A Soviet navy captain who defected to the United States in 1959 and was turned into a double agent by the FBI in 1966 disappeared in Vienna 18 months ago when he was supposed to be meeting Soviet intelligence agents.

The man who disappeared had defected under the name Nikolai F. Artamonov. In the early 1960s he became a consultant to the Defense Intelligence Agency with the name Nicholas G. Shadrin.

Since his disappearance the U.S. government has repeatedly asked the Soviet Union for information about Shadrin, or Artamonov, but without substantial result.

Whatever his name, his case hitherto unreported anywhere, is a remarkable cold war espionage tale with a plot that might have been invented by John Le Carre or Len Dieghton. Only it happened.

Shadrin's wife - Dr. Blanka Shadrin, a Polish-born dentist who defected with him in 1959 - said she believes that her husband was kidnaped by two Soviet Secret Police (KGB) officers on the streets of Vienna while she was waiting for him in a room in that city's elegant Hotel Bristol. The American officials who know the story of Shadrin say they generally believe that this is what happened to him, but not all are certain.

According to well-placed sources, questions were raised about Shadrin - then Artamonov - when he was first interrogated by American officials in 1959 at a reception center for defectors in Frankfurt, West Germany. At least a few U.S. officials questioned whether he was a legitimate defector a plant by the Soviet Union.

These doubts were soon rejected, however, and Artamonov was welcomed to the United States as a genuine defector. In 1960 he testified before the House Committee on Un-American Activities warning that the Soviet Union had a secret plan to launch a surprise nuclear attack against the United States.

Then, after changing his name to Shadrin (though doing nothing to change his physical appearance, according to his wife), he went to work as a "consultant" to the Defense Intelligence Agency, (DIA), the Pentagon's intelligence agency. His job there was "not important," according to his wife, although she and others referred to Artamonov slash Shadrin's "brilliance." Government sources said he did not hold a sensitive position. He was a specialist on the Soviet navy, they say.

Many of his colleagues in government service attest to his reliability and loyalty to his new country.(He became an American citizen, by special act of COngress, in 1965.) Yet in the upper reaches of the intelligence establishment, persons responsible for protecting against Soviet "penetration" of American intelligence agencies - persons for whom suspicion is an instinct as strong as any other - doubts lingered about this defector.

Despite that, in 1966 the FBI turned Shadrin into a double agent, and authorized a series of contacts between him and Soviet agents in the United States, in Montreal and in Vienna. He was on a counterintelligence mission for the FBI when he disappeared in Vienna in December, 1975.

Jack Anderson, the syndicated columnist, learned of Artamonov/Shadrin's disappearance a year ago, and was preparing to write an article about it last July. He was told by a lawyer for Mrs. Shadrin and by "others", Anderson said last night, that if he published the story a man might be killed. Anderson decided not to go ahead. "There's not another reason that I'd have held up that story," he said.

The Washington Post learned of the story last month and began to make inquires. The Post confirmed from government sources the central elements of Artamonov/Shadrin's defection and ultimate disappearance. Mrs. Shadrin and her lawyer, Richard D. Copaken of the firm of Covington and Burling, at first asked Tht Post not to publish a story, also on the grounds that Shadrin's life might be endangered, and because there was still some chance that he might be returned to his wife.

Copaken also said, earlier this month, that he felt time was running not in the case, and that he expected to "go public" with it soon.

Unbeknownst to The Post, Copaken took the story to The Wall Street Journal, apparently because he feared that The Post would portray Aramonov/Sardrin as a voluntary re-defector in its account of the affair. The Wall Street Journal prepared an article reportedly for publication today. A Final Suggestion

Then, yesterday afternoon, a State Department official telephoned Copaken to say that a final suggestion he had made for a possible approach to the Soviets aimed at eliciting at least an acknowledgment that they hold Shadrin might be attempted. Previously Copaken held out little hope that this idea would be taken up by the Carter administration. He called it a long-shot, but declined to describe it.

But Mrs. Shardin said she thought the sudden call from the State Department was a ploy to prevent publication of newspaper stories about the affair, and she was inclined to let the papers go ahdad. "It was the end of the road," she said last night. "I decided that the only way to go was through the press."

Mrs Shadrin says she believes the United States has not done what it could have or should have to try to get her husband back. Her lawyer accuses the government - primarily the Ford administration, but the Carter administration too - of a series of "blunders."

The State Department told The Post that publication of a story now would jeopardize the chances of "our present actions" to help Shadrin, but refused to describe those actions. The Post decided to print the story.

In a more formal statement last abandoning him[Artamonov Shadrin] have not abandoned him, abandoning him (Artamonov/Shadrin) have not abandoned him and we are making every effort to determine his fate and get him back. We don't know if he's alive, and are operating on the assumption that he is."

By Mrs. Shadrin's account, this tale from out of the cold begins in 1958, when a handsome young Soviet naval officer - Artamonov, then 30 - came to Poland on an assignment to help his comrades in the Polish navy train sailors from Indonesia. She met him then and they fell in love. They spent eight months together in Poland. Escape in a Launch

As captain of a destroyer, Artamonov had a 22-foot launch for his personal use, according to Mrs. Shadrin. The two of them decided to use the launch to defect, she said yesterday. "He did it mostly for me," she explained. They took the launch from Poland across the Baltic to Sweden, where they defected. The Swedes turned them over to the United States, which took them both to a "safe house" on the outskirts of Frankfurt, Mrs. Shadrin recounted.

Several sources from the intelligence community said this was all possible, but also somewhat suspicious. One source noted that Mrs. Shadrin placed telephone calls freely to her family right after she arrived in Sweden, "and this wasn't normal in those days, to get right through on the telephone." A serious grounds for suspicion? Yesterday Mrs. Shadrin readily admitted those telephone calls. She laughed at the significance attributed to them by the intelligence community sources.

Sources said government records show that questions were raised by officials who questioned him in Frankfurt about the legitimacy of Artomonov's defection. But - as always - those suspicious were difficult to formulate in concrete terms, and they had to be weighed against the enormous interest in Artamonov's knowledge about the Soviet navy which - sources said - fairly erupted from within the American intelligence community as soon as he defected.

"We didn't know much of anything about the Soviet navy then," one source said. Approach by the KGB

In any case, by no means every American official who interviewed Artamonov shared suspicions about him. Many accepted his defection at face value, as is demonstrated by the decision to put him to work inside the DIA, whatever the sensitivity of his post there.

In the summer of 1966, Mrs. Shadrin said yesterday, two agents of the Soviet Committee for State Security, the KGB, approached Artamonov Shadrin in Washington. Though he had changed his name, she said, he did not change his appearance. She didn't know how the KGB found him here.

The KGB agents asked him to spy for his motherland. Mrs. Shadrin said that he reported this approach to the FBI, which asked him to accept the KGB's proposition. In other words, the FBI proposed that he become a double agent, feeding doctored "intelligence" back to his Soviet contacts.

Other government sources confirmed that the FBI turned Artamonov/Shadrin into a "doble."

Mrs. Shadrin's lawyer, Copaken, said he had been told by government officials that Artamonov/Shadrin agreed to work as a double without pay - he volunteered his services. But this way only after one of his superiors at the DIA told Artamonov/Shadrin that he ought to accept the FBI's proposition, Copaken said. He was originally reluctant, because he had been told he had been sentenced to death in abstentia in the U.S.S.R. the lawyer said.

According to Copaken, Artamonov/Shadrin went on missions for the FBI to Montreal in 1971 and Vienna in 1972. In the Austrian capital, the lawyer said, the KGB gave him training in the use of the various secret spying devices. 'Doctored in Langley'

In all these contacts with the KGB, Copaken said, Artamonov/Shadrin fed material "doctored inLangley" (at Central Intelligence Agency headquarters in suburban Virginia) to the Russians. The FBI regarded this operation as a way of learning more about KGB operations in the United States, Copaken said.

In 1975 the Soviets asked Artamonov/Shadrin to return to Vienna. Copaken said. Until that time the lawyer said, it was his understanding that the FBI never fully informed the CIA (or DIA) of Artamonov/Shadrin to Vienna.

Copaken - who has been working on the case for nearly 18 months and says he has talked to countless government officials about it - says this is what happened next.

The FBI and CIA argued about how to deal with the Soviet request to Artamonov/Shadrin to come to Vienna. They compromised on this formula: the CIA would prepare phony "intelligence" for him to pass to the Soviets , and would provide an agent to "run" the operation. But it was regarded as an FBI operation, and the CIA station in Vienna would have nothing to do with it.

That agreed, Mr. and Mrs. Shadrin went to Vienna and checked into the Hotel Bristol. On Dec. 18 Artamonov/Shadrin went, as he had been instructed, to the steps of the Votivkirche, a Catholic cathedral on the Ringstrasse in Vienna. There he met a man who invited him into a car, where a second man waited. The trio then drove to a fish restaurant on the outskirts of Vienna. When the meeting ended, the Soviets asked him to return to the same meeting place two days later. They also told him he had been given the rank of lieutenant colonel in the KGB. No Survillance

The FBI had insisted that there be no surveillance of Artamonov/Shadrin's contacts with the KGB in Vienna for fear that the Soviets might spot surveillance and realize he was a double. The FBI didn't realize this is still Copaken's version that the U.S. consulate was located on the 7th floor in an office building in clear view of the steps of the Votivkirche - so photo surveillance would have been simple. But there wasn't any, according to the lawyer.

The evening of Dec. 20 Artamonov/Shadrin left his wife in the Bristol and took a cab to the church. No American official of any kind has seen him since.

Still, according to Copaken, a profoundly mysterious aspect of the tale occurred at this point. By late evening Mrs. Shadrin got nervous, and she began to call the CIA agent "running" the operation. The agent was supposed to be in a safe house in Vienna, but wasn't. The agent, according to Copaken, was at a dinner party. (Copaken says he later had a chance to "interrogate" this agent, and that he will "go to my grave" baffled by the agent's role.)

Even the dinner party story didn't entirely explain the agent's absence. Copaken says, because the party ended at midnight at the latest, and Mrs. Shadrin who was by then calling repeatedly, didn't make contact until 1:55 a.m.

In any case, Artamonov/Shadrin was gone.