The defection of the chief of Soviet KGB intelligence in Britain could provide valuable assistance to counterspies in the United States and other countries by revealing Soviet techniques and possibly agents in many countries, according to Sen. David F. Durenberger (R-Minn.), chairman of the Senate Select Committee on Intelligence.

Durenberger, briefed about 10 days ago on the defection of Oleg A. Gordievski, the KGB chief in the Soviet Embassy in London, called it "a very good thing" for the West.

Despite a report from Denmark indicating that Gordievski may have been a double agent since the 1970s, Durenberger said his information is that the defector has "no past relationship" with western intelligence.

The motive for the defection, according to the senator, was described by U.S. officials as the attraction of "Western values." Gordievski "got tired; he couldn't live the facade any more," Durenberger said.

A variety of Western intelligence agencies, including those of the United States, may obtain valuable information on KGB operational methods and possibly identities of other espionage agents from the senior defector, according to Durenberger.

Former Cenatral Intelligence Agency director Stansfield Turner called the development "a very nice coup for British intelligence."

He added, "It should do a great deal to dampen spying against Great Britain" because of the likelihood "it could disrupt the whole system" there. "We can assume they [British authorities] have the names of traitors there. Some might be Americans," Turner said.

Benefits for the United States from the defection include the possibility that "it could help us understand techniques" used in Soviet espionage, especially if the latest sophisticated methods are in use in Britain, he said.

It is also possible, he said, that Gordievski could provide information on "vulnerabilities," including personal weaknesses, of KGB agents with whom he had worked in other countries.

But Turner said that, due to "compartmentalization" of information practiced by Soviet and other intelligence agencies, it is unlikely that Gordievski would have current information on Soviet espionage activities outside of his field of direct responsibility.

Even "small pieces of the puzzle" can prove to be valuable when fitted into information already known or suspected, Turner said.

Ray Cline, a former CIA deputy director and former head of the State Department Bureau of Intelligence and Research, called the defection "a great break" for the west and "one of the rare breakdowns in the elaborate Soviet system of international espionage in democratic countries."

"Most people don't realize how valuable it is when we get a defection like this . . . . He can tell you things about how the system works that confirm other data and research and analysis" which are done without certain knowledge, Cline said.

According to a State Department report issued last January, at least 230 Soviet nationals were expelled in 1981-84 for "inappropriate activities," mostly spying, from countries around the world.

One of the largest expulsions was of 47 Soviet diplomats, journalists and others from France in 1983. But the British seem to have set the record for espionage expulsions in 1971 when 90 Soviet citizens were expelled and 15 others prevented from returning to Britain after defection of a KGB official in London.

A State Department official said it is unlikely that the new developments will affect "the fall agenda" of East-West arms talks and summit meetings.