PHILADELPHIA (AP) _ The federal government is mailing radiation exposure records of 50,000 nuclear weapons workers to researchers who suspect low-level radiation causes more cancer than the government says.

The Energy Department, which for years resisted releasing the data, said on Monday that computer tapes concerning the Hanford, Wash., nuclear reservation would be put in the overnight mail.

The move fulfills an agreement the Energy Deparment reached last month with a Philadelphia-based group that monitors plant safety, the Three Mile Island Public Health Fund.

''It's been a long struggle and I'm very gratified that we've been successful,'' said Daniel Berger, a lawyer for the group which prodded the Energy Department into releasing the information.

In Washington, Energy Department spokesman Bob Griffin said officials in Hanford were ''making last-minute adjustments, working feverishly'' to prepare the tapes, which he said would be sent late Monday or early Tuesday.

The department agreed to release records of workers at 10 weapons plants in four batches over the next 10 months. All told, the information will cover 200,000 of the 300,000 current and former workers at the plants since World War II.

Researchers Thomas Mancuso of the University of Pittsburgh and Alice Stewart and George Kneale of Birmingham University in England studied Hanford records in the late 1970s for the Energy Department but were discharged after publishing preliminary findings showing high cancer rates.

''We left the story rather abruptly because we produced a risk estimate that was considered impossibly high,'' Stewart recalled Monday.

The Energy Department stopped financing their research and denied access to the records, citing patient confidentiality. The Three Mile Island Public Health Fund sued for access and the department agreed to reopen the files, giving the researchers access to the records again.

''It won't be very dramatic, but it's a great moment in history of this research,'' Stewart said.

The release means that ''whoever owns the industry must never be totally in charge of health records,'' she said.

It also enables the resumption of research done more than 10 years ago, Stewart said.

''We're hoping that, say by the end of year, we'll establish some very firm points,'' she said.

Stewart estimated cancer rates may be shown to be three to five times higher than most experts previously thought, in line with the preliminary findings of 13 years ago.

The next batch of records to be released will over workers from these plants: Rocky Flats, Colo.; Los Alamos National Laboratory, N.M.; Mound Laboratory, Miamisburg, Ohio; and the Pantex facility in Amarillo, Texas.

After that, records will be released from plants at Oak Ridge, Tennessee and Sanvannah River, S.C.; followed by records from the Fernald Feed Plant, Fernald Ohio; the Mallinckrodt Chemical Works in St. Louis and the K-25 Plant in Oak Ridge.