An imprecise word was used in a headline in Saturday's editions of the Washington Post in a story about the Nuclear Regulatory Commission withholding an operating license authorized earlier this week for the Virginia Electric and Power Co.'s nuclear power plant at North Anna. The headline said the permit for the plant had been "revoked." Actually, Vepco had not received a license for North Anna, but only authorization for one.

The Nuclear Regulatory Commission staff reversed itself yesterday and decided to withhold an operating license authorized earlier this week for Virginia Electric and Power Co.'s nuclear power plant on the North Anna River 70 miles from Washington.

The reason for the extraordinary action, the NRC staff announced, was that Vepco waited until after the operating license was authorized before informing the NRC that it had discovered a potentially serious safety problem two weeks earlier.

The staff asked the NRC licensing board to reopen public hearings on the controversial plant to consider the new information.

The safety problem concerns an error in the computer codes used to decide whether various pipes and connections in the backup and safety systems of the nuclear plant will perform correctly. Such an error could mean that arrangements thought to be safe might fail during an emergency. "All the pipes could be screwed up," and industry safety official summarized bluntly.

The problem is a potential one, however, since the error must still be evaluated. It could have had the effect of making the safety systems stronger than required, rather than weaker.

Until that is determined, however, the "danger of a danger" remains, the official said, and would normally be reported immediately upon discovery to the NRC. Vepco reported that problem Thursday, Dec. 15, two days after its operating license was authorized. Vepco first learned of it on Dec. 1, the NRC staff said.

"The staff believes that the timing of the communication by Vepco to the NRC of this new, potential safety problem raises questions that may have an impact on the conclusions reached by the staff . . . and on conclusions reached by the (licensing) board in its initial decision? to authorize the license, the announcement said.

The board said in its Dec. 13 authorization that although Vepco had behaved badly enough in the past five years to be fined on three occasions - more than any utility - it had shown enough improvement in most areas to convince NCR staff and the board of the company's commitment to safety and its technical capacity to achieve it.

"This issue - Vepco's commitment and technical qualifications - was a hotly contested issue that played a critical role in the hearings" that preceded the license authorization, the staff announcement said yesterday.

"Accordingly, the staff believes the circumstances warrant the reopening of the record for the limited purpose of receiving testimony on the manner in which Vepco reported this (computer-coding problem) matter to the (NRC) staff and the impact, if any, of the matter."

An NRC spokesman, Frank Ingram, described the staff action as "unusual but not unprecedented." A similar case occurred in Michigan in 1974, he said.

June Allen, president of the North Anna Environmental Coalition that has fought the North Anna plant for five years, was jubilant at the news."This is just part of a pattern we have been arguing before the boards in every hearing," she said. "Vepco's commitment to safety has been questioned by the coalition since . . . 1973."

Controversy over the plant has been continuous, centering on allegations that materials used were faulty and that their assembly was slipshod. The coalition sparked disclosure of a geological fault under the facility that the Justice Department later found Vepco had known about for three months before the public became aware of it. Faults are common sites of earthquakes.

The Justice Department charged the NRC staff with having had a part in concealment of the fault, and Senate hearings were held into the matter in October. The record has not yet been closed in that investigation.

The latest difficulty was reported as "a potential problem" by the Stone & Webster Engineering Co. to Vepco on Dec. 1, according to a chronology of the matter that Vepco supplied to the NRC staff yesterday at the staff's request. Stone & Webster confirmed that the computer error existed on Dec. 9, the staff said, and "several Vepco employees" then reviewed it and decided on Dec. 12 that it should be reported to the NRC.

On Dec. 13, the day the license was authorized, a Vepco vice president agreed that the matter should be reported. NRC spokesman Frank Ingram identified the official as S. C. Brown Jr., Vepco vice president for power station engineering. "It would seem that the thing should have been reported at least by the 13th when a vice president had decided it should," Ingram said.

In a statement, Vepco's senior vice president for power, William L. Proffitt, expressed regret at the NRC action. "Vepco employees were following established procedures to review matters that may require reporting to the NRC," he said. He added that the calculations involved had been checked and that all safety requirements had been met.

"The piping systems do not present any threat to public health or safety," he said.

Reached at home in Richmond.Proffitt explained that Brown's decision to report the computer problem "was passed on to another employee on the 13th who happened to be way from his desk, on assignment in North Anna, and there was a delay of about 36 hours until he returned."

Proffitt said the delay was "purely administrative" and added that Vepco's certainty the pipe systmes are safe is "much more important than the precise delay in reporting, although of course we have to meet the regulations."