The Nuclear Regulatory Commission said yesterday it will keep Maryland's Calvert Cliffs nuclear power plant on its "watch list" of troubled facilities that receive closer-than-usual monitoring, but dropped Virginia's Surry station from the list, saying it had made significant improvements.

The Calvert Cliffs facility in Lusby on the western shore of the Chesapeake Bay was put on the list in December 1988 after several safety-related incidents. It has not operated for more than a year, with the exception of a short period in April.

Charles Franklin, a spokesman for the Baltimore Gas & Electric Co., which runs the plant, said the utility hopes to have one nuclear unit in service by the end of the summer, and the other on line by year's end. "We've made a lot of progress," he said, "but we still have work to do."

The NRC staff said Calvert Cliffs is implementing procedures to ensure that the steel vessel containing the reactor fuel is not put under too much pressure when it is cold. Other problems, including a significant maintenance backlog, also need attention, the NRC said.

Virginia Power's Surry plant, southeast of Richmond, was added to the list a year ago after the company was fined hundreds of thousands of dollars for safety violations. In taking Surry off the list, NRC cited improvements in all areas, particularly safety attitudes, but said Virginia Power needs to upgrade its maintenance and procedures.