Two Nuclear Regulatory Commission members yesterday vigorously defended the decision last year not to require emergency planning for earthquakes before the NRC licensed the Diablo Canyon plant in California.

At a stormy hearing before a House Energy and Conservation subcommittee, Chairman Nunzio J. Palladino and Commissioner Frederick J. Bernthal disputed charges by subcommittee members and California congressmen that during deliberations, the NRC was motivated solely by avoiding delay in licensing the plant, relied on off-the-record information and improperly failed to hold public hearings.

The charges were raised by Commissioner James K. Asselstine, the dissenter last August from a 4-to-1 NRC decision that emergency procedures for responding to an earthquake -- such as providing for transportation and communications access -- were not material to licensing of the $5.6 billion plant.

The NRC's decision relied on a 1981 commission opinion about another California nuclear plant that said the issue "should be addressed as a generic matter." However, Palladino acknowleged yesterday that the NRC had "goofed" by not pursuing the impact of earthquakes. A recently proposed NRC rule would make responses to earthquakes immaterial even as a generic matter.

Palladino said the record demonstrated that the earthquake issue "was not required to be addressed by regulations and was not significant from a safety standpoint." He said he had based his vote on on-the-record information and was "not afraid to delay a plant." He also said a subcommittee staff memorandum saying the NRC had probably violated the law was "replete with inaccuracies and outright errors."

But Rep. Edward J. Markey (D-Mass.), chairman of the subcommittee on energy conservation and power, referred to transcripts from the NRC's closed hearings shortly before its August ruling and said the transcripts and "a coverup" of the use of off-the-record information reminded him of Watergate.

"It appears that the commission has set up a giant shell game here, the effect of which is to preclude any public hearing on the complicating effects of earthquakes on emergency plans," he said.

Addressing the commissioners, Dennis E. Eckart (D-Ohio), also evoked Watergate and said, "You've perverted the process, you've perverted the procedure and you've subverted the safety of those people living near these plants."

Visibly angered, Palladino shot back: "We did neither of those things, sir."

Rep. Leon E. Panetta (D-Calif.) questioned the commission's August decision in light of other NRC regulations stating that earthquakes are material to the design and construction of the facility.

The panel also released a July 5 memorandum to the commissioners from Executive Director William J. Dircks that said the NRC needed more technical information to justify the proposal eliminating emergency planning for earthquakes.

Asselstine told the subcommittee that the NRC's handling of the earthquake issue had led him to question the integrity of the commission's licensing process.

Transcripts of closed NRC deliberations show that the commission wrestled with a rationale for its ultimate decision not to consider the effects of earthquakes.

At the time, Pacific Gas & Electric Co., which owns the Diablo Canyon plant, complained that every day of delay was costing millions of dollars. The Atomic Energy Act prohibits consideration of economic costs in deliberations touching public safety.

According to the transcripts, in a closed meeting July 30, Palladino said, "At this late stage, requiring a delay while we wait for a hearing is not in the best national interest."