[Libertarian_4_eva]

If new york city had a dirty bomb explode inside of it the whole city would be closed off for the before mentioned 30,000 years or longer maybe one or two outer parts of the city like brooklyn and parts of staten island would have to be abondoned as well buildings left standing for us to show countless generations of americans.

It depends on how high up or were the bomb is exploded to determine how much is affected.

[WIMom]

What type of effect would this type of bomb have in a subway system?

[Wonder Warthog]

"If new york city had a dirty bomb explode inside of it the whole city would be closed off for the before mentioned 30,000 years "

Bogus. The time would be a function of which radioactive materials were used to build the "dirty bomb". Other factors involved as well--weather in particular--dictate how extensively the radioactivity would be spread.