TalkOrigins is not a legitimate source for scientific facts. That nonsense has been refuted:
In Dobzhansky’s work, numerous varieties resulted from radiation bombardment: fruit flies with extra wings, fruit flies with no wings, fruit flies with huge wings, fruit flies with tiny wings... In the end, however, they were all ... fruit flies! Dobzhansky meddled with the genetic code of an organism and effected changes on the organism’s offspring. Nearly all of the changes were detrimental to survival, and none of them resulted in an advantage over other fruit flies.
From: Refutation of True Origins article .
It also should be noted that there were numerous mutations resulting from the bombing of Hiroshima and Nagasaki. None have been reported to have been favorable.
If you had been paying attention, you might have noticed there are other kinds and sources of genetic variation. Besides, how would you know if a variation is favorable? Is sickle-cell trait favorable? "Favorability" depends on environment, which changes over time.
Where's the refutation? You have new species with more chromosones than previous species. That's what you asked to see.