Temporarily averting a possible nationwide rail strike, a federal judge has barred the Brotherhood of Railway and Airline Clerks from spreading its walkout against the Norfolk & Western Railway to other carriers.

U.S. District Judge Aubrey E. Robinson Jr. signed the order Sunday day prohibiting the BRAC from establishing picket lines at any of 73 railroads which are financially aiding the N&W during its current strike.

Robinson's order was sought by the railroads. They are supporting the N & W, which was struck July 10. Under the terms of a mutual aid pact, the 73 railroads - members of the National Railway Labor Conference - pay a daily indemnity to the N & W while the strike goes on . The payment is reportedly $80,000 a day.

According to an affidavit filed by the railroads in their injuction request, the carriers claimed the BRAC was contemplating "selective strikes" against railroads aiding the N & W.

National Railway Labor Conference president Charles I. Hopkins filed an affidavit in which he said BRAC president Fred Kroll had told him that the union was contemplating such strikes against some railroads. Hopkins said Kroll mentioned the Southern Railway, the Seaboard Coast Line Railroad, the Union Pacific and the Southern Pacific.

Hopkins' affidavit said that Kroll later stated in a radio interview that the union was making additional strike plans. Hopkins said a strike was scheduled to begin at 12:01 a.m. Monday.

Robinson's order sets a hearing on the matter for Thursday. The temporary restraining order signed by Robinson Sunday expires Sept. 5 if no further action is taken to bar the expanded strike action.

Neogiators for N & W and the union, at odds over work rules, met again yesterday here. A spokesman for the railraod said that "no settlement is imminent."