Boston — On Long Island, $120 million worth of a half-built particle accelerator at the Brookhaven National Laboratory sits in mothballs - its construction funding suspended. In California, the Lawrence Livermore National Laboratory, already having laid off 600 employees in anticipation of a 20 percent budget cut in 1983 , may decide to abandon its alternative-energy program.
''Running a lab these days is like being on the end of a yo-yo,'' Ames National Laboratory director Robert Hanson says of the gyrations in government funding over the past few years.
The labs have been at the cutting edge of America's technological prowess for more than 30 years. But four major government inquiries and unprecedented competition from universities and private industry for increasingly scarce scientific talent and government grants are forcing these research facilities to grope for a new identity.
At the same time, they are unable to sustain ambitious Carter-era federal research and development (R & D) plans on a shoestring Reagan budget. As a result, programs that only three years ago were stated national priorities are being hastily dismantled.
In the process, some say, the labs' historic scientific preeminence is being threatened. ''One fell budget cut can wipe out a first-rate research team that took 10 years to build up,'' warns Lawrence Livermore National Laboratory deputy director James S. Kahn. The labs, he says, ''should be supported and certainly not decimated as they apparently are by these massive reductions of support.''
Others agree. In a letter to Energy Secretary James Edwards last March, Sen. Charles H. Percy (R) of Illinois expressed concern that an ignorance of the necessary ''critical mass of talent'' within Illinois's Argonne Lab threatened to ''significantly degrade its capabilities'' to conduct research. Argonne is facing a budget cut of more than 17 percent in fiscal 1983.
Four federal studies are currently examining different aspects of the labs. The President's Private Sector Survey on Cost Control is investigating general laboratory business practices. The General Accounting Office of Congress is studying how the labs set research priorities and evaluate the importance of work done. The White House Science Council has appointed a panel to look into the possible capacities of all the federal laboratories. And the Department of Energy's Energy Research Advisory Board is probing the optimal roles of nine of the biggest DOE labs.
Observers say they think it is likely that the largest, most diverse research laboratories will have to limit the focus of their research. Emphasis will be on closer cooperation with universities and industry by increasing accessability to lab ''user'' facilities.
By a recent count, the government runs some 779 research facilities. They range in size and scope from one-man environmental observation outposts to sprawling weapons labs. But it is the 12 DOE multiprogram, multipurpose laboratories sprinkled across the United States which are getting the most attention.
Taken together, these multipurpose labs are a huge investment in the federal R & D effort. One-twelfth of the nation's PhD scientists work there. More than 50,000 people, half of whom are scientists and engineers, are employed there. And these labs consume more than a quarter of the DOE's total budget and represent about $25 billion in capital facilities.
Nuclear power was developed largely from the research of national labs at Argonne, Ill., and Oak Ridge, Tenn. The weapons labs at Lawrence Livermore, Los Alamos, and Sandia are responsible for the US nuclear weapons arsenal. By maintaining the big, expensive research equipment necessary for basic research, the Brookhaven lab has spawned Nobel Prize-winning research in high-energy physics.
Perhaps as a consequence of their success, the scope of activities at the labs was broadened to include the life sciences and biomedical, environmmental, and energy research. It is in these areas that the Reagan administration, with an R & D policy emphasizing basic and military research, has imposed the cutbacks.
Douglas Pewitt, assistant director of the White House Office of Science and Technology, looks on the cuts as corrective measures. ''The labs got involved in a lot of silliness'' - short- and middle-term applied research that administration spokesmen say is the province of private industry. ''They're having to readjust after a period of growth not appropriate to their, or the government's, mission.''
Louis Roddis Jr., chairman of the Energy Department's Energy Research Advisory Board, agrees. ''I don't believe that any of the national laboratories are hurting that badly.'' Despite the cutbacks, he points out, the labs still employ more people than they did in 1978. ''There's a fairly large swing between minimum critical mass size and what makes a lab unmanageably large.''