WASHINGTON (AP) _ Reactors at the Savannah River nuclear production plant operated for six years at higher power levels than may have been safe for the cooling system in case of an accident, federal officials said Thursday.

Keith Fultz, an associate director of the General Accounting Office, told the Senate Governmental Affairs Committee that power levels at the South Carolina plant were reduced by 26 percent in 1986.

The reductions came after questions were raised by plant operators about whether the emergency cooling system was capable of preventing fuel melting during an accident when the reactor was operating at maximum power, he said.

''The circumstances we have just described illustrate that the reactors had operated for about six years at a higher power level than may have been safe for the emergency cooling system in the event of an accident,'' Fultz testified.

Joe Spencer, program manager of nuclear reactor technology with Savannah River Laboratory, said that while new experiments on power levels had raised some concerns, they ''did not reveal that we were operating in unsafe conditions.''

And he said the concerns were based on the worst-case scenario of loss of cooling water, a very low-probablity event.

Fultz said the operator, Du Pont, believes the recent reductions bring power to a conservative level until final limits are established, scheduled for sometime this fall.

''Production goals have taken precedence in the past too often over safety concerns,'' said Sen. John Glenn, D-Ohio, the committee chairman. ''I hope DOE (the Energy Department) has gotten the message that we're not going to sacrifice safety and health for production goals.''

Fultz also said marks on the stainless steel walls of one reactor were detected last fall during a maintenance shutdown, but that no cracks were found and the reactor was restarted in December 1986.

Energy Department spokesman Jim Gaver said two of Savannah River's three operating reactors have been 100 percent inspected - both visually and with a dye-penetration process - ''and there are no cracks.'' An inspection of 25 percent of the third reactor has turned up no cracks, and it is to be completely inspected next month, said Gaver.

Fultz said dye-testing is limited because it cannot determine the depth of a crack and that ultrasonic inspection used by the commercial nuclear industry is superior. Use of ultrasonic inspection at Savannah River is not expected until 1988.

Fultz also told the committee that trainees make up 40 percent of the maintenance work force at Savannah River.

''Therefore, we are concerned that inexperienced personnel are maintaining the reactors without adequate training and, in some cases, without proper written procedures,'' Fultz said.

Charles Ahlfeld, Savannah River's program manager for reactors, acknowledged that the plant has been experiencing a high turnover of maintenance workers. However, he said a trainee can have as much as five years' experience and is always accompanied by a full-fledged maintenance worker.

J. Dexter Peach, an assistant comptroller general for GAO, told the committee that outside, independent oversight of the Energy Department's nuclear production plants is critical to provide a high degree of public assurance that its operations are safe.

Mary Walker, the department's assistant secretary for safety and health, said it is using outside technical experts, but that another permanent layer of oversight would not provide significant added assurance. However, she said the department is keeping an open mind on the matter.