Three House subcommittees and the Nuclear Regulatory Commission are investigating allegations of misconduct by NRC officials at the commission's regional office in Atlanta, according to sources at the NRC and on Capitol Hill.

One subcommittee is looking into whether any officials may have tipped off a utility company that it was under investigation, and whether any officials allowed a plant to operate while they knew of legal and regulatory violations. Two other subcommittees and the NRC are looking into whether any officials failed to follow up charges by whistle blowers that they were being harassed or whether any officials otherwise failed to enforce regulations.

A House subcommittee is investigating allegations of official misconduct involving the Grand Gulf nuclear plant in Vicksburg, Miss. Two other House subcommittees and the NRC are looking into alleged improprieties concerning the Tennessee Valley Authority (TVA). Another review has been started by NRC into possible misconduct by NRC officials in connection with the General Electric Plant in Wilmington, N.C. The sites fall under the authority of NRC Region II, which has headquarters in Atlanta.

NRC Commissioner James K. Asselstine said it was unclear whether the allegations into Region II "represent a pattern or are just isolated incidents." He added that the region, which consists primarily of states in the southeast, historically "has not been as vigorous as some of the other regions."

J. Nelson Grace, the regional administrator, said he "cannot understand reports on our lack of vigor."

He said that the region has found more violations than any other region in the country.

In one investigation involving Grand Gulf, the House Energy and Commerce subcommittee on energy conservation and power is examining information that suggests "two instances of possible regulatory misconduct," according to a staff member.

Other sources familiar with Grand Gulf said the investigation was looking into whether any regional officials allowed the plant to operate, knowing that operator training licenses had been falsified.

Last summer the NRC fined Mississippi Power & Light Co., the utility that runs Grand Gulf, $500,000 for supplying false statements about the qualifications of plant operators.

A related probe by the subcommittee is examining whether any regional officials improperly tipped off utility officials about the NRC investigation, sources said.

In an apparently unrelated matter, two other subcommittees and the NRC are looking into whether any Region II officials have not vigorously pursued possible regulatory violations reportedly committed by TVA.

A recent report issued by NRC's office of inspector and auditor found no basis for allegations that former Region II administrator James P. O'Reilly prevented other officials from exposing information about safety violations at the TVA in 1980.

The House Energy and Commerce subcommittee on oversight and investigations and the House Interior and Insular Affairs subcommittee on energy and the environment are investigating the same matter.

NRC spokesman Frank L. Ingram said investigations are being conducted by the commission's office of inspector and auditor -- the equivalent of an inspector general's office -- and the office of investigation in connection with the General Electric plant. He declined to comment on the exact nature of the probes.