The Navy is considering using a four-mile stretch of Chesapeake Bay to test how its ships' electronic equipment resists an energy pulse that follows a nuclear explosion.

The Navy will bombard its ships with high energy radio waves to simulate the effect of EMP--electromagnetic pulse.

Navy Cmdr. William Tate, the project engineer, said the Navy may ask to place a four-mile-wide section of the bay off limits to boaters about 60 days a year so the testing does not short-circuit radio and navigational equipment of boaters on the bay.

The program is called EMPRESS II, an acronym for Electromagnetic Pulse Radiation Environmental Simulator for Ships.

The goal for the program, which could cost between $10 to $20 million, is to test the modern Navy's vulnerability to EMP, Tate said.

The pulses occur after a nuclear explosion when a form of radiation, called gamma rays, flashes through the atmosphere, bumping electrons from molecules in the air. The result is an electromagnetic wave that can destroy sophisticated electronic and communications equipment.

The Navy has been testing its equipment for EMP since 1972 when it set up a facility at Solomons, Md., on the Patuxent River. But new, large ships are unable to reach the test center because the channel is too narrow and a 144-foot-high bridge stands in their path.

Sites on the bay and one in the Atlantic Ocean off Virginia Beach are being considered.