Nuclear Regulatory Commissioner Thomas M. Roberts, against a U.S. attorney's advice, met with a lawyer for a nuclear power plant under investigation by a federal grand jury, a House panel disclosed yesterday.

Roberts said that he did not believe the meeting was improper.

The meeting occurred in September 1985 when a grand jury was investigating whether the D.C. Cook Nuclear Plant in southwest Michigan had willfully made false statements about its compliance with Nuclear Regulatory Commission fire regulations.

According to documents released by the Interior and Insular Affairs investigations subcommittee, Roberts and his legal assistant, James M. (Max) Cutchin IV, met with D.C. Cook lawyer Gerald Charnoff in Roberts' office for about 90 minutes on Sept. 4.

Less than two hours earlier, NRC solicitor William H. Briggs Jr. had reminded Cutchin that federal attorneys had asked that commissioners not talk to lawyers for the nuclear plant without Justice Department lawyers present. At the time, the U.S. attorney for the western district of Michigan was considering calling NRC commissioners to testify before the grand jury.

Roberts has been under fire for allegedly mishandling the probe of a leaked NRC document that apparently made its way from his office to a Louisiana utility's files. Seven congressional chairmen have urged Roberts to resign for that episode, which involved the Waterford Nuclear Plant near New Orleans.

Flanked by his lawyer, Roberts yesterday again denied any impropriety in the Waterford case and said he could not recall what he and the D.C. Cook lawyer talked about. "I don't think anything improper was discussed at that meeting," he said.

Asked if he discussed his potential grand jury testimony, Roberts replied: "Absolutely not." According to a memo written later by Cutchin, the discussion centered on "what had been said by Commissioner Roberts during his meeting with the U.S. attorney."

The commission had earlier declined to cite D.C. Cook for making false statements. The grand jury later returned a nine-count indictment, but it was dismissed in U.S. district court on grounds that the five-year statute of limitations had expired. The case is under appeal.

Yesterday's disclosure was the latest in a recent barrage of allegations that the NRC has become too close to the industry it regulates. "I am concerned that the NRC may not be maintaining an arm's length regulatory posture with the commercial nuclear power industry," said subcommittee Chairman Samuel Gejdenson (D-Conn.).

His remarks were echoed by Commissioner James K. Asselstine, who testified that industry pressure on the NRC's top staff three years ago resulted in significant weakening of fire regulations that had been drawn up after a near-disastrous fire at the Browns Ferry Nuclear Plant in 1975.

Asselstine, whose six-year term expires this month, said the rules were modified by order of Victor Stello Jr., the agency's top administrative officer, after the nuclear industry failed to win a court challenge. The changes were strongly opposed by NRC technical experts, he said.

"One has to conclude that this process was wrong," Asselstine said. "The industry came in, went straight to Stello and he accommodated them without even giving the fire-protection engineers a chance to comment."

After consulting with Stello, NRC Chairman Lando W. Zech Jr. told the Gejdenson panel that the rule modifications were "not abnormal."