A picnic, dance, and nuclear war evacuation

Diane Tomaney plans to get out of town this weekend. But Soviet President Leonid Brezhnev need not be alarmed.

Mrs. Tomaney and about 150 fellow residents of Burlington, Conn., are planning the nation's first practice run of atown evacuation plan in the event of a nuclear attack.

The residents' 60-mile emergency move to Becket, Mass., is included in a federal plan to build up civil defense. The US House of Representatives has approved the 1983 installment of the Reagan administration's requested seven-year, $4.2 billion plan to double civil defense spending.

Mrs. Tomaney of the Burlington Organization for Movement of Bodies to Safety (BOMBS) says several residents of the Connecticut town had been ''talking about nuclear warfare'' when they realized they ''didn't really know where we were supposed to go'' in case it threatened.

When they learned the plan called for their town of 5,000 to remove itself to Becket (population 1,251), BOMBS members asked Becket selectmen if they might practice the move. The selectmen ''loved'' the idea, according to Mrs. Tomaney.

Becket is 12 miles from a GE plant that produces parts for the Polaris missile, making it a prime target in an attack, so its residents ''would all be in Canada by the time we got there'' during a genuine emergency, Mrs. Tomaney says. But Becket will stay put for a festive welcome Sept. 11.

George Moffitt, a former Foreign Service officer, is BOMBS's ''official ambassador'' to Becket. As such he will cable President Brezhnev that the ''Bombs Away Weekend'' is ''just a test and not to overreact,'' says Diane Harakas, a fellow BOMBS member.

Weekend plans include a parade and a ceremonial presentation of a charred key to the city of Burlington. A softball game will pit evacuees against Becket's fire department. A potluck supper and square dance will follow.

Those fleeing Burlington will caravan in private cars with a police escort along the federally prescribed 60-mile route.

Diane Harakas, a BOMBS member, will take her two children, but the family cat , Smoky, must stay behind, according to civil defense plans. The Tomaneys will leave Patrick, their golden retriever, but Mr. Tomaney suggested they take crash helmets.

Mrs. Harakas says many BOMBS members are former Boy Scouts and Girl Scouts who thought they should ''be prepared'' so they could act ''reflexively'' in a true emergency. Burlington residents, she adds, also wanted an opportunity ''to know Becket under good conditions'' and to thank their designated host town.