotten but not gone, the waste from more than 100 nuclear reactors that the federal government was supposed to start accepting for burial 10 years ago is still at the reactor sites, at least 20 years behind schedule. But it is making itself felt in the federal budget. With court orders and settlements, the federal government has already paid the utilities $342 million, but is virtually certain to pay a total of at least $7 billion in the next few years and probably over $11 billion, government officials said. The industry said the total could reach $35 billion. The payments come from an obscure and poorly understood government account that requires no new Congressional appropriations, and will balloon in size, experts said. The payments are due because the reactor owners were all required to sign contracts with the Energy Department in the early 1980s, with the government promising to dispose of the waste for a fee of a 10th of a cent per kilowatt-hour. It was supposed to begin taking away the fuel in the then far-off year of 1998. Since then, the utilities have filed 60 lawsuits. The main argument