The depopulation of Russia and some of its former associated republics, in its most recent incarnation, began about 1985-1990, and is only incidentally at about the same time as the Chernobyl nuclear accident (1986). Even though there are large increases in death rates after 1990 it is unlikely that more than a small fraction of these is are associated with the Chernobyl accident in 1986. Sizable decreases in birth rates also occurred after 1990, but these were in line with expectations based on a number of sociopolitical factors. Also, unique changes began to occur in 1990 with the disintegration of the old USSR into the Russian Republic and all of the individual satellite republics formerly associated with the USSR. Ethnic Russians began returning from the republics back to Mother Russia, but not too rapidly at first. Thus, emigration of Russians began to exceed their migration elsewhere, and also immigration of others notably from China and Mongolia started to occur to increase the rate or development of Siberia. Indeed, more Russians were coming home than were leaving and this helped to offset a portion of the negative influences of the declining birth rate and increasing death rate on the size of the population. Nevertheless, the latter two factors were still allowing the relatively rapid decline of the population of Russia which went from about 148 million in 1991 to about 143 million in 2014.
Russia is only about 80 percent ethnic Russian, and many minorities live and work in Russia either in the cities in the west or in the still relatively unpopulated Siberian frontier. As the Russian population may still be declining overall for many years to come, there is every reason to believe that increasing immigrant populations should become increasingly welcome. Without immigrants and with continued declines in birth rate and increases in death rates, net population decline could become a serious problem for Russia. Indeed at a population rate of decline of about 0.5 percent per year the population of Russia could move to under 100 million by 2050. On the other hand, Russia seems committed to doing what it can to increase birth rate, while improving public health, cleaning up the environment and doing whatever else it can to improve a longevity pattern that is headed in the wrong direction. They may also elect to make up what remains to fill in the population decline curve with further increases in immigrants into the far eastern Siberian lands from which it may launch more and more mining and mineral expeditions into the open, ice-free Arctic. All this may help Russia to keep the population up and even increasing a bit which will offset the chances of significant economic decline.
The number of Russians living in poverty had increased after the economic crisis that accompanied the breakdown of the USSR in 1990, and the subsequent improved economy that accompanied the aggressive mining of oil and natural gas deposits, and other businesses. That also helped improve the birth rate as well as increased emigration of Russian expatriots and others. The Russians are clearly developing their own capitalistic styles, and it seems unlikely that they will fade away into a depopulated pastoral society.