A "Dirty Bomb" is just a conventional explosive surrounded by radioactive material. Think of a pipe bomb surrounded by hazardous materials. Its explosion would create a hazardous radioactive mess but the explosion would be no larger than the power of the conventional explosives. Critical mass would not be acheived in the detonation. There would be no fissionable or thermonuclear components to the explosion.
The data on the N.E.S.T. hard-drives would not be applicable in this instance. Disarming a "Dirty Bomb" would be similar to handling a conventional bomb in a Hazmat suit. Nothing high-tech just messy and dangerous.
My brother was on the N.E.S.T team several years ago.