This year marks the 60th anniversary of the construction of the first nuclear powered sub, the USS Nautilus. Completed in 1955, the Nautilus served until 1980, at which point it became a museum ship. Since the Nautilus, over 400 nuclear subs have been built, most of them (254) Russian. As was their custom the Russians went for quantity rather than quality. As a result of this, some 80 percent of those Russian boats have since been retired. Not only did Russian subs wear out quickly but they were not able to get to sea as often as their Western counterparts. When they did get to sea they had more problems with radiation and reactor reliability.
Thus, the peak year for Russian nuclear sub patrols was 1984, when they had 230 patrols. That number rapidly declined until, in 2002, there were none. Since the late 1990s, the Russian navy has been hustling to try and reverse this decline. But the navy budget, despite recent increases, is not large enough to build new ships to replace the current Cold War era fleet that is falling apart. The rapid decline of Russia's nuclear submarine fleet needed international help to safely decommission over a hundred obsolete, worn out, defective or broken down nuclear subs. This effort has been going on for nearly a decade and was driven by the Russian threat to just sink their older nuclear subs in the Arctic Ocean. That might work with conventional ships but there was an international uproar over what would happen with all those nuclear reactors sitting on the ocean floor forever. Russia generously offered to accept donations to fund a dismantling program that included safe disposal (of the nuclear reactors).
While Western nuclear subs can last for about thirty years, Russian models rarely get past twenty. That means two new SSN or SSGN type subs has to be put into service each year to maintain a Russian force of forty boats. Unless the sub construction budget get billions more dollars a year, that is not going to happen. Right now, the priority is on producing a new class of SSBNs (11 more Boreis are planned or under construction). These Boreis are critical because they carry SLBM (Sea Launched Ballistic Missiles) that provide a critical (they are much harder to destroy in a first strike than land based missiles) portion of the nuclear deterrent. The rest of the Russian armed forces, like most of the navy, is in sad shape and unable to resist a major invasion. Only the ICBMs and SLBMs guarantee the safety of the state. So the way things are going now, in a decade or two, Russia will end up with a force consisting of a dozen SSNs and a dozen SSBNs.
The current Russian fleet of nuclear subs is tiny and the Russians would rather keep them tied up at dock most of the time. The crews can do a lot of training at dockside and only go to sea a few times a year, to check on their state of training. Given the number of accidents their subs have had in the past decade, the training the crews are getting now is not sufficient.
Only the U.S. and Britain were able to build nuclear subs that could stay at sea regularly and for long periods. French nukes were nearly as reliable but the Chinese built nuclear boats have, so far, been of lower quality than three decade old Russian designs. India is also in the midst of getting its first generation nuclear subs operational and it has been rough going.
While nuclear subs are a much feared weapon, they have gone sixty years with only one instance of combat. That was in 1982, when a British SSN sunk an Argentinian cruiser (the former World War II era USS Phoenix). Nuclear subs have been much more active in espionage work. While not as flashy as sinking other ships, it is dangerous, demanding, and rewarding work. Most of these efforts during the Cold War are still secret.