Opponents of California's Diablo Canyon nuclear power plant have asked Nuclear Regulatory Commission Chairman Joseph M. Hendrie to remove himself from considering the plant's license application on grounds of possible bias in the case.

Attorney David S. Fleischaker charged in a formal petition to the NRC that Hendrie wrongly held a private, off-record meeting last week with officials of Pacific Gas and Electric Co., which is building the Daiblo Canyon plant, to discuss substantive issues in the case.

NRC regulations forbid such talks with individual parties to a contested matter. In a memo made public Wednesday, Hendrie said he had not thought at first that the meeting came under the NRC rule "because we did not discuss the facts in the case."

He added, however, the NRC General Counsel Leonard Bickwit had researched the matter and "has come to a different conclusion, which I share." rBickwit found that the NRC rule ought to be broadly interpreted, Hendrie's memo said, and so, "to resolve any doubts that exist," he had made public a summary of the meeting.

Diablo Canyon lies 4.5 miles from an earthquake fault off the coast of California. The NRC's Advisory Commission on Reactor Safeguards (ACRS) had listed 13 questions it thought the Three Mile Island accident in March had raised regarding the effects of earthquakes on the Diablo Canyon plant.

In the meeting with Hendrie and Bickwit, according to the summary Hendrie made public, PG&E board chairman Frederick Mielke asked "that-the Three Mile Island issues should be addressed generically for all pressurized water reactors . . . he felt that NRC should avoid any discrimination procedurally against Diablo Canyon in the treatment on TMI issues."

Hendrie responded, according to the memo, that he saw no reason to treat Diablo Canyon differently than other plants in most cases. Hendrie noted that he later told other NRC officials that "the staff should continue its work Diablo Canyon just as it was doing."