Tennessee Valley Authority Chairman Charles H. (Chili) Dean Jr. told the Nuclear Regulatory Commission last month that the TVA's first priority for its ailing nuclear program is to continue the "exemplary performance" at the Sequoyah plant in Daisy, Tenn.

On Friday, the TVA shut down Sequoyah indefinitely after an outside consulting firm, Westec Services Inc. of Philadelphia, reported that it was unclear whether the facility's electrical system could withstand leaking steam, heat or radiation in the event of an accident.

Dean's remark last month came in response to an NRC report critical of TVA's nuclear program. He also wrote that a high priority would be to "pursue licensing" of TVA's Watts Bar Unit 1 in Spring City, Tenn., "on an expeditious but not crisis basis."

The authority, which is the only federally owned utility, also announced Friday that it was suspending welding work at Watts Bar Unit 2. The move comes after reports that unqualified welders may have worked on the project. It also follows a report by a second outside consultant, Quality Technology Company (QTC) of Kansas, that TVA improperly permitted workers at Watts Bar Units 1 and 2 to inspect welds after they were painted.

The decision to close the four-year-old Sequoyah leaves the nation's most ambitious nuclear-power program without any nuclear power. In March, the authority, facing pressure from the NRC, closed the only other TVA plant then operating, Browns Ferry in Decatur, Ala., the nation's largest nuclear-energy site.

The authority is now generating all its electricity at coal and hydroelectric facilities.

The TVA originally planned to build 17 reactors to supply 40 percent of the Tennessee Valley's power. The authority abandoned eight reactors during construction, encountered substantial delays in the construction of four others and completed the remaining five.

The five, two at Sequoyah and three at Browns Ferry, cost $3 billion and have the capacity to produce 5,500 megawatts, almost 7 percent of the nation's nuclear capacity.

Two House subcommittees are investigating whether the NRC over the past five years has ignored problems reported by TVA engineers, including use of substandard parts, harassment by TVA officials of whistle blowers and failure to follow certain NRC safety regulations. A Senate subcommittee is investigating TVA's entire program.

The Westec report states that there is insufficient documentation to show that Sequoyah equipment designed to shut the plant down during an accident could withstand the effects of heat, steam or radiation.

A TVA official who attended a Westec briefing two weeks ago said similar problems with documentation exist at other TVA nuclear plants.

The official's account was partially confirmed by Worth Wilkerson, a TVA spokesman, who said yesterday that other plants in the program may have the same problem. He said the matter was being examined.

The Sequoyah site has been plagued with other problems. Eleven workers were contaminated on July 30 when 600 gallons of irradiated water leaked from a system used to cool the reactor of Unit 2. Another leak, reported to be smaller, occurred at Unit 1 on Aug. 11.

In June, the NRC sent a critical letter to the TVA for failure to inform the commission about possible problems with equipment at Sequoyah designed to measure the pressure inside the building containing the reactor. And last year eight workers were almost scalded to death at Sequoyah in an incident the utility originally reported to be a relatively minor leak. The NRC fined TVA $112,500 for failing to describe the accident accurately.

Dean said yesterday in a telephone interview that the Sequoyah facility "was working in apple-pie order" when it was closed Friday. He said the TVA decided to shut the plant "because of documentation problems."

"We took the conservative course of action," he said. "The closing doesn't change our priorities, which is first to have Sequoyah running in an exemplary manner."

He said TVA estimated the closing of the 2,000-megawatt facility will cost the utility about $400,000 daily. He added that the cost might be substantially less than that because the plant was closed at a time of low electric demand.

"If there is such a thing as a fortuitous time for this to happen, it is now," he said, estimating that the plant might be able to resume operations in six to eight weeks.

He also said Watts Bar Unit 1 may apply to the NRC for a low-power license in early 1986.

QTC, the outside contractor, has been hired for $3.6 million to interview TVA's 4,800 employes at Watts Bar for safety concerns. According to TVA, QTC has verified 22 safety complaints out of 38 that have been examined. More than 2,000 complaints have been made by employes to QTC, according to Wilkerson.

Because of the shutdown of the nuclear power sites, as well as the dry weather, the TVA on Thursday will consider raising its rates by 6.9 percent.