The Department of Energy denied yesterday that unsafe nuclear-powdered devices were supplying electricity to oil rigs in the Gulf of Mexico and to navigational buoys in Baltimore harbor and the coastal waters of Bermuda.

The charges that unsafe nuclear generators were being used in nearby waters were made by the Rolling Stone magazine, Ralph Nader's Critical Mass Energy Project and three Democratic congressmen, John D. Dingell of Michigan, Richard L. Ottinger of New York and Andrew Maguire of New Jersey.

At a press conference in the Rayburn House Office Bldg., Ottinger said a nuclear generator fueled by the radioactove isotope strontiium-90 had been placed in a directional buoy by the Navy in Baltimore harbor and removed when the Navy realized it could be rammed by a passing ship.

DOE said the Coast Guard had installed in a Baltimore lighthouse and buoy two generators fueled by strontium-90 and that both were removed after a demostration period because they were too expensive.

"The lighthouse and buoy units were installed in 1964 and removed in 1966," DOE spokesman said. "They were removed bacause they were uneconomic. They would have cost $250,000 apiece once the demonstration period (which was free) came to an end."

Similar strontium-90 generators were put aboard oil rigs in the Gulf of Mexico in 1965 and 1966 to run foghorns and navigational lights. Both generators were removed and replaced by battery or diesel-powered generators in 1967. Again, the reason they were replaced was that they cost too much, the agency said.

Three more strontium-90 generators were placed in an Antarctic weather station, a weather-watching vessel in the gulf of Mexico and an underwater sonar device off the island of Bermuda. All three were removed when their demonstration periods were over and never replaced with operational generators.

DOE denied that any of these devices were unsafe.