Sounds like nonsense. But that may only be because it's presented poorly.
Scientists have unearthed an ancient city where evidence shows an atomic blast dating back thousands of years, from 8,000 to 12,000 years, destroyed most of the buildings and probably a half-million people.
Nobody, except for a small clique of fringe historians* (most of them, Indian) believes there was any kind of civilization in India between 10,000 and 6,000BC. The earliest buildings appeared in different parts of the world around 7000BC, in the neolithic age. At 6000BC, there were likely between one and two million people in the whole world. Besides, I don't believe a 10-20 kilton nuke can take out half a million people unless for some crazy reason, the population density in the middle of the Rajasthan desert 10,000 years ago was comparable to an densely populated urban area today (the city of Jodhpur has a population of about a million people today, and less than 50,000 a century ago).
Historian Kisari Mohan Ganguli says that Indian sacred writings are full of such descriptions, which sound like an atomic blast as experienced in Hiroshima and Nagasaki. He says references mention fighting sky chariots and final weapons. An ancient battle is described in the Drona Parva, a section of the Mahabharata. "The passage tells of combat where explosions of final weapons decimate entire armies, causing crowds of warriors with steeds and elephants and weapons to be carried away as if they were dry leaves of trees," says Ganguli.
There are descriptions of hundreds of different weapons in the Mahabharata (which was written around 1000BC according to most historians; Ganguli might be one of those that insist it was written closer to 5000BC.) There's one weapon that bring torrential rain, one which rains down fire from the skies, one which brings heavy winds, another that digs tunnels into the earth, one that wipes out every armed person in sight (you defeat it by dropping your weapons)...I'm sure you can find an analog to any modern day device in the Mahabharata if you use a little imagination.
As for the radioactivity, it would seem, to my naive mind, that this is easiest explained by means of a natural fission reactor like the one at Oklo.
* Admittedly, some of the early archeological and other historical treatises that proposed the Aryan migration theory were penned by scholars with an agenda (e.g., Max Mueller). I can't say I know very much about this, but I believe there's now tons more evidence that all points to roughly the same timeline and historical narrative.
