The U.S. Appeals Court here yesterday ordered the Energy Research and Development Administration to prepare a new environmental impact statement for nuclear waste storage tanks under construction in Richland, Wash., and Aiken, S.C.

However, the appellate panel refused to halt the project while the new study is prepared, because the wastes are leaking from existing tanks at the Hanford Reservation in Richland and the Savannah River Plant in Aiken.

The new study must focus on design and safety features that can be incorporated into the planned double-wall carbon steel tanks, according to the appeals court opinion. If the new features are worthwhile, the plans should be modified to include them, the panel added.

Congress authorized funds for the construction of the 22 tanks in 1976 and 1977. They will be used for the storage of nuclear wastes generated by ERDA's nuclear weapons materials production program, and are scheduled for completion by next year.

The Natural Resources Defense Council, an environmental group, had claimed that the tanks should be licensed as long-term storage bins by the Nuclear Regulatory Commission. The appeals court yesterday disagreed, saying that it seems clear that the tanks are for short-term storage, until ERDA comes up with a long-range storage plan.

The environmental group also challenged the adequacy of the environmental study prepared in connection with the construction of the 22 tanks. The appellate court agreed on that point, noting that the study "did not discuss safety and design features that could be incorporated in waste storage tanks."

The appellage opinion was written by U.S. Circuit Court Judge Edward A. Tamm, who was joined by Judges Harold Leventhal and George A. MacKinnon.