One third of U.S. nuclear power plants still have work to do on their non-safety computer systems if they are to be ready for Y2K, the Nuclear Regulatory Commission said yesterday. But computers controlling safety systems at all 103 nuclear plants are free of problems that could cause radiation leaks, the NRC claims. However, Rep. Edward Markey (D- Mass.) said the report “confirmed my fears about the lack of preparation of nuclear plants for the Y2K bug.” He said that any malfunctioning system at a nuclear power plant could cause safety problems.