I have a slighty different take on the dirty bomb issue. I did environmental cleanup for a while, mostly groundwater but a bit of nuke work.
If the contaminate is very finely divided and air dispersed, cleanup of the old porous concrete and brick is going to take more than a firehose and coat of paint. Even if it's just an alpha and beta emitter, IMO the affected areas would end up demo'ed - you guys know 'acceptable levels' at the plant will not be acceptable on the street. I don't think it would be a big killer like dropping the WTC, but if half a dozen blocks in midtown Manhattan have to be demo'ed that's a truly effective terrorist attack.
Radioactive contamination presents two type of risks, external and internal exposure with differing consequences. The most damaging long term is internal contamination because it has a half life that is a product of the biological and radiological half life. Any radiocactive isotope with a long biological and radiological half life may cause cancer and other health problems. External radioactive exposure is short term, confined to the period of exposure, and if beta or alpha, stopped by clothing or a piece of paper. Only gamma rays present a risk. External expsore if within Federal Regulations has little likey hood for long term health problems. A 'Dirty Bomb' would pose internal risks for those in the blast zone at the time of the blast. External contamination left would be washed off in decontamination procedures. After the blast and decontamination, what is left is fixed by coatings will only present external exposure risk to individuals in the area. The exposure can be measured and stay times determined. If truly blasted into porous structures, subsurface grinding would eliminate the material. I am quite confident that the monetary cost to demolish large infrastructure would be orders of magnitude greater than procedures to assure external exposure within Federal Regulations. In short, NO PROBLEM. -Dick
