Minutes after Irina Astakhova McClellan, a 47-year-old citizen of the Soviet Union, stepped off a plane at Baltimore-Washington International Airport today, she and husband Woodford McClellan embraced with an intensity fueled by more than 11 years of separation and pain.

After exchanging welcomes in Russian, Irina McClellan joined arms with her 51-year-old husband, a professor of Russian history at the University of Virginia, and the couple walked together into their new lives. Elena Kochetkova, 26, Irina McClellan's daughter from a previous marriage, was with her mother, having been allowed to emigrate after long negotiations.

"I am very hopeful about my life here," a beaming, although obviously fatigued, Irina McClellan said in English, minutes into her first visit to the United States. "It was a real fight for reunification of my family."

The McClellans had not seen each other since just after their marriage in Moscow in May 1974. Shortly after the wedding, the couple learned that the Soviet government was rejecting Irina McClellan's request to emigrate to the United States.

Although officials in successive U.S. administrations had intervened on the couple's behalf several times, little headway was made until November last year, when Soviet officials told the Reagan administration they would grant visas to 10 Soviets who had applied. The move was perceived to be a token of good will in advance of the Nov. 19-20 summit in Geneva between President Reagan and Soviet leader Mikhail Gorbachev.

McClellan said his wife, through a friend, gave him just one instruction before her arrival: "We're going someplace warm."

Therefore, after a two-day layover in the District, Irina McClellan will head south to recover from the chill of winter in Moscow. After the vacation, the couple will return to Charlottesville to begin their new life.

"Of course we're apprehensive," McClellan said in an interview before his wife's plane landed. "We clearly have to get to know each other again slowly, gently . . . . It's a delicate matter because we realize people change. We have both grown over 11 1/2 years, but we've grown separately."

The McClellans met in 1972 while he was traveling as a guide on a tour of the Soviet Union and she was a protocol officer with a state agency.

"We had such a beautiful relationship . . . and this shared suffering has created such a bond," he said.

While waiting for the plane from Moscow, McClellan -- a graying man who sports a moustache and was dressed today in corduroy and tweed -- still projected an outward demeanor of calm and professorial detachment.

Inside, he acknowledged, his anxiety of 11 years was mounting. "I hate to tempt fate. Call it superstition," McClellan said of his refusal to rejoice until he and his wife were actually face to face.

Some of the fear was justified. In December, Irina McClellan's plans were stalled when the Soviets said they would not allow Kochetkova to leave with her. That decision was later reversed.

On Wednesday, according to news reports from Moscow, McClellan and her daughter came within 30 seconds of missing their plane because Soviet clerks insisted they pay an excess baggage fee with foreign currency rather than rubles.

"The harassment followed them right to the end. That's the Soviets' way," McClellan said. "It's torture and it's utterly senseless."

McClellan said when he and Irina married neither expected she would have difficulty leaving the country. He said they had followed procedures to the letter.

Even after initial delays, he said, no one imagined a wait of 11 years. "We figured two years at the most. We could handle that."

McClellan, who specializes in Russian history prior to the revolution, doesn't know why the Soviets had difficulty with his wife's case. One explanation, he said, is that Soviet officials wrongly suspect that he is an important figure in the U.S. intelligence community because he taught Russian history at West Point in the early 1960s.

Just as likely, he said, is that he and his wife fell victim to "petty mid-level bureaucrats" in the Soviet Union who did not want to be seen as capitulating to U.S. demands.

Irina McClellan, a thin, poised woman with blond hair, said her jubilation over being reunited with her husband is tempered by sadness at leaving friends behind in her native country.

Both said that although they are grateful for the publicity given their plight by the news media, they are eager to begin a routine outside the international spotlight.

Said Woodford McClellan: "We both treasure our obscurity."