A battle over jobs and nuclear safety that has been running for years at the Nuclear Fuel Services plant in Erwin, Tenn., has broken into a new round of work stoppages, charges of excessive radiation in the work place and violence against union members.

The Nuclear Regulatory Commission is investigating union charges of poor safety practices and radioactive contamination, and has found at least some of the workers' complaints to be true, according to Kenneth Clark, NRC spokesman in the regional office in Atlanta, which has jurisdiction over the Tennessee facility.

But, Clark said, none -- with the possible exception of a shooting inciddent -- has yet been found serious enough to warrant fines or other penalties. The Oil, Chemical and Atomic Workers International Union charges that a truck driver smuggled a loaded handgun into the nuclear facility and that as he was leaving with a full load of uranium nitrate, he fired it near picketing union members.

Rep. Edward J. Markey, (D-Mass.), chairman of a House Energy and Commerce subcommittee has begun his own investigation, to look at the alleged violations at the fuel-making plant and at how well the NRC has monitored the facility.

"If worker concerns prove valid, it would not only mean a major regulatory breakdown at Nuclear Fuel Services in Erwin, but would tend to indicate a regulatory failure of the Nuclear Regulatory Commission," Markey said.

"I am very troubled by both the number and seriousness of the allegations. The subcommittee is initiating an investigation that will get to the bottom of this mess," he said.

Officials of the NFS facility failed to return calls from The Washington Post. The plant fabricates fuel rods for the Navy's nuclear reactors and a substantial amount of highly enriched, radioactive uranium is on the site.

It is all complicated by a strike that began May 15 over issues related to job security and safety. Since then other workers, brought into the plant in protected buses, have replaced many of the union veterans, thus raising emotions.

Lonnie Tolley, president of the local chapter of the Oil, Chemical and Atomic Workers International Union, said shots have been fired into union headquarters, bricks have been tossed through windows of one union member's home and union workers have received telephone threats.

The key charges made by the workers and under investigation by the NRC and Markey's subcommittee include:

*Reports of recurring contamination in the lunchroom and locker rooms.

*Repeated instances of airborne releases and radioactive contamination of sites on and off the plant grounds.

*Improper burial of radioactive wastes on the grounds, leading to leaks and "hot spots" in the plant area and in ponds on the site.

*Failure to carry out proper monitoring, including use of malfunctioning measuring equipment and deliberate avoidance of sampling expected hot spots.

The NRC investigation is nearly complete and Kenneth Clark said that the charges that have been substantiated are in the lowest two of five categories of seriousness. They fall mainly in the category in which the company is required to change procedures or clean up hot spots.

Among the 60 charges, one that has not been substantiated is high contamination in the lunchroom, Clark said. He said NRC officials rely chiefly on samples taken by the company and recorded by it to assess the allegations. Surprise inspections from the NRC regional office helped check the conclusion.

The NRC is expected to report its findings and give background documents to Markey's subcommittee by Feb. 3.

Douglas Collins, NRC's chief of radiological programs for the region, said the Erwin plant has in recent years received many more inspections than other plants because "quite a few violations have been found there," in an almost steady run over the past five years.

The most recent penalties levied against NFS came last May and brought about $18,000 in fines.