Eleven hundred federal workers will move out of a downtown Washington building to make room for 1,000 other federal government workers who have been based in Montgomery County.

The giant reshuffle will cost $3 million and take 18 months, Walter V. Kallaur of the General Services Administration told the Senate Committee on Environment and Public Works last week.

Within three years, about half the employes will move again to another building in Washington or to Silver Spring.

The employes who will move twice -- first from Montgomery County and then from 1717 H St. NW -- work for the Nuclear Regulatory Commission. The employe who will move out of 1717 H St. NW, to make room for the NRC employees, work for the Equal Employment Opportunity Commission, the Department of Interior's Bureau of Fish and Wildlife, the International Communications Agency and the Office of Personnel Management. They will move to offices in Virginia and to offices vacated by the NRC in Montgomery County.

The plan to twice move the NRC employes resulted from reports by two groups that investigated the Three Mile Island nuclear accident.Both groups, the Kemeny Commission and a special inquiry group headed by lawyer Mitchell Rogovin, said that the NRC should be located in one place, instead of having its offices scattered in downtown Washington, Silver Spring, Rockville and Bethesda.

Congress is expected to approve a new building for the NRC, but it could take another five or six years before one is constructed.

In the meantime, half of the NRC's employes will move to downtown Washington because of a decision by the director of the Office of Management and Budget that "there is a pressing and immediate need to improve the headquarters operations of the NRC.

At present, 152 NRC commissioners work in downtown Washington, at 1717 H St. NW, the location where 1,000 NRC employes will be moved.

Sen. Paul Sarbanes (D-Md.) told the Senate Committee that it would make more sense for the 152 commissioners to move to Bethesda, where much of their staff is located.

"The plan is the result of leveraging by 152 of the NRC's top brass who have to be in sight of the White House or they just can't do their jobs," Sarbanes said. "They may go to the White House once a week, and that's being kind to them."

Senate committee member Daniel Patrick Moynihan of New York told Sarbanes that he did not think it was within the committee's jurisdiction to decide on the short-term relocation of the NRC. But Moynithan said he would ask the OMB to consider moving the commissioners to Bethesda, instead of reshuffling more than 2,000 federal workers.

Moynihan said he would tell the OMB, "If you want our opinion, fine; if you don't, just come to us for money sometime."

But John F. Ahearne, chairman of the NRC, told Moynihan that the NRC commissioners could not move to Bethesda because they and their staffs would be scattered among three buildings on one block, instead of working in one building.

The Senate committee also was urged to stipulate that, when a building is finally constructed or leased for the NRC, it will be in Silver Spring. i

Montgomery County Executive Charles W. Gilchrist told Moynihan that the NRC's permanent office should be in Silver Spring because some of its offices are already there, because it is an urban area that needs revitalization, because a Metro stop is there and because 80 percent of NRC workers live in the county.

Moynihan said he agreed that the permanent location of the NRC should be in Silver Spring, rather than in the District.