Prominent dissident author Lev. Z. Kopelev and his wife today received Soviet permission to travel abroad for a year, ending months of uncertainty about the fate of a couple who have been under attack and reprisal for their activities.

Kopelev, 68, said he and Raisa Orlova, his wife, will leave the Soviet Union next month to accept a year's invitation from West German novelist and friend Heinrich Boll to research and write in West Germany. A noted scholar of German literature, Kopelev said the Soviet approval "is hard to believe, a dream come true," that should enable him to finish what he calls his life's work, an interpretation of the image of Russia in German literature.

Early this year, Kopelev was attacked as a "Judas" by the Communist Party newspaper Pravda, which called his small Moscow apartment "a nest of ideological subversion and meeting place of Western emissaries." The attack came after the writer, whose memoirs of his years in Stalinist labor camps have been published in the West but suppressed here, denounced the internal exile of dissident leader Andrei Sakharov.

Mrs. Kopelev, 62, later was expelled from the Communist Party and the official Writer's Union in the same crackdown against Soviet inttellectuals who dared speak up in defense of Sakharov after he was banished Jan. 22 to the closed city of Gorki, 200 miles east of Moscow.

The Kopelevs said they plan to return here when their Soviet international passports expire next year. Kopelev declined the first Boll invitation three years ago, out of fear the Soviets would not allow him to return to Russia to rejoin his wife.

Mrs. Kopelev, a specialist in American literature, was a well-known lecturer here until her husband's activism led authorities to cancel her tours. l

Kopelev, a barrel-chested, white-bearded man, robust despite heart and liver troubles that are a legacy of his nine years in the camps, has occupied a unique position in Moscow's intellectual community, counseling young writers, speaking up in defense of longtime friend Sakarov, and espousing freedom of expression in the society. The Kopelev's apartment for years has been a major meeting point for Soviet intellectuals of every age and profession.

His first camp memoir, "To Be Preserved Forever," was published in the United States in 1977. A second volume, "Confessions of a True Believer," has just appeared, to favorable reviews. Neither book could be published here, and his scholarly official works on German literature have all been suppressed.

The authorities' decision to grant the couple passports is in line with their handling of another well-known dissenting author, Vasili Aksyonov, who was permitted last summer on a two-year passport and now lives in Ann Arbor, Mich. Vladimir Voinovich, the dissident satirist, also has applied to visit West Germany, but has received no official answer yet.

The kopelevs have family here and he has a daughter by a previous marriage who lives in Tarrytown, N.Y.

In a related development, the official news agency Tass today defended Moscow's record of justice in dealing with political or religious dissidents. Commenting on the trial of Viktor Kapitanchuk, a religious dissident who has pleaded guilty to anti-Soviet activities, Tass said his criticism of Soviet justice was "slanderous."

Tass denied Kapitanchuk's charge that innocent persons were subjected to criminal prosecution because of their beliefs. The same is true of allegations of psychiatric abuse, Tass said, "since the persons he mentioned have really been suffering from mental diseases for prolonged periods and in view of this were treated in psychiatric hospitals."

Kapitanchuk, 35, secretary of the Christian Committee for the Defense of Believers' Rights, was charged with printing and distributing anti-Soviet materials with the help of Westerners, notably correspondents accredited here. m

Kapitanchuk, who is currently on trial, could get a maximum sentence of seven years in labor camp and five years' internal exile.