When this topic was discussed in the past, it was generally ALWAYS accepted that we had to fear dirty bombs, not nuclear. Sadly, dirty bombs are all to great a reality, in that they are NOT difficult to produce if you are bent enough to do so...
Google and "Dirty bomb ingredients" produces some scary shit. One page of 83,000 hits
"Radioactive caesium chloride used in medical and research equipment can be used as a deadly ingredient in a "dirty bomb" and US leaders should try to curb its use, the US National Research Council (NRC) said on Wednesday in a report commissioned by Congress.
About 1300 machines at US hospitals and universities used for irradiating blood for transplant patients and other purposes contain caesium-137 in the form of caesium chloride stored in stainless steel capsules, said the council, which is part of the National Academy of Sciences and provides advice to US policymakers on science, technology and health issues.
"The presence of these sizable sources in areas that are potentially attractive targets [for attack] is a major factor making radioactive caesium chloride such a concern to the committee," according to the report.
The fear is that individuals or groups eager to detonate a dirty bomb in a US city could steal this caesium chloride and combine it with conventional explosives such as dynamite to produce a "dirty bomb" or radiological dispersal device."
"But America, the overwhelmingly dominant nuclear power, is also a possible source. Its Nuclear Regulatory Commission admits that at least 835 devices containing radioactive material have vanished in the past five years.
The most reliable assessment of the worldwide problem comes from the Institute for International Studies at Stanford University, whose database records some 850 incidents from the past decade.
If anything, databases understate the difficulties. Lyudmila Zaitseva, a researcher from Kazakhstan, said only a fraction of incidents in the former Soviet Union are detected and recorded. "We calculate that radioactive material being detected as missing or stolen is probably 10 to 30 per cent of what's really gone," she said.
Estimates put the world stock at hundreds of tons of plutonium and enriched uranium. A small nuclear bomb could be made from less than 50lbs of uranium, or from a sample of plutonium small enough to fit inside a Coke can."