Federal officials who favor moving the Nuclear Regulatory Commission (NRC) and its 2,300 employes out of scattered Montgomery County offices and into a single headquarters in downtown Washington appear to be bolstered by a new environmental study of the proposed move.

The study, by the General Services Administration (which handles housing for federal agencies), concludes that any of the five areas now being considered for a consolidated headquarters - three in Montgomery County and two in downtown Washington - are acceptable. This apparently leaves the final decision to Congress.

The GSA study contradicts Montgomery County estimates that a move to downtown Washington would add about 30 minutes a day to NRC employes' commuting time and cost employes an additional $1.40 to $4.20 a week. About 70 percent of the agency employes now live in Montgomery County, and commuting has become the most controversial aspect of the proposed moved.

GSA estimates that because of the Metro subway, commuting to a Washington headquarters would be significantly cheaper - up to $3.55 a week less - than traveling to a new headquarters in Montgomery County and that it would add only about 15 minutes a day to the average employe's round-trip commuting time.This assumes that most of the employes will continue to live in Montgomery County. Many new employes, however, are expected to move near a new headquarters. The NRC expects to have another 800 employes by the time the move is completed in 1982 and there is an annual employe turnover of about 9 percent.

Taking Metro to downtown would cut automobile commuting by NRC employes more than 50 percent, conserve energy and help reduce regional air pollution the GSA study says. If a Montgomery County site is selected, most employes would be expected to drive to work since there is little cross-county public transportation. Gasoline prices, expected to increase significantly in the next year, would presumably make auto commuting even more expensive.

Employes themselves estimate commuting to Washington would take an hour longer and cost $100 more a month. A recent employe survey found, however, that those estimates apparently were based on the assumption that employes would drive and paak in downtown Washington.

The stakes are high for Montgomery County and the District because the 600,000 square feet of office space NRC hopes to lease for at leass 20 years - comparable in size to the Justice Department building at Pennsylvania Avenue and 9th Street NW - could produce $1.2 million a year in local tax revenues.

The NRC, formed in 1975 to regulae and safeguard commercial use of atomic energy (replacing part of the old Atomic Energy Commission), last year proposed consolidating its operation by moving to downtown Washington instead of continuing in the nine separate office buildings it now occupies. Eight of the buildings are in Montgomery County (five in Bethesda, one in Silver Spring and two in Rockville) and one is in the District at 17th and H streets NW.

The consolidation, estimaed to save about $5 million a year by eliminating duplicate jobs and services - $800,000 a year in security costs alone - was approved by a House subcommittee in October 1977. But it was held up in the Senate when senators asked the GSA to go back and study possible sites in Montgomery County as well as in the District.

Five possible locations, three in Montgomery County and two in downtown Washington, were proposed by GSA last July and a "draft" environmental impact statement was prepared to assess the advantages of the sites. The draft, released earlier this month, will be completed next spring after a public hearing on all five pound proposed locations.

The hearing has been set for 4:30 p.m. Dec. 11 at Walter Johnson High School in Bethesda. Earlier this week, however, County Executive James P. Gleason asked that the hearing will be postponed at least until January to give the county and NRC employes more time to study the draft environmental impact statement. GSA is expected to make a decision within the next few days on postponing the hearing. Written comments, in any case, will be accepted until Jan. 1.

The two proposed downtown Washington sites are in urban renewal areas near Union Station and in the central business district north of Pennsylvania Avenue between 3rd and 15th streets NW.

The Montgomery County sites includes downtown Silver Spring, Bethesda and at Nicholson Lane and Rockville Pike. All three county areas are within walking distance of existing or proposed Metro subway stops.

The District and Silver Spring sites, all considered economically depressed areas, would benefit most from the influx of a large federal agency and 3,100 employes.

There also will be some unavoidable "adverse impacts," the study concludes: No matter where the new headquarters is, commuting time and expense will increase for some NRC employes and, in general, probably more employes will be adversely affected by the move than will be benefited.