Technical advisers to the Nuclear Regulatory Commission called yesterday for a range of design and operating changes in the nation's nuclear power reactors that they said would reduce the chances of another Three Mile Island incident.

Presenting the results of two days of deliberations to the NRC, the Advisory Commottee on Reactor Safeguards (ACRS) focused on changes that would get more imformation to control room operators and get it there faster.

"These things should be done quite soon; not necessary today, but they should be receiving attention at a very early date," committee chairman Dr. Max W. Carbon told the NRC.

Utilities should focus particularly on the natural circulation process of cooling reactors, not only under normal circumstances but in emergencies, the committee said. Operators should be trained in the procedure, instruments to help them judge its progress should be installed and "a suitable display of this information should be provided the plant operator at all times," the group told the NRC.

tThe experts asked for more instruments to diagnose and follow the course of an accident and suggested that existing temperature sensors be rigged to provide readings at higher levels.

A crucial set printed nothing but question marks for hours when temperatures rose during the Three Mile Island accident, and then operators were unsure whether it could be trusted when it once again began printing lower readings. If they had trusted it immediately, NRC staff members have been quoted as saying, the operators would have known much earlier that there was extensive damage to the nuclear reactor core.

"The ACRS wishes to reiterate its previous recommendations that a high priority be given to research to improve reactor safety," the group continued.

"We urge more simulation, more compilation and more studies in-house by the [NRC] staff rather than relying as mich upon [industry] vendors as has been the case, " Carbon , a University of Wisconsin nuclear engineering professor, added.

The closest thing to disagreement among group members occurred in discussing whethers there was a need for indicators on each of a reactor's 1,000-plus cvalves that would show whether each was open or closed, and indicators on other safety-related switches, circuit breakers and other items.

Committee member Jeremiah J. Ray of Philadelhhia, a retired electrical engineer, endorsed the idea. "It's just a matter of putting the right components into the system to pick this up and crank into the computer," he said.

Consultant Walter Lipinski, an instruments specialist at Argonne National Laboratories, concurred: "Indication of position is a minimum," he said.

Operators at Three Mile Island did not notice for eight crucial seconds that the two main auxiliary feewater system valves were closed, moments in which core temperature skyrocketed.

Once cooling water was restored, the operators did not know for more than two hours that another valve had struck open, allowing the water to leave the reactor instead of cooling it. Major core damage occurred during that time.

Another consultant, however, Dr. Carl Michelson of the Tennessee Valley Authority, said the committee "could create safety problems with such a high degree of complexity" as indicators for each valve would cause.

"Some of the limit switches can be bigger than the valves," he said, and might "clutter up the place and involve massive amounts of wiring,"

In its recommendations to the NRC, dthe committee adopted a neutral position, asking the NRC to give "consuderation" to the idea of requiring installation of position monitors.

The advisers made a hurried presentation of their findings to the five member NRC before a jammed audience , and jumped up to race to catch airplanes back to their full-time jobs before the NRC could ask any questions.

Clearly nonplussed, acting chairman Victor Gilinsky said the commission would submit questions later. "We're at the mercy of the airlines," he said.