The Nuclear Regulatory Commission probably would have shut down all eight Babcock & Wilcox Co. nuclear power reactors as soon as Pennsylvania's Three Mile Island accident occurred March 28 if commissioners had fully understoodthe situation, transcripts of a close commission meeting revealed yesterday.

Discussiong April 5 what they should say in a bulletin to the B&W plants, the five commissioners complained that, eight days after the accident, they still were not confident they knew what had caused it.

"The transient [unusual event] indicates an operational failure," said John Austin, a technical assistant to NRC Chairman Jseph Hendire. "It's either on or off."

"John, what your'e saying," responded Commissioner Victor Gilinsky, "you're saying we should have turned them [the B&W plants] off Wednesday and be turning them back on today."

"I think that's probably right," echoed Commissioner Peter Bradford. Later, he added, "maybe not Wednesday, but at least Friday [March 30]."

In a telephone interview last night, Bradford said "there was a fairly general feeling around the table that if we had fully understood what had happened on Wednesday [March 28] that serious consideration should have been given to the question of closing the other plants. But we were so concerned with the question of Three Mile Island that the other plants didn't get much consideration."

By April 5, the commissioners knew that the two main valves of the emergency feedwater system at Three Mile Island somehow had been left closed for a crucial eight seconds after the main feedwater pump failed, thus preventing cooling water from reaching the reactor core. Such a loss of feedwater, Bradford observed, might occur again at any time in any B&W plant.

"The probability-sure it's low, but it's not all that low," he said. "You're talking about something like a 1 in 30 probability that you'd see one in one of these [B&W] plants in the next couple of months."

California Gov. Edmund G. (Jerry) Brown Jr. had asked the commission to close California's Rancho Secoplant, built by B&W, and Bradford argued that the NRC could not say with confidence that it knew all the ways in which an accident similar to the one at Three Mile Island might start. Therefore, he said, the commission could not really assure the operators of all B&W plants that if they followed certain instructions all would go well.

"That's what I think we're all saying," agreed Commissioner Richard T. Kennedy, "and somehow we've got to get that flavor here," in the bulletin to B&W plants.

But the resulting bulletin, which listed a number of reviews and precautions the plants were to take, showed none of the uncertainty Bradford described. The commission spent some time composing a qualifying statement that "our staff is reasonably confident that it has identified the principal factors" in the Three Mile Island event, but the phrase was deleted.

Earlier on April 5, the commission was astounded to hear that there were 40,000 gallons of highly radio-active water sloshing around in the the Three Mile Island auxiliary building. An automatic sump pump-"that fool pump," as Hendire called it-had come on in the early stages of the accident and pumped the water from the basement of the reactor building to tanks next door, which had over responsible for radiation released into the environment.

"It wasn't until yesterday [April 4] that I sat down and got a full briefing from some of our people and found that it is such a hot, highly contaminated building," reported Harold Denton, the NRC's senior staff member at the scene.

The commission members and their staff repeatedly expressed anger that they had no clear idea of the depth of the water in the building, the exact location of instruments inside, or whether any of the instruments might be endangered by the water.

"Where in hell are the instruments?" said Victor Stello, director of the division of operating reactors.

There was nothing much to be done, the commissioners learned, because "they don't have any tanks left where you could put the water."

Trying to put everything together in order to give the best possible advice to other plant operators, the regulators came to the tentative conslusion that if the operators at Three Mile Island had done nothing else but open the auxiliary pump valves, things might have worked out better.

"We could have a series of stickers made up required to be posted on each operating panel there that say 'Do not twiddle with the knobs," said Hendrie.

In addition, the transcripts indicate that the NCR:

Seriously considered simulating some of the conditions at Three Mile Island at an Oconee, S.C., nuclear plant in an attempt to find a solution to continuing recovery problems. This plan was later dropped.

Ignored recommendations that potassium iodide tablets or vials be distributed to people in the plant area to block absorption of radioactive iodine in thyroid glands because it feared residents would confuse the tablets with poisonous iodine used for treating cuts and bruises.

Became preoccupied with the fear that commissioners and staff members would have to spend much of the rest of their lives trying to explain their actions to inquiring congressional committees and other investigative bodies.

Rejected the idea of any public discussion of investigatiions into the accident, despite lawyers' advice that their grounds were "weak".

"We have a delicate continuing relationship with the licensee [Metropolitan Edison Co.] which can hardly have been helped by their reading in the paper that it was our preliminary staff conclusion that they blew it," commissioner Bradford said at one point. "Even if they fully share it."