There's a new list on Wikipedia that has a better breakdown of Russian nuclear power systems in space. It lists 32 BES-5 thermoelectric reactors, 2 Topaz reactors, 5 RTGs and 2 '2 kWe' reactors. At least 6 of those have reentered.

There's a new list on Wikipedia that has a better breakdown of Russian nuclear power systems in space. It lists 32 BES-5 thermoelectric reactors, 2 Topaz reactors, 5 RTGs and 2 '2 kWe' reactors. 

At least 6 of those have reentered. The Wikipedia article does not give current status for many of these missions. Its source lists those missions as still in orbit. So 36 reactors and 5 RTGs have been flown, 6 of those have reentered for a total of 31 reactors and 4 RTGs still in orbit.