A form of "Russian Nazism" may begin to emerge in the Soviet Union unless the West does something to prevent it.

That is the conclusion of an experienced Soviet journalist and political scientist who has used his privileged position in the Soviet Union to study the likely course of his country's development. For 15 years he traveled around the Soviet Union, interviewed hundreds of people and published articles in teh official Soviet press - but not, of course, on the politically delicate subject on which he was so well qualified to write. Now Dr. Alexandria Yanov is in the West.

He believes the West has the means to prevent the worst, and to promote peacefully the development of an alternative system, but he is not sure we have the will to do so. "If Russian Nazism becomes an accomplished fact and begins to march to power," he said, "it may prove too late to influence the process."

His analysis is based on the existence of a "new class" of privileged officials in Russia, but he differs from Previous writers, such as Trotsky and Djilas, who saw the new class as an unwelcome, parasite growth. He does not admire the new class, but he believes that we can use its efforts to perpetuate its privileged position, and in a way that could direct the evolution of the Soviet system in more desirable directions.

There is something inherently distasteful about the idea of helping the new class cling to its privileges and maintain itself in power. There is something questionable about the feasibility of manipulating it in a way that would redound to the West's advantage - and also, as Yanov argues, to the advantage of the Soviet people. A brief summary cannot do full justice to his analysis, "Detente after Brezhnev." But his paper presents an elaborate and sophisticated argument that deserves serious attention.

The Yanov model of the Soviet system proceeds from the fact that the gradual development of detente in recent years has given the new class an added interest in maintaining its privileges. Breakdown of detente would lead to the replacement of the present "centrist" Brezhnev leadership by a Communist-nationalist regime, which would follow an isolationist policy and could evolve into a Russian Nazi system. The seeds of some such system were implanted long before the Communists came to power, and have let out a number of clearly discernible new shoots in recent years.

The reactionary wing of Soviet communism, the "little Stalins" who retain a good deal of power in certain parts of the Soviet structure, constitute a threat to the centrist leadership that has evolved under Brezhnev. The centrists can overcome that threat only by allying themselves with the managerial technocracy. The managers' interest in economic efficiency gives them an incentive to support a policy of detente, which would provide the technology they hanker after. It would also enable the new class to retain and expand its access to Western luxury goods and travel, which are two of the most sought-after attributes of privilege in the Soviet Union.

The political power wielded by members of the Soviet elite under Stalin could be withdrawn from them at a moment's notice. The higher they rose the lower they fell - often with a bullet in the back of the head. Although Khrushchev got rid of the terror, his reformist zeal lead to a feeling of insecurity in a bureaucracy whose members were judged by results and often lost their posts when they failed to deliver. Under Brezhnev, the bureaucracy reasserted itself, its job security was reestablished and its age rose. The usual age of the top officials, which was between 30 and 40 under Stalin, is now 60 to 70.

The officials now in power throughout the Soviet structure, whatever their age, want not only to retain their positions and privileges while they live, but also to have them bequeathed to their children. They are succeeding this to a greater extent than they did under Stalin and Khrushchev. The unstable elite of previous years is gradually becoming a hereditary aristocracy.

But the aristocracy can secure its position only by limiting the absolute power of the top Kremlin rulers, much as the barons of feudal times fought to limit the power of the kings in order to increase their own power and security. Such attempts to put certain restraints on the power of the central authorities, undertaken in the selfish interests of the new class, ultimately serve to extend the process of liberalization to the nation at large. Therefore, Yanov believes, the West should help the new class to assert and extend its own authority in the interest of producing a regime able and willing to cooperate in a new international system.

Many strands of Yanov's analysis have appeared in Western writings on the subject. But this is the first time that an analysis of this kind has come from a Soviet writer, one who uses the experience and the evidence acquired in the Soviet Union to bolster his conclusions and recommendations. It deserves attention.