A careful reader of the discussion in the Russian and American national security community could conclude that Americans are more concerned about the threat of a nuclear terrorist attack than are Russians. Specifically, American experts have described more vividly potential nuclear terrorist attacks on U.S. soil than have Russians, at least in the writings and conversations that are publicly accessible. Why this is the case is a puzzle. No one doubts that in Chechen fighters Russia faces serious, capable, determined adversaries. Moreover, if Chechnya succeeded in capturing, stealing, or buying a nuclear weapon (or material from which they could make a nuclear weapon), their first target would surely be Moscow, not New York or Washington DC.
Allison, Graham. "Nuclear Terrorism: How Serious a Threat to Russia?" Russia in Global Affairs (online edition). September/October 2004.