The reports that someone in Moldova was going to see radioactive material to terrorists to make a dirty bomb is not to alarming. Offers such as this happen frequently in the criminal underworld. Radioactive materials, such as cesium are fairly available in small quantities from sources such as old hospital radiation therapy machines. In Brazil about 30 years ago, such a machine was broken open in a junkyard by curious workers who ended up polluting and poisoning a good part of the city of Goiania. When I was in Poland, there were frequent rumors of people with radioactive materials in Ukraine or Moldova who were willing to sell. In most of these cases the sellers had very little material, and probably had access to little more, usually just mishandled medical or scientific samples.
Here are some examples of earlier cases.