NEST is short for Nuclear Emergency Search Team.
A Radiological Dispersion Device (RDD) or "Dirty Bomb" is radiological material strapped to a conventional explosive .
The grenade that Bozer grabs in the beginning of the episode is an M26 fragmentation hand grenade. Which have a 4-5 second friction fuse. So the fact that the one in the episode exploded immediately after the toothpick broke is not very realistic