Did the Soviet Union ban microwave ovens in 1976? No

No, there was no such ban. Several sources:
http://impiorg.wordpress.com/2012/06/13/did-russia-ban-microwave-ovens-at-some-point-in-the-past/

One such rumor that has been lighting up the internet is the claim that, in the past, Russia had banned microwave ovens. Within IMPI we could not find a source for this assertion, though one of our members, the eminent engineer and scientist Dr. John Osepchuk wrote the rebuttal, below.

http://wiki.answers.com/Q/Why_were_microwaves_banned_in_Russia

There was no law that banned microwave ovens in the old Soviet Union, William Kopp made this up for his article many years ago. Several debunkers have trawled the USSR legal code without success trying to find the law - or the law that repealed it during perestroika.

http://itsaweirdweirdworld.blogspot.nl/2010/05/are-microwave-ovens-safe.html

A number of internet sites will tell you that Russia banned microwave ovens in 1976 -- and yet these web authors always offer this claim without footnotes and without any hyperlink to a reliable source. The Wikipedia discussion here offers convincing details about the types of microwave ovens produced in Russia during the 1980s -- including model numbers and the names of the factories where the product was manufactured.

(If the former Soviet Union really had banned microwave ovens in 1976, Western propagandists would have discussed the matter endlessly in the 1980s and late 1970s. They didn't. Similarly, Soviet propagandists would have scored the U.S. for promoting a dangerous device. They didn't.)

http://skeptoid.com/episodes/4080 asserts that the claim may related to the fact that microwave ovens were simply not available in the USSR for economic reasons, turned by conspiracy theorists into a non-existent ban.

The Microwave Militia also makes claims such as microwave ovens are illegal in Russia or other parts of Europe. This is just a straight-up lie. Microwaves are perfectly legal in Russia and everywhere else in Europe. In fact I was not able to find a single country in the world that bans microwave ovens. They're regulated, of course, like all electric appliances; but regulation should not be mischaracterized as a ban.