Russia's nuclear stockpile -- at least the strategic warheads -- have all been built anew since the end of the Cold War. The US is also modernizing its stockpile in the same way, but it has not finished yet.
"built anew": made with all new components except that the fissile material is recycled from an old Cold-War-era warhead. (They probably re-cast and re-machine the fissile material.)
The reader might be asking, How can Russia, a poor country, afford that? Well, nukes aren't that expensive once you have the fissile material and the design and manufacturing expertise and infrastructure. The pay for the soldiers to guard the nukes and constantly be on the ready to launch them is more expensive, according to one report I saw recently (and Russia has low personnel costs).