Five Soviet citizens who have been trying for many years to emigrate held their new hopes tightly in check yesterday after hearing that they and other would-be emigrants may soon be granted exit visas.

Sen. Edward Kennedy (D-Mass.) told a press conference in Washington Monday that the Kremlin had agreed to reconsider their applications and that he is confident they soon will be allowed to leave.

Kennedy, who was in the Soviet Union last week and met for two hours with Soviet leader Leonid Brezhnev, said he expects exit visas to be granted to about 50 persons in 18 families.

They are among hundreds of Jews who have been refused permission to emigrate to Israel. The plight of the so-called refusedniks, well publicized in the west, has been one of the irritants in relations between Washington and Moscow, and a genuine Soviet move to allow some of the better-known refusedniks to leave would be regarded here as a step toward lessening tensions.

The five interviewed yesterday are physicist Benjamin Levich and his wife, Tanya, who have been trying for six years to leave; Boris and Natalya Katz, whose baby daughter's illness has sparked widespread American sympathy and support, and Olga Serova, a young actress almost unknown in the West.

"Of course we are very happy and hopeful . . . . It is a good sign," Levich said in his apartment in Central Moscow. "But I will be absolutely sure only when I receive my small green ticket (the exit permission)."

"I can't afford to be disappointed," said his wife. Mrs. Levich suffers from a heart condition she traces in part to an accident in 1974 when Soviet officials without warning reversed themselves and refused to let the couple emigrate to join their two sons in Israel, despite repeated promises.

"We should hear by Oct. 1," Mrs. Levich said. "If we don't hear by then, it will mean something bad."

Levich is a world-renowned physicist and a corresponding member of the Soviet Academy of Sciences. He was dismissed from the directorship of a laboratory he had founded and fired from his teaching position at Moscow State University in 1972 after he applied for a visa to go to Israel.

The Katzes said they heard the news in an early morning phone call from an excited friend, who had learned of it from the morning Russian-language newscast on Voice of America. They went on and bought a cake, a rich Russian two-layer dessert with thick icing. Their reaction, they said, was dampened by the passport offices recent refusal to approve their exit application after they thought they had been officially assure of approval.

"So, I try not to think of it," said Boris Katz, a bearded computer programmer whose mother and two brothers live in the Boston area. Nevertheless, the hope is there. Natalya Katz, seven months pregnant, said with a shy smile that she harbors the notion that their second child will be born in America.

The Katz's daughter, Jessica, suffers from inability to digest food, a malady called malabsorption syndrome, and the family's appeal for help in the form of special baby formula and U.S. medical treatment has brought them a flood of letters and offers of assistance, as well as dozens of cans of a special dried milk that the baby can digest without difficulty. Jessica, now 11 months old, took her first steps yesterday in their cramped, one-room apartment.

They said that since they applied to leave in 1975 their request has been reviewed eight times by passport officials and turned down each time.

Olga Serova, who gives plays in her apartment dealing with the isolated life of refusedniks, was in bed with a leg infection and was inclined not to trust the reports from America. She said he has been threatened by the KGB and subjected to intimidating acts by other Soviet officials, and said she doubted the reports. "I'm very pessimistic that anything will come of it," she said.

Kennedy met Saturday night with 11 dissidents or refusedniks and their wives at the apartment of Alexander Lerner, a prominent mathematician who has been publicly vilified as a traitor.

According to several who were there, the Kennedy party, including the senator and four others, came accompanied by a KGB security man, who politely waited outside during the meeting. Participants said Kennedy asked their views on how the U.S. Senate could help the cause of the activitists, and whether in voting for a strategic arms limitation agreement, he should take the human rights struggle here into account when he cast his vote.

"We were very eloqeunt and wordy," recalled one Russian who was present, and he was very businesslike."