The problem with Naomi's references is that the Mahabharata's full text is some five thousand pages long. To read the whole thing through is going to take basically weeks. And if I don't find what I'm apparently looking for then maybe it's because I've gone for a translation that missed it, so I might have to read another one. And then the other five texts are of similar lengths. That's a lot of reading, and if I'm not quite sure what I'm looking for it's hard to see how its even going to be useful (at least, for the purposes of the discussion).
I'm assuming Naomi that your remarkable, almost throwaway, references to an ancient nuclear war would be similar to this site here (putting the case for):
http://ancientnuclearwar.com/
(and a site against)
http://ancientaliensdebunked.com/references-and-transcripts/ancient-nuclear-warefare/
(these are just the first two hits in google).
The first one talks about how there's evidence for a nuclear-like weapon based on a phrase "bright as ten thousand suns" and other such. Now my full text of the Mahabharata is a) nearly 6,000 pages and b) luckily searchable. I've been unable to find the phrase above but that may not mean much as it's sensitive to precise translation. What I do note is that "ten thousand" crops up no fewer than 147 times: "ten thousand camels/ asses/ horse/ serving-girls/ elephants" etc. (somewhere in section 60 it's even "ten thousand cars and vehicles"). That seems to me to imply that the phrase is meant to be poetic, evocative of merely "a lot". Someone is supposed to have slain "ten thousand warriors for ten days".
This is hardly surprising, as the text in question is an epic poem. It's meant to be filled with imagery, and imagination, and given the theme it wouldn't be entirely surprising that at times it goes for imaginative and epic destructions. It's a shame they didn't have that disclaimer "and resemblance to actual events is purely coincidental" at the end.
So far, the "ten thousand suns" phrase has appeared only in connection with Sesha the serpent, and nowhere else, so on the face of it the ancientnuclearwar.com site is either lying about its sources or using a different translation. (I also tried corpses, but couldn't find any reference to their being burnt. Eaten a lot by rats and jackals, and strewn all over the place, but never burnt. "Vimana" is translated as "car" in my version.)
This is a scattergun approach, and not meant to be conclusive, but it has to be conceded that referring someone to a 6,000-page poem (or several of them) as a source for a variously-translated account is less than impressive. A more precise citation would be welcome.