"We are progressing," the Nuclear Regulatory Commission's chief investigator told his bosses, 'in our normal superb fashion."

It was two weeks after the accident at the Three Mile Island reactor, and John G. Davis, acting director of the NRC's Inspection and Enforcement Division, was trying to assure the five commissioners that his office was capable of uncovering what happened at the Pennsylvania plant to bring on the nation's most serious nuclear accident.

But the commissioners, apparently, were not so sure. Transcripts of commission meetings between April 6 and April 13 indicate that the NRC members devoted hour after hour that week to meandering discussions of how to investigate the Pennsylvania accident-and whether any NRC investigation would be believable.

Davis, appearing before the commissioners on April 13, tried to convice them that his staff investigators were up to the job. "We have done this before," Davis said. "We have gone through this on the Kerr-McGee incident, which is also known as the Karen Silkwood affair . . . we've done a couple of air transport investigations. So we are not untried novices."

But Commissioner John F. Ahearne was not completely persuaded. "All I can say," Ahearne said, "is that I hope we can establish a higher degree of public credibility than a couple of those mentioned."

Another problem was that Davis' office was not the only part of the NRC that had plans to investigate Three Mile Island. At least two other divisions had probes under way, and the commissioners were continually debating setting up an independant investigator-a "special prosecutor," the commissioners called it-to move ahead separately of the three staff investigations.

All of this effort was complicated by news that President Carter had announced plans to create a citizens' commission to look into the accident.

The NRC members were confused about the relationships between their investigations and the president's. To resolve their confusion, they decided to approach the White House on the question the way reporters try to ferret out a story. "And I think," Chairman Joseph M. Hendrie directed his colleagues, "you know, why don't people who have contacts sort of probe over there."

The NRC members argued repeatedly whether the public would believe any investigation bearing the commission's imprimatur.

Commissioner Peter Bradford, the youngest member, thought the public probably would not. "This is obviously an area in which the susceptibility of NRC and [the Department of Energy] to being charged with having something to hide is pretty high, "Bradford said, in urging the appointment of an independent investigator.

But Bradford's argument angered Commissioner Richard Kennedy, the oldest member. "Let the record be clear that I don't think that's a correct statement," Kennedy said. He said if government employes are not trusted by the public, they might as well resign.

At another point in their deliberations, the NRC members debated whether to send thank you letters to all the federal agencies that had contributed engineers, scientists and equipment to the effort to control the Three Mile Island accident.

Hendrie told colleagues that he was getting complaints from other agencies that they had not received any thanks for help. Ahearne, who had been talking to Vice Adm. H. G. Rickover, head of the Navy's nuclear fleet, which had sent several experts to the scene, chimed in that he had received a similar complaint from the admiral.

NRC officals also seemed perplexed when the Food and Drug Aministration reported that it had found radioactive elements in milk produced in the rich dairy lands around Three Mile Island in the days after gases were vented into the winds over the plant.

This was confusing because the NRC was reporting, on the basis of its own tests, that there was no radiation in the milk. "We've got some people looking at this," Harold Denton, head of the agency's reactor division, told the commissioners. "Why is the FDA finding it and we're not?"