Moscow — From children's gas-mask drills to instruction on protecting clothes from radiation, the Soviet Union is working on civil defense for a nuclear age. For foreign ears, the Soviets play down their civil defense program. They blast more modest US efforts as proof of American war fever or, as a Moscow radio report puts it, of ''paranoid delusion.''
President Reagan's talk of upgrading US civil defense is, the Soviets charge, a reflection of an ''insane'' belief that nuclear conflict is survivable.
A 1978 CIA study said that although Soviet civil defense efforts had increased since the 1960s, the program is ''not a crash effort.'' It is seen by the Kremlin as a way of reducing nuclear casualties, yet not sufficiently advanced to make Moscow significantly more likely to risk atomic war, the study concluded.
Still, virtually all Western analyses concur that Moscow's civil defense efforts far outweigh recent programs in the West. Various studies have held that Soviet ''survivability'' in nuclear war is likely to be correspondingly higher than that of the US.
And, as a sampling of domestic radio reports over the past two years or so suggests, there has been a serious Soviet bid to protect the population and economy from the weapons of the 1980s.
There are, for instance, ''civil defense corners.'' These are displays that are typically found on farms and in factories in the Baltic state of Lithuania.
''The contents of the civil defense corner,'' a recent local radio program said, ''must convince people of the real possibility of reliable defense against modern means of destruction.''
The official Kremlin line is that there can be no such defense.
A broadcast in neighboring Estonia spoke of civil defense ''instruction classrooms at practically all farms and enterprises,'' and added: ''As we know, new housing is being equipped, as required, with protective structures.''
Another Estonian broadcast reported a civil defense inspection in one area, adding that prime attention had been paid to shelter facilities and, ''most important, whether establishments are capable of continuing regular production in an emergency.''
A Lithuanian experiment involved organizing Communist Party meetings, meetings with workers, and broadcasts on an internal factory radio station so that ''the overall training in this enterprise took place in an atmosphere closely resembling battle conditions.''
But an official radio commentary lamented that the exercise had proven only atmospheric, with ''few workers and employees involved,'' and that ''practical measures were not carried out. Even dispersals were carried out only theoretically.''
In the Asian state of Kazakhstan, the local radio spoke of the population's being ''trained morally, politically, and psychologically to take action in circumstances where modern means of attack are used.''
And a Lithuanian radio report seemed to provide a guide as to what to wear for nuclear war. The broadcast was aimed at people who ''are not members of civilian civil defense units,'' and thus not supplied with special protective garb.
''Everyday clothing and footwear may be used as protection for the skin against radioactive dust and bacteriological weapons. . . .
''Clothing made of synthetic and rubberized fabric, rubber footwear, and gloves have the best protective qualities,'' the report said, adding: ''In order to increase the protective properties of everyday clothing, it must be subjected to additional sealing . . . fastened tightly.
''It is recommended that extra flaps be sewn into openings. . . . A cowl can be sewn to protect the neck and exposed part of the head.
''The population is obliged to know that, on announcement of the threat of attack, means of personal protection must be kept constantly at hand,'' the report concluded.
Soviet Turkmenia, in Central Asia, has set up ''support schools'' for civil defense training. As of late last year, 59 such establishments were in place, complete with ''children's gas masks.''
At about the same time a children's hospital in Estonia held a special civil defense exercise that included handing out gas masks or protective gauze to child patients.
Civil defense ''competitions'' are held in various areas across the country. A report from Estonia late last year said the ''results'' in the ''traditional'' competition there had improved, with a shorter gap separating ''the winners . . . from last place.''
In at least some parts of the Soviet Union, efforts may also have expanded since the advent in 1981 of a US administration portrayed here as bent on ''unleashing nuclear war.''
In the Ukraine, a ''mass defense month'' was held shortly after Ronald Reagan took office. It focused attention on ''checking the condition and use of protective structures and the civil defense training and material base, as well as the storage and condition of means of human protection.''
A radio report detailing the campaign added: ''The role and tasks of civil defense have immensely increased in the present complicated political atmosphere , due to aggressive imperialist circles led by the USA.''