Dirty nuke material is already available on the black market. A small nuclear attack should not be surprising.
The following three previous posts support this:
Islamic State May Possesss Nuclear Material Stolen From Iraq: Report
Uranium Thieves Arrested In Soviet Material Selloff
According to the International Luxembourg Forum, Europe is at an increased risk of a nuclear attack since World War II with the ISIS trying to acquire weapons of mass destruction.
“ISIS has already carried out numerous chemical weapons attacks in Syria; we know it wants to go further by carrying out a nuclear attack in the heart of Europe. This, combined with poor levels of security at a host of nuclear research centres in the former Soviet Union, mean the threat of a possible ‘dirty-bomb’ attack on a Western capital is high,” the Independent quoted Moshe Kantor, the president of the organization, as saying.
Global Geopolitics 