a lab in virginia, it assesses the air we breathe, the water we drink and the food we eat. they are watching that cloud monitoring and if the national center up in livermore, they use supercomputers to crunch real time weather data and tell us when and where that nuclear material will make landfall. the most important factor is our wind, speed, direction and turbulence. >> after an accident the atmosphere can make a tremendous tkeuf refpblts it can make the delusion of radiation in the atmosphere makes the difference between a very serious health consequence and a trivial, unimportant health consequence. >> reporter: gus to give you an idea of what can happen, the image you're seeing now comes from cher r-frplt you can see the spread of the nuclear crowd across european russia.